A model of focal Light Emitting Diode‐Induced photoreceptor degeneration in pigmented mice

Abstract

AbstractPurposeTo develop a new model of focal Light Emitting Diode‐Induced photoreceptor degeneration in adult pigmented mice.MethodsIn adult female C57 mice (20 g) dark adapted, the left eye was dilated with clycopentolate. Mice were anesthetized and exposed during 45 seconds to a blue (400 nm) light emitting diode (LED) (500 lux) placed 2 mm in front of the corneal apex. Animals were sacrificed 1, 3, 5 or 7 days (n = 6 each) after LED exposure, their retinas were dissected, prepared as whole‐mounts, doubly immunolabeled with antibodies against arrestin and Iba‐1 to identify cones and microglial cells and examined under fluorescence and confocal microscopy. Spectral Domain Optical Coherence Tomography (SD‐OCT, Spectralis, Heidelberg) was used to examine longitudinally in vivo the retinal thickness in both eyes at the different intervals after LED exposure.ResultsSD‐OCT eye fundus imaging with infrared reflectance allowed to document in vivo in the supero‐temporal quadrant of the LED exposed retina a rounded less reflective area that showed progressive thinning of the outer retina (approximately 75%) from 1–7 days after LED exposure. This light‐sensitive area showed by 1 day shortened cone outer segments, by 3 days a clear diminution of cone density, and by 7 days additional cone loss. The outer layers of the retina in the light‐sensitive area showed 1 day after LED exposure Iba1+ cells in the center that remained in the same location for 5–7 days. The morphology of these Iba1+ cells was dendritic at 1 day, became ameboid at 3 days and dendritic again at 5–7 days.ConclusionsLED can be used to produce a focal phototoxic lesion in the retina. The focal lesion shows decreased retinal thickness, cone densities and an activation of microglial cells in the outer retinal layers.