Homonymous visual field defects (HVFDs) have a prevalence of 0.8% in the general population older than 49 years.¹ They are caused by lesions in the postchiasmal visual pathways, primarily due to strokes and, to a lesser extent, trauma and tumors.² Patients with HVFDs have difficulty detecting obstacles on the side of the loss, resulting in impaired mobility. The main vision-based rehabilitation strategies include provision of optical aids (eg, prismatic corrections to expand or relocate the visual field)³; visual search training to improve the efficiency of visual exploration on the side of the loss^4-7; and visual restoration training to recover lost visual function.⁸ Herein we report, to our knowledge, the first multicenter evaluation of a novel prismatic device to expand visual fields for patients with HVFDs.

Purpose.: This study was designed to examine the effect of homonymous hemianopia (HH) on detection of pedestrian figures in multiple realistic and hazardous situations within the controlled environment of a driving simulator. Methods.: Twelve people with complete HH and without visual neglect or cognitive decline and 12 matched (age, sex, and years of driving experience) normally sighted (NV) drivers participated. They drove predetermined city and rural highway routes (total, 120 minutes) during which pedestrian figures appeared at random intervals along the roadway (R-Peds; n = 144) and at intersections (I-Peds; n = 10). Detection rates and response times were derived from participant horn presses. Results.: Drivers with HH exhibited significantly (P < 0.001) lower R-Ped detection rates on the blind side than did NV drivers (range, 6%–100%). Detection of I-Peds on the blind side was also poor (8%–55%). Age and blind-side detection rates correlated negatively (Spearman r = −0.71, P = 0.009). Although blind-side response times of drivers with HH were significantly (P < 0.001) longer than those of NV drivers, most were within a commonly used 2.5-second guideline. Conclusions.: Most participants with HH had blind-side detection rates that seem incompatible with safe driving; however, the relationship of our simulator detection performance measures to on-road performance has yet to be established. In determining fitness to drive for people with HH, the results underscore the importance of individualized assessments including evaluations of blind-side hazard detection.

Although prismatic corrections have been used in the rehabilitation of homonymous hemianopia (HH) for at least the last 80 years,¹ evidence for their effectiveness is almost exclusively based on anecdotal case reports^2-4 and open-label evaluations without a control condition.^5-10 Recent reviews of a range of interventions for patients with homonymous visual field loss have underscored the need for randomized controlled clinical trials in this area.^11-14 To the best of our knowledge, there have only been 3 controlled studies^15-17 of prismatic devices for HH, and each had substantial limitations (eTable 1 in the eAppendix in the Supplement).

Background:Previous studies have compared low vision reading performance at optimal task illuminance and consulting room illuminance (500 to 600 lux). However, it is uncertain the extent to which low vision reading performance can be improved when task illumination is increased from levels more representative of those found in the typical living room (50 lux) to levels likely to maximise performance. Methods:Reading performance of 20 subjects with age‐related macular degeneration (AMD) was assessed for a range of print sizes using sentence reading charts at six levels of task illuminance (50 to 5,000 lux). Subjects read without low vision devices. Results:Sentence reading acuity and critical print size improved by a factor of two over the 50 to 5,000 lux range, while maximum reading rate improved by a factor of 1.4. For the majority of subjects (70 per cent), the optimal task illuminance (determined objectively) was higher (median 3,500 lux) than the subjectively preferred task illuminance (median 2,450 lux). Reading performance was significantly better at the optimal illuminance than at illuminances equivalent to those found in the domestic environment (50 lux) or consulting room (600 lux). Conclusions:The majority of AMD patients will require task illumination of at least 2,000 lux to maximise reading performance. Optimal illumination should be determined individually for each patient using both objective measures of performance, such as reading acuity, and subjective assessments of visual comfort.