Can the Dyop, a dynamic target, replace traditional eye charts ?

Recent Dyop Research:

Subjective Comparison Between Dyop and Snellen Refractions

Author: Isiaka Oluwasegun Sanni, OD

Date: December 2020


Background: A Dyop (or dynamic optotype) is a spinning visual target which uses the strobic detection of the spinning gaps/segments of the ring to measure visual acuity.

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Methods: Forty subjects with visual acuity better than 6/12 (20/40) and ages between 20 and 28 years (24.48 ± 2.01 years) were recruited at the University of Benin Optometry Clinic. Snellen and Dyop acuity charts were displayed on a monitor at a distance of 6 meters. The assessment sequence between the two acuity chart formats was alternated for every other patient to reduce potential refractionist bias. Subjective refraction was measured in both eyes, and the duration of testing for each patient and each method was recorded.

Results: There was no significant mean Thibos notations difference, M (p = 0.77), J0 (p = 0.27), and J45 (p = 0.57) using the Bland-Altman plot and 95% limits of agreement between the two charts, and there were no differences as to age or gender. There was, however, a disparity in the mean acuity of about 0.25 diopters with the mean Snellen acuity of 1.60 ± 0.21 decimal units and the mean Dyop acuity of 1.17 ± 0.14 decimal units with a linear relationship: y = 0.3121x + 0.6709 (p = 0.00). The refraction with a Dyop acuity chart also typically took half as long (339 ± 122 seconds) as the refraction with a Snellen acuity chart (680 ± 281 seconds), p = 0.00.

Conclusions: Subjective refractions with a Dyop chart were comparable to a Snellen chart. The
efficiency of a Dyop refraction, however, was typically twice that of the Snellen chart, with a
narrower variance in visual acuity measurements and an improved level of acuity of about 0.25

Keywords: Dyop acuity chart, Snellen acuity chart, subjective refraction, visual acuity

A Comparison of Dyop Color Perception and Dyslexia Diagnosis

Journal of Optometry & Visual Performance, vol. 8, Issue 4, pp.176-190. 

Author: Sandra Stark, B. Optom, B.Sc. Hons.

Date: December 2020


Background: Acuity and accommodation result from an array response of the L (red), M (green), and S (blue) cone photoreceptors and the relative refractive focal depths of those specific colors.

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A Dyop® (or dynamic optotype) is a spinning segmented ring visual target which uses the strobic detection of the spinning gaps/segments of the ring to measure visual function.  Dyop gap/segment color/contrast permutations have distinctive, and corresponding, acuity
endpoints. This study’s objective was to compare the qualitative acuity responses of a specific Dyop color/contrast combination to diagnosed symptoms of dyslexia.

Methods: One hundred and eighty-eight patients, ranging in age from 4 years to 44 years, were examined as patients of the Stark-Griffin Dyslexia Academy to compare their relative color/contrast
acuity endpoint perception of a spinning green-on white Dyop versus a spinning blue-on-black Dyop and the possible diagnosis of types of dyslexia. The Stark-Griffin Dyslexia Academy trains eye care professionals as to how to diagnose and treat patients with potential symptoms of dyslexia. The patients were diagnosed as to their prevalent type of dyslexia, if any, through the Stark-Griffin Dyslexia Assessment. The patients were then presented
with, as part of the Chart2020 vision test platform, a display which has an identical-diameter spinning
green-on-white Dyop and spinning blue-on-black Dyop with sufficient arc width diameter such that both Dyop rings were detected as spinning. Those identically sized Dyop rings were then reduced in arc width until spinning of each of the colored rings was not detected. The smallest diameter ring where spinning was detected for each of the
color/contrast combinations (corresponding to the acuity endpoint metric value) was recorded as the color acuity endpoint.

Results: Of the 188 patients, 166 (88% of the total) were formally diagnosed with dyslexia, and 22 patients (12% of the total) were diagnosed as not having dyslexia. Of the166 patients diagnosed with dyslexia, 151 patients (86% of that group) detected a smaller angular arc width diameter for the spinning blue-on-black Dyop, while 9 patients
(5% of that group) detected a smaller angular arc width diameter for the spinning green-on white Dyop. Of the 22 patients (12% of the total) diagnosed as not having dyslexia, 12 patients (55% of that group) detected a smaller angular arc width for the spinning green-on-white Dyop, while 9 patients (41% of that group) detected a smaller angular arc width for the spinning blue-on black Dyop. Of the 22 patients diagnosed as not having dyslexia, one was diagnosed as “cognitively challenged,” one was diagnosed as a “slow reader” (albeit not dyslexic), and one was diagnosed as having ADHD. There was an additional group of 16 patients (9% of the total) which responded by
detecting identical acuity endpoints for both the green-on-white Dyop and the blue-on-black Dyop. Of the patients who detected an identical acuity endpoint for both color options, 1 patient (5% of that group) was diagnosed as not having dyslexia, and 15 patients (95% of that group) were diagnosed with dyslexia. Of the 151 patients with a definitive color response and diagnosed dyslexia, 142 (94%) detected a smaller angular arc width for the spinning blue-on-black Dyop. Of the 21 patients with a definitive color response and diagnosed as not having dyslexia, 12 (57%) detected a smaller angular arc width for the spinning green-onwhite Dyop. While this is only a preliminary study, the correlation of detecting a smaller angular arc width for a spinning blue-on-black Dyop with the 86% association with diagnosed dyslexia definitely deserves further evaluation.

Conclusions: This preliminary evaluation of the disparity of color perception versus diagnosed symptoms of dyslexia showed a strong positive association (~86%) between color perception and diagnosed symptoms of dyslexia. The findings suggest that symptoms presented by dyslexics could be better understood or analyzed by their color perception.

Keywords: color perception, visual acuity, dyslexia, Dyop acuity chart

Visual Acuity Assessment with a DYOP® versus a Snellen acuity chart for pre and post cataract surgery

Journal of Optometry & Visual Performance, vol. 9, Issue 2

Author: Dr. Peter Gordon, MD, Kimberly Brewer, COA

Date: June 2021


Purpose: To compare the visual acuity of pre and post cataract surgery’s patients using a Snellen acuity chart and a Dyop acuity chart as to differences in resolution acuity versus recognition acuity.

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Methods: Fifty-nine patients (105 eyes) with senile cataracts aged 40 years or older, and with no other ocular pathologies, were evaluated as to visual acuity for pre and post cataract surgery using the Snellen acuity and Dyop acuity charts.

Results: Cataracts were nuclear in 50 eyes, nuclear and posterior sub capsular in 24 eyes, nuclear and cortical in 23 eyes, nuclear, cortical and posterior sub capsular in 4 eyes as well as nuclear, anterior and posterior sub cortical in 2 eyes, pre cataract surgery. The average spherical equivalents pre cataract surgery refractive assessments for the patients were -0.61±2.81D and -0.63±3.22D for right and left eye respectively. The mean VA measured at pre cataract surgery were significantly overestimated with Snellen (OD: 0.64 ± 0.15, OS: 0.69 ± 0.23 decimal units) versus Dyop (OD: 0.53 ± 0.25, OS: 0.55 ± 0.24 decimal units), for both eyes (OD: p = 0.01, OS: p = 0.01). The mean VA measured at post cataract surgery were also significantly overestimated with Snellen (OD: 0.88 ± 0.22, OS: 0.85 ± 0.20 decimal units) versus Dyop (OD: 0.72 ± 0.22, OS: 0.72 ± 0.23 decimal units), for both eyes (OD: p = 0.00, OS: p = 0.01). The Bland Altman plots of difference in the means for assessment of visual acuity with the two charts against the average means for assessment of visual acuity with the two charts for both eyes, were not within clinically acceptable levels, pre and post cataract surgery.

Conclusions: Visual acuity measurements for pre and post cataract surgery were different with a
Snellen acuity chart and a Dyop acuity chart in that the Dyop test was a more precise indicator of acuity resolution. These two charts cannot be used interchangeably. The apparent strength of the Dyop acuity assessment is that it primarily utilizes resolution acuity, thus preventing overestimation of visual acuity which is inherent in the recognition acuity of the Snellen test.

Keywords: Visual Acuity; Visual acuity charts; Age-Related Cataract; Cataract Surgery

A New Visual Acuity Test for Use in Children age 4-17

American Association for Pediatric Ophthalmology and Strabismus, 2021 Annual Meeting, Poster #C66, Sunday, April 11, 2021, 11:30 AM – 12:30 PM

Author: Guy Barnett-Itzhaki 1,2, Zohar Barnett-Itzhaki 3,4 and Noa Ela-Dalman1,2

Date: April 2021


Introduction: A century and a half ago, Herman Snellen, developed a chart for vision testing. This chart has been adopted worldwide and is widely used since then. Although the computer age has encouraged the development of new approaches and platforms to measure visual acuity, they mainly reflect the original Snellen charts and they do not pose a genuine novel approach for acuity tests.

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Recently, a new chart using a dynamic target visual assessment tool was developed. This chart, called the Dynamic Optotype chart (DYOP) uses a segmented, circular figure composed of equally spaced gaps/segments that spin at a constant velocity. Our study goal was to evaluate the DYOP chart. Children were tested with the DYOP visual acuity test and the ETDRS Lea numbers chart. The results of both tests were compared.

Design and Methods:

• Prospective study.
• Consecutive patients ,ages of 4 – 17 years, presenting for eye examinations at the
Pediatric Ophthalmology section of Meir Medical Center.
• N=157: 76 males and 81 females, mean patient age: 8.4 years (±2.88 years);
range: 4–17 years
• Visual acuity in at least one eye in the range 6/4.8 to 6/60 as determined
previously with Lea numbers ETDRS chart
• Distance visual acuity was determined monocularly using both the Lea numbers
ETDRS chart and the Dyop test , alternating the order of administration between
patients; The worst-seeing eye of each patient was tested.

• A strong linear correlation (r =0.88) between the
visual acuity measures was found . The mean
difference in acuity was -0.01 (95%,CI) -0.02 to
• The 95% limits of agreement were ±1.2 lines. The
logMAR, equivalent was about less than 1 letter.
• The DYOP test underestimated vision (not clinically
significant) relative to the Lea numbers ETDRS
• The results of this study, the first prospective study
in pediatric population, support the DYOP eye chart
as a valid measure of visual acuity among pediatric
patients 4 to 17 years-of-age, with vision ranging
from 20/16 to 20/200.

(1) Tsou BC, Bressler NM. Visual acuity reporting in clinical research publications. JAMA Ophthalmol. 2017;135:651-653.
(2) Cromelin CH, Candy TR, Lynn MJ, Harrington CL, Hutchinson AK. The handy eye chart: a new visual acuity test for use in children.
Ophthalmology. 2012;119:2009-13.
(3) Anstice NS, Thompson B. The measurement of visual acuity in children: an evidence-based update. Clin Exp Optom.
(4) Harris P. Validation of the DYOP Acuity Test, ARVO annual meeting, 2015.

The dynamic optotype (DYOP): a new visual acuity test for use in children.

Author: Guy Barnett-Itzhaki [1,2]; Zohar Barnett-Itzhaki [3,4,5]; Noa Ela-Dalman[1,2]



Optimal rotation speed for maximum visual acuity using dynamic rotating optotypes

Author: Hagar Sabag, Dinah Paritzky, Einat Shneor, Sara Baruch, Vered Milman, Liat Gantz



A new method of testing visual acuity (VA) by using dynamic acuity

Author: Dinah Paritzky, Hadassah Academic College HAC, Jerusalem, Israel

Nadav Wolf, HAC, Jerusalem, Israel
Inbar Wunch, HAC, Jerusalem, Israel
Dr Liat Gantz, HAC, Jerusalem, Israel

Date: 2019

Content: Optometrists test VA using the Snellen or LogMar charts, which were developed in 1862 and 1976 respectively. The LogMar chart is devoid of the many of the problems of the Snellen chart such as non-linear crowding, optotypes of varying difficulty, non-geometrical changes between the lines, and varying number of optotypes per line. However, both charts are limited by the fact that they measure static acuity, whereas everyday tasks involve both moving and static objects. Furthermore, two patients may have the same quantitative VA whilst having different qualitative VA. In addition the end-point is often difficult to ascertain, with a patient able to identify some optotypes on several different lines.

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A new type of test for VA has been designed to overcome these problems:

The DYOP® (figure 1) is a dynamic segmented optotype that can rotate clockwise or anticlockwise. VA threshold is measured by using DYOPs of constant color, contrast, and speed rotation and decreasing the diameter of the DYOPs until the direction of motion can no longer be recognized. This method solves the problems of literacy, memorizing, and crowding, whilst at the same time enabling a more precise endpoint. In addition there is no limit to the number of DYOPs that can be shown for a given line of VA.


Actions taken
VA measurements with the DYOP have been compared with Landolt C, with the DYOP yielding a clearer endpoint. The DYOP is highly correlated with a standard Sloan LogMAR as well as Sloan acuity chart. It has also been found to obtain similar VA scores for the same refraction values when compared with LogMAR E chart in adults. We are currently carrying out a study of the repeatability, reproducibility and speed of exam, and also assessing the subjective experience of the patients.

Initial results indicate that the DYOP gives good results for and is well tolerated by patients. Given its advantages over Snellen/LogMAR, the DYOP may be a superior VA test. It is possible that after 150 years the time has come to change how we measure VA in the clinic.


Harris P.A., & Keim E. (2015). Validation of the Dyop™ Visual Acuity Test. Invest Ophthalmol Vis Sci.,.56, 3888.

Hayes JR., Tai, YC., Jang, SO. & Sheedy, JE, (2011) Visual acuity with a motion detection target compared to Landolt Rings. Vis Sci Soc.,  11th Annual Meeting 2011, Volume: 2

Muzdalo NV. (2013) The importance of measuring dynamic visual acuity. Coll Antropol. 37 (Suppl1):275-85.

Sum R. & Woo G.C. (2017). Comparison of subjective refraction findings with Dyop® acuity chart and LogMAR E Chart. American Academy of Optometry Annual Meeting, Chicago, USA,. Poster presentation.

Sum R. & Woo G.C. (2016). Dyop® acuity test-application in elderly patients. School of optometry, the Hong Kong Polytechnic University, Hong Kong, China,. Poster presentation.

A Comparison of Dyop Acuity vs. Snellen Tumbling “E” Acuity Visual Screening  

Author: Stephen Meyerowitz, Shemesh Health Solutions


Test results: A Dyop® (or dynamic optotype) is a spinning visual target which uses the strobic detection of the spinning gaps/segments of the ring to measure visual acuity. The Tumbling “E” acuity test is a variation of the Snellen acuity test using only the letter “E” as displayed in four orientations and with a decreasing size. This study evaluated the acuity findings using Dyop and Tumbling “E” acuity charts on each of the subjects with the aim of comparing the two methods.

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Methods: A total of over sixty subjects with ages of approximately between 20 and 60 years were
selected from workers at two South African manufacturing facilities. Tumbling “E” Snellen acuity
tests and then Dyop acuity charts were utilized on a monitor and the subjects were screened for
these visual acuity thresholds at a distance of 3 metres. The subjects were first tested on
Tumbling “E” Acuity by one tester and then immediately tested by another tester on the Dual
Dyop Screening test. The scores were written down and analyzed after all subjects had been
screened. Of critical importance was the ability of the test to screen for individuals with acuity of
6/9.5 or worse in both eyes or 6/14 or worse in one eye (refer/not refer criteria).
Results: There was a high level of correlation between the acuity assessments using the two
charts. There was, however, a disparity in the mean acuity of about ‐0.5 meters (‐0.04 LogMAR
units) with a mean Tumbling “E” acuity of 6/6.4 versus a mean Dyop acuity of 6/5.8. The typical
acuity testing with a Dyop acuity chart also took half as long as the acuity with the Tumbling “E”
acuity chart.

Conclusions: Acuity testing with a Dyop chart is comparable to a Tumbling “E” Snellen chart. The
efficiency (in terms of time) of the Dyop acuity test, however, was typically twice that of the
Tumbling “E” vision chart, with a narrower variance in visual acuity measurements and an
improved level of acuity equivalent to about 0.125 diopter.

Keywords: Dyop® acuity chart, Tumbling “E” vision chart, Snellen acuity chart, visual acuity.

Initial Validation of the Dyop Infant Acuity Test –  Proof-of-Concept Test

Author: Allan Hytowitz – Dyop Vision Associates

Date: October 2020


Test results: The Dyop Infant Acuity Test was used to determine visual acuity of an infant 3.5 months-old (14-weeks). The infant acuity values are based on the documented Dyop acuity values for adults. (A bigger the arc width diameter of a Dyop indicates less visual clarity.) The infant’s basic acuity (Black/White on Gray) was in the range of 44 arc minutes (20/440 or 6/135) to 40 arc minutes (20/375 or 6/115).

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The Dyop test has previously proven to be a more precise and efficient method of measuring visual acuity in
Adults and Children versus the Snellen test. Due to the not yet fully developed nature of the infant visual
system, the significantly more subtle methodology for Adult and Children’s testing is not simple enough. By
implementing a simpler single Dyop with a basic Black/White strobic acuity dynamic stimulus, the Dyop
Infant acuity test should prove to be a precise and efficient methodology of measuring infant vision using the
same metrics and parameters as adult vision and based on identical technology. When used with
color/contrast permutations, the Dyop Infant Acuity Test might also be a diagnostic for potential symptoms of
dyslexia, migraines, and epilepsy. It should also prove to be a far more precise, more efficient, more
convenient, and less expensive method of measuring infant acuity than use of the Teller Acuity Cards for
infant acuity testing.

1. Hytowitz, Allan, Dyop Test Instructions:
2. Harris, PA, and Keim, E. Validation of the Dyop™ Visual Acuity Test. Investigative Ophthalmology & Visual
Science. 2015 Jun 11; 56(7): 3888-
3. Chase C, Dougherty RF, Ray N, Fowler S, Stein J. L/M speed-matching ratio predicts reading in children.
Optom Vis Sci. 2007 Mar;84(3):229-36. doi: 10.1097/OPX.0b013e31803399df. PMID: 17435537.
4. Esposito C, Harris P. Relieve Migraines with Tinted Contact Lenses, Optometry Times. 2015 Jan 15.
5. Drew S, Borsting E, Stark L, Chase C. Chromatic Aberration, Accommodation, and Color Preference in
Asthenopia. Optometry and Vision Science: July 2012 – Volume 89 – Issue 7; p 1059–1067

The Dyop Revolution and Acuity Measurement

Author: Allan Hytowitz, Dyop Vision Associates

Date: 2021

Cyclops –  The World’s Largest Visual Acuity Test

Author: Allan Hytowitz, Dyop Vision Associates

Date: 2010

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