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Purpose The purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT). Methods In the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation. Results At baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT. Conclusions Phoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.

Vergence eye movements are the inward and outward rotation of the eyes responsible for binocular coordination. While studies have mapped and investigated the neural substrates of vergence, it is not well understood whether vergence eye movements evoke the blood oxygen level-dependent signal reliably in separate experimental visits. The test–retest reliability of stimulus-induced vergence eye movement tasks during a functional magnetic resonance imaging (fMRI) experiment is important for future randomized clinical trials (RCTs). In this study, we established region of interest (ROI) masks for the vergence neural circuit. Twenty-seven binocularly normal young adults participated in two functional imaging sessions measured on different days on the same 3T Siemens scanner. The fMRI experiments used a block design of sustained visual fixation and rest blocks interleaved between task blocks that stimulated eight or four vergence eye movements. The test–retest reliability of task-activation was assessed using the intraclass correlation coefficient (ICC), and that of spatial extent was assessed using the Dice coefficient. Functional activation during the vergence eye movement task of eight movements compared to rest was repeatable within the primary visual cortex (ICC = 0.8), parietal eye fields (ICC = 0.6), supplementary eye field (ICC = 0.5), frontal eye fields (ICC = 0.5), and oculomotor vermis (ICC = 0.6). The results demonstrate significant test–retest reliability in the ROIs of the vergence neural substrates for functional activation magnitude and spatial extent using the stimulus protocol of a task block stimulating eight vergence eye movements compared to sustained fixation. These ROIs can be used in future longitudinal RCTs to study patient populations with vergence dysfunctions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12264-019-00455-9) contains supplementary material, which is available to authorized users.

PURPOSE: To describe the design and methodology of the Convergence Insufficiency Neuro-mechanism in Adult Population Study (CINAPS), the first randomized clinical trial (RCT) studying young adults with symptomatic convergence insufficiency (CI) using a combination of traditional clinical tests, objective eye movement recordings, and functional brain activities as outcome measures. METHODS: In this double-masked RCT, binocularly normal controls (BNC) (N=50) and CI patients (N=50) are randomized into office-based vergence/accommodative therapy (OBVAT) or office-based placebo therapy (OBPT). Outcome measures included clinical signs and symptoms, phoria adaptation, forced fixation disparity curves, binocular rivalry, vergence and saccadic objective eye movements, and task-induced functional brain activities. This study is registered on ClinicalTrials.gov . RESULTS: No significant baseline differences are observed between the BNC (p>0.4) or CI (p>0.3) participants assigned to OBVAT or OBPT for age, near point of convergence (NPC), positive fusional vergence (PFV), phoria at distance and near, amplitude of accommodation, or the Convergence Insufficiency Symptom Survey (CISS). Significant differences are observed between the CI and BNC cohorts at baseline measurements for NPC, PFV, difference in phoria from far to near, amplitude of accommodation, and CISS (p

Office-Based Vergence/Accommodative Therapy (OBVAT) is an effective treatment for convergence insufficiency (CI) and remediates symptoms in about 75% of patients. Hence, the study of CI patients can serve as a systems-level model to understand the neural mechanisms evoked from rehabilitation. Symptomatic young adult CI patients (N=25) participated in 12 hours of OBVAT and were compared to 25 binocularly normal controls (BNC) using unpaired t-tests. CI patients have significantly lower near point of convergence and positive fusional vergence and were more symptomatic compared to BNC (p; 0.0001). Using paired t-tests, significant differences (p; 0.0001) were observed between CI patients' baseline and post-OBVAT measurements where the near point of convergence decreased, positive fusional vergence increased, and the results from the Convergence Insufficiency Symptom Survey (CISS) decreased. Using paired t-tests, the mean beta weights of the functional activity significantly increased for the frontal eye fields (p; 0.01) and the oculomotor vermis (p; 0.05) for CI patients post-OBVAT compared to baseline measurements. These data demonstrate that OBVAT increases functional activity within the brain and improves clinical function and visual symptoms in CI patients.

This study was designed to identify the neural substrates activated during a phoria adaptation task using functional magnetic resonance imaging (MRI) in young adults with normal binocular vision and to test the repeatability of the fMRI measurements for this protocol. The phoria adaptation task consisted of a block protocol of 90 seconds of near visual crossed fixation followed by 90 seconds of far visual uncrossed fixation, repeated three times; the data were collected during two different experimental sessions. Results showed that the oculomotor vermis, cuneus, and primary visual cortex had the greatest functional activity within the regions of interest studied when stimulated by the phoria adaptation task. The oculomotor vermis functional activity had an intraclass correlation coefficient (ICC) of 0.3, whereas the bilateral cuneus and primary visual cortex had good ICC results of greater than 0.6. These results suggest that the sustained visual fixation task described within this study reliably activates the neural substrates of phoria adaptation. This protocol establishes a methodology that can be used in future longitudinal studies investigating therapeutic interventions that may modify phoria adaptation.

Visual attention is an important aspect of everyday life, which can be incorporated in the assessment of many diagnoses. Another important characteristic of visual attention is that it can be improved via therapeutic interventions. Fifteen subjects with normal binocular vision were presented with visual distractor stimuli at various spatial locations while initiating disparity vergence eye movements (inward or outward rotation of eyes) within a haploscope system. First, a stationary distractor stimulus was presented in either the far, middle, or near visual spaces while the subjects were instructed to follow a target stimulus that was either stationary, converging (moving toward subject), or diverging (moving away from subject). For the second experiment, a dynamic distractor stimulus within the far, middle, or near visual space that was converging or diverging was presented while the target stimulus was also converging or diverging. The subjects were instructed to visually follow the target stimulus and ignore the distractor stimulus. The vergence responses had a final vergence angle between the target and distractor stimuli which has been termed a center of gravity (CoG) effect. Statistically significant differences were observed between the convergence peak velocities (p < 0.001) and response amplitudes (p < 0.001) comparing responses without distractors to responses with the presence of a vergence distractor. The results support that vergence eye movements are influenced by visual distractors, which is similar to how distractors influence saccadic eye movements. The influence of visual distractors within vergence eye movements may be useful to assess binocular dysfunction and visual distraction which are common post brain injury.