In vivo characterization of photoreceptor and vascular blood cell response to laser-induced trauma in the small eye model

Abstract

The small eye model of the snake permits the imaging of the photoreceptor layer as well as the retinal vasculature and individual blood cells when imaged with a confocal scanning laser ophthalmoscope (CSLO). Snake photoreceptors can be imaged down to their internal mode structure, providing comparison between normal and laser damaged photoreceptor internal mode structure. Moving the CSLO into anterior retina provides imaging of the retinal vasculature and individual blood cell response to acute laser photoreceptor injury. Alteration in individual blood cell activity is readily apparent within seconds post laser exposure, as blood cells cumulate and show charactistic "sticky cell" leukocyte behavior. At energy levels near thermal threshold damage levels, damage down to a single photoreceptor is detectable within 24 hours post exposure with near IR laser imaging sources (780 nm), and visualization of internal mode structure disruption mediated at the outer segment of the photoreceptor. Utilization of in vivo biochemical tags for oxidative stress demonstrates that thermal/mechanical and non-thermal mechanisms of photoreceptor damage can reside in adjacent photoceptors. Preliminary studies with actin based biochemical markers indicate the presence of actin in both the photoreceptor and retinal nerve fiber layer, suggesting the possibility of both active recovery and support processes.