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Dyop® - Dynamic Optotype™

Helping the world see clearly, one person at a time.




Personal Vision Test

Children’s Vision Test

Color Screening

Professional Test


  How it works

Experimental Dyop Test

Visual Impairment

Dyslexia Screening

Using the Test 

Induced Dyslexia  



Vision Scientists and Eye Care Professionals have known for decades -

that the Snellen test is inaccurate and inconsistent.


"Results confirm the arbitrary nature of the Snellen fraction and warn about the accuracy of visual acuity determined by using charts of different letter types, calibrated by Snellen's system."

A. Medina, B. Howland - Ophthalmic and Physiological Optics, January 1988

A novel high-frequency visual acuity chart



The Dyop® test optimize the refraction and acuity processes to generate a more precise and consistent refraction

 to reduce both patient and refractionist visual stress. 


In an era where Smartphones and computers are ubiquitous, the errors inherent in Snellen testing are no longer acceptable. 


Preliminary studies indicate that Dyop® acuity tests:

·          are more accurate (up to 6x) than Snellen/Sloan tests,

·          are more consistent (up to 8c) than Snellen/Sloan tests,

·          are potentially faster (up to 3x) to use than Snellen/Sloan tests,

·          maintain greater precision as refractive power increases,

·          inherently avoids overminused and underminused refractions,

·          minimize optotype fixation and decision fatigue,

·          minimize image memorization,

·          do not require the ability to read to measure visual acuity,

·          allows for precise color acuity measurement for potential diagnostic and therapeutic applications.

·          potentially save doctors and patients’ time and money in determining visual needs.

·          consistently evoke 0.25 to 0.50 diopters of less minus refractive power than Snellen testing.



Clinical results demonstrate improved Dyop precision, consistency, efficiency, and reduced excess minus.





Gordon Paper – Pre/Post Cataracts






Dyop® acuity tests are intended to be a more precise and faster to use replacement for Snellen, Sloan, and Landolt visual acuity/refraction tests. 



Free iPhone Controller for Dyop® iPad test



Chart2020 Brochure

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Chart2020 Manual

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Dyop® Refraction Procedure

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Dyop® Professional Users’ Guide

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Dyop® Clinical Trial Report – ARVO 2015

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Dyop® tests use apparent motion detection from the strobic stimulus and refresh rate of the photoreceptors to determine the visual acuity and refraction endpoints.  Snellen letters are culturally derived, NOT proportional, and do NOT provide a consistent basis for determining visual acuity.  As a result, Dyop® tests are more accurate and efficient than the 1862 classic Snellen test, and create a visual acuity test based on physiology rather than subjective and imprecise cognition. 


Dyop® tests enable patients to have a visual acuity endpoint which avoids overminused refractions which seem to be inherent with static image fixation.  It is typically difficult for patients to perceive when optotypes are "too crisp" (over- minused), despite the discomfort and visual stress, which is one of the inherent inadequacies with Snellen and other static image tests. 


Dyop® tests determine visual acuity based upon photoreceptor physiology with a precision (approximately +/- 0.04 diopters) not previously available with traditional static image visual acuity tests.  Unlike static image tests, which may be dependent upon cognition as much as they are for visual acuity, Dyop® tests also maintain a higher level of accuracy as visual acuity decreases with increased blur. 


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Is 1862 Vision Technology Making

21st Century Patients Blinder?

The Dyop strobic stimulus has greater precision and less variance than static visual targets

 The increased precision and consistency and “resolution acuity” of Dyop tests are intended as a global replacement for static letter-based “recognition acuity” tests such as Snellen, Sloan, and Landolt optotypes, and can provide a more universal and efficient method of vision measurement.

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The 2013 projected Sloan optotypes are “fuzzier” than the 2013 computer generated Sloan optotypes, and thereby give a “fuzzier” acuity response.


The 0.54 arc minutes squared Dyop® visual stimulus area (the arc width of the gap/segments) is smaller and inherently more precise than the 1.0 arc minute squared visual stimulus area (the “Minimum Area of Resolution”) of Snellen/Sloan/Landolt optotypes.  The 0.54 arc minutes squared Dyop® visual stimulus area correlates to about 20 photoreceptors.


Fixating on static Snellen/Sloan images also increases accommodative stress, which leads to an overminused acuity response and possible overminused refraction.  The visual dissonance/stress from an overminused refraction is frequently a major reason for patients’ complaining about their lenses and/or not wearing their lenses at all. 


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The Dyop® Acuity/Refraction Test can be used on virtually any personal computer system with minimal setup-up and training.  Dyop® vision testing should increase the accuracy of prescriptions, let patients more easily know when their vision is not proper, maintain higher practitioner testing consistency, and potentially save doctors and patients’ time and money when getting their vision checked.


The Dyop® concept is revolutionary, both literally and culturally.  Previous static methodologies for measuring visual acuity were culturally based and a combination of the perceptual guesses of the subject and the observational guesses of the examiner.  The 1862 Snellen test, and the 1888 Landolt ring as an attempt at a “culturally neutral” test, use static images with a limited precision increment range that is no longer adequate for a society where much of the day is spent looking at the precision of a computerized display and/or regularly travelling at speeds greater than 55 miles per hour (88.5 kilometers per hour).  Snellen letters are culturally derived, NOT proportional, and do NOT provide a consistent basis for determining visual acuity:   Snellen tests also ignore the fact that the visual stimulus is the “Minimum AREA of Resolution” rather than the “Minimum ANGLE of Resolution.”


Visual acuity measurement in increments of +/- 0.25 diopters was acceptable and adequate in 1862 because of the difficulty of making lenses more precisely than +/- 0.25 diopters.  Visual testing in increments of +/- 0.25 diopters was also adequate because of the small percentage of the population able to read, or needed to be able to read.


Varying Difficulty of Snellen Letters and Common Errors in Amblyopic and Fellow Eye

PDF File





Snellen test responses also are NOT equivalent to the responses from the academically preferred Landolt ring test.  Because of the increased cognition factor inherent in the non-uniformity of the Snellen letters, for them to be equivalent to the 5 arc minute size of Landolt rings, Snellen letters should actually be only 4.25 arc minutes in size (15% smaller) and NOT the currently accepted 5.0 arc minute height.


Correlation of Optotypes with the Landolt Ring

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Recognition versus Resolution

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Note: Dyop® tests are for vision screening purposes only and are NOT a substitute for an examination by a licensed vision care professional.  


The Dyop® (Dynamic Optotype™) tests and concept are covered under U.S. Patent US 8,083,353

and International Published Patent WO 2011/022428.

For further information contact: Allan Hytowitz at Allan@DyopVision.com

5035 Morton Ferry Circle, Alpharetta, GA, 30022   /   404-281-7798

Copyright©2023 DyopVision™ Associates.  All Rights Reserved.