Aetna considers artificial retina devices experimental and investigational because there is insufficient scientific evidence of the safety and effectiveness of these devices in restoring vision.

Researchers have been testing microelectronic retinal implants as a method of restoring vision in patients rendered blind by degenerative diseases of the retina such as retinitis pigmentosa (RP) and age-related macular degeneration (ARMD).  Tests of electrical stimulation of the retinal surface have demonstrated that such stimulation may induce light sensation.  These studies have shown that retinal neurons are preserved after death of photoreceptors in retinitis pigmentosa. 

Two types of retinal implant systems are under development: (i) epiretinal implants, designed to communicate directly with the ganglion and bipolar cells; and (ii) subretinal implants, designed to replace photoreceptors in the retina.  Both types of implants are intended to restore some vision through electrical stimulation of functional neurons in the retina.  Retinal implants require an intact optic nerve pathway to allow them to function.  Both systems translate incoming light, whether from a camera or the environment, to electrical stimulation of the functional neurons in the retina.

Epiretinal implants are positioned on the surface of the retina and receive light signals from external camera systems.  An electronic chip camera mounted in the frame of special glasses captures images and transmits the images via electrical impulses to a second chip, which is implanted in the retina.  Epiretinal implant systems may include other components such as image processing electronics, a telemetry system to provide power and data to the implanted subsystems, implanted electronics for signal decoding and stimulus generation, and an electrode array to deliver the electrical charge to the retina.

Subretinal implants are positioned behind the retina and receive light directly from the environment.  In this approach, light is converted into electrical signals that stimulate remnant cell layers of the retina. 

Artificial retina devices are not currently approved for marketing by the U.S. Food and Drug Administration.  Clinical trials of artificial retinal devices are currently ongoing.  One trial is a phase II feasibility study to evaluate the safety and utility of the Argus II Retinal Stimulation System in providing visual function to blind subjects with severe to profound RP.  While this is a technology that may be shown in the future to be effective, at this time the effectiveness, safety, and durability of artificial retina devices need to be established.

Ahuja et al (2011) examined to what extent subjects implanted with the Argus II retinal prosthesis can improve performance compared with residual native vision in a spatial-motor task.  High-contrast square stimuli (5.85 cm sides) were displayed in random locations on a 19 inches (48.3 cm) touch screen monitor located 12 inches (30.5 cm) in front of the subject.  Subjects were instructed to locate and touch the square center with the system on and then off (40 trials each).  The coordinates of the square center and location touched were recorded.  A total of 96 % (26/27) of subjects reported a significant improvement in accuracy and 93 % (25/27) demonstrated a significant improvement in repeatability with the system on compared with off (p < 0.05, Student t test).  A group of 5 subjects that had both accuracy and repeatability values less than 250 pixels (7.4 cm) with the system off (i.e., using only their residual vision) was significantly more accurate and repeatable than the remainder of the cohort (p < 0.01).  Of this group, 4 subjects showed a significant improvement in both accuracy and repeatability with the system on.  The authors concluded that in a study on the largest cohort of visual prosthesis recipients to date, these investigators found that artificial vision augments information from existing vision in a spatial-motor task.

The clinical trial "Argus™ II Retinal Stimulation System Feasibility Protocol" is still ongoing; another clinical trial on "Safety and Efficacy of Subretinal Implants for Partial Restoration of Vision in Blind Patients" is recruiting subjects (CliniaclTrials.gov, 2011). 

Weiland et al (2011) stated that degenerative diseases such as ARMD and RP primarily affect the photoreceptors, ultimately resulting in significant loss of vision.  Retinal prostheses aim to elicit neural activity in the remaining retinal cells by detecting and converting light into electrical stimuli that can then be delivered to the retina.  The concept of visual prostheses has existed for more than 50 years and recent progress shows promise, yet much remains to be understood about how the visual system will respond to artificial input after years of blindness that necessitate this type of prosthesis.  In this review, the authors focused on 3 major areas: (i) the histopathologic features of human retina affected by ARMD and RP, (ii) current results from clinical trials, and (iii) challenges to overcome for continued improvement of retinal prostheses.  They noted that "the routine nature of intraocular lens implantation today belies decades of hard-won surgical and biomaterial advances.  Retinal prostheses are following a similar roadmap, and to realize their full potential, we have to allow time not only for the clinical and biological testing, but also for engineering and technical advances".

In a single-arm, prospective, multi-center clinical trial, Humayun and colleagues (2012) evaluated the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc., Sylmar, CA) in blind subjects with severe outer retinal degeneration.  A total of 30 subjects were enrolled in this study.  All subjects were followed-up for a minimum of 6 months and up to 2.7 years.  The electronic stimulator and antenna of the implant were sutured onto the sclera using an encircling silicone band.  Next, a pars plana vitrectomy was performed, and the electrode array and cable were introduced into the eye via a pars plana sclerotomy.  The microelectrode array then was tacked to the epiretinal surface.  The primary safety end points for the trial were the number, severity, and relation of serious adverse events (SAEs).  Principal performance end points were assessments of visual function as well as performance on orientation and mobility tasks.  Subjects performed statistically better with the system "on" versus "off" in the following tasks: object localization (96 % of subjects), motion discrimination (57 %), and discrimination of oriented gratings (23 %).  The best recorded visual acuity to date is 20/1,260.  Subjects' mean performance on orientation and mobility tasks was significantly better when the system was "on" versus "off"; 70 % of the patients did not have any SAEs.  The most common SAE reported was either conjunctival erosion or dehiscence over the extra-ocular implant and was treated successfully in all subjects except in 1, who required explantation of the device without further complications.  The authors concluded that the long-term safety results of Second Sight's retinal prosthesis system are acceptable, and most subjects with profound visual loss perform better on visual tasks with system than without it.  It is unclear whether these statistically better findings are translated into better clinical outcomes.  The results of this small feasibility study need to be validated by further investigations.