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Dyop® - Dynamic Optotype™

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



Personal Vision

Children’s Vision

Color Screening

Professional Use


How it works

Experimental Test

Visual Impairment

Dyslexia Screening

Using the Test

Induced Dyslexia



wE rEad wOrdS aNd nOt jUst lEttErs.”


Or what you thought you saw:


We read words, not just letters.


The letters in the two sentences above seem the same, but the words are different because the letters are different.  The CAPITALS of some of the letters in the first version of the sentences slow down your ability to read and understand those words and that sentence.  The de-coding (cognition) of letter-based words requires a symbiotic recognition of the letters to form a word, and the recognition of the relationship of that word to the words adjacent to it.  Focusing on static letters results in a loss of cognition and reading skills/speed.


A refraction which uses static images has a tendency for a person to want to maximize the static image letter contrast.  The result is that those extra-crisp static letters induce an overminus (excess spherical power) in the refraction.  That excess minus power in your lenses has the effect of reducing the ability to properly decode letters into words and reduces cognition.




Are your glasses making you blinder?

Take the Dyop® ten second visual precision test.




Stand ten feet (3 meters) from the monitor and note the smallest

diameter spinning ring Dyop you can clearly detect as spinning.




Dyop® Professional Vision Test Video


Dyop® Concept Summary

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The Dyop® Test is also available as an iPad app.


Dyop® iPad Test


Free iPhone Controller for Dyop® iPad test


How a Dyop® works-Tablet


Dyop® Patient Brochure

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Adobe Acrobat document



It is easy to notice when your glasses “need to be stronger” and do NOT have sufficient minus spherical magnification power.  If you are “nearsighted” (myopic) the images you see typically will be blurry. 


However, your glasses may actually be making you “blinder” by having too much minus spherical magnification power if you are “near sighted” (myopia).   Your glasses may also be making you “blinder” by not having enough plus spherical power if you are “far sighted” (hyperopia).


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A simple test as to whether your glasses have the correct spherical power is to move your glasses one half to one inch forward from your face as you read this text.  The movement of your glasses AWAY from your face should change the refractive power of your lenses by about +/- 0.25 diopters.  If you are near-sighted (myopia), and your refraction is proper, the words may get smaller, but the clarity of the words does not improve.  You have PASSED the test.


However, if the words you are reading become clearer and MORE legible when you move your glasses forward, you may inadvertently have too much minus power in those lenses, and you glasses FAILED the test.  They are making you blinder!


Because of the need for cylinder compensation, it is virtually impossible to have a refraction without the professional assistance of an optometrist, ophthalmologist, or optician.  Your online acuity response is NOT the same as a refraction.


If you are nearsighted, you may not realize that you have excess minus spherical power.  The images look clear.  Perhaps TOO clear.  If you move your glasses about 1 inch forward from your eyes you may notice that not only do the words get smaller, but the words get more coherent and easier to read.  The increase in cognition is indicative of an overminused refraction (too much spherical minus power).  That overminus is likely an inherent flaw in 1862 based static image tests where fixation on letters is the determinant of the refraction rather than the ability to decode and read words.


If you are “far sighted” (hyperopia), not having enough plus spherical power may let you see the letters despite the visual strain.   However, the inherent fixation on static image tests may also result in not enough plus spherical power to compensate for the hyperopia and an inadvertent reduction in cognition.


A possible explanation for that excess minus power is that focusing on static letters during a refraction encourages a tendency to fixate and strain to see those letters as clearly and crisply as possible.  Seeing individual letters as “extra-crisp” interferes with the cognition of letter-based words


Having too much power in your current refraction likely increases visual stress, reduces cognition, and reduces productivity.  It is induced dyslexia  (reduced ability to read words) from an improper refraction.


That visual stress from fixating on static letter targets something most people do NOT notice during the refraction process.  Instead, it gets noticed as visual strain while driving, reading, or using a computer.  When people have “computer vision syndrome,” most people fail to realize that the problem is their glasses rather than their eyes.


The clarity of what we see in the 21st century is significantly more precise (crisp) than anything conceivable to Herman Snellen in 1862 when he created the classic static letter-based vision test.  That need for increased visual precision due to computer use was also something Snellen could not have envisioned.


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Your biological lens changes its shape to focus the image you want to see on the retina.  The muscular tension on the lens flattens it to help see distant images.  The lens relaxes and flattens to better see close image.  The refraction process for glasses and contact lenses compensates for the imperfections of the biological lens by making adjustments for sphere, cylinder, and axis of the lens.




If you wear glasses or contact lenses, those lenses help you see more clearly by bending light to compensate for the lack of perfection of your biological lenses.  If you are nearsighted (myopia), the lens will be a converging lens.  If you are farsighted (hyperopia), the lens will be a Concave lens.   The lens will likely also have a subtle tilt either forwards or backwards to compensate for cylinder adjustments, and possibly a horizontal tilt to compensate for axis adjustments.



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Converging lens for myopia

Concave lens for hyperopia

Adjustment for cylinder

Adjustment for axis



The Dyop® test measures visual acuity (clarity) and is NOT a refraction.  A refraction measures sphere, cylinder, and axis - the components essential for glasses and contacts.  For a refraction you need to see an Optometrist or Ophthalmologist, and NOT an on-line vision test.


The Dyop® Vision Test is intended to be a precise indication of visual clarity, regardless of your monitor size.  Select the correct monitor size for the test.  Use the Up/Down Arrows or the mouse scroll wheel to adjust the Dyop® image size until you have the smallest gap/segment you can clearly detect as spinning /moving.  The smallest Dyop® diameter where you can still detect gap/segment spinning determines the acuity endpoint and corresponds to your visual clarity.  Since we see in RedGreenand Blue rather than just Black and White, you can also check your acuity endpoint and visual clarity in color. 


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   Cell: 404-281-7798

Copyright©2023 DyopVision™ Associates.  All Rights Reserved.