Surgical Procedure

The microsurgical procedure involves a standard ophthalmic operation called a vitrectomy and retinotomy with an additional step for the sub-retinal implantation of the ASR chip (Charters).

1. Vitrectomy—Three tiny incisions are made in the white part of the patient's eye. The operating instruments will be inserted through these openings.
2. Retinotomy—The vitreous gel that fills the eyeball is replaced by a saline solution.
3. Implantation—A small incision is made in the retina about 20Å above and to the side of the macula region. Saline is injected into the retina in order to create a small pocket in the sub-retinal space where the ASR microchip will be implanted. After the chip is placed inside the pocket and positioned correctly, air is introduced into the eye to gently push the retina back down. (Over the period of two weeks, the air bubble and saline solution are absorbed and replaced by vitreous gel.)

Clinical Trials

Since its their January 2000 FDA approval to conduct a safety and feasibility trials, the ASR and MARC microchips has have been implanted in ten 20 patients who were rendered legally blind by RP and AMD. So far, Dr. Chow reports,Both Dr. Chow and Dr. Humayun report that their devices is are producing lasting visual improvements among the patients. Participants report improved visual acuity, contrast perception, and increases in visual-field size. Some patients are even capable of seeing letters on standard optometric ETDRS charts (Groves).. In addition, none of the patients has shown signs of implant rejection, infection, or any other biocompatibility issues. Though only partial vision has been restored in the patients, these experiments mark the first time where progress has been made in reversing the effects of AMD and RP. The success of these trials has given hope to those who suffer from these debilitating diseases. Dr. Chow and Dr. Humayun are confident that their retinal prostheses will prove their long-term safety, efficacy, and suitability (Groves). They are both very optimistic, saying that, in the future, these devices will be able to completely restore vision in AMD and RP patientsHowever, Dr. Chow made it clear that the long-term safety, efficacy, and suitability of the ASR implant have yet to be determined (Groves).

Future Impact and Conclusion

Because of the advancements made in biomedical engineering, individuals suffering from the blinding effects of Age-Related Macular Degeneration and Retinitis Pigmentosa now have hope that one day they may be able to see again. The innovations in silicon chips and microcircuitry as well as the discovery that electrical stimulation can excite retinal neurons have given ophthalmologists the means to create prosthetic devices to replace damaged retinal cells. The two newest retinal prostheses, ASR and MARC, re-establish the visual neural pathway by replacing the neural cells damaged by AMD and RP. These devices have shown great promise in restoring vision to patients, and as research continues, physicians and scientists are confident that the retinal prosthetics will one day Although the devices currently restore only partial vision, it is expected that continued success with clinical trials and research will aid physicians in completely reverseing the affects of retinal disease. Clearly, the advent of these retinal prosthetics has made the impact of biomedical engineering more deeply appreciated.