Luminance Thresholds and Their Correlation With Retinal Structure in X-Linked Retinoschisis

PURPOSE.To provide a comprehensive analysis of light- and dark-adapted luminancethresholds and their associations with retinal structure in X-linked retinoschisis (XLRS).METHODS.Nine subjects with XLRS and 10 visually-normal individuals participated.Threshold was measured at 15 locations along the horizontal meridian of the visualfield at several adaptation levels (5x10-5to 50 cd/m2) after dark-adaptation. The rela-tionship between threshold and adaptation level across the field was described using astandard "threshold-versus-illuminance" model. Optical coherence tomography imageswere obtained and segmented to quantify outer nuclear layer (ONL+) and outer segment(OS+) thickness. A linear structure-function model was used to describe the relationshipbetween threshold and the product of ONL+and OS+thickness.RESULTS.For peripheral field measurements, thresholds were generally normal for mostsubjects with XLRS. All subjects had perifoveal and parafoveal threshold elevations underdark-adapted and high illuminance conditions, with thresholds at moderate illuminancesbeing closer to normal. For foveal measurements, seven of nine subjects with XLRShad normal dark-adapted thresholds, and all had abnormally elevated high illuminancethresholds. Threshold-versus-illuminance curves in the fovea, parafovea, and perifoveawere abnormally steep for subjects with XLRS, appearing similar to the normal peripheralfield shape. Under both dark- and light-adapted conditions, threshold was predicted byONL+xOS+thickness at nearly all field locations.CONCLUSIONS.Threshold elevation in XLRS is complex, depending on both the adaptationlevel and the visual field location. The pattern of threshold-versus-illuminance suggeststhat macular function in XLRS is similar to the periphery of controls.