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The Crystal Key VR game is designed to provide an engaging experience to enhance eye coordination skills. However, this game is not a medical device and should not be considered as a replacement for professional medical advice, diagnosis, or treatment.


If you have any concerns about your vision or eye health, we strongly recommend seeking advice from a qualified eye care professional.  To find an optometrist who specializes in binocular vision, please visit the College of Optometrists in Vision Development at  They can provide a comprehensive evaluation of your visual abilities and determine whether vision therapy or other medical interventions are necessary.

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Research and Publications

The Role of Visual Factors in Dyslexia

Arni Kristjansson, PhD and 

Heida Maria Sigurdardottir

J Cogn. 2023; 6(1):31.


Emphasizes the need to recognize that dyslexia does not have a unitary “cause,” but is instead the result of many interacting factors – including several aspects of vision. Cites over 200 articles in supporting the multifaceted causality, from auditory to attention. States that more research needs to be done, and that some studies have tended to diminish the role of hearing and some have elevated the role of vision. After all, the eyes must transmit information on a page to the brain, and to the extent that that is not done efficiently and with accuracy, symptoms of dyslexia can occur.

Fixing My Gaze: A Scientist's Journey into Seeing in Three Dimensions

Susan Barry, PhD

Basic Books, August 2010


Dubbed "Stereo Sue" by renowned neurologist Oliver Sacks, Dr Susan Barry shares her remarkable journey to treat her strabismus and achieve depth perception.  Dr Barry is a neuroscientist who explains concepts of vision and neural plasticity from the point of view of a scientist and a patient.

A Randomized Clinical Trial of Treatments for Convergence Insufficiency in Children


In this pilot study, vision therapy/orthoptics was more effective than pencil push-ups or placebo vision therapy/orthoptics in reducing symptoms and improving signs of convergence insufficiency in children 9 to 18 years of age. Neither pencil push-ups nor placebo vision therapy/orthoptics was effective in improving either symptoms or signs associated with convergence insufficiency.

Effectiveness of Vision Therapy for Children With Symptomatic Convergence Insufficiency With or Without Attention Deficit Hyperactivity Disorder

Sun Haeng Lee, PhD,

Chun Man Park, PhD

Sang Chul Park, OD, PhD, FCOVD-A, 

Willis Clem Maples, OD, MS, FCOVD,

Hoy Sun Shin, OD, PhD, FCOVD-A

Vision Dev Rehab 2015; 1(3):229-242


A total of 1,090 children attending grades 1 to 6 in one primary school completed a visual symptom checklist. Their parents also completed a checklist of ADHD symptoms.  A group of symptomatic students were given full eye exams, then selected into either a therapy group or control group.  Results: Visual symptoms and ADHD symptoms were negatively correlated with academic scores for both reading and mathematics. Children with ADHD symptoms were 9-times more likely to have visual symptoms than children without ADHD symptoms. Likewise, ADHD children were 30-times more likely to have CI than children without ADHD symptoms. Visual and ADHD symptom scores, and objective visual measures were statistically improved after 12 weeks of (vision) therapy.

Selected research studies in visual skills and human performance by Eyes in Sync Founders

The 3D Learner – Transform Stress to Outrageous Success for your Child

Mira and Mark Halpert


The 3D Learner method is based on a wide-ranging, personalized approach for each child. The book emphasizes the fundamental role of visual and auditory processing speed and accuracy in maximizing efficient learning; one section is devoted to this (pp 33-44). There are plenty of real-life examples of improvement in academic and sports performance among their clients, and information on how to assess a child's learning needs.

Improving visual skills:  A new internet application.


The object of this paper is to describe an internet-based system and technique for improving performance on visuomotor tasks.

Visual skills of poor readers in high school

Grisham DG, Powers MK, Riles PR

Optometry, 2007;78:542-549. 


Visual skills and visual acuity were measured in 461 students (average age 15.4 years) in 4 California high schools within the same school district. Participating students had been identified by their schools as poor readers.  In this sample, 80% of the students were found to be inadequate or weak in 1 or more of the following visual skills: binocular fusion ranges at near, accommodative facility, and convergence near point.  In contrast, only 17% had deficient visual acuity—20/40 or worse in 1 eye—the standard model of deficiency for school vision screenings.

Saccadic tracking skills of poor readers in high school

Powers MK, Grisham DG, Riles PR

Optometry, 2008;79:228-234


The saccadic eye movement efficiency of 684 ninth grade students, identified as poor readers in 5 California high schools, was quantified using the Developmental Eye Movement test.  Overall, fewer than 10% of students scored above the 50th percentile for eighth grade.  The results indicate that poor readers in high school may be at high risk for poor saccadic tracking skill.

 Binocular vision problems in refractive surgery patients: Vision therapy case reports


Patients complaining of distance blur following refractive surgery may have undiagnosed binocular vision problems. Vision therapy incorporating an internet orthoptics component improved convergence ability in the cases reported here, and most patients reported symptomatic relief.

Vision and athletic performance:  Data from agility dogs


To explore the relationship between vision problems and athletic performance, we measured refractive error and binocular vision in highly trained canine athletes. 210 dogs were recruited via word of mouth and examined at agility events in California, Texas, and Washington for cover test near and far, prism bar vergence near and far, Hirschberg and Bruckner tests for eye alignment, and retinoscopy.  Refractive error and binocular problems can affect jumping behavior in highly trained canine athletes.   The results support the importance of vision, and in particular binocular and refractive problems, to athletic performance for humans as well as canines.

Advances in measuring visual symptoms and visual skills


Optometry, survey, and reading assessment data are evaluated in a common frame of reference. Thirty-three students performed vergence and tracking exercises in about 12 to 38 sessions each involving a sequence of five computerized training modules.   Paired comparison t-tests of early and late measures show significant gains in vision quality. Two regression models predict reading scores on the basis of vision data. Results support further study of how training in Functional Binocular Vision might contribute to improved outcomes in reading education.

Physical and psychological measures underlying functional binocular vision


Visual optometry, survey ratings, and reading assessment data are evaluated in a common frame of reference, with the aim of determining the extent to which an overall model of functional binocular vision might be feasible.  Preliminary results include estimates of optometric, survey, and assessment results in a common multidimensional framework, and regression predictions of reading fluency from visual skills and acuity optometry, and a survey of convergence insufficiency symptoms.

Privacy Policy: The Crystal Key application

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Eyes in Sync Inc

November 25, 2023

1. No user data is collected by The Crystal Key.

2. Meta may collect information which Eyes in Sync may access, but if so it will be the type of information that is essential for running any app on the Meta App Store.

3. However, The Crystal Key will not access any information collected by Meta.

4. If you are concerned about the nature of personal data collected by Meta and how it may be used, you should refer to the Meta Store Privacy Policy at

5. The Eyes in Sync Privacy Policy for The Crystal Key (this document) can be found at

6. Any questions regarding this policy can be sent to us at

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