Surgically Implanted Visual Aids
In eyes with end-stage AMD, external visual aids, such as hand-held magnifying glasses and video magnifiers, are routinely used to facilitate specific tasks. However, recent surgical advances could now provide new options for optimization of visual function.
The implantable miniature telescope (IMT) (Visioncare Ophthalmic Technologies, Inc.; Saratoga, California) was FDA-approved in 2010 for placement in eyes with end-stage AMD that have visual acuity of 20/160 to 20/800 with bilateral geographic atrophy or long-standing, inactive CNVM. In October 2014, the FDA lowered the age limit for the IMT from 75 years to 65 years or older.
The device provides 2.2- to 2.7-fold magnification of images onto the retina, placing the image outside of the area of retinal degeneration and affording improvement in central visual function. Only one eye is implanted with the IMT, so that the second eye continues to provide peripheral vision. After 2 years in a prospective trial studying the IMT, mean best-corrected visual acuity improvement was 3.6 lines. This represents a substantial improvement, which was correlated with functionally meaningful improvements in general vision, near and distance activities, social functioning, mental health, and dependency.
Although the device is FDA approved to be implanted into the capsular bag at the time of cataract surgery, recent reports indicate that the device may also be effective if fixated to the sclera. This potentially allows pseudophakic patients access to the device through lens exchange; a prospective trial to investigate this possibility is being considered.
Argus® II (Second Sight Medical Products, Inc.; Sylmar, California), which is surgically implanted directly onto the retina, is the first retinal prosthesis to be FDA-approved. Its FDA approval as a humanitarian device allows implantation in patients with profound visual loss secondary to outer retinal degeneration from retinitis pigmentosa. Preoperatively, these patients have no light perception or bare light perception. Although not directly applicable to patients with AMD, the development and clinical application of this device indicates that retinal prostheses are possible, and future generations may be applicable to a broader range of patients.