Status of the feline retina after subretinal
implantation of an artificial silicon retina for three years
MT Pardue, PhD; SL Ball, PhD; AY Chow, MD; JI
Perlman, MD, PhD; EB Stubbs Jr., PhD; VY Chow, MS; NS Peachey, PhD
Atlanta VA Medical Center, Cleveland VA Medical
Center; Optobionics Corporation, Hines VA Medical Center
Objectives: The artificial silicon retina
(ASR) consists of an array of photodiodes that are designed to replace
photoreceptors in patients that have retinal diseases in which only the
photoreceptors degenerate. This retinal prosthetic, which is designed
to lie within the subretinal space, is powered solely by incident light
and requires no external power supply. In order to evaluate the feasibility,
biocompatibility and functionality of placing an ASR in the subretinal
space, a cat model has been developed. In cats followed for one year post-operative,
the ASR maintains a stable position, continues to generate electrical
current in response to light, and does not induce overall tissue rejection.
However, in the retina immediately overlying the ASR, photoreceptors degenerate
and changes are also observed in the inner retina. The present work evaluates
cats implanted for 3 years to determine if the ASR will continue to function
and if any progressive changes occur in retinal appearance.
Methods: A total of 8 cats were implanted
with a 1.8 mm solid disk ASR and followed for 3 or more years post-operatively.
Implant durability was examined by recording the electrical response of
the implant to infrared light. The overall status of the neural retina
was assessed by electroretinography using white light stimuli. Fundus
photos were taken every 2 months to document implant position and to evaluate
retinal health. At 36 months, cats were sacrificed, and eyes were enucleated
and fixed for plastic embedding. Sections (0.5 micron in thickness) were
stained with toluidine blue and examined.
Results: The ASR remains in a stable location
and continues to function electrically for 3 years. The overall retinal
appearance resembles that of cats examined at 1 year post-operative, indicating
no progressive deterioration of retinal anatomy due to the presence and
activity of the ASR.
Conclusions: These results further support
the idea that an ASR can be implanted in patients long-term without deleterious
effects.
Funding acknowledgment: This study was funded
by the VA Rehabilitation Research and Development Service, project C2675CA.