Abstract
Purpose:
About 30% of population may experience problems of binocular vision related to vergence insufficiency. Rehabilitation of vergence is mostly based on push-up exercises or use of prisms. We have developed a real space visual-acoustic rehabilitation device (patent US 8851669). We aim to validate its clinical efficiency.
Methods:
Nineteen students (20 to 27 years old) underwent ophthalmologic and orthoptic examination; 8 of them were diagnosed for vergence disorders (high CISS scores, see CITT study 2009).<br /> All subjects performed a vergence test with video-oculography (Eyee See Cam). Subjects with vergence disorders performed 5 sessions of vergence rehabilitation 30 min each, over 5 weeks. The vergence test was repeated 1 month after the rehabilitation.<br /> Subjects were seated in front of the trapezoid tablet composed of LEDs along the median plane.<br /> Vergence test: twenty convergence and twenty divergence eye movements were randomly interleaved starting always from an LED at 40 cm and going to an LED at 20cm or 150 cm.<br /> Vergence rehabilitation protocol: convergence trials always started by fixating (for 1000 - 1600 ms) an LED at 150 cm; the target LED was presented at 90cm or 23 cm for 1300 ms after stepping for 200 ms at a distance 20% shorter (double step paradigm); the two types of trials were randomly interleaved. Subjects performed a total of 2200 movements.
Results:
In healthy latency was 194 vs 203ms for convergence vs divergence; the gain was 0.97 vs 0.76, and mean velocity 26°/s vs 16°/s. Subjects with vergence disorders showed lower gain (0.71 vs 0.54), significantly higher variability for convergence gain, and significantly lower mean velocity (22°/s vs 13°/s). After the 5 sessions of rehabilitation we observed: significant reduction of latency (dropping to 155ms vs 181ms for convergence and divergence); the gain increased significantly for convergence (1.0) and to a less extent for divergence (0.85). Moreover, variability of latency, gain and mean velocity decreased significantly, to values even lower than those from healthy subjects. The CISS decreased significantly.
Conclusions:
This research based device allows objective evaluation of vergence disorders and efficient rehabilitation, leading to normalization of vergence. The efficiency is due to regular and frequent timing of vergence trials with a double step paradigm, a widely established method for saccade adaptation in research that we now extend for clinical use in patients.