Convergence insufficiency (CI), a prevalent binocular vision disorder in adults and children, is characterized by greater exophoria at near than at distance, reduced fusional convergence amplitude, receded near point of convergence, and a reduced accommodative convergence over accommodation ratio (AC/A). CI is associated with symptoms that include double/blurred vision, eyestrain, and headaches when engaged in reading or other near work, thus interfering with activities of daily living. The recent NEI/NIH multi-center randomized clinical trial, the Convergence Insufficiency Treatment Trial (CITT), demonstrated the effectiveness of Office-Based Vergence and Accommodative Therapy with home reinforcement (OBVAT) for CI, reporting 73% of patients have sustained improvements of vision function and symptoms. Our team published the first fMRI neural substrate data evoked using convergence eye movements in CI patients before and then post- OBVAT. Our results support that with the reduction of visual symptoms, the following were observed: 1) an increase in the percent signal change of functional activity in the frontal eye fields, posterior parietal cortex and the cerebellar vermis, 2) an increase in convergence peak velocity, 3) a decrease in the near point of convergence, 4) an increase in positive fusional amplitude, and 5) a reduction in the amount of exophoria at near.5 The aims of our current proposal are to test the following two hypotheses as potential underlying mechanisms of CI that may be improved post OBVAT: 1) a reduced ability to adapt vergence in near and far space via the 'slow'component of vergence and 2) a reduced ability to quickly diminish disparity error via the 'fast'component of vergence. Not only will our quantitative methods integrated with established CITT standards address important questions about potential mechanisms causing CI, our proposal seeks to identify how a validated vergence therapy may remediate symptoms. Our proposal will determine whether either of these two potential mechanisms are causing CI by quantifying the following: 1) rate and magnitude of phoria adaptation, 2) forced vergence fixation disparity curves, 3) peak velocity of convergence eye movements (studying visual cues such as disparity, accommodation and proximal stimuli in isolation and combination), and 4) the functional activity of the fast and slow vergence neural substrates prior to, and then after, OBVAT. The assembled study team is particularly knowledgeable in terms of OBVAT, convergence insufficiency, optometry, vision science, oculomotor research, functional imaging, modeling and statistics with the necessary resources to successfully complete both aims of this study. Results from our project's aims can lead to targeted treatments with improved success rates, potentially reducing the time to remediate symptoms, and ultimately reducing health care costs.

Public Health Relevance

Convergence insufficiency (CI) is a prevalent binocular vision disorder with symptoms that include double/blurred vision, eyestrain, and headaches when engaged in reading or other near work that negatively impacts activities of daily living. CI is present in 4% of the population where approximately 27% of CI patients do not improve even with validated therapy. Our project studies two potential mechanisms causing CI which may be improved via validated therapy by quantifying phoria adaptation, neural substrates and behavioral eye movements. This knowledge can lead to targeted therapeutic interventions, improved success rates, reduction in the time to remediation, and reduced healthcare costs.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
1R01EY023261-01A1
Application #
8691212
Study Section
Special Emphasis Panel (SPC)
Program Officer
Araj, Houmam H
Project Start
2014-04-01
Project End
2019-03-31
Budget Start
2014-04-01
Budget End
2015-03-31
Support Year
1
Fiscal Year
2014
Total Cost
$380,919
Indirect Cost
$126,581
Name
Rutgers University
Department
Biomedical Engineering
Type
Schools of Engineering
DUNS #
075162990
City
Newark
State
NJ
Country
United States
Zip Code
07102