Abstract
Purpose: :
To evaluate the histopathology in donor eyes from patients with LCA.
Methods: :
Eyes were obtained from a 3 year-old male who died from undiagnosed genetic abnormalities through the donor program of the FFB. The eyes were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer within 11 hours postmortem. Eyes were analyzed through the use of macroscopic fundus photography (MF), confocal scanning laser ophthalmoscope (cSLO) and spectral-domain optical coherence tomography (SD-OCT). After that, small areas from the fundus macula and periphery were processed for electron microscopy and indirect immunofluorescence, using specific antibodies to retinal proteins such as rhodopsin, cone arrestin, and RPE65 among others. The content of autofluorescent material was analyzed in epifluorescence. The donor eye was compared to a matched normal eye (3 y.o.) and to additional eyes from another young donor with LCA (11 y.o. female).
Results: :
MF, cSLO and SD-OCT images of LCA eyes revealed atypical retinas lacking distinct morphological detail typically observed using these techniques even in post-mortem eyes. MF images of the LCA eye revealed a "photonegative effect". This effect is punctuated by a hypopigmented macula relative to a hyperpigmented, dark retinal background. cSLO infrared (IR) imaging identified the optic disk and the hypopigmented macula region seen by MF. cSLO autofluorescence (AF) imaging revealed some weak AF signal that was largely devoid of any structural detail compared to the control which clearly showed retinal vasculature and lipofuscin AF background. SD-OCT revealed structural differences in the retina that suggested disorganization of the affected retina, absence of a photoreceptor layer, and degeneration of the choroid in the macular area. Retinal vessels appear to be absent or atrophic in the retina even around the optic nerve. Histologic findings revealed a highly disorganized photoreceptor layer in the macula and periphery. The RPE layer displayed thinning in some regions of the periphery and decreased pigmentation in most areas. In addition, pigmented cells were also observed within the retina. Rods were virtually absent in the affected retina. Cones were present in the macula, but were mostly absent from the retinal periphery. Cone synapses were not observed. Autofluorescent material was greatly reduced in the RPE in all areas studied.
Conclusions: :
These patients showed an absence of rods and cones in the periphery. In the macula, a few cone photoreceptors were present, albeit highly disorganized.
Keywords: retinal degenerations: cell biology • pathology: human • retina