Paraphenylenediamine (PPD) stain of (A) age-matched normal optic nerve, (B) age-matched RP optic nerve, (C) patient's left optic nerve, and (D) patient's right optic nerve (the implant eye). PPD highlights the myelinated axons. The patient's right optic nerve demonstrates a significant amount of atrophy when compared to the left optic nerve. Atrophy is apparent by the increased connective tissue between nerve fascicles, decrease in total number of axons, and decreased overall size of the patient's right optic nerve. The temporal quadrant appears to have the greatest number of preserved axons within the right optic nerve. The patient's right and left optic nerves and RP control optic nerve appear to have significant atrophy when compared to the age-matched normal optic nerve. S, superior; T, temporal; I, inferior; N, nasal. Bar, 500 μm.