Icon  Freiburg Vision Test (‘FrACT’)  Icon

by Prof. Michael Bach

Vs 3.8.2 as of 2014-04-15
Downloads | Checklist | Manual

FrACT on Google+

Vs 3.8.2 changes include:
• generalised exentric targets, etc.

This is the free, multi-platform Freiburg Visual Acuity Test + Contrast Test + Vernier Test + Grating Test. You can run the tests below within your browser (for security, “result→clipboard” is then disabled) or download as a stand-alone program.

Response keys: For 4 directions (tumbling E or Landolt set to “4 choices” in Settings) the cursor keys are fine, for 8 directions the response keys are geographically arranged on a numeric keypad. To abort a test run, press the key ‘5’ twice or <escape>. For reliable results, please observe the checklist. Your feedback is welcome and has frequently lead to improvements and extensions. FrACT was employed in over 100 papers (“Who used FrACT” below).

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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 measurement of visual acuity (Bach 1996), contrast sensitivity and vernier acuity. The progression of optotype sizes is determined by the “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 in over 100 publications) and has been verified in independent laboratories (→Descriptions & Validations).
– Optotypes include Landolt ring, tumbling E, Sloan letters, and faces.
– Results can be displayed as logMAR, Snellen fraction, or decimal acuity; full details can be exported for data processing.

One particular advantage of FrACT is its wide range  

Where can I get it? →Downloads

Where can I learn more?  

For an overview see this English introduction or eine deutsche Einführung. Detailed information on the program is available in “Bach M (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 built-in help file, and a detailed discussion of the various settings here: “FrACT3_Manual.pdf”. Finally, →here (General Pertinent Sources) is a literature list.

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 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 in many laptops; more); 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   [DOI]   [→PDF]

The briefest way to refer to the present page (its URL): <http://michaelbach.de/fract/>.


If you ran a previous version, all settings in “Setup” 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 “Setup” interface. Be sure to have enough distance from the screen, so pixel resolution does not limit acuity. Also ponder about every entry in the Setup 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 detail.

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

All settings in Setup are automatically saved.

Starting the test

Apart from using the obvious buttons a test run can also be conveniently 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?

Tumbling E has only 4 directions, 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 entailing a higher number of trials; 8 positions allow more rapid determination of visual acuity as 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 setups

Often one wants different sets of Setups, 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 setup each time (with the danger to forget something), be informed that the Setup 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’ Setup; to switch between different sets of setups, 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.

 Key Action
5 start the test as defined in Settings 
astart Acuity
l start acuity Letters
cstart Contrast
vstart Vernier
e start Tumbling E
u settings
qQuit = Exit
 55 or <esc>   abort running test


I am lazy and prefer to start actions without mousing, thus I added a number of shortcuts:

Literature & Background

Who used FrACT?  

Here are studies that employed FrACT. I rarely find the time to systematically analyse the citations whether FrACT was used, so the list is incomplete. I'd appreciate a reprint if you profited from FrACT.

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. 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
  3. Britz J, Diaz Hernandez L, Ro T, Michel CM (2014) EEG-microstate dependent emergence of perceptual awareness. Front Behav Neurosci 8:163
  4. 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:1–10
  5. Cappe C, Clarke A, Mohr C, Herzog MH (2014) Is there a common factor for vision? J Vis 14:4
  6. Chicherov V, Plomp G, Herzog MH (2014) Neural correlates of visual crowding. NeuroImage 93, Part 1:23–31
  7. Clarke AM, Grzeczkowski L, Mast FW, Gauthier I, Herzog MH (2014) Deleterious effects of roving on learned tasks. Vision Res. 99:88–92
  8. 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
  9. 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
  10. 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]
  11. 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
  12. 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
  13. 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
  14. Matas NA, Nettelbeck T, Burns NR (2014) Cognitive and visual predictors of UFOV performance in older adults. Accident Analysis & Prevention 70:74–83
  15. Meyberg S, Werkle-Bergner M, Sommer W, Dimigena O (2014 in press) Microsaccade-related brain potentials signal the focus of visuospatial attention. NeuroImage
  16. Müller-Oehring EM, Jung Y-C, Pfefferbaum A, Sullivan EV, Schulte T (2014) The Resting Brain of Alcoholics. Cereb. Cortex:bhu134
  17. Niemann C, Godde B, Staudinger UM, Voelcker-Rehage C (2014) Exercise-induced changes in basal ganglia volume and cognition in older adults. Neurosci
  18. 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
  19. Nikitin J, Freund AM (2014) Adult age differences in frequency estimations of happy and angry faces. Int J Behav Dev 0165025414542838
  20. 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
  21. Quigley C, Müller MM (2014) Feature-Selective Attention in Healthy Old Age: A Selective Decline in Selective Attention? J. Neurosci. 34:2471–2476
  22. 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
  23. Sayim B, Manassi M, Herzog M (2014) How color, regularity, and good Gestalt determine backward masking. J Vis 14:8
  24. 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
  25. 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
  26. 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
  27. 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. [Contrast]
  28. Vestergaard AH (2014) Past and present of corneal refractive surgery. Acta Ophthalmol (Copenh) 92:1–21. [Contrast]
  29. Wenner Y, Heinrich SP, Beisse C, et al. (2014) Visual evoked potential-based acuity assessment: overestimation in amblyopia. Doc Ophthalmol 128:191–200
  30. Whiting WL, Sample CH, Hagan SE (2014) Top-down processing modulates older adults’ susceptibility to noise. Aging Neuropsychol Cogn 21:370–385
  31. 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
  32. Zhang T, Nefs HT, Heynderickx I (2014) Human discrimination of depth of field in stereoscopic and nonstereoscopic photographs. Perception 43:368–380

    Examples from 2013 (end of 2013: 395 {59 + 336 citations})
  33. 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
  34. 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
  35. 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
  36. Badham SP, Hutchinson CV (2013) Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome. Graefes Arch Clin Exp Ophthalmol 251:2769–2776
  37. 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
  38. 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
  39. 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
  40. 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
  41. 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
  42. Gonzalo-Fonrodonaa I, Porrasb MA (2013) Scaling effects in crossmodal improvement of visual perception by motor system stimulus. Neurocomputing 114:76–79
  43. Grainger JE, Scharnowski F, Schmidt T, Herzog MH (2013) Two primes priming: Does feature integration occur before response activation? J Vis 13:19–19
  44. Greenaway R, Davis G, Plaisted-Grant K (2013) Marked selective impairment in autism on an index of magnocellular function. Neuropsychologia 51:592–600
  45. Grimsen C, Brand A, Fahle M (2013) No Evidence for Prolonged Visible Persistence in Patients with Schizophrenia. PLoS ONE 8(3): e58940
  46. 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
  47. 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
  48. Herbik A, Hölzl GC, Reupsch J, Hoffmann MB (2013) Differential effects of optic media opacities on mfERGs and mfVEPs. Clin Neurophys 124:1225–1231
  49. 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
  50. 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]
  51. Hutchinson CV, Badham SP (2013) Patterns of Abnormal Visual Attention in Myalgic Encephalomyelitis. Optom Vis Sci 90:607–614
  52. 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
  53. 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
  54. 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
  55. Manassi M, Sayim B, Herzog MH (2013) When crowding of crowding leads to uncrowding. J Vis 13:10
  56. 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
  57. 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
  58. 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
  59. Piepenbrock C, Mayr S, Mund I, Buchner A (2013) Positive display polarity is advantageous for both younger and older adults. Ergonomics 56:1116–1124
  60. 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
  61. Rüter J, Sprekeler H, Gerstner W, Herzog MH (2013) The Silent Period of Evidence Integration in Fast Decision Making. PLoS ONE 8(1): e46525
  62. 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
  63. Sreenivasan V, Aslakson E, Kornaus A, Thibos LN (2013) Retinal image quality during accommodation in adult myopic eyes. Optom Vis Sci 90:1292–1303
  64. 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}
  65. 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
  66. Strasburger H, Malania M(2013) Source confusion is a major cause of crowding. J Vision 13 (1)
  67. Piepenbrock C, Mayr S, Mund I, Buchner A (2013) Positive display polarity is advantageous for both younger and older adults. Ergonomics 1–9
  68. 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:
  69. 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:
  70. Weibel S, Giersch A, Dehaene S, Huron C (2013) Unconscious task set priming with phonological and semantic tasks. Conscious Cogn 22:517–527
  71. Weigel D, Jungnickel H, Babovsky H, Kiessling A, Kowarschik R (2013) Untersuchung des Seheindrucks mittels adaptiver Optik. Klin Monatsblätter Augenheilkd 230:1199–1206
  72. 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
  73. Wijesuriya W, Perera AHP, Gayan JMU, et al. (2012) Intelligent Lighting Controller for Domestic and Office Environments [PDF]

    Examples from 2012 (end of 2012: 268 citations)
  74. 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
  75. Bennett SJ Elliott D, Rodacki A (2012) Movement strategies in vertical aiming of older adults. Exp Brain Res 216:445–455
  76. Bornschlegl MA, Fahle M, Redding GM (2012) The role of movement synchronization with an auditory signal in producing prism adaptation Perception 41:950–962
  77. 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
  78. 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
  79. 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
  80. 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]
  81. Ghose T, Hermens F, Herzog MH (2012) How the global layout of the mask influences masking strength. J Vision 12 (13)
  82. 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}
  83. Kraehenmann R, Vollenweider FX, Seifritz E, Kometer M J (2012) Crowding Deficits in the Visual Periphery of Schizophrenia Patients. PLOS ONE 7;9:e45884
  84. 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
  85. Manassi, M; Sayim, B; Herzog, MH (2012) Grouping, pooling, and when bigger is better in visual crowding. J Vision 12 (10): 2012
  86. Roeber U (2012) Neural processing of orientation differences between the eyes' images. JOV:12 20
  87. Traschutz A, Zinke W, Wegener D (2012) Speed change detection in foveal and peripheral vision. Vision Res 72:1–13
  88. 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
  89. 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
  90. Linhart F, Scartezzini JL (2011) Evening office lighting – visual comfort vs. energy efficiency vs. performance? Building Environ 46:981–989
  91. Nielsen E, Hjortdal J (2011) Visual acuity and contrast sensitivity after posterior lamellar keratoplasty. Acta Ophthalmologica 1–5
  92. 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
  93. 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
  94. Sayim B, Westheimer G, Herzog MH (2011) Quantifying target conspicuity in contextual modulation by visual search. J Vision 11:1;6
  95. Straube S, Fahle M (2011) Visual detection and identification are not the same: Evidence from psychophysics and fMRI. Brain Cognition 75: 29–38
  96. Tavassoli T, Latham K, Bach M, Dakin SD, Baron-Cohen S (2011) Psychophysical measures of visual acuity in autism spectrum conditions. Vision Res
  97. 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)
  98. Brittain PJ, Surguladze S, McKendrick AM, Ffytche DH (2010) Schizophrenia Res 124:134–141
  99. Costello MC, Madden DJ, Mitroff SR, Whiting WL (2010) Age-related decline of visual processing components in change detection. Psychol Aging 25:356–368
  100. 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
  101. Gurnsey R, Troje NF (2010) Peripheral sensitivity to biological motion conveyed by first and second-order signals. Vision Res 50:127–135
  102. 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
  103. Jägle H, Zobor D, Brauns T (2010) Accommodation limits induced optical defocus in defocus experiments. Doc Ophthalmol 121:103–109
  104. 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
  105. Legras R, Benard Y, Rouger H (2010) Through-focus visual performance measurements and predictions with multifocal contact lenses. Vision Res 50:1185–1193
  106. 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
  107. Mund I, Bell R, Buchner A (2010) Age differences in reading with distraction: Sensory or inhibitory deficits? Psychol Aging 25:886–897
  108. 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
  109. 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
  110. Sayim B, Grubert A, Herzog MH, Krummenacher J (2010) Display probability modulates attentional capture by onset distractors. JOV 10(3):10, 1–8
  111. Slica S, Ikaunieks G, Rinkus D (2010) Effect of Yellow Filters on the Vision. Latvian Journal of Physics and Technical Sciences 47:37–43
  112. 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
  113. Straube S, Fahle M (2010) The electrophysiological correlate of saliency: Evidence from a figure-detection task. Brain Res 1307:89–102
  114. 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
  115. Wrobel WG (2010) The Value of Retinal Implants. Biomed Tech 55 (Suppl. 1) [PDF]

  116. 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
  117. 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
  118. 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
  119. Dimigen O, Valsecchi M, Sommer W, Klieg R (2009) Human Microsaccade-Related Visual Brain Responses. J Neurosci 29:12321–12331
  120. 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
  121. 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
  122. 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
  123. Ohlendorf A, Schaeffel F (2009) Contrast adaptation induced by defocus – A possible error signal for emmetropization? Vision Res 49:249–256
  124. 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
  125. 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
  126. 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]
  127. 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
  128. 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
  129. Chung ST, Jarvis SH & Cheung SH (2007) The effect of dioptric blur on reading performance. Vision Res 47:1584-1594
  130. 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
  131. 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
  132. Rémon L, Tornel M, Furlan WD (2006) Visual Acuity in Simple Myopic Astigmatism: Influence of Cylinder Axis. Optom Vision Sci 83:311–315
  133. 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
  134. Peters BT, Bloomberg JJ (2005) Dynamic visual acuity using ‘‘far’’ and ‘‘near’’ targets. Acta Oto-Laryngologica 4:353–357
  135. Hoffmann MB, Tolhurst DJ, Moore AT, Morland AB (2003) Organization of the visual cortex in human albinism. J Neurosci 23:8921–8930
  136. 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
  137. Collins MJ, Franklin R, Davis BA (2002) Optical Considerations in the Contact Lens Correction of Infant Aphakia. Optom Vis Sc 79:234–240
  138. Hazel CA, Elliott DB (2002) The Dependency of LogMAR Visual Acuity Measurements on Chart Design and Scoring Rule. Optom Vis Sci 79:788–792
  139. 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
  140. Fahle M, Biester A, Morrone C (2001) Spatiotemporal interpolation and quality of apparent motion. J Opt Soc Am A:18;2668–2678
  141. 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     (→even more early history details)

2014-04-15 3.8.2 · harmonised choices in“Which test on 5”
· systematic treatment of exentric presentation across tests
· maxVAdecimal now takes the tresholdtype setting into account (a little higher if not DIN)
2013-11-29 3.8.1 · 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 (thank, 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)
2013-06-18 3.8.0e · 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
2013-03-27 3.8.0d · 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
2012-12-07 3.8.0 · 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
2012-06-19 3.7.4c · 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 persistant history
· grating: added some Gaussian windowing and made patch-diameter a user-defined setting.
2011-10-27 3.7.1b • 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)]
2011-04-29 3.7l preview, 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
2010-09-01 3.6.3 • 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.
2010-07-29 3.6.2 • 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 Setup frame
• solved problem of not being able to enter "5" into the subjectID field
2010-03-21 3.6beta • 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 <http://fatal-exception.co.uk/blog/?p=69#more-69>
• for FrACT letters the history is now correctly exported, with the letters. Checked LandoltC and SloanC size, they are identical, as should be.
2009-11-11 3.5.5 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 Setup screen to make them more obvious
• set focus to stage (now it responds to keyboard shortcuts after returning from Setup etc.)
• now possible to start with numkey-5 irrespective of numlock setting
2009-09-16 3.5.4 made the calibration bar blue; increased PEST-grain from 500 to 5000; added contrast with Weber definition; improved manual
2009-08-20 3.5.3 • fixed background glitch, a regression from the new contrast polarity setting
• rearranged the setup a little around the calibration bar
2009-07-19 3.5.2 • 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)
2009-05-27 3.5 • 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]
2009-04-21 3.4.3 • 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
2008-12-08 3.3 timeout > 30 seconds now possible (current maximum: 999 s); improved Flash version display; corrected a missing help button
2008-11-16 3.2 ported to Flash CS4, added calibration alert
2008-09-10 3.1.3 fixed a capitalisation issue in a sound resource
now ignoring letter capitalisation in shortcuts
2008-09-10 3.1.2 added optional Sloan letters . Range-checked timeout-value (reported by Frank Schmidtborn, more fields need to be checked)
2008-06-20 3.1 All 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.
2008-05-30 3.0.4 “auditory feedback when done” now preserved, made sound resources more generic, improved internal debugging
2008-05-06 3.0.3 Corrected time-out (error diagnosed by Frank Schmidtborn), added a positional jitter to vernier test (as suggested by Wolf Harmening)
2008-04-26 3.0.2 Complete 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.
2007-12-24 2.3 fixed a bug of incorrectly formatted Snellen fractions under certain rare conditions
2007-11-19 2.2 re-enabled the “bonus trial” option for the contrast & Vernier test, improved FrACT documentation
2007-10-30 2.1 improved contrast dither for oblique orientations. Thanks to Hendrik Jungnickel at the Ammersee meeting!
2007-07-25 2.0.5 • 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
2007-06-02 2.0.3 • added a "which test on pressing ‘5’" option, changed contrast-Ø default to 30'
• finally found how to abort using <esc>
2007-05-23 202a • 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
2007-04-11 2.0 Contrast 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.
2007-01-06 1.10 negative 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)
2006-11-30 1.9 the 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
2006-11-15 1.8a • 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
2006-10-01 1.6a • 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.
2006-08-09 1.5a • 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.
2006-04-28 1.3 • 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?)
2005-11-22 1.1.3 added "frame" (square + circular) to crowding options
2005-11-21 1.1.2 in "results2clipboard" trial number starts with 1, not 0; added "maxAcuity" in Prefs, framePrefs & Acuity
2005-10-25 1.1 added crowding flankers (on request of Bruce Evans)
2005-10-10 1.0.9 switched 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
2005-04-22 1.0.6 • added a "mirroring" option (requested by Laura Gibson & Ken Nakayama
• added luminance linearisation calibration
2004-10-07 1.0.5 added facility to change eccentricity, made feedback-expansion a bit slower
2004-05-28 1.0.1 fixed 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

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.
• Newman WM & Sproull RF (1979) New York: McGraw-Hill, Inc.
• Lieberman HR & Pentland AP (1982) Microcomputer-based estimation of psychophysical thresholds: The Best PEST. Behaviour Research Methods & Instrumentation 14:21–25
• Bach M (1997) Anti-aliasing and dithering in the Freiburg Visual Acuity Test. Spatial Vision 11:85–89

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.








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Last update 2014-10-10 by Michael Bach (G+)