We thank Dr Del Priore for his letter to the editor regarding our article. He highlights findings that are well known in the retinal prostheses and retinal transplantation community, findings that surgical manipulation or injury to the eye or retina alone can temporarily up-regulate neurotrophic factors that exert a short-term neuroprotective effect on the retina. The following comments allow us to clarify a few points.
The neuroprotective effects from surgery or injury in the rat model have been reported to last for only 3 months.1,2 In comparison, we reported on visual function improvements in some of the patients with chip implants that have now persisted for longer than 3 ½ years,3 a timeframe longer than would be expected from just a surgical or placebo effect. To further investigate the possible sources of neuroprotection, we have compared neuroprotection after implantation of active or inactive chips with sham surgeries in the Royal College of Surgeons rat model of photoreceptor degeneration.4
Chow AY. Effect of Sham Surgery on Retinal Function After Subretinal Transplantation of the Artificial Silicone Retina—Reply. Arch Ophthalmol. 2005;123(8):1156-1157. doi:10.1001/archopht.123.8.1156-b