Morphometric analysis of the extramacular retina from postmortem eyes withretinitis pigmentosa

PURPOSE. To evaluate the degree of inner retinal preservation in the extram acular regions of postmortem retinitis pigmentosa (RP) eyes. METHODS. Eighteen RP retinas and 11 age-matched healthy retinas were sectio ned for morphometric analysis by light microscopy. The 18 RP retinas were c lassified by disease severity and mode of inheritance. Cell nuclei in the o uter nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell laye r (GCL) were counted in adjacent 125-mu m segments from an area spanning th e region between 4 mm and 10 mm from the fovea. RESULTS. A mixed-effects model showed a decrease in mean cell counts for ea ch of the cell layers when the severity groups and inheritance types compar ed with those of control retinas. There was no statistically significant di fference in the number of nuclei preserved in the INL and GCL in the modera te group compared with the severe group. Results from the INL counts for th e different inheritance types of RP showed a higher overall mean percentage of cells was preserved for the autosomal dominant RP (ADRP) group when com pared with the X-linked (XLRP) and simplex RP groups. Analysis of the GCL c ounts revealed significantly more counts only in the ADRP group compared wi th the XLRP group; the other group comparisons were not significant. CONCLUSIONS. Retinitis pigmentosa results in, cell loss in all retinal laye rs, with the most profound loss in the ONL, followed by the GCL and then th e INL. The preservation of the INL and GCL in the extramacular region is le ss than that previously reported for the macular region of the same retinas .