Distance perception in mild traumatic brain injury (mTBI).

BACKGROUND: The purpose of this study was to assess monocular and binocular distance perception, and stereoacuity, in individuals with mild traumatic brain injury (mTBI) who reported the symptom of "poor depth perception"; METHODS: Ten patients with mTBI were tested and compared with ten visually-normal asymptomatic individuals in the following areas: perceived distance, stereoacuity at distance (3 meters) and near (40 cm), and a 9-item 5-point rating-scale questionnaire related to distance perception. Distance perception was assessed under monocular and binocular viewing conditions in both clustered and isolated static environments. Magnitude estimation was used to obtain the distance perception response function of physical versus perceived distance using common objects positioned at distances of 0.77 to 12.84 meters. RESULTS: The mean distance perception response function slopes were not significantly different in the two groups for any of the test conditions. Stereoacuity (sec arc) was slightly reduced at both near and distance in the individuals with mTBI (36 ± 24.58 and 84 ± 68.34, respectively) as compared with the normal subjects (20 ± 0 and 51 ± 9.93, respectively). The mTBI group mean symptom score was 3.24 ± 0.26 indicating a moderate problematic level; CONCLUSIONS: Similarity of the mean distance response functions in the mTBI group under monocular and binocular viewing conditions suggested that their misperception of distance was not due to a "binocular vergence" problem. Similarly, the slightly reduced stereoacuity in the mTBI group was not sufficient to explain their symptom of "poor depth perception." Thus, it is speculated that this problem reflects a higher-level cortical perceptual phenomenon related to diffuse brain damage in areas dealing with visuo-spatial mapping.

Vision therapy for basic exotropia in adults: 2 case studies.

BACKGROUND: Basic exotropia accounts for approximately 50% of all intermittent exotropias. Many clinicians view treating these patients, especially adults with childhood-onset exotropia, as challenging. Conflicting opinions still exist regarding prescribing any treatment for adult strabismics, including surgical realignment and optometric vision therapy (VT). CASE REPORTS: Two cases are discussed, both of which are adult patients with moderate-size intermittent exotropia of the basic type who presented with asthenopia, headaches, and/or diplopia. Twenty to 30 in-office VT sessions were recommended to reduce the magnitude and frequency of the deviation as well as improve their binocularity and decrease their symptoms. After completing VT, both patients became phoric for all distances, had normal vergence ability, and had normal near points of convergence. In the second case, the long-term outcome was evaluated 5 years post-therapy. CONCLUSION: Optometric VT was highly successful in both patients with childhood intermittent exotropia of the basic type. Most important, optometric VT eliminated the patients' symptoms of asthenopia and diplopia without the need for surgery.