Retinal changes after macular translocation with 360-degree retinotomy in monkey eyes

Fundus autofluorescence after full macular translocation surgery for myopic choroidal neovascularization

BACKGROUND

To investigate fundus autofluorescence (FAF) findings in patients who underwent full macular translocation surgery with 360-degree retinotomy (MT360) for myopic choroidal neovascularization (CNV).

METHODS

Observational case series. Thirty-one eyes of 31 patients who underwent MT360 for myopic CNV from February 1999 through September 2005 were included. We measured the best-corrected visual acuity and obtained color fundus photographs, optical coherence tomography (OCT) images, and fluorescein angiography images. FAF imaging by confocal scanning laser ophthalmoscope was obtained postoperatively in all study eyes and preoperatively in two study participants. FAF features at the new macula were qualitatively evaluated and compared with preoperative lesions associated with CNV. The FAF features at the retinal pigment epithelial (RPE) area with preoperative CNV also were evaluated.

RESULTS

The mean interval between MT360 and the final FAF examination was 58 months (range, 8-94 months). FAF imaging was almost normal in five eyes (16%), the increased FAF was well defined at the new macula area in 23 eyes (74%), and the FAF was decreased in three eyes (10%). Neither newly developed CNV nor subretinal fluid was seen at the new macular region in any eyes on fluorescein angiography or OCT imaging. The configurations of well-defined increased FAF in 23 eyes corresponded with the preoperative CNV in two eyes (9%) and subretinal hemorrhages in five eyes (22%). Well-defined increased FAF larger than the CNV or subretinal hemorrhage was seen in 16 eyes (69%). The RPE area located at the area of the preoperative CNV had a FAF defect or decreased FAF in 30 eyes (97%) on postoperative FAF imaging; there were no increased FAF changes.

CONCLUSIONS

Well-defined increased FAF at the new macula after MT360 suggests that FAF reflects not only fluorophores in the RPE but also in the neurosensory retina. These fluorophores may result from interactions between the retina and CNV/pathologic RPE.

Electrophysiological and histological studies of chronically implanted intrapapillary microelectrodes in rabbit eyes

PURPOSE

To determine the safety and efficacy of transsclerally placed intrapapillary wire microelectrodes implanted chronically into the optic nerve head of rabbit eyes.

METHODS

Four platinum wire microelectrodes were passed through the sclera and implanted into the optic nerve head of five rabbit eyes for 4-6 months. Color fundus photography, fluorescein angiography, electroretinograms (ERGs), and visually evoked potentials (VEPs) were used to monitor the retina. Electrically evoked potentials (EEPs) were elicited by bipolar electrical stimulation of the optic nerve axons by different combinations of the four electrodes immediately after the implantation and at 1-month intervals thereafter. The effects of the chronic implantation of the electrodes on the morphology of the optic nerve were evaluated by histological and immunohistochemical examinations at 4 and 6 months after the implantation.

RESULTS

All of the electrodes remained stable in the implanted sites throughout the post-implantation period, except for one electrode that had pulled out of the optic nerve head at 1 month after implantation. No intraocular infection, inflammation, or vitreoretinal proliferation was observed in any eye. EEPs could be elicited from each pair of electrodes at all testing times. The mean threshold currents (charge densities) to evoke EEPs increased from 19.3 +/- 9.2 microA (6.0 +/- 2.9 microC/cm2) on the implantation day to 78.8 +/- 31.9 microA (24.6 +/- 10.0 microC/cm2) at 1 month after implantation, but did not change significantly thereafter. The implicit time and amplitude of the a- and b-waves of the ERGs and of P1 of the VEPs did not change significantly throughout the post-implantation period. Histological evaluation of the optic nerve head revealed slight tissue encapsulations surrounding the electrode and increased expression of glial fibrillary acidic protein near the surface of the optic nerve.

CONCLUSIONS

Implantation of transscleral intrapapillary microelectrodes appears to be safe and effective. These findings indicate that the implantation of microelectrodes in the optic nerve head should be considered for an optic nerve-based prosthesis.