Abstract
Purpose: :
To assess the effects of OBVR on clinical and laboratory oculomotor parameters, and visual attention, in an individual with mTBI.
Methods: :
A 16-year-old female patient presented with reading difficulty, focusing problems, and poor attention, along with frequent headaches and eyestrain, following a motor vehicle accident. Brain scans (CT and MRI) and visual-evoked potential (VEP) responses were unremarkable. Oculomotor parameters were assessed using standard clinical and laboratory test procedures before and after 6 months of OBVR (combined in-office and home; 50 hrs combined total; emphasis on blur and vergence-driven accommodation). Near reading spectacles (+1 D) were also prescribed. Accommodative dynamics (2D step; monocular) were assessed objectively using the WAM-5500 open-field autorefractor (5Hz sampling rate). In addition, visual attention was assessed objectively with the VEP (DIOPSYS Inc.; alpha band power spectrum; 10 Hz component). The ratio of eyes-closed to eyes-open conditions was compared, with > 2.0 being normal. It was also assessed subjectively using the clinical Visual Search and Attention Test (VSAT).
Results: :
Before OBVR, the clinical binocular vision examination revealed reduced accommodative amplitude (D) [OD/OS/OU: 7.6/7.1/9] and decreased accommodative dynamic facility (cycles/min) [OD/OS/OU: 5/5.5/7]. Objective recordings of accommodative dynamics found markedly reduced peak velocity (~5°/sec) with concomitantly increased time constant (~400 msec) and increased steady-state (SS) response variability (~±0.23D) for both increasing and decreasing accommodation. After OBVR, marked improvement was found in the accommodative amplitude (D) [OD/OS/OU:10.5/11/12.5], and accommodative dynamic facility (cycles/min) [OD/OS/OU: 14.5/15.5/7.5]. These clinical findings were consistent with an improvement in accommodative dynamics as evident from increased peak velocity (9°/sec) with concomitant normalization in time constant (~250 msec). Steady-state response variability (~0.08-0.1D) decreased markedly. The objectively-based attention ratio increased by ~60% following OBVR (2.96 versus 4.7). Similarly, the VSAT percentile increased.
Conclusions: :
Normalization of clinical and laboratory measures of accommodation following OBVR demonstrates robust oculomotor learning effects. Similarly, the objective and subjective visual attention test results suggest increased attentional capabilities during the OBVR. These results were consistent with the reduction in near-vision symptoms.
Keywords: eye movements • accommodation • neuro-ophthalmology: cortical function/rehabilitation