Illumination and reading performance in age-related macular degeneration.
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.