Persisting retinal ganglion cell axons in blind atrophic human eyes

Purpose: To evaluate enucleated blind atrophic human eyes for the persistence of retinal ganglion cell axons. This might be of relevance for contact to an electronic prosthesis in the future. Methods: A total of 2460 surgically enucleated eyes were studied in our ophthalmic pathology laboratory between 1981 and 1996. All eyes histopathologically classified as displaying ocular atrophy with shrinkage (axial length less than or equal to 21 mm) and with an available optic nerve cross section without crush artifacts were selected. Only eyes of patients older than 18 years and without light perception prior to enucleation were analyzed (n=57). Optic nerve fibers were counted under light microscopy in semithin optic nerve sections. Results: Axons amounting to more than 5% of the mean axon count in normal eyes (>57,950 axons) were detected in 24 (42%) of 57 optic nerves, and an axon count more than 10% of the mean normal count (>115,900 axons) was found in 15 (26%) of 57 optic nerves. The retina was at least partially detached and disoriented in all 57 eyes. The inner nuclear layer was detectable in 46 (81%) of eyes, whereas the outer nuclear layer was present in 13 (23%) of 57 eyes; photoreceptors were detectable by light microscopy in only 3 eyes (5%), Intraocular calcification due to osseous metaplasia of the retinal pigment epithelium was present in 62% of the globes. Conclusion: Blind atrophic human eyes reveal persisting retinal ganglion cell axons. Whether direct electrical stimulation of these axons or their retinal ganglion cells has the potential to create visual information remains to be studied.