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R. N. Agrawal, Y. I. Morales, A. Beremesh, G. J. Chader, R. J. Greenberg, J. D. Weiland, N. A. Rao, M. S. Humayun; Chronic Epiretinal Array Implant in Advanced Retinitis Pigmentosa: Morphometric Analysis of Retina in Post-Mortem Eyes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4583.
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To characterize histopathological changes in the retina of a human subject with advanced Retinitis Pigmentosa (RP) implanted with an active epiretinal prosthesis.
A 69-year old female subject with advanced RP was implanted with a 16-electrode active epiretinal array in the left eye in April 2004. She had initially noticed decreased vision at age 6, followed by loss of form recognition vision at age 62. The patient had multiple sessions of stimulation for one year following the implant, when due to repeat conjunctival buttonholing and cable exposure, the intraocular cable was cut and removed, while the inactive array was rotated to examine the underlying retinal surface and left in place. Routine follow-up included Optical Coherence Tomography and Fluorescein Angiography. The inactive array remained in the eye for about 3 additional years until the subject’s death at age 73 due to head trauma suffered from an accidental fall. Both eyes were enucleated post-mortem and fixed in Davidson’s medium, and processed and stained with Hematoxylin and eosin & with special stains. Retina under the array and the perimacular region was analyzed. Total and inner retinal thickness was measured along with retinal ganglion cells (RGC) count in these sections. These were compared to macula and perimacular regions in age-matched postmortem controls in 2 RP eyes and 2 normal eyes.
In the macular and perimacular region, there was a significant reduction in numbers of RGC in both eyes (implanted and non-implanted) of the subject when compared with normal controls groups but there was no significant difference when compared with RP controls. The mean percentage of preserved ganglion cells in the subject’s eyes with RP was compared with that of the normal controls. On average in the macular area of the implanted eye, the ganglion cell layer retained 40.3% of cells; the non-implanted eye was 32.2%. Total retinal thickness in the macular area was significantly decreased in both eyes of the subject compared with the normal controls. No significant difference was found in the inner nuclear thickness. In the perimacular area, no significant difference was found in the thickness of the retinal layers compared with normal and RP controls.
Chronic implantation of the array for over 4 years (and electrical stimulation for the initial one year) with an epiretinal array shows no evidence of damage to the retinal layers and cells in an RP eye when compared to known results from previous studies.
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