The Convergence Insufficiency Neuro-mechanism in Adult Population Study (CINAPS) Randomized Clinical Trial: Design, Methods, and Clinical Data

Abstract

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 NCT03593031.Results: No significant baseline differences are observed between the BNC (p > .4) or CI (p > .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 < .001). For the CI patients, 26% had a comorbidity of accommodation insufficiency, and 16% self-reported ADHD.Conclusion: Features of the study design include the following: standardized diagnostic and office-based therapeutic intervention, placebo treatment arm, masked clinical outcome examinations, objective eye movement recordings, functional imaging, phoria adaptation, fixation disparity curves and binocular rivalry measurements.

Keywords: Convergence insufficiency; eye movement; functional MRI; randomized clinical trial; vergence.

Conflict of interest statement

Declaration of interest statement

No potential conflict of interest is reported by the authors.

Figures

Figure 1:

Study Design

Figure 2

A: Instrumentation and 2B: Visual Stimuli for the Objective Eye Movement Experiments. SM = Stimulus Monitor; M = Mirror; LE =Left Eye; RE = Right

Figure 3

A: Eye movement data analysis showing latency, time to peak velocity, peak velocity and final amplitude of eye movements for position trace as a function of time blue line) and velocity as a function of time (red line). 3B: Phase plane analysis showing raw eye movement trace (blue line) and 2nd order polynomial fit (green line). The nonzero root is the fusion initiating component of disparity vergence.

Figure 4

A: Functional MRI experimental set-up. 4B: Timing Sequence diagram of rest, FLO (few) stimuli, and FHO (many) stimuli blocks. 4C: Visual stimuli showing the difference of far and near disparity, 4D: 3D representation of visual perception of visual stimulus converging and diverging.

Figure 5:

Baseline clinical signs and symptoms used to diagnosis patients with CI (gray bars) compared to baseline data for BNC (black bars). 5A: Near point of convergence. 5B: Positive Fusional Vergence. 5C: Difference in near and far phoria where on average participants are more exophoric at near compared to far. 5D: Visual symptoms documented by CISS.