All platforms, including mobile; tablets are fine, smartphones too small even if rotated. Try out above.
If you use FrACT₁₀ for studies, select the latest frozen version. Best install as Web App.
“Frozen” versions: 2021-06 | 2021-12 | 2022-03 | 2023-11 | 2024-04 | 2024-07 | 2024-09

FrACT₁₀ is a Web App (details: blog) that can be installed for off-line use like so: First open it in its own window/tab (or open a “frozen” version) and look for the “3 dot” or sandwich menu:

Chrome/Brave · MacOS	Chrome/Brave · Windows	Edge · Windows/MacOS
3 dots ︙ >Save and share>Install or whatever… changes all the time	3 dots ︙ > Install	3 dots ··· > Apps

• Other desktop browsers
  • Safari (MacOS ≥ Sonoma): File > Add to Dock …
• In all cases the Web App will be saved here:   «user»/Applications/…
• Firefox doesn’t (openly) support Web Apps
• Linux:  depends on your specific flavor. I found various recipes, e.g. for “Web App Manager”
• iOS:   Add to Home Screen in the Share menu and proceed as suggested
• Android:   depends on the specific brand, I have no further knowledge, unfortunately

“FrACT” is a semi-automatic visual test battery available as a free computer program. It employs psychometric methods combined with anti-aliasing and dithering to provide self-paced assessment of visual acuity (Bach 1996), contrast sensitivity (with optotypes or gratings) and Vernier acuity. The progression of optotypes relies on a Bayesian approach and is determined by a modified “Best PEST” strategy (see General Pertinent Sources below). FrACT complies with the international norm for acuity testing (EN ISO 8596) and is one of the “Recommended Methodolog(ies) for Assessment of Visual Acuity” by the Harmonization of Outcomes and Vision Endpoints in Vision Restoration Trials Taskforce. It is used world-wide in vision labs, by optometrists, ophthalmologists, and in clinical trials (→Who used FrACT). It has been validated in independent laboratories (→Descriptions & Validations). The code for FrACT₁₀ is →open source (→commit history).

• Optotypes: Sloan letters, Landolt rings, tumbling Es, symbols, gratings; Vernier patterns for hyperacuity. Gratings: sinusoidal or square-wave.
• Results Display: As LogMAR, Snellen fraction, or decimal acuity; full details can be exported for further processing.
• Customizable Parameters: Many parameters can be set, such as for testing low contrast acuity, and results include not just acuity/contrast thresholds but also reaction time and further specific settings.
• Technical Capabilities: Equipment resolution limits in space and luminance are mitigated by antialiasing and dithering.

Where and why to use?

• Participants’ screening in research settings: This is where I have personally used FrACT the most.
• Clinical Studies: Ideal for studies where visual acuity or contrast sensitivity is an outcome variable, aided by FrACT’s Presets for reproducibility, and Export options for reporting, e.g., Chang et al. 2022, Palanker et al. 2022, Nanoscope’s RESTORE Trial 2024. It can even be embedded in larger systems and fully controlled via HTML messages.
• Acuity detail studies: Useful for research on specific acuity properties such as contrast, exposure time, reaction time, feedback, noise, and hyperacuity, as evidenced by numerous papers.
• Perfect for keeping your waiting patients entertained :) !

• One particular advantage of FrACT: its ultra-wide range
  • For (ultra) low vision: FrACT can reproducibly assess CF and even HM, briefly: Counting Fingers, CF≈1.9 LogMAR; Hand Movement, HM≈2.3 LogMAR. →Sources and more detail.
  • For normal vision: FrACT can assess acuities beyond 2.0 decimal = 40/20Snellen = –0.3 LogMAR.
    [Although 20/20 vision is commonly labeled as “normal,” lots of research (e.g., Frisén & Frisén (1981), Elliot et al. 1995, Pointer 2006) indicates that the true average acuity among the general population is nearly double that figure. Consider: If Snellen had adopted the population average as the standard for “normal” vision, approximately half of the population would have fallen below this threshold.]
  • This wide range needs appropriate visual display units, see “A note on display resolution…” in the Manual.
• Low contrast optotypes for Acuity: Settings>Acuity>Optotypes/background color>b/w
• Color for Acuity: Settings>Acuity>Optotypes/background color>Color
• Mirror support: Settings>General>Display transformation
• Gratings: Can sweep (find threshold) for contrast or spatial frequency
• Eccentricity for Acuity and Contrast: Settings>General>Optotype eccentricity [°]
• Timing control: ISI, display time, response time: Settings>General>Timeouts
• Noise embedding for Acuity and Contrast: Settings>Misc>Noise embedding
• More to be found on perusing the Settings.

Test-retest variability = precision can be effectively quantified with the 95%-confidence interval (CI95) of the the Bland-Altman Limits of Agreement (LoA). For example, a CI95 of ±0.2 LogMAR indicates that in 95% of the cases, results will fall within a ±2 lines range. FrACT’s variability has been documented across various studies, as outlined below. My conclusion: The 95% confidence interval of FrACT’s LoA is approximately ±0.2 LogMAR in patients/participants with acuities at hand movement or better.

CF: counting fingers, HM: hand movement (→how to derive quantitive values for these).
The values for the 2006, 2007, 2009 & 2016 studies are based on re-analysis of the original data sets because formerly I sometimes used decimal acuity and idiosyncratic measures of variability, obnoxious to convert [pertinent publication in preparation].

Statistical Intricacies

1. To evaluate test-retest variability, a common approach involves calculating a correlation (e.g., ICC). However, this method is inappropriate because correlations are range-normalized. Simply adding one very poor acuity and one very good acuity can automatically yield a misleadingly high correlation coefficient. Therefore, I employ Bland-Altman’s (1986) limits of agreement (LoA) for a more accurate assessment.
2. An alternate measure to quantify test-retest variability is the “coefficient of variability” CoR, which is √2·LoA (Bland-Altman 1996) when there is no bias. In vision assessment, I always find a tiny bias, probably due to learning. When it’s not significant, I average the upper and lower LoAs. When CoR is preferred, multiply by √2.

Cost, in one word: Nothing.

Please remember to cite it when used in scientific settings. As this is free software, there is no warranty for anything. Your feedback is warmly welcomed. Should you desire to contribute: . Thank you in advance.

So where can I get it?

FrACT₁₀: on-line (as running embedded above) or as Web App. Since the Web App can be installed as app on all platforms, the former downloads for MacOS & Windows are deprecated.

• FrACT₁₀ on-line: Any modern browser running on Android, iOS, MacOS or Windows
• FrACT₁₀ Web App: Chrome/Edge/… browser, or Safari on MacOS, also Android, iOS, Linux

For remote input see the response box below in Usage Details. Please observe the Checklist for reliable results.

Over 1600 papers cite FrACT, and ≈40% are actively using it. Usage and citations have been increasing for over two decades, as shown in the adjoining figure.

Examples of FrACT in clinical trials: Zrenner et al. 2010, Stingl et al. 2013, Stingl et al. 2021, Chang et al. 2022, Palanker et al. 2022, Nanoscope’s RESTORE trial (→early results). Recommended in this review: Schmetterer et al. 2023.

• For a (rather old) overview see this English introduction or eine deutsche Einführung
• Detailed information on the program is available in “Bach (1996) The “Freiburg Visual Acuity Test” – Automatic measurement of the visual acuity. Optometry & Vision Sci 73:49-53” [PDF], more background on acuity testing can be found in this German paper.
• There is a very brief built-in help file, and a detailed discussion of the various settings in the FrACT₁₀ Manual or classic FrACT3.x Manual [PDF].
• “Tooltips” are fully implemented in FrACT₁₀: Hover with the mouse over any questionable GUI element, and it will tell you more.
• Visual Acuity “Cheat Sheet” – high and low vision
• It’s open source, →commit history
• Finally, →here (under General Pertinent Sources) is a references list.

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?

Very easy: Enter the width of the calibration bar (easiest with plastic card) and the observation distance in the “Settings” interface. Be sure to have enough distance from the screen, so pixel resolution does not limit acuity. Also consider entries 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 FrACT₁₀ Manual or classic FrACT3.x Manual [PDF] all settings are explained, probably in more detail than you wished…

For the Contrast Test, you also need to go to Settings>Gamma in FrACT₁₀ or Settings>Luminance Linearisation in classic FrACT. There you can interactively linearise the luminance transfer function (“gamma correction”) before testing. But see below for a cautionary note on the difficulties of contrast testing. Or use a screen calibrator (see What is special about the Contrast Test?).

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 optotypes orientation via the numerical digit keys, or use the alternatives. 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, participants are used to enter responses themselves.

The two examples here are for Landolt Cs with their 8/4 alternatives as optotypes. For Sloan letters, any standard keyboard is fine.

Number of trials?

• Firstmost, this depends on the number of choices with your chosen optotype: Sloan letters have 10 choice, Landolt Cs 8 (or 4), gratings 4 (or 2), Vernier lines 2.
• The default number of trials is set at 18 with 8/10 choices, 24 with 4 choices, and 32 with 2 choices. A paper on this: Bach M (2024) Freiburg Vision Test (FrACT): Optimal number of trials?
• For scientific applications, rather than increasing number of trials, best repeat each condition (e.g. each eye at 18 trials, ideally in an ABBA scheme) and take the mean; this also allows test-retest quality quantification.
• Why are all the above trial numbers divisible by 6? Because every 6th trial is a “bonus” or “easy” trial (if enabled), where the optotype is presented at 3 times its current threshold estimate. This keeps your participants happy, especially since the last trial is thus always a ‘success’ experience.

4 or 8 gap positions?

Sloan Letters have 10 alternatives, Tumbling E has 4 possible orientations, for Landolt C there are 4 or 8. Depending on your application, you may wish to use only the 4 primary Landolt 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 previous item.

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 and archiving the result. More export options: FrACT₁₀ Manual>Exporting.

What is special about the Contrast Test?

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

• Avoid stray light falling on the screen; a “monitor hood” may be sufficient
• Be sure to linearise luminance (“gamma correction”) before you test contrast (go to “Settings>Luminance Linearisation”); the best approach is to employ a screen calibrator (I’m using the Spyder, but must be the “Elite” or better version to allow gamma=1), to calibrate the screen/computer with a gamma of 1.0, and set it thus in “Settings>Luminance Linearisation” with the “gamma=1” button.
• In contrast to acuity testing, the time taken to inspect the optotype plays a sizable role.
• Normal contrast vision is better than normal screen luminance resolution (256 steps are not enough, especially after loosing a bit or two via linearizing (“gamma correction”). This is solved via dithering (Bach (1997) Anti-aliasing and dithering in the “Freiburg Visual Acuity Test’. Spatial Vision 11:85–89).

Mirroring, or more generally “Display transformation”

In many environments the standard 4 m distance may be difficult to achieve. In such conditions, high-quality front surface mirrors can extend the effective viewing distance. Their image-flip can be compensated for by Settings>Display transformation.

Shortcuts

I am lazy and prefer to start actions without mousing, thus I added a number of shortcuts, see also FrACT₁₀ Manual or classic FrACT3.x Manual [PDF]. Casing is irrelevant for shortcuts.

Avoiding more mousing: Use the tab key (⇥) to move between fields in Settings (shift-tab for backwards). The blue 🆗 button is activated by the return key.

Clinical trials demand more rigor than what’s mentioned in the Checklist. Such a trial will be professionally directed, and I’ve had the pleasure to collaborate with a number of excellent clinical scientists, statisticians etc. So many of my suggestions will state the obvious; they here appear in random order and are not meant to be comprehensive:

• If it’s an (ultra) low vision study: Run the acuity test for yourself a couple of times wearing (strong) blur filters (e.g. foils that simulate cataract). Really! All personell, namely lead personell, should do this, once. This will change your outlook.
• After you have established all settings (that differ from FrACT’s defaults), let’s make a PRESET for your study.
• Make yourself independent from my website (after initial install), at least by installing a “frozen” version of FrACT₁₀. Better: run form your own servers, as described in Long term support (at the end).
• Document the version of FrACT, don’t change it during the course of the study.
• Run every condition twice. That yields a measure of reproducibility (e.g., the Bland-Altman limits of agreement), then average.
• Choose an (extended) ABBA design.
• For every session, apply your preset, check luminance of the VDU, and verify size calibration (with “plastic card”).
• Find an easy and reproducible way to ensure a well-controlled observation distance.
• Make use of automated results export / integration with your hospital documentation system. Never type a result manually.
• Don’t hesitate to contact me.

Main motto: Move with adequate speed and don’t break things.

FrACT began 39 years ago and is available on the Internet in one form or another for 29 years now. I strive to cater for decade-long support. “Classic” FrACT was last (and finally) updated in 2020, and will continue to work in the two major operating systems as it’s a 64-bit app.

FrACT₁₀ was initially web-only, then also available as app, based on Electron. When you have one of these apps, they will continue to work while not gaining new features. These apps were replaced in 2023 by a platform-agnostic Web App (details: blog) – this makes FrACT₁₀ available on all platforms and also allows for continuous updates, if so wished.

• If you want to run the “leading edge” most recent FrACT₁₀, install the Web App from here. Whenever I update FrACT₁₀, your Web App to automatically update in the background: Give it a minute, then reload, voilà!
• If you want a stable version for long-term usage (studies, clinical trials, student assignments, ESU, what have you), install the Web App from the latest “frozen” version. Even if you clear your browser caches, specifically the cache which Chrome calls “Hosted app data”, the Web App will reinstall to the same version. Frozen versions will remain on the server for years, even if I remove the direct links to them.
• FrACT₁₀’s code is open source on GitHub (commit history). So even if I don’t, FrACT₁₀ will live on :).

To make yourself completely independent from me (advised), install all files at an HTTP server of your own choosing, like so:
Got to https://michaelbach.de/fract/FrACT10/FrACT/ (or a frozen version of your choosing). Download the entire contents of that directory (≈15 MB) and copy to an appropriate location on your HTTP server (e.g. with a “site sucker”). Then open the index.html therein and lo, FrACT₁₀ runs from your server!

• Jolly et al. (2019) A Randomized Crossover Study to Assess the Usability of Two New Vision Tests in Patients with Low Vision. Optomet Vision Sci 96(6): 443–452 [comparison of the Berkeley Rudimentary Vision Test (BRVT) & FrACT]
• Bach & Schäfer (2016) Visual acuity testing: feedback affects neither outcome nor reproducibility, but leaves participants happier. PLOS ONE 11(1):e0147803
• Tsai L, Thomas E, Tarrant J, Bentow S, Kasthurirangan S (2015) A Comparative Clinical Evaluation of Two Visual Acuity Testing Systems: ETDRS vs. FrACT. IOVS 56:3890 [meeting abstract]
• Tarrant J, Thomas E, Tsai L, Kasthurirangan S (2015) Evaluation of defocus curve performance with two visual acuity testing systems: ETDRS and FrACT. IOVS 56:3891 [meeting abstract]
• Kollbaum, Jansen, Kollbaum, Bullimore (2014) Validation of an iPad test of letter contrast sensitivity. Optom Vis Sci 91:291–296 [Contrast, comparison of Pelli-Robson, FrACT, and a new iPad test]
• Kurtenbach, Langrová, Messias, Zrenner, Jägle (2013) A comparison of the performance of three visual evoked potential-based methods to estimate visual acuity. Doc Ophthalmol 126:45–56 [Acuity, comparison of FrACT and ETDRS]
• Lange, Feltgen, Junker, Schulze-Bonsel, Bach (2009) Resolving the clinical acuity categories “hand motion” and “counting fingers” using the Freiburg Visual Acuity Test (FrACT). Graefe’s Arch Clin Exp Ophthalmol 247:137–142 [→PDF] [Acuity, ETDRS & FrACT in very low acuity]
• Bach, Schulze-Bonsel, Feltgen, Burau, Hansen (2007) Author Response: Numerical Imputation for Low Vision States. IOVS, eLetter Aug 2007 [Acuity]
• Bach (2007) The Freiburg Visual Acuity Test – Variability unchanged by post-hoc re-analysis. Graefe’s Arch Clin Exp Ophthalmol 245:965–971 [→PDF] [Acuity, methodology]
• Bühren, Terzi, Bach, Wesemann, Kohnen (2006) Measuring contrast sensitivity under different lighting conditions: Comparison of three tests. Optom Vision Sci 83:290–298 [Contrast]
• Schulze-Bonsel, Feltgen, Burau, Hansen, Bach (2006) Visual acuities “hand motion” and “counting fingers” can be quantified with the Freiburg visual acuity test. IOVS 47:1236–1240 [Acuity, ETDRS & FrACT in very low acuity]
• Dennis, Beer, Baldwin, Ivan, Lorusso, Thompson (2004) Using the Freiburg Acuity and Contrast Test to measure visual performance in USAF personnel after PRK. Optom Vis Sci 81:516–524 [Contrast]
• Terzi, Bühren, Wesemann, Kohnen (2004) Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) – A new test to determine contrast sensitivity under variable ambient and glare luminance levels [Article in German]. Ophthalmologe 102:507–513 [Acuity]
• Loumann Knudsen L (2003) Visual acuity testing in diabetic subjects: the decimal progression chart versus the Freiburg visual acuity test. Graefes Arch Clin Exp Ophthalmol 241:615–618 [Acuity]
• Neargarder, Stone, Cronin-Golomb, Oross 3rd. (2003) The impact of acuity on performance of four clinical measures of contrast sensitivity in Alzheimer’s disease. J Gerontol B Psychol Sci Soc Sci 58:54–62 [Acuity]
• Wesemann (2002) Visual acuity measured via the Freiburg visual acuity test (FVT), Bailey Lovie chart and Landolt C chart [Article in German] Klin Monatsbl Augenheilkd 219:660–667 [Acuity]
• Bach (1997) Anti-aliasing and dithering in the “Freiburg Visual Acuity Test’. Spatial Vision 11:85–89 [Methodology]
• “Generic description” Bach (1996) The “Freiburg Visual Acuity Test” – Automatic measurement of visual acuity. Optometry and Vision Science 73:49–53  [PDF] Also consider the FrACT₁₀ Manual or classic FrACT3.x Manual [PDF] which describes all options [PDF]

Glad you asked! If you used FrACT for your research, please cite it.

• Bach M (2024) Freiburg vision test (FrACT): optimal number of trials? [PDF] (most recent)
  or
• Bach (1996) The “Freiburg Visual Acuity Test” – Automatic measurement of visual acuity. Optometry and Vision Science 73:49–53 [PDF] (the “generic” paper)
  or
• Bach (2007) The Freiburg Visual Acuity Test – Variability unchanged by post-hoc re-analysis. Graefe’s Arch Clin Exp Ophthalmol 245:965–971 [PDF]

Also mention the version plus release date (top left). The briefest way to refer to the present page (its URL):
<https://michaelbach.de/fract/>

• Lieberman & Pentland (1982) Microcomputer-based estimation of psychophysical thresholds: The Best PEST. Behavior Research Methods & Instrumentation 14:21–25
• Newman & Sproull (1979) Principles of Interactive Computer Graphics. New York, McGraw-Hill, Inc.
• Metha, Vingrys, Badcock (1993) Calibration of a color monitor for visual psychophysics. Research Methods, Instruments, & Computers 25:371–383
• Mittelviefhaus, Bach, Jedynak, Kommerell (1993) Der Freiburger Visustest. Ophthalmologe 90:1320–135
• Pelli (1996) VideoToolbox
• Pentland (1980) Maximum likelihood estimation: The Best PEST. Perception & Psychophysics 28:377–379
• Petersen (1990) Zur Fehlerbreite der subjektiven Visusmessung. Fortschr Ophthalmol 87:604–608
• Treutwein (1995) Adaptive Psychophysical Procedures. Vision Res 35:2503–25
• Visual Standards – Aspects and Ranges of Vision Loss
• Bach (1997) Anti-aliasing and dithering in the “Freiburg Visual Acuity Test’. Spatial Vision 11:85–89

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

• Quantitative correctness of the optotype geometry: This is easily verified on the screen with a ruler and a little trigononometry.
  • To make this easier, you can use this tip:
    At a distance of 57.29 cm, one degree of visual angle corresponds to 1 cm. Multiply this with 6 and set the resulting 344 cm as testing distance. Calibrate the ruler (e.g. with plastic card), then:
    → 1 millimeter on the screen corresponds to one minute of arc. Use, e.g., tumbling E, and if you have the Starting LogMAR at 1.0, the first optotype’s stroke width should be 10 mm.
  • For very low acuity, when converting between angle 𝛼 and screen pixels x, be sure to use this formula
    x = 2 · distance · arctan(𝛼 / 2), and not x = distance · arctan(𝛼).
• Quantitative correctness of the threshold outcome: This was done by controlled comparisons to chart testing in my lab and in independent laboratories.
• Robustness with respect to subject input: In testing mode, FrACT acts as a “state machine”, and the numerical keys 0–9 accessible to the subject can switch between well-defined states only.
• Robustness with respect to operator input: The Settings dialog has been augmented with plausibility checking of the input values. E.g., when a numerical entry has incorrect number formatting or an implausible value, the parameter is reset to its default value.
• The code for FrACT₁₀ is open sourced as of 2021-06, allowing external verification.
• Low-level programming details can only be mentioned in passing here
  • Descriptive long variable names rather than going overboard with comments
  • Systematic modularization
  • Unit testing
  • Automated GUI testing with Cypress
  • Source control. Issues and their solutions are tracked with git; for a brief exerpt see Version history of classic FrACT below, or FrACT₁₀’s commit history.

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. Also see Bugs? below.

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) in assembly language just to draw the Landolt C. It became more than a curio after porting to Pascal and incorporation of the Best PEST threshold algorithm (Lieberman & Pentland, 1982) [nowadays one would call this Bayes-based] 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).

In 1996 the first Internet version was made available after adding gamma correction for better quantitative definition. The rich feedback spurred many bug fixes and feature expansions, paving the way from a ‘hobby’ to a professional application, 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 I chose ActionScript/Flash (formerly Macromedia, acquired by Adobe). Consequently the program then ran in near identical fashion on the Macintosh, Linux and Windows operating systems for nearly two decades.

Anticipating the demise of Flash, in 2020 I ported the program to a JavaScript-based framework (Cappuccino); thus it runs on all platforms, including tablets. In 2021, after FrACT₁₀ had achieved near parity with the last “classic” FrACT3.10.5, the code for FrACT₁₀ was open sourced. In 2022 the browser-only FrACT₁₀ was complemented by apps for MacOS & Windows, based on Electron, which can package JavaScript into stand-alone applications. In 2023 the install hassles of apps were circumvented by packaging FrACT₁₀ as a Web App on all platforms. In 2024, I implemented HTML messages to control FrACT₁₀ and read/set its Settings. This allows embedding FrACT₁₀ into larger systems.

Version history of classic FrACT

[→even earlier history details]

• Bugs in FrACT₁₀
  • Currently (2024-10) no known bugs (except with the grating’s circular mask, only on Safari, that’s actually a Safari bug)
  • My issues section on GitHub lists bugs (if known) and also lists planned improvements and new ideas. Please alert me if you find problems, or file a bug report / issue. Usually I respond rapidly.
  • Closed issues.
• Bugs in “classic” FrACT
  • At this time (2024-10), I am not aware of any bugs in classic FrACT. Please tell me should you find problems.
  • Resolved
    • 2020-03-06 Bug: When the optotype contrast is reduced, the Vernier rendering is wrong, because the Vernier doesn’t take contrast into account, but the background does. ←Solved in 3.10.5
    • 2019-05 Enhancement: Indicate in the results whether a ceiling/floor effect occurred. ←Added in 3.10.2

Donations gladly accepted: