WP 2.3: Using pulsed light as a diagnosis tool in eyes with cataract

Light scatter introduced by cataract can mask early functional changes in standard clinical tests using visible light. However, infrared light is less affected by scattering in ocular media than visible wavelengths. This research project therefore develops a non-invasive perimeter that uses pulsed infrared light (1064 nm) to measure retinal luminance sensitivity at different eccentricities. Unlike conventional perimetry, this infrared approach remains reliable in the presence of cataracts, enabling functional assessment in patient groups often excluded from standard examination.

The instrument exploits two-photon absorption in the rhodopsin of the photoreceptors, making infrared stimuli perceived as visible green light. The instrument integrates a picosecond pulsed infrared source with precise power control, a scanning system for testing multiple eccentricities, a system for compensating refractive error, and fixation and pupil tracking for accurate stimulus delivery. After dark adaptation, small stimuli are presented at central and near peripheral locations and thresholds are estimated with an adaptive procedure, producing a three-dimensional map of retinal sensitivity. Next steps are pilot studies in older adults, including those with cataract, to establish clinical feasibility as a robust tool for functional retinal sensitivity assessment.