Freiburg Vision Test (‘FrACT’)
by Prof. Michael Bach

FrACT10 Vs. 2020-09-29
classic FrACT 3.10.5 · 2020-04-06

This is the free, multi-platform Freiburg Visual Acuity Test + Contrast Test + Vernier Test + Grating Test. For reliable results please observe the checklist. Your feedback is welcome and has frequently led to improvements and extensions. FrACT was employed in hundreds of papers and cited in well over 1000 papers.

There are two (2) versions

(1)  FrACT10   –   new, all platforms, beta stage, on-line only

This new version runs on-line only on all platforms (including Android and iOS).
Here it is alone allowing full-screen operation.

(2)  FrACT3.10.5   –   long-standing, well-tested, widely deployed, online + downloadable app

If the on-line version of FrACT right below is blocked by your browser: consider enabling Flash temporarily on this page. The downloadable stand-alone version does not need Flash. The option “result→clipboard” cannot be enabled in a browser.

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What is it?

“FrACT” is a widely used visual test battery in form of a free computer program. It uses psychometric methods combined with anti-aliasing and dithering to provide automated, self-paced assessment of visual acuity (Bach 1996), contrast sensitivity and vernier acuity. The progression of optotype sizes relies on a Bayesian approach and is determined by a modified “Best PEST” strategy (Lieberman & Pentland, see General Pertinent Sources below). FrACT complies with the European Norm for acuity testing (EN ISO 8596) and is endorsed by the DOG. It is employed all over the world in vision labs, by optometrists, ophthalmologists and in clinical trials (→Who used FrACT) and has been verified by independent laboratories (→Descriptions & Validations).

One particular advantage of FrACT is its ultra-wide range
Where can I get it?


Where can I learn more?
Where to use?
What equipment do I need?

Just about any state-of-the-art computer (be it running the Macintosh operating system, Linux or Windows). For remote input see the response box below in Usage Details.

If you are using an LCD and want to measure contrast thresholds, be sure the display is not of the 6-bit type (as it is was in many laptops; more in Usage Details); for acuity those would be fine. Make certain that the best possible color depth is chosen. Older versions of FrACT remain available and run just fine on older equipment.

What does it cost?

Nothing; but feedback is warmly appreciated. And please cite it when you’ve used it in scientific settings.

How do I cite it?

If you used FrACT for your research, please cite it. The “generic” publication is:

Bach M (1996) The “Freiburg Visual Acuity Test” – Automatic measurement of visual acuity. Optometry and Vision Science 73:49–53   [pubmed]  [→PDF],
or, more recent:
Bach M (2007) The Freiburg Visual Acuity Test – Variability unchanged by post-hoc re-analysis. Graefe’s Arch Clin Exp Ophthalmol 245:965–971   [DOI] [→PDF]

The briefest way to refer to the present page (its URL):  <>.

Usage Details

If you ran a previous version, all selections in “SETTINGS” may automatically be defaulted in order to update internal structures (depends on the exact versions).

How to calibrate?

Enter the width of the calibration bar & the observation distance in the “SETTINGS” interface. Be sure to have enough distance from the screen, so pixel resolution does not limit acuity. Also ponder about every entry in the SETTINGS interface and set them appropriately; the defaults can not be optimal for every situation. The Checklist is a must-read, in the “FrACT3_Manual.pdf” all settings are explained in more detail than you probably wished…

For the Contrast Test, you also need to go to “SETTINGS>Luminance Linearisation” to linearise luminance (“gamma correction”) before testing. But see below for a cautionary note on the difficulties of contrast testing.

All selections in SETTINGS are automatically saved.

Starting the test

Apart from using the obvious buttons a test run can also conveniently be started from the numerical keypad (digit 5). Enter the position of the appearing Landolt-C’s gap via the numerical digit keys. These are spatially mapped to the 8 possible gap positions in an obvious way (“8”=top, “9”=top right, etc.). The digit key “5”, pressed twice, aborts an ongoing test run (and inhibits display of the premature result).

Response box

Working with patients you may want to enter results yourself. In lengthy vision experiments, subjects are used to enter responses themselves.

image of keypad 1
For direct response entry by the subject, these keypads are useful. They come in various versions. Most have only a short cable, for remote entry you will want to add a USB extension cable.
image of keypad 2
This one even sports fancy labels.

4 or 8 gap positions?

The Tumbling E has possible 4 orientations, the Landolt-C allows 4 or 8. Depending on your application, you may wish to use only the 4 primary gap positions or to supplement it with the four oblique directions; FrACT allows both. Briefly: 4 directions are less easily confused, but guessing probability is higher making more trials necessary; 8 positions allow more rapid determination of visual acuity(less trials) as the guessing probability is lower. Final outcome should be identical, but the number of runs must be adequately chosen; see next item.

Number of trials?

Default: 24 trials with 8 gap orientation choices, 30 trials with 4 gap orientations (because the guessing rate is higher). For ‘real’ scientific applications choose 8/30, or, better, repeat each condition (e.g. each eye at 18 trials, ideally in an ABBA scheme) and take the mean. Why are all these numbers divisible by 6? Because every 6th trial is a “bonus trial”, where the optotype is presented at 3 times its current threshold estimate. This keeps your subjects happy, especially since the last trial is thus always a ‘success’.

Keeping different Settings

Often one wants different sets of SETTINGS, e.g., for training vs. assessment, for near vs. far vision, for different age ranges, with vs. w/o crowding etc. Rather than change the settings each time (with the danger to forget something), be informed that the SETTINGS state is stored per FrACT file. Thus, if you duplicate (appropriately renaming it) or put a copy in a different location, each will have their ‘personal’ SETTINGS; to switch between different sets of SETTINGS, just quit/exit and start the other version.

Results Export

The test result is presented on the screen. Additionally, the result can be transferred to the clipboard (in a simple, final-result-only or full-history fashion); so just switching to a spreadsheet program running in the background allows pasting the result. As of version 3.6, TCP/IP-based result transmission is also available, using a standard URL-request GET call.

What is special about the Contrast Test?

Experience taught me that contrast testing is technically much more demanding than acuity testing.

5start a test as defined in SETTINGS
astart Acuity
lstart Acuity Letters
cstart Contrast
vstart Vernier Acuity
e start Acuity Tumbling E
q or xQuit = eXit
 55 or <esc> abort running test


In narrow environments the standard 4 m distance may be difficult to achieve. In such conditions, high-quality front surface mirrors can be employed. In SETTINGS, you can switch from “normal display” (default) to mirroring horizontally, vertically or to 180° rotation.


I am lazy and prefer to start actions without mousing, thus I added a number of shortcuts, see Manual).

Who used FrACT?

Over 1000 studies cite FrACT. Previously I found the time to systematically analyse whether FrACT was actually used, but the list of examples below is no longer maintained.

Examples from 2017
  1. Bach M, Hoffmann MB, Jägle H, et al (2017) Kontrastsehen – Definitionen, Umrechnungen und Äquivalenztabelle. Ophthalmologe 114:341–347 . doi: 10.1007/s00347-016-0379-5
  2. Berger N, Richards A, Davelaar EJ (2017) When Emotions Matter: Focusing on Emotion Improves Working Memory Updating in Older Adults. Front Psychol 8: . doi: 10.3389/fpsyg.2017.01565
  3. von Castell C, Hecht H, Oberfeld D (2017) Measuring perceived ceiling height in a visual comparison task. The Quarterly Journal of Experimental Psychology 70:516–532. doi: 10.1080/17470218.2015.1136658
  4. Favrod O, Sierro G, Roinishvili M, et al (2017) Electrophysiological correlates of visual backward masking in high schizotypic personality traits participants. Psychiatry Research 254:251–257 . doi: 10.1016/j.psychres.2017.04.051
  5. Grzeczkowski L, Clarke AM, Francis G, et al (2017) About individual differences in vision. Vision Research 141:282–292 . doi: 10.1016/j.visres.2016.10.006
  6. Grzeczkowski L, Cretenoud A, Herzog MH, Mast FW (2017) Perceptual learning is specific beyond vision and decision making. Journal of Vision 17:6–6 . doi: 10.1167/17.6.6
  7. Hoffmann MB, Brands J, Behrens-Baumann W, Bach M (2017) VEP-based acuity assessment in low vision. Doc Ophthalmol 135:209–218 . doi: 10.1007/s10633-017-9613-y
  8. Hughes AR, Mallen EAH, Elliott DB (2017) The Visual Impact of Lens-Induced Astigmatism is Linked to Habitual Axis. Optometry and Vision Science 94:260 . doi: 10.1097/OPX.0000000000001000
  9. Ioannou C, Zein ME, Wyart V, Scheid I, Amsellem F, Delorme R, Chevallier C, Grèzes J (2017) Shared mechanism for emotion processing in adolescents with and without autism. Scientific Reports 7:42696. doi: 10.1038/srep42696
  10. Jensen BH, Bram T, Kappelgaard P, Arvidsson H, Loskutova E, Munch CI, Larsenet M (2017) Visual function and retinal vessel diameters during hyperthermia in man. Acta Ophthalmol
  11. Johnson AP, Woods-Fry H, Wittich W (2017) Effects of Magnification on Emotion Perception in Patients With Age-Related Macular Degeneration. Invest Ophthalmol Vis Sci 58:2520–2526. doi: 10.1167/iovs.16-21349
  12. Jones DJW, Harris JP, Butler LT, Vaux EC (2017) Stereopsis in end-stage renal disease (ESRD). Physiol Behav. doi: 10.1016/j.physbeh.2016.12.029 [acuity & vernier]
  13. Kiefer M, Kammer T (2017) The Emergence of Visual Awareness: Temporal Dynamics in Relation to Task and Mask Type. Front Psychol. doi: 10.3389/fpsyg.2017.00315
  14. Kornmeier J, Friedel E, Wittmann M, Atmanspacher H (2017) EEG correlates of cognitive time scales in the Necker-Zeno model for bistable perception. Consciousness and Cognition 53:136–150 . doi: 10.1016/j.concog.2017.04.011
  15. Kornrumpf B, Dimigen O, Sommer W (2017) Lateralization of posterior alpha EEG reflects the distribution of spatial attention during saccadic reading. Psychophysiology. doi: 10.1111/psyp.12849
  16. Kornmeier J, Friedel E, Wittmann M, Atmanspacher H (2017) EEG correlates of cognitive time scales in the Necker-Zeno model for bistable perception. Consciousness and Cognition 53:136–150 . doi: 10.1016/j.concog.2017.04.011
  17. Liston DB, Wong LR, Stone LS (2017) Oculometric Assessment of Sensorimotor Impairment Associated with TBI. Optom Vis Sci 94:51–59. doi: 10.1097/OPX.0000000000000918
  18. Madden DJ, Parks EL, Tallman CW, Boylan MA, Hoagey DA, Cocjin SB, Johnson MA, Chou Y, Potter GG, Chen B, Packard LE, Siciliano RE, Monge ZA, Diaz MT (2017) Frontoparietal activation during visual conjunction search: Effects of bottom-up guidance and adult age: Effects of Bottom-Up Guidance and Adult Age. Human Brain Mapping. doi: 10.1002/hbm.23509
  19. Madden DJ, Parks EL, Tallman CW, et al (2017) Sources of Disconnection in Neurocognitive Aging: Cerebral White Matter Integrity, Resting-state Functional Connectivity, and White Matter Hyperintensity Volume. Neurobiology of Aging. doi: 10.1016/j.neurobiolaging.2017.01.027
  20. Meyberg S, Sinn P, Engbert R, Sommer W (2017) Revising the link between microsaccades and the spatial cueing of voluntary attention. Vision Res 133:47–60. doi: 10.1016/j.visres.2017.01.001
  21. Misson GP, Anderson SJ (2017) The spectral, spatial and contrast sensitivity of human polarization pattern perception. Sci Rep 29;7(1):16571. doi: 10.1038/s41598-017-16873-6
  22. Monge ZA, Geib BR, Siciliano RE, et al (2017) Functional modular architecture underlying attentional control in aging. NeuroImage 155:257–270 . doi: 10.1016/j.neuroimage.2017.05.002
  23. Motamed A, Deschamps L, Scartezzini J-L (2017) On-site monitoring and subjective comfort assessment of a sun shadings and electric lighting controller based on novel High Dynamic Range vision sensors. Energy and Buildings. doi: 10.1016/j.enbuild.2017.05.017
  24. Petoe MA, McCarthy CD, Shivdasani MN, et al (2017) Determining the Contribution of Retinotopic Discrimination to Localization Performance With a Suprachoroidal Retinal Prosthesis. Invest Ophthalmol Vis Sci 58:3231–3239 . doi: 10.1167/iovs.16-21041
  25. PochopienK , Fahle M (2017) Influence of Visual Prism Adaptation on Auditory Space Representation. i-Perception 8:2041669517746701 . doi: 10.1177/2041669517746701
  26. Pochopien K, Spang K, Stemmler T, Fahle M (2017) On the Mechanics of Immediate Corrections and Aftereffects in Prism Adaptation. Vision 1:27 . doi: 10.3390/vision1040027
  27. Rizio AA, Moyer KJ, Diaz MT (2017) Neural evidence for phonologically based language production deficits in older adults: An fMRI investigation of age-related differences in picture-word interference. Brain and Behavior e00660. doi: 10.1002/brb3.660
  28. Schilling T, Ohlendorf A, Leube A, Wahl S (2017) TuebingenCSTest – a useful method to assess the contrast sensitivity function. Biomedical Optics Express 8:1477. doi: 10.1364/BOE.8.001477
  29. Vanmarcke S, Wagemans J (2017) Priming Facial Gender and Emotional Valence: The Influence of Spatial Frequency on Face Perception in ASD. Journal of Autism and Developmental Disorders. doi: 10.1007/s10803-016-3017-9
  30. Vanmarcke S, Noens I, Steyaert J, Wagemans J (2017) Spatial Frequency Priming of Scene Perception in Adolescents With and Without ASD. J Autism Dev Disord. doi: 10.1007/s10803-017-3123-3
  31. Wiese H, Komes J, Tüttenberg S, Leidinger J, Schweinberger SR (2017) Age-Related Differences in Face Recognition: Neural Correlates of Repetition and Semantic Priming in Young and Older Adults. J Exp Psychol Learn Mem Cogn. doi: 10.1037/xlm0000380
  32. Xu R, Wang H, Thibos LN, Bradley A (2017) Interaction of aberrations, diffraction, and quantal fluctuations determine the impact of pupil size on visual quality. Journal of the Optical Society of America A 34:481. doi: 10.1364/JOSAA.34.000481
Examples from 2016
  1. Bach M, Reuter M, Lagrèze WA (2016) Vergleich zweier Visustests in der Einschulungsuntersuchung – E-Haken-Einblickgerät versus Freiburger Visustest. Der Ophthalmologe 113:684–689
  2. Bach M, Schäfer K (2016) Visual acuity testing: feedback affects neither outcome nor reproducibility, but leaves participants happier. PLOS ONE 11(1):e0147803
  3. Barnes N, Scott AF, Lieby P, et al (2016) Vision function testing for a suprachoroidal retinal prosthesis: effects of image filtering. Journal of Neural Engineering 13:36013. doi: 10.1088/1741-2560/13/3/036013
  4. Bartholomew AJ, Lad EM, Cao D, Bach M, Cirulli ET (2016) Individual differences in scotopic visual acuity and contrast sensitivity: genetic and non-genetic influences. PLOS ONE 11(2):e0148192
  5. Brückner S, Kammer T (2016) No Modulation of Visual Cortex Excitability by Transcranial Direct Current Stimulation. PLoS ONE 11:e0167697
  6. Camilleri R, Pavan A, Campana G (2016) The application of online transcranial random noise stimulation and perceptual learning in the improvement of visual functions in mild myopia. Neuropsychologia 89:225–231
  7. von Castell C, Hecht H, Oberfeld D (2016) Measuring perceived ceiling height in a visual comparison task. The Quarterly Journal of Experimental Psychology 1–17. doi: 10.1080/17470218.2015.1136658
  8. Cavallet M, Chaim-Avancini TM, Biazoli CE, Bazán PR, da Silva MA, Cunha PJ, Miguel CS, Busatto GF, Louzã MR, Gawryszewski LG (2016) Influence of emotional stimulus valence on inhibitory control in adults with and without ADHD. Exp Brain Res 234:3213–3223. doi: 10.1007/s00221-016-4719-0
  9. Duval CZ, Goumon Y, Kemmel V, et al (2016) Neurophysiological responses to unpleasant stimuli (acute electrical stimulations and emotional pictures) are increased in patients with schizophrenia. Scientific Reports 6:22542. doi: 10.1038/srep22542
  10. Garcia GA, Khoshnevis M, Yee KMP, Nguyen-Cuu J, Nguyen J, Sebag J (2016, in press) Degradation of Contrast Sensitivity Function Following Posterior Vitreous Detachment. American Journal of Ophthalmology
  11. Hertenstein H, Gross NJ, Bach M, Beisse F (2016) Marked dissociation of photopic and mesopic contrast sensitivity even in normal observers. Graefes Arch 254(2):373–384 [acuity & contrast]
  12. Kornmeier J, Wörner R, Bach M (2016) Can I trust in what I see? EEG evidence for a cognitive evaluation of perceptual constructs: Can I trust in what I see? Psychophysiology 53:1507–1523. doi: 10.1111/psyp.12702
  13. Kornrumpf B, Niefind F, Sommer W, Dimigen O (2016) Neural Correlates of Word Recognition: A Systematic Comparison of Natural Reading and Rapid Serial Visual Presentation. Journal of Cognitive Neuroscience 28:1374–1391. doi: 10.1162/jocn_a_00977
  14. Lauffs MM, Shaqiri A, Brand A, Roinishvilic M, Chkoniac E, Öğmenf H, Herzog MM (2016) Local versus global and retinotopic versus non-retinotopic motion processing in schizophrenia patients. Psychiatry Research. doi: 10.1016/j.psychres.2016.09.049
  15. Leube A, Ohlendorf A, Wahl S (2016) The Influence of Induced Astigmatism on the Depth of Focus: Optometry and Vision Science 93:1228–1234. doi: 10.1097/OPX.0000000000000961
  16. Li TK, Chung STL, Hsiao JHW (2016) Music reading expertise modulates visual spans in both music note and English letter reading. CogSci 2016 Conference Proceedings p. 1499–1504,
  17. Liaci E, Bach M, Tebartz van Elst L, et al (2016) Ambiguity in Tactile Apparent Motion Perception. PLOS ONE 11:e0152736. doi: 10.1371/journal.pone.0152736
  18. Manassi M, Lonchampt S, Clarke A, Herzog MH (2016) What crowding can tell us about object representations. Journal of Vision 16:35. doi: 10.1167/16.3.35
  19. Milston R, Madigan MC, Sebag J (2016) Vitreous floaters: Etiology, diagnostics, and management. Survey of Ophthalmology 61:211–227. doi: 10.1016/j.survophthal.2015.11.008
  20. Mira-Agudelo A, Torres-Sepúlveda W, Barrera JF, Henao R, Blocki N, Petelczyc K, Kolodziejczyk A (2016) Compensation of Presbyopia With the Light Sword Lens. Invest Ophthalmol Vis Sci 57:6870–6877. doi: 10.1167/iovs.16-19409
  21. Molloy CS, Stokes S, Makrides M, et al (2016) Long-term effect of high-dose supplementation with DHA on visual function at school age in children born at <33 wk gestational age: results from a follow-up of a randomized controlled trial. American Journal of Clinical Nutrition 103:268–275. doi: 10.3945/ajcn.115.114710
  22. Niefind F, Dimigen O (in press) Dissociating parafoveal preview benefit and parafovea-on-fovea effects during reading: A combined eye tracking and EEG study. Psychophysiology
  23. Pilz KS, Kunchulia M, Parkosadze K, Herzog MH (2016) Spatial and temporal aspects of visual backward masking in children and young adolescents. Atten Percept Psychophys 78:1137–1144. doi: 10.3758/s13414-015-1050-y
  24. Ringer RV, Throneburg Z, Johnson AP, Kramer AF, Loschky LC (2016) Impairing the useful field of view in natural scenes: Tunnel vision versus general interference. JOV 16(2):7, 1–25
  25. Stronks HC, Mitchell EB, Nau AC, Barnes N (2016) Visual task performance in the blind with the BrainPort V100 Vision Aid. Expert Review of Medical Devices 0:null. doi: 10.1080/17434440.2016.1237287
  26. Szumska I, van der Lubbe RHJ, Grzeczkowski L, Herzog MH (2016) Does sensitivity in binary choice tasks depend on response modality? ConsciCognition 43:57–65
  27. Thunell E, van der Zwaag W, Ögmen H, et al (2016) Retinotopic encoding of the Ternus-Pikler display reflected in the early visual areas. Journal of Vision 16:26. doi: 10.1167/16.3.26
Examples from 2015
  1. Bubl E, Ebert D, Dörr M, Philipsen A, Bach M, Tebartz van Elst L (2015) Elevated retinal background noise in ADHD. PLOS ONE 10(2):e0118271
  2. Bubl E, Kern E, Ebert D, Riedel A, Elst LT van, Bach M (2015) Retinal dysfunction of contrast processing in major depression also apparent in cortical activity. Eur Arch Psychiatry Clin Neurosci 265:343–350
  3. Caspi A, Zivotofsky AZ (2015) Assessing the utility of visual acuity measures in visual prostheses. Vision Research 108:77–84
  4. Chicherov V, Herzog MH (2015) Targets but not flankers are suppressed in crowding as revealed by EEG frequency tagging. NeuroImage 119:325–331
  5. Collignon O, Dormal G, de Heering A, Lepore F, Lewis TL, Maurer D (2015) Long-Lasting Crossmodal Cortical Reorganization Triggered by Brief Postnatal Visual Deprivation. Current Biology 25(18):2379–2383 [acuity, contrast & vernier]
  6. Costello MC, Bloesch EK, Davoli CC, Panting ND, Abrams RA, & Brockmole JR (2015) Spatial Representations in Older Adults are Not Modified by Action: Evidence from Tool Use. Psychology and Aging. 30(3):656–668 PDF
  7. Frömer R, Dimigen O, Niefind F, Krause N, Kliegl R, Sommer W (2015) Are Individual Differences in Reading Speed Related to Extrafoveal Visual Acuity and Crowding? PLoS ONE 10:e0121986
  8. Geringswald F, Herbik A, Hofmüller W, Hoffmann MB, Pollmann S (2015) Visual Memory for Objects Following Foveal Vision Loss. J Exp Psychol Learn Mem Cogn
  9. Giesen C, Eberhard M, Rothermund K (2015) Loss of attentional inhibition in older adults—Does it really exist? An experimental dissociation of inhibitory and memory retrieval processes. Psychology and Aging 30:220–231
  10. Heinrich SP, Lüth I, Bach M (2015) Event-Related Potentials Allow for Optotype-Based Objective Acuity Estimation. Investigative Opthalmology & Visual Science 56:2184–2191
  11. Joshi MR, Falkenberg HK (2015) Development of radial optic flow pattern sensitivity at different speeds. Vision Research 110A:68–75
  12. Kloth N, Damm M, Schweinberger SR, Wiese H (2015) Aging affects sex categorization of male and female faces in opposite ways. Acta Psychologica 158:78–86
  13. Kornrumpf B, Sommer W (2015) Modulation of the attentional span by foveal and parafoveal task load: An ERP study using attentional probes. Psychophysiol
  14. Marhöfer DJ, Bach M, Heinrich SP (2015) Objective measurement of visual resolution using the P300 to self-facial images. Documenta Ophthalmologica 131:137–148
  15. Meyberg S, Werkle-Bergner M, Sommer W, Dimigen O (2015) Microsaccade-related brain potentials signal the focus of visuospatial attention. NeuroImage 104:79–88
  16. Mamou J, Wa CA, Yee KMP, Silverman RH, Ketterling JA1 Sadun AA, Sebag J (2015) Ultrasound-based quantification of vitreous floaters correlates with contrast sensitivity and quality of life. Invest Ophthalmol Vis Sci 56:1611–1617 [Contrast]
  17. Manassi M, Hermens F, Francis G, Herzog MH (2015) Release of crowding by pattern completion. J Vis 15:16
  18. Meyberg S, Werkle-Bergner M, Sommer W, Dimigen O (2015) Microsaccade-related brain potentials signal the focus of visuospatial attention. NeuroImage 104:79–88
  19. De Moor K, Andrén B, Yi G, Brunnström K, Wang K, Drott A, Hermann DS (2015) Influence of high ambient illuminance and display luminance on readability and subjective preference. In:, p. 93941E–93941E–12
  20. Morikawa K, Matsushita S, Tomita A, Yamanami H (2015) A real-life illusion of assimilation in the human face: eye size illusion caused by eyebrows and eye shadow. Frontiers in Human Neuroscience:139
  21. Nau AC, Pintar C, Arnoldussen A, Fisher C (2015) Acquisition of Visual Perception in Blind Adults Using the BrainPort Artificial Vision Device. Am J Occup Ther 69:6901290010 p 1–8
  22. Nikitin J, Freund AM (2014) Adult age differences in frequency estimations of happy and angry faces. International Journal of Behavioral Development:0165025414542838
  23. Olderbak S, Hildebrandt A, Wilhelm O (2015) Examining age-related shared variance between face cognition, vision, and self-reported physical health: a test of the common cause hypothesis for social cognition. Front Psycho.:1189 [acuity & contrast]
  24. Phillips JB, Hørning D, Funke ME (2015) Cognitive and Perceptual Deficits of Normobaric Hypoxia and the Time Course to Performance Recovery. Aerospace Med Hum Perf 86(4):357–365
  25. Pilz KS, Kunchulia M, Parkosadze K, Herzog MH (2015) Ageing and visual spatiotemporal processing. Exp Brain Res 233(8):2441–2448
  26. Pochopien K, Fahle M (2015) How to Get the Full Prism Effect. i-Perception 6(4):2041669515599308
  27. Rieger V, Aryan NP, Brendler C, Rothermel A (2014) Benefit of spatial filtering for visual perception with a subretinal implant. In: 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), pp. 6112–6115
  28. Roinishvili M, Cappe C, Shaqiri A, Brand A, Rürup L, Chkonia E, Herzog MH (2015) Crowding, grouping, and gain control in schizophrenia. Psychiatry Research 226:441–445
  29. Phillips JB, Hørning D, Funke ME (2015) Cognitive and Perceptual Deficits of Normobaric Hypoxia and the Time Course to Performance Recovery. Aerospace Medicine and Human Performance 86:357–365
  30. Shaqiri A, Willemin J, Sierro G, Roinishvili M, Iannantuoni L, Rürup L, Chkonia E, Herzog MH, Mohr C (2015) Does chronic nicotine consumption influence visual backward masking in schizophrenia and schizotypy? Schizophrenia Research: Cognition 2(2):93–99
  31. Tebartz van Elst L, Bach M, Blessing J, Riedel A, Bubl E (2015) Normal visual acuity and electrophysiological contrast gain in adults with high functioning autism spectrum disorder. Front Hum Neurosci 9:460
  32. Teupner A, Bergenek K, Wirth R, Miñano JC, Benítez P (2015) Optimization of a merit function for the visual perception of color uniformity in spot lights. Color Res Appl 40:287–296
Examples from 2014
  1. Anton A, Böhringer D, Bach M, et al. (2014) Contrast sensitivity with bifocal intraocular lenses is halved, as measured with the Freiburg Vision Test (FrACT), yet patients are happy. Graefes Arch Clin Exp Ophthalmol 252:539–544
  2. Ayton LN, Blamey PJ, Guymer RH, et al. (2014) First-in-Human Trial of a Novel Suprachoroidal Retinal Prosthesis. PLoS ONE 9:e115239.
  3. Bednář M, Kubová Z, Kremláček J (2014) Lack of visual evoked potentials amplitude decrement during prolonged reversal and motion stimulation in migraineurs. Clin Neurophys 125:1223–1230
  4. Britz J, Diaz Hernandez L, Ro T, Michel CM (2014) EEG-microstate dependent emergence of perceptual awareness. Front Behav Neurosci 8:163
  5. Bürki CN, Ludwig C, Chicherio C, Ribaupierre A de (2014) Individual differences in cognitive plasticity: an investigation of training curves in younger and older adults. Psychological Research 78:821–835
  6. Camilleri R, Pavan A, Ghin F, Battaglini L, Campana G (2014) Improvement of uncorrected visual acuity and contrast sensitivity with perceptual learning and transcranial random noise stimulation in individuals with mild myopia. Front. Psychol. 5:1234
  7. Camilleri R, Pavan A, Ghin F, Campana G (2014) Improving myopia via perceptual learning: is training with lateral masking the only (or the most) efficacious technique? Atten Percept Psychophys: 76(8):2485–2494
  8. Campana G, Camilleri R, Pavan A, Veronese A, Lo Giudice G (2014) Improving visual functions in adult amblyopia with combined perceptual training and transcranial random noise stimulation (tRNS): a pilot study. Front Psychol 5:1402
  9. Cappe C, Clarke A, Mohr C, Herzog MH (2014) Is there a common factor for vision? J Vis 14:4
  10. Chicherov V, Plomp G, Herzog MH (2014) Neural correlates of visual crowding. NeuroImage 93, Part 1:23–31
  11. Clarke AM, Grzeczkowski L, Mast FW, Gauthier I, Herzog MH (2014) Deleterious effects of roving on learned tasks. Vision Res. 99:88–92
  12. Frässle S, Sommer J, Jansen A, Naber M, Einhäuser W (2014) Binocular Rivalry: Frontal Activity Relates to Introspection and Action But Not to Perception. J. Neurosci. 34:1738–1747
  13. Gledhill D, Grimsen C, Fahle M, Wegener D (2015) Human feature-based attention consists of two distinct spatiotemporal processes. J Vision 15(8):8
  14. Herbik A, Geringswald F, Thieme H, Pollmann S, Hoffmann MB (2014) Prediction of higher visual function in macular degeneration with multifocal electroretinogram and multifocal visual evoked potential. Ophthal Physiol Opt 34:540–551
  15. Herbik A, Reupsch J, Thieme H, Hoffmann MB (2014) Differential effects of optic media opacities on simultaneous multifocal pattern electroretinograms and visual evoked potentials. Clin Neurophysiol 125:2418–2426
  16. Kiral-Kornek FI, OʼSullivan-Greene E, Savage CO, McCarthy C, Grayden DB, Burkitt AN (2014) Improved visual performance in letter perception through edge orientation encoding in a retinal prosthesis simulation. J. Neural Eng. 11:066002
  17. Kollbaum PS, Jansen ME, Kollbaum EJ, Bullimore MA (2014) Validation of an iPad test of letter contrast sensitivity. Optom Vis Sci 91:291–296 [Contrast]
  18. Komes J, Schweinberger SR, Wiese H (2014) Fluency Affects Source Memory for Familiar Names in Younger and Older Adults: Evidence from Event-related Brain Potentials. NeuroImage 92:90–110
  19. Komes J, Schweinberger SR, Wiese H (2014) Preserved fine-tuning of face perception and memory: evidence from the own-race bias in high- and low-performing older adults. Front Aging Neurosci 6:60
  20. Kumaran V, Mudvari PR, Dhital R (2014) Changes in visual acuity as a function of defocus induced by positive lenses. Int J Biol Sci Appl 1(1), April, 7–10
  21. Kunchulia M, Pilz KS, Herzog MH (2014) Small effects of smoking on visual spatiotemporal processing. Sci Rep 4
  22. Lee VK, Nau AC, Laymon C, Chan KC, Rosario BL, Fisher C (2014) Successful tactile based visual sensory substitution use functions independently of visual pathway integrity. Front Hum Neurosci 8:291
  23. Liston DB, Stone LS (2014) Oculometric assessment of dynamic visual processing. J Vis 14:12
  24. Madden DJ, Parks EL, Davis SW, Diaz MT, Potter GG, Chou Y, Chen N, Cabeza R (2014) Age mediation of frontoparietal activation during visual feature search. NeuroImage 102(2):262–274
  25. Matas NA, Nettelbeck T, Burns NR (2014) Cognitive and visual predictors of UFOV performance in older adults. Accident Analysis & Prevention 70:74–83
  26. Müller-Oehring EM, Jung Y-C, Pfefferbaum A, Sullivan EV, Schulte T (2014) The Resting Brain of Alcoholics. Cereb. Cortex:bhu134
  27. Niemann C, Godde B, Staudinger UM, Voelcker-Rehage C (2014) Exercise-induced changes in basal ganglia volume and cognition in older adults. Neurosci
  28. Niemann C, Godde B, Voelcker-Rehage C (2014) Not only cardiovascular, but also coordinative exercise increases hippocampal volume in older adults. Front Aging Neurosci 6:170
  29. Nikitin J, Freund AM (2014) Adult age differences in frequency estimations of happy and angry faces. Int J Behav Dev 0165025414542838
  30. Pérez-Vives C, Belda-Salmerón L, García-Lázaro S, Ferrer-Blasco T, Montés-Micó R (2014) Optical and visual simulation of standard and modified spherical aberration implantable Collamer lens post myopic LASIK surgery. European Journal of Ophthalmology 24:330–337
  31. Plank T, Rosengarth K, Schmalhofer C, Goldhacker M, Brandl-Rühle S, Greenlee MW(2014) Perceptual learning in patients with macular degeneration. Front Psychol 5:1189
  32. Quigley C, Müller MM (2014) Feature-Selective Attention in Healthy Old Age: A Selective Decline in Selective Attention? J. Neurosci. 34:2471–2476
  33. Riediger M, Studtmann M, Westphal A, Rauers A, Weber H (2014) No smile like another: adult age differences in identifying emotions that accompany smiles. Front. Psychol. 5:480
  34. Sayim B, Manassi M, Herzog M (2014) How color, regularity, and good Gestalt determine backward masking. J Vis 14:8
  35. Schega L, Hamacher D, Erfuth S, Behrens-Baumann W, Reupsch J, Hoffmann MB (2014) Differential effects of head-mounted displays on visual performance. Ergonomics 57:1–11
  36. Sheldon S, Quint J, Hecht H, Bowers AR (2014) The Effect of Central Vision Loss on Perception of Mutual Gaze: Optometry and Vision Science: 91(8):1000–1011
  37. Steinbrink C, Zimmer K, Lachmann T, Dirichs M, Kammer T (2014) Development of Rapid Temporal Processing and Its Impact on Literacy Skills in Primary School Children. Child Dev 85:1711–1726. doi: 10.1111/cdev.12208
  38. <a href=" target="_blank" class="external"">Teupner A, Bergenek K, Wirth R, Miñano JC, Benítez P (2015)</a> Optimization of a merit function for the visual perception of color uniformity in spot lights. Color Res. Appl. 40:287–296
  39. Vancleef K, Acke E, Torfs K, Demeyere N, Lafosse C, Humphreys G, Wagemans J, de-Wit L (2014) Reliability and validity of the Leuven Perceptual Organization Screening Test (L-POST). J Neuropsychol
  40. Vaucher P, Cardoso I, Veldstra JL, Herzig D, Herzog M, Mangin P, Favrat B (2014) A neuropsychological instrument measuring age-related cerebral decline in older drivers: development, reliability, and validity of MedDrive. Front Hum Neurosci 8:#772
  41. Vaucher P, Herzig D, Cardoso I, Herzog MH, Mangin P, Favrat B (2014) The trail making test as a screening instrument for driving performance in older drivers; a translational research. BMC Geriatrics 14:123
  42. Vestergaard AH, Grauslund J, Ivarsen AR, Hjortdal J (2014) Efficacy, safety, predictability, contrast sensitivity, and aberrations after femtosecond laser lenticule extraction. Journal of Cataract & Refractive Surgery 40(3)403–411 [Contrast]
  43. Vestergaard AH (2014) Past and present of corneal refractive surgery. Acta Ophthalmol (Copenh) 92:1–21. [Contrast]
  44. Wegener D, Galashan FO, Aurich MK, Kreiter AK (2014) Attentional spreading to task-irrelevant object features: experimental support and a 3-step model of attention for object-based selection and feature-based processing modulation. Front Hum Neurosci 8:414
  45. Wenner Y, Heinrich SP, Beisse C, et al. (2014) Visual evoked potential-based acuity assessment: overestimation in amblyopia. Doc Ophthalmol 128:191–200
  46. Whiting WL, Sample CH, Hagan SE (2014) Top-down processing modulates older adults’ susceptibility to noise. Aging Neuropsychol Cogn 21:370–385
  47. Wilkins L, Gray R, Gaska J, Winterbottom M (2014) Motion Perception & Driving: Predicting Performance through Testing and Shortening Braking Reaction Times through Training. Invest. Ophthalmol. Vis. Sci.: IOVS–13–12774
  48. Zhang T, Nefs HT, Heynderickx I (2014) Human discrimination of depth of field in stereoscopic and nonstereoscopic photographs. Perception 43:368–380
Examples ≤ 2013


  1. Arena A, Hutchinson CV, Shimozaki SS, Long MD (2013) Visual discrimination in noise: Behavioural correlates of age-related cortical decline. Behavioural Brain Research 243:102–108
  2. Atchison DA, Valentine EL, Gibson G, Thomas HR, Oh S, Pyo YA, Lacherez P, Mathur A (2013) Vision in water. J Vis 13; no. 11, article 4
  3. Bach M, Ramharter-Sereinig A (2013) Pattern electroretinogram to detect glaucoma: comparing the PERGLA and the PERG Ratio protocols. Doc. Ophthalmol. Adv. Ophthalmol. 127:227–238
  4. Badham SP, Hutchinson CV (2013) Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome. Graefes Arch Clin Exp Ophthalmol 251:2769–2776
  5. Banissy MJ, Tester V, Muggleton NG, Janik AB, Davenport A, Franklin A, Walsh V, Ward J (2013) Synesthesia for Color Is Linked to Improved Color Perception but Reduced Motion Perception. Psychol Sci 24:2390–2397
  6. Belda-Salmerón L, Ferrer-Blasco T, Albarrán-Diego C, Madrid-Costa D, Montés-Micó R (2013) Diurnal Variations in Visual Performance for Disposable Contact Lenses. Optom Vis Sci 90:682–690
  7. Bieg H-J, Bresciani J-P, Bülthoff HH, Chuang LL (2013) Saccade reaction time asymmetries during task-switching in pursuit tracking. Exp Brain Res 230:271–281
  8. Clarke AM, Repnow M, Öğmen H, Herzog MH (2013) Does spatio-temporal filtering account for nonretinotopic motion perception? Comment on Pooresmaeili, Cicchini, Morrone, and Burr (2012) J Vis 13
  9. Geringswald F, Baumgartner FJ, Pollmann S (2013) A behavioral task for the validation of a gaze-contingent simulated scotoma. Behav Res Methods 45:1313–1321
  10. Gonzalo-Fonrodonaa I, Porrasb MA (2013) Scaling effects in crossmodal improvement of visual perception by motor system stimulus. Neurocomputing 114:76–79
  11. Grainger JE, Scharnowski F, Schmidt T, Herzog MH (2013) Two primes priming: Does feature integration occur before response activation? J Vis 13:19–19
  12. Greenaway R, Davis G, Plaisted-Grant K (2013) Marked selective impairment in autism on an index of magnocellular function. Neuropsychologia 51:592–600
  13. Grimsen C, Brand A, Fahle M (2013) No Evidence for Prolonged Visible Persistence in Patients with Schizophrenia. PLoS ONE 8(3): e58940
  14. Haigh A, Brown DJ, Meijer P, Proulx MJ (2013) How well do you see what you hear? The acuity of visual-to-auditory sensory substitution. Front Psychol 4:330
  15. Heinrich A, Szostek A, Meyer P, Nees F, Rauschenberg J, Gröbner J, Gilles M, Paslakis G, Deuschle M, Semmler W, Flor H (2013) Cognition and Sensation in Very High Static Magnetic Fields: A Randomized Case-Crossover Study with Different Field Strengths. Radiology 266:236–245
  16. Herbik A, Hölzl GC, Reupsch J, Hoffmann MB (2013) Differential effects of optic media opacities on mfERGs and mfVEPs. Clin Neurophys 124:1225–1231
  17. Hessels RS, Hooge ITC, Snijders TM, Kemner C (2013) Is there a limit to the superiority of individuals with ASD in visual aearch? J Autism Dev Disord 1–9
  18. Hobé M, Lingelbach B, Jendrusch G (2013) Extreme Blickbewegungen im Sport – Welches System funktioniert besser? Moderne, durchgebogene und optimierte Sportbrillengläser oder Kontaktlinsen? DOZ 6:30–35 [PDF]
  19. Hutchinson CV, Badham SP (2013) Patterns of Abnormal Visual Attention in Myalgic Encephalomyelitis. Optom Vis Sci 90:607–614
  20. Kurtenbach A, Langrová H, Messias A, Zrenner E, Jägle H (2013) A comparison of the performance of three visual evoked potential-based methods to estimate visual acuity. Doc Ophthalmol 126:45–56
  21. Ling Ya, Nefs HT, Brinkman WP, Qua C, Heynderickx I (2013) The relationship between individual characteristics and experienced presence. Computers in Human Behavior 29:1519–1530
  22. López-Gil N, Martin J, Liu T, Bradley A, Díaz-Muñoz D, Thibos LN (2013) Retinal image quality during accommodation. Ophthalmic Physiol Opt 33:497–507
  23. Manassi M, Sayim B, Herzog MH (2013) When crowding of crowding leads to uncrowding. J Vis 13:10
  24. Margalit N, Shahar T, Barkay G, Gonen L, Nossek E, Rozovski U, Kesler A (2013) Tuberculum Sellae Meningiomas: Surgical Technique, Visual Outcome, and Prognostic Factors in 51 Cases. J Neurol Surg B 74:247–258
  25. Müller-Oehring EM, Schulte, T, Rohlfing T, Pfefferbaum A, Sullivan EV (2013) Visual search and the aging brain: Discerning the effects of age-related brain volume shrinkage on alertness, feature binding, and attentional control. Neuropsychology, 27:48–59
  26. Pérez-Vives C, Domínguez-Vicent A, Madrid-Costa D, Ferrer-Blasco T, Montés-Micó R (2013) Myopic astigmatism correction: comparison of a Toric Implantable Collamer Lens and a bioptics technique by an adaptive optics visual simulator. OPO 33:114–122
  27. Piepenbrock C, Mayr S, Mund I, Buchner A (2013) Positive display polarity is advantageous for both younger and older adults. Ergonomics 56:1116–1124
  28. Rao X, Wang N-K, Chen Y-P, Hwang Y-S, Chuang L-H, Liu I-C, Chen K-J, Wu W-C, Lai C-C (2013) Outcomes of Outpatient Fluid-Gas Exchange for Open Macular Hole After Vitrectomy. Am J Ophthalmol 156:326–333.e1
  29. Rüter J, Sprekeler H, Gerstner W, Herzog MH (2013) The Silent Period of Evidence Integration in Fast Decision Making. PLoS ONE 8(1): e46525
  30. Ruiz-Alcocer J, Madrid-Costa D, García-Lázaro S, Albarrán-Diego C, Ferrer-Blasco T (2013) Visual simulation through an aspheric aberration-correcting intraocular lens in subjects with different corneal profiles using adaptive optics. Clin Exp Optometry 96:379–384
  31. Sreenivasan V, Aslakson E, Kornaus A, Thibos LN (2013) Retinal image quality during accommodation in adult myopic eyes. Optom Vis Sci 90:1292–1303
  32. Stainthorp R, Powell D, Stuart M (2013) The relationship between rapid naming and word spelling in English. J Res Read 36:371–388. 10.1111/jrir.12002 {DOI does not work}
  33. Stingl K, Bartz-Schmidt KU, Besch D, et al. (2013) Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS. Proc R Soc B Biol Sci 280,no. 1757 20130077
  34. Strasburger H, Malania M(2013) Source confusion is a major cause of crowding. J Vision 13 (1)
  35. Piepenbrock C, Mayr S, Mund I, Buchner A (2013) Positive display polarity is advantageous for both younger and older adults. Ergonomics 1–9
  36. Van Den Boomen C, de Graaff JC, de Jong TP, et al. (2013) General anesthesia as a possible GABAergic modulator affects visual processing in children. Front Cell Neurosci 7:
  37. Van Rhijn M, Roeber U, O’Shea RP (2013) Can eye of origin serve as a deviant? Visual mismatch negativity from binocular rivalry. Front Hum Neurosci 7:
  38. Weibel S, Giersch A, Dehaene S, Huron C (2013) Unconscious task set priming with phonological and semantic tasks. Conscious Cogn 22:517–527
  39. Weigel D, Jungnickel H, Babovsky H, Kiessling A, Kowarschik R (2013) Untersuchung des Seheindrucks mittels adaptiver Optik. Klin Monatsblätter Augenheilkd 230:1199–1206
  40. Wiese H, Kachel U, Schweinberger SR (2013) Holistic face processing of own- and other-age faces in young and older adults: ERP evidence from the composite face task. NeuroImage 74:306–317
  41. Wijesuriya W, Perera AHP, Gayan JMU, et al. (2012) Intelligent Lighting Controller for Domestic and Office Environments [PDF]
  42. Wilkins L, Gray R, Gaska J, Winterbottom M (2013) Motion Perception and Driving: Predicting Performance Through Testing and Shortening Braking Reaction Times Through Training. IOVS 54:8364–8374

    Examples from 2012 (end of 2012: 268 citations)
  43. Aberg KC, Clarke AM, Sandi C, Herzog, MH (2012) Trait anxiety and post-learning stress do not affect perceptual learning. Neurobiol Learn Memory 98(3):246–253
  44. Bennett SJ Elliott D, Rodacki A (2012) Movement strategies in vertical aiming of older adults. Exp Brain Res 216:445–455
  45. Bornschlegl MA, Fahle M, Redding GM (2012) The role of movement synchronization with an auditory signal in producing prism adaptation Perception 41:950–962
  46. Brittain PJ, ffytche DH, Surguladzec S (2012) Emotion perception and functional outcome in schizophrenia: The importance of negative valence and fear. Psychiatry Res 200:208–213
  47. Brosnan MJ, Gwilliam LR, Walker I (2012) Brief Report: The Relationship Between Visual Acuity, the Embedded Figures Test and Systemizing in Autism Spectrum Disorders. J Autism Dev Disord 42:2491–2497
  48. Bubl E, Kern E, Ebert D, Tebartz van Elst L, Bach M (2012) The impact of antidepressive therapy on retinal contrast processing in depressive disorder. Brit J Psychiat 201:151–158
  49. Cappe C, Herzog MH, Herzig DA, Brand A, Mohr C (2012) Cognitive disorganisation in schizotypy is associated with deterioration in visual backward masking. Psychiatry Res 200:652–659
  50. Chkonia E, Roinishvili M, Reichard L, Wurch W, Puhlmann H, Grimsen C, Herzog MH, Brand A (2012) Patients with functional psychoses show similar visual backward masking deficits 198:235–240
  51. Federal Highway Administration, US Department of Transportation (2012) Evaluating Driver Performance on Rural Two-Lane Horizontal Curved Roadways Using A Driving Simulator. Publication Number: FHWA-HRT-12-073 [PDF]
  52. Ghose T, Hermens F, Herzog MH (2012) How the global layout of the mask influences masking strength. J Vision 12 (13)
  53. Ikaunieks G, Caure E, Kassaliete E, Meskovska Z (2012) Determination of myopes' visual acuity using stimuli with different contrast. Latvian J Physical Technical Sci 49:18–23. DOI: 10.2478/v10047-012-0026-0 {DOI does not work}
  54. Kraehenmann R, Vollenweider FX, Seifritz E, Kometer M J (2012) Crowding Deficits in the Visual Periphery of Schizophrenia Patients. PLOS ONE 7;9:e45884
  55. Kunchulia M, Pilz KS, Herzog MH (2012) How alcohol intake affects visual temporal processing. Vision Res. 66:11–16
  56. Madrid-Costa D, Perez-Vives C, Ruiz-Alcocer J, Albarran-Diego C, Montes-Mico R (2012) Visual simulation through different intraocular lenses in patients with previous myopic corneal ablation using adaptive optics: Effect of tilt and decentration. J Cat Ref Sorg 38:774–786
  57. Manassi, M; Sayim, B; Herzog, MH (2012) Grouping, pooling, and when bigger is better in visual crowding. J Vision 12 (10): 2012
  58. Roeber U (2012) Neural processing of orientation differences between the eyes' images. JOV:12 20
  59. Tartaglia EM, Bamert L, Herzog MH, Mast FW (2012) Perceptual learning of motion discrimination by mental imagery. J Vis 12:14
  60. Traschutz A, Zinke W, Wegener D (2012) Speed change detection in foveal and peripheral vision. Vision Res 72:1–13
  61. Wiese H, Komes J, Schweinberger SR (2012) Daily-life contact affects the own-age bias and neural correlates of face memory in elderly participants. Neuropsychologia 50:3496–3508

    Examples from 2011
  62. Bode SFN, Jehle T, Bach M (2011) Pattern electroretinogram (PERG) in glaucoma suspects – new findings from a longitudinal study. Invest Ophthalmol Vis Sci 52:4300–4306
  63. Linhart F, Scartezzini JL (2011) Evening office lighting – visual comfort vs. energy efficiency vs. performance? Building Environ 46:981–989
  64. Nielsen E, Hjortdal J (2011) Visual acuity and contrast sensitivity after posterior lamellar keratoplasty. Acta Ophthalmologica 1–5
  65. McCulloch DL, Loffler G, Bruce N, Dutton G, Bach M (2011) The effects of visual degradation on face discrimination. Ophth Physiol Optics 31:240–248
  66. Roinishvili M, Chkonia E, Stroux A, Brand A, Herzog MH (2011) Combining vernier acuity and visual backward masking as a sensitive test for visual temporal deficits in aging research. Vision Res 51:417–423
  67. Sayim B, Westheimer G, Herzog MH (2011) Quantifying target conspicuity in contextual modulation by visual search. J Vision 11:1;6
  68. Straube S, Fahle M (2011) Visual detection and identification are not the same: Evidence from psychophysics and fMRI. Brain Cognition 75: 29–38
  69. Tavassoli T, Latham K, Bach M, Dakin SD, Baron-Cohen S (2011) Psychophysical measures of visual acuity in autism spectrum conditions. Vision Res
  70. Voelcker-Rehage C, Godde B, Staudinger UM (2011) Cardiovascular and coordination training differentially improve cognitive performance and neural processing in older adults. Frontiers Hum Sci 5:26;1–12

    2010 (end of 2010 ≈140 citations)
  71. Brittain PJ, Surguladze S, McKendrick AM, Ffytche DH (2010) Schizophrenia Res 124:134–141
  72. Costello MC, Madden DJ, Mitroff SR, Whiting WL (2010) Age-related decline of visual processing components in change detection. Psychol Aging 25:356–368
  73. Costello MC, Madden DJ, Shepler AM, Mitroff SR, Leber AB (2010) Age-related preservation of top-down control over distraction in visual search. Exp Aging Res 36:249–272
  74. Gurnsey R, Troje NF (2010) Peripheral sensitivity to biological motion conveyed by first and second-order signals. Vision Res 50:127–135
  75. Hoffmann MB, Spors F, Langenbucher A, Walter S, Behrens-Baumann W, Reupsch J, Viestenz A (2010) Minor effect of blue-light filtering on multifocal electroretinograms. J Cat Refr Surg 36:1692–1699
  76. Jägle H, Zobor D, Brauns T (2010) Accommodation limits induced optical defocus in defocus experiments. Doc Ophthalmol 121:103–109
  77. Keir N, Woods CA, Dumbleton K & Jones L (2010) Clinical performance of different care systems with silicone hydrogel contact lenses. Cont Lens Anterior Eye 33:189-195
  78. Legras R, Benard Y, Rouger H (2010) Through-focus visual performance measurements and predictions with multifocal contact lenses. Vision Res 50:1185–1193
  79. Metzler-Baddeley C, Baddeley RJ, Lovell PG, Laffan A, Jones RW (2010) Visual impairments in dementia with Lewy bodies and posterior cortical atrophy. Neuropsychology 4:35–48
  80. Mund I, Bell R, Buchner A (2010) Age differences in reading with distraction: Sensory or inhibitory deficits? Psychol Aging 25:886–897
  81. Rey G, Knoblauch K, Jouvent R, Collet L, Dubal S (2010) The experience of pleasure before and after hearing rehabilitation. Int J Rehab Res 33:158–164
  82. Rocha KM, Vabre L, Chateau N, Krueger RR (2010) Enhanced visual acuity and image perception following correction of highly aberrated eyes using an adaptive optics visual simulator. J Refr Surg 26:52–56
  83. Sayim B, Grubert A, Herzog MH, Krummenacher J (2010) Display probability modulates attentional capture by onset distractors. JOV 10(3):10, 1–8
  84. Slica S, Ikaunieks G, Rinkus D (2010) Effect of Yellow Filters on the Vision. Latvian Journal of Physics and Technical Sciences 47:37–43
  85. Stainthorp R, Stuart M, Powell D, Quinlan P, Garwood H (2010) Visual Processing Deficits in Children With Slow RAN Performance. Scientific Studies of Reading 14:266–292
  86. Straube S, Fahle M (2010) The electrophysiological correlate of saliency: Evidence from a figure-detection task. Brain Res 1307:89–102
  87. Werheid K, Gruno M, Kathmann N, Fischer H, Almkvist O, Winblad B (2010) Biased recognition of positive faces in aging and amnestic mild cognitive impairment. Psychol Aging 25:1–15
  88. Wrobel WG (2010) The Value of Retinal Implants. Biomed Tech 55 (Suppl. 1) [PDF]

  89. Aberg KC, Tartaglia EM, Herzog MH (2009) Perceptual learning with Chevrons requires a minimal number of trials, transfers to untrained directions, but does not require sleep. Vision Res 49:2087–2094
  90. Ashwin E, Ashwin C, Rhydderch D, Howells J, Simon Baron-Cohen S (2009) Eagle-Eyed Visual Acuity: An Experimental Investigation of Enhanced Perception in Autism. Biol Psychiatry 65:17–21 [PDF]
    But see: Bach M, Dakin SC 2009 Commentary on “Eagle-Eyed Visual Acuity: An Experimental Investigation of Enhanced Perception in Autism” Biol Psychiat 66:e19-e20 [PDF]
    Crewther DP, Sutherland A (2009) The more he looked inside, the more piglet wasn’t there: Is autism really blessed with visual hyperacuity? Biol Psychiat 66:e21-e22
    Tavassoli T, Latham K, Bach M, Dakin SD, Baron-Cohen S (2011) Psychophysical measures of visual acuity in autism spectrum conditions. Vision Res
  91. Bulters DO, Shenouda E, Evans BT, Mathad N, Lang DA (2009) Visual recovery following optic nerve decompression for chronic compressive neuropathy. Acta Neurochirurgica 151:325–334
  92. Dimigen O, Valsecchi M, Sommer W, Klieg R (2009) Human Microsaccade-Related Visual Brain Responses. J Neurosci 29:12321–12331
  93. Golomb JD, McDavitt JRD, Ruf BM, Chen JI, Saricicek A, Maloney KH, Hu J, Chun MM, Bhagwagar Z (2009) Enhanced visual motion perception in major depressive disorder. J Neurosci 29:9072–9077
  94. Ivanov I, Werner A (2009) Colour in action: evidence for a redundancy signal effect when driving motor responses by combined colour and spatial cues. Psychol Neurosci 2:17–24
  95. Li S, Xiong Y, Li J, Wang N, Dai Y, Xue L, Zhao H, Jiang W, Zhang Y, He JC (2009) Effects of monochromatic aberration on visual acuity using adaptive optics. Optom Vis Sci 86:868–874
  96. Ohlendorf A, Schaeffel F (2009) Contrast adaptation induced by defocus – A possible error signal for emmetropization? Vision Res 49:249–256
  97. Plomp G, Mercier MR, Otto TU, Blanke O, Herzog MA (2009) Non-retinotopic feature integration decreases response-locked brain activity as revealed by electrical neuroimaging. NeuroImage 48: 405–414

    Examples from 2008 and earlier
  98. Gurnsey R, Roddy G, Ouhnana M, Troje NF (2008) Stimulus magnification equates identification and discrimination of biological motion across the visual field . Vision Res 88:2827–2834
  99. Legras R, Rouger H (2008) Calculations and Measurements of the Visual Benefit of Correcting the Higher-order Aberrations Using Adaptive Optics Technology. J Optometry 1:22–29 [PDF]
  100. Walsh KM, Waldmann T (2008) The influence of nursing home residency on the capacities of low-dependency older adults. Aging & Ment Health 12:528–535
  101. Wegener D, Ehn F, Aurich MA, Galashana FO, Kreiter AK (2008) Feature-based attention and the suppression of non-relevant object features. Vision Res 48:2696–2707
  102. Chung ST, Jarvis SH & Cheung SH (2007) The effect of dioptric blur on reading performance. Vision Res 47:1584-1594
  103. Farmer CM, O’Donnell BF, Niznikiewicz MA, Voglmaier MM, McCarley RW, Shenton ME (2000) Visual Perception and Working Memory in Schizotypal Personality Disorder. American Journal of Psychiatry [Contrast]
  104. Hoffmann MB, Lorenz B, Preising M, Seufert PS (2006) Assessment of Cortical Visual Field Representations with Multifocal VEPs in Control Subjects, Patients with Albinism, and Female Carriers of Ocular Albinism. IOVS 47:3195–2101
  105. Jägle H, de Luca E, Serey L, Bach M & Sharpe LT (2006) Visual acuity and X-linked color blindness. Graefe’s Arch Clin Exp Ophthalmol 244:447–453
  106. Rémon L, Tornel M, Furlan WD (2006) Visual Acuity in Simple Myopic Astigmatism: Influence of Cylinder Axis. Optom Vision Sci 83:311–315
  107. Dennis RJ, Beer JMA, Baldwin JB, Ivan DJ, Lurosso FJ, Thompson WT (2005) Using the Freiburg Acuity and Contrast Test to Measure Visual Performance in USAF Personnel After PRK. Optom Vis Sci 81:516–524
  108. Peters BT, Bloomberg JJ (2005) Dynamic visual acuity using ‘‘far’’ and ‘‘near’’ targets. Acta Oto-Laryngologica 4:353–357
  109. Hoffmann MB, Tolhurst DJ, Moore AT, Morland AB (2003) Organization of the visual cortex in human albinism. J Neurosci 23:8921–8930
  110. Ruamviboonsuk P, Tiensuwan M, Kunawut C, Masayaanon P (2003) Repeatability of an Automated Landolt C Test, Compared With the Early Treatment of Diabetic Retinopathy Study (ETDRS) Chart Testing. Am J Ophthalmol 136:662–669
  111. Collins MJ, Franklin R, Davis BA (2002) Optical Considerations in the Contact Lens Correction of Infant Aphakia. Optom Vis Sc 79:234–240
  112. Hazel CA, Elliott DB (2002) The Dependency of LogMAR Visual Acuity Measurements on Chart Design and Scoring Rule. Optom Vis Sci 79:788–792
  113. Camparini M, Cassinari P, Ferrigno L, Macaluso C (2001) ETDRS-Fast: Implementing Psychophysical Adaptive Methods to Standardized Visual Acuity Measurement with ETDRS Charts. Invest Ophthalmol Vis Sci 42:1226–1231
  114. Fahle M, Biester A, Morrone C (2001) Spatiotemporal interpolation and quality of apparent motion. J Opt Soc Am A:18;2668–2678
  115. von Boehmer H & Kolling GH (1998) Effect of exposure time using single Landolt-rings on visual acuity in normal individuals and in patients with nystagmus. Der Ophthalmologe 95:717–720
Descriptions & Validations
General Pertinent Sources
Version history
2020-04-053.10.5 · Vernier: contrast now adjustable, higher max possible values,
  better shape parameterisation (for MBH & JR)
· reward pictures also for Letter and Vernier acuity
· no more "contrast screening"
· masking now works again (thanks, DH)
· corrected “VA Snellen Letters” to “VA Sloan Letters” (thanks, KW)
· [internal: 'var' → 'const' where possible]
2019-05-103.10.2 · added "bonusEmoji" [Settings>reward pictures (top right). Recommended]
· block-randomiser, now fully ISO/DIN compatible for oblique directions
· added ETDRS to crowding, crowding choices also now work for Letters
· stimulus sequence, all VAs: 0.1 / 0.2 / 0.4 now also 0.8, same ×2 for contrast
· added ceiling/floor detection for acuities: rangeOK, atFloor, atCeiling
· added field for possible range limit in 1st results line
· added "secondsPresentation" to results export
· added cpd info to contrast grating results
· added contrast info to acuity results
· removed feedback info from results (no longer necessary)
· added header line for full history in results
· Vernier ceiling: 1000 → 3000 arcmin (request by MBH)
· fixed occasional Øsaving in luminance linearisation (thanks, SPH)
· partial fix of crashes in FrameCalCheck after any test (thanks, OKolbe)
2018-02-143.9.9a· button Settings>Kg. → to ESU (Einschulungsuntersuchung)
· now ignoring the modifiers: command, control, shift, tab
· for ContrastLandolt choice of fixed pedestal luminance (for SPH)
· Spezial Aalen: fester Visus (deactivated in standard edition)
· fixed: in Contrast Grating, the #of choices was always 4 (thanks, SJAnderson)
· CHANGE: inappropriate keys now interpreted as incorrect response
· fixed regression in persistent history (3.9.8→3.9.9)
· moved "Kindergarten" to a button in Settings, pertinent code → Prefs
· added "FrACT3_lastTrialResult.sol" (for Leipzig collab.)
· displayTransform: works with contrast-C, (2) & letter "S"
2016-10-273.9.8· trialInfoFontSize: default→9, kindergarten→24,
· Quit/eXit via "Q" or "X"
· more selections for spatial frequeny (on request by Zeiss)
· more crowding options
· Vernier: contrast can be inverted, added type (3-line etc.) & scale (for low vision)
· added sounds for stimulus on/off
· shape corrections for Sloan letters K and S (error in Pelli's Sloan font)
· rewrote the squarewave grating for less aliasing
2015-06-013.9.3· "z" entry could be interpreted incorrectly in Letter Acuity depending on locale (was a QWERTZ vs. QWERTY problem)
2015-04-243.9.2· more options for crowding
· added logCS(Weber) to optotype contrast results
· improved color picker behaviour (minor bugfix)
2015-01-283.9.1· corrected incomplete random assignment for letters
· added one more option to crowding (now first is better names as “flanking rings”)
· corrected missing result info on normal trial exit (a regression in 3.9)
2014-11-243.9· added optional incomplete runs (→modified format of export2clipboard)
· VA tracking now works (no longer using Pest, thanks Ross!)
· added kVersionPraeventiometer
· added “Kindergarten” screening preset
2014-04-153.8.2· harmonised choices in “Which test on 5”
· systematic treatment of exentric presentation across tests
· maxVAdecimal now takes the thresholdtype setting into account (a little higher if not DIN)
2013-11-293.8.1 · extended & generalised visual feedback situation
· feedback optotype red with reduced contrast
· sequence: first auditory, then the visual feedback
· updated gamma value now stored without needing to click a button (thanks, Nia)
· possible to have no result displayed at all (to avoid subject influencing)
· tried to really hide mouse cursor (Flash player bug)
· largest Landolt C little smaller, margin one full gap until screen edge (thanks, Mark)
2013-06-183.8.0e· renamed "FrACT3_preferences_history.sol" to "FrACT3_preferences_trialHistory.sol", same for the class
· changed type of "precision" in the rStrN* class to int
· "whichTestOn5" now defaults to acuity in the internal case construct
· removed the (by now) obsolete "T" option
2013-03-273.8.0d· removed hi-res timestamp from results, increased displayed precision of results, added distance to results, units for landoltC-contrast in Weber
· added 1500 ms background mask (for Ralf Kredel)
· default number of trials reduced to 18 (8 choices) and 24 (4 choices) based on recent study
2012-12-073.8.0 · added grating acuity (useful only for low vision!)
· display transform now also works with tumbling E and with Sloan letters (thanks to Paul Artes)
· harmonized terminology across tests;
· Vernier clipboard results now in arcsecs; ISO date form
2012-06-193.7.4c· improved color bit stealing & added to GUI
· added simplified bit-stealing (Tyler1997SpatVis)
· introduced "dir2"-pref to switch between hor/ver which is, in principle, more versatile
· increased the z-mode callback to 50 (for Liz)
· added tracking mode for contrast
· added testType to the persistent history
· grating: added some Gaussian windowing and made patch-diameter a user-defined setting.
2011-10-273.7.1b• added grating test as requested by Jens (work in progress, not yet in the manual)
• added timestamps (milliseconds since 1970) to the full history
• [3.7.m special version for Paik with long Verniers (40x longer)]
2011-04-293.7lpreview, work in progress
• added display transformations: mirroring vertically and 180°
• delt with blocked information storing (due to new Adobe settings)
• new flash player module (10.2 with 3.7l)
• added “Contrast screening”
    – calibration accessible via shift key, changed sequence logic, now respects the number of orientations (4/8)
• corrected threshold for “red condition” acuity warning in SETTINGS
• added visual feedback (growing optotype)
• rearranged value/label placement on the settings screen, main screen buttons, response key graphics
• removed display size from key settings (caused misunderstanding)
• changed default contrast-dia 30→50 arcmin, max 300→999
• internal class rearranging (LandoltC→Optotypes)
• various minor improvements
• added face files
2010-09-013.6.3• corrected Michelson→Weber contrast calculation: the previous Weber value had been c·W%-times too high (e.g. 1.01% instead of 1.0%, 11% instead of 10%, etc.). Thanks to Prof. von Handorff and his students for spotting this.
• This is the last version that runs on Mac OS/PowerPC.
2010-07-293.6.2• added tumbling E
• added optional on-line trial info
• added persistent history (copied to clipboard with "z")
• modernized writing to the clipboard
• centered parameter-input in the SETTINGS frame
• solved problem of not being able to enter "5" into the subjectID field
2010-03-213.6beta• Quit button now labelled "Exit" in Windows
• added TCP/IP based results transmission
• deleted the flawed and effectless manipulation of presented direction depending on response correctness
• added face recognition paradigm (experimental)
• improved Alert class from <>
• for FrACT letters the history is now correctly exported, with the letters. Checked LandoltC and SloanC size, they are identical, as should be.
2009-11-113.5.5 Quite a number of tiny improvements:
• added screen dimension to main screen info
• added "force Snellen denominator to 20 ft" on request
• added option for colour Landolt Cs on request
• set uncalibrated values bold & red in the SETTINGS screen to make them more obvious
• set focus to stage (now it responds to keyboard shortcuts after returning from SETTINGS etc.)
• now possible to start with numkey-5 irrespective of numlock setting
2009-09-163.5.4made the calibration bar blue; increased PEST-grain from 500 to 5000; added contrast with Weber definition; improved manual
2009-08-203.5.3 • fixed background glitch, a regression from the new contrast polarity setting
• rearranged the setup a little around the calibration bar
2009-07-193.5.2• added option to set contrast polarity
• fixed silly error (fixation target in contrast testing staying on) introduced recently
• added option not to go full screen (this can help with multiple screen setups)
2009-05-273.5 • fixed errors in the calibration check GUI resulting from the new mask code
• renamed "Preferences" into "Setup", put key settings on main screen
[all thanks to Daphne McCulloch's thoughtful suggestions]
2009-04-213.4.3• Improved coding around the sound channels (fixed the ‘hang’), cleaned up the Pest code (no performance change, just more elegant :) )
• Added detection of sound capabilities and disabled sound settings when appropriate (does not seem to work correctly)
• added a blank (or grey for contrast) mask after the response key. Option in Prefs. Currently fixed at 200 ms.
• Keypad now works without numlock
• Maximal distance increased (9999 cm instead of 999 cm),
• Vernier size now scales with distance (as it should have): 0.5° total height, 0.5 arcmins bar sigma, 0.2 arcmins gap height
• separate timeouts for showing the optotype (down to 0.1 s) and for responding to it
• and further trivia
2008-12-083.3timeout > 30 seconds now possible (current maximum: 999 s); improved Flash version display; corrected a missing help button
2008-11-163.2ported to Flash CS4, added calibration alert
2008-09-103.1.3fixed a capitalisation issue in a sound resource
now ignoring letter capitalisation in shortcuts
2008-09-103.1.2added optional Sloan letters . Range-checked timeout-value (reported by Frank Schmidtborn, more fields need to be checked)
2008-06-203.1All numerical preferences now range-checked
corrected the logic in the response key evaluation (didn't stop after first match). Added acuity based on Sloan letters. Rewrote response code to use key-value pairs.
2008-05-303.0.4“auditory feedback when done” now preserved, made sound resources more generic, improved internal debugging
2008-05-063.0.3Corrected time-out (error diagnosed by Frank Schmidtborn), added a positional jitter to vernier test (as suggested by Wolf Harmening)
2008-04-263.0.2Complete re-write of FrACT, now called FrACT3. Reason for re-write was that I wanted to improve the contrast dithering. This entailed updating to the (totally underwhelming) Adobe's Flash CS3 development system. This required changes in nearly every line of code. A major chore, which markedly improved the program internally, while not showing the changes externally. There is also a new icon, thanks to Inga.
A comparison in 54 eyes found that acuity results differed between FrACT2 and FrACT3 by ≈0.01 LogMAR, thus below noise limit. Contrast testing is improved, the vernier test is being evaluated.
2007-12-242.3fixed a bug of incorrectly formatted Snellen fractions under certain rare conditions
2007-11-192.2re-enabled the “bonus trial” option for the contrast & Vernier test, improved FrACT documentation
2007-10-302.1improved contrast dither for oblique orientations. Thanks to Hendrik Jungnickel at the Ammersee meeting!
2007-07-252.0.5• added 2 new sounds: (1) run done, and (2) incorrect response. Now I prefer the purely auditory feedback to the visual one. Give it a try!
• switch to Flash CS 3 with only few nasty side effects
• internal changes to the PEST procedure: code “beautification” without changes in the basic logic
2007-06-022.0.3• added a "which test on pressing ‘5’" option, changed contrast-Ø default to 30'
• finally found how to abort using <esc>
2007-05-23202a• There was a problem with the final contrast value in the “export to clipboard” record (thanks to Hendrik Jungnickel!)
• Added sanity check for acuity formats. If all are switched off, decimal is switched on
2007-04-112.0Contrast now employs dithering to achieve normal thresholds (currently using a 2×2 dithermatrix, increasing luminance resolution by a factor of 4).
Added target cross for Contrast. Gamma adjustment via cursor keys, reference lines now use 0.5±0.3 luminance, thus avoiding the extremes, better for LCDs.
2007-01-061.10negative optotype contrast now works again (had been lost when making the program more robust with respect to non-sensible preference values, probably back around version 1.2)
2006-11-301.9the smallest gap size had been reduced to 0.5 pixel. Tests now showed that this does not result in reliable optotype quality, and has been reset to 1.0
2006-11-151.8a• Extended warning when the highest possible VA is below 2.0
• Vernier result now honours the preferred decimal point character
• Rewrite of the contrast routines (help from Hendrik Jungnickel gratefully acknowledged): Correct setting of contrast and readback honouring gamma correction, back luminance clamped to 50%; “results2clipboard” now works with contrast;
• contrast now also allows a position shift, added by request
2006-10-011.6a• fixed decimal point internationalisation, fixed tab sequence in Preferences
• “Bonus trials” now have the setting {never | every 6th trial | always}, added by request. This allows to create a separate easy training version.
2006-08-091.5a• added Vernier measurement (first attempt, feedback welcome)
• fixed error that had based the 4afc psychometric function on the 8afc guessing rate
• increased the default trial setting (now at 24 for 8 alternatives)
The documentation does not yet reflect the Vernier addition – but it's rather obvious to operate, methinks.
2006-04-281.3• allowed multiple combination of result formats (decimal, LogMAR, Snellen fractions),
• choose better ranges for rounding of decimal VA,
• switched off the distance information in the result string (anyone needs this?)
2005-11-221.1.3added "frame" (square + circular) to crowding options
2005-11-211.1.2in "results2clipboard" trial number starts with 1, not 0; added "maxAcuity" in Prefs, framePrefs & Acuity
2005-10-251.1added crowding flankers (on request of Bruce Evans)
2005-10-101.0.9switched to Flash 8, some slight changes in the preferences dialog (now a combobox for decimal point)
• added “results2clipboard” (see Help>More Help for format)
• added internationalisation of numerical output (the decimal point)
• unfinished contrast test now defaults to off
2005-04-221.0.6• added a "mirroring" option (requested by Laura Gibson & Ken Nakayama
• added luminance linearisation calibration
2004-10-071.0.5added facility to change eccentricity, made feedback-expansion a bit slower
2004-05-281.0.1fixed a size error introduced in vs 1.0 (due to work on the contrast test some acuity routines were affected)
2004-02-11 1.0 re-implemented old direction strategy: When wrong, then reduce likelihood to present at the responded direction
2004-01-08 added contrast setting for the acuity optotype (suggestion by Lea Hyvärinen)
2002-08-24 ported to Flash
1996-09-07 available on the Internet
1992-11-21 ported to Macintosh
1985 first implementation on a Z80 with a 7220-graphics board

[→even earlier history details)]

A brief history of FrACT

In 1985 I programmed the first version, using a custom-built Z80 CP/M computer with a graphics board based on the NEC 7220 graphics chip, using serious digital differential algorithms (Newman & Sproull, 1979) just to draw the Landolt C. It became more than a curio after incorporation of the Best PEST threshold algorithm (Lieberman & Pentland, 1982) and was routinely employed in my lab to screen subjects’ acuities before experiments. The port to the Macintosh in 1992, translating from Pascal to C++, facilitated the use of anti-aliasing (Bach, 1997), which immediately made the measurements more precise (by allowing intermediate pixel values) and enabled a higher acuity limit at practical distances (a few meters). After adding gamma correction for better quantitative definition, in 1996 the first Internet version was made available. The rich feedback spurred many bug fixes and feature expansions, paving the way from a ‘hobby’ to a professional program, now validated in independent laboratories. The pressure of requests finally motivated me in 2002 to port the program to an operating system-agnostic environment, for which Macromedia’s (now Adobe’s) Flash was chosen. Consequently the program now runs in near identical fashion on the Macintosh, Linux and Windows operating systems.

Good programming practice

While FrACT initially began as a “hobby project” (see History above), its widespread application made more rigorous quality control necessary.

As is well known, any interesting computer program cannot be shown to be entirely correct, and usually isn’t. Thus the ongoing validation by independent and critical users is most important for the verification of FrACT. Thank you! All pertinent comments welcome.


At this time, I am not aware of any bugs proper in FrACT. Please tell me if you find problems.