Implantable Telescope
The Implantable Miniature Telescope (IMT) was FDA-approved in July 2010 for end-stage AMD. This device is manufactured by VisionCare Ophthalmic Technologies Inc. of Saratoga, California, and its approval followed a 219-patient, multi-center clinical study in which 90 percent of patients achieved at least a 2-line gain in either their distance or best-corrected visual acuity, and 75 percent their level of vision from severe or profound impairment to moderate impairment.
Patients 75 years or older with stable to severe profound vision impairment due to blind spots (bilateral central scotoma) are now eligible for surgical implantation of this device, which projects images at greater than two times magnification onto the retina to improve central vision. Options are available for 2.2 and 2.7x magnification. Pre-training with an external telescope with a low vision specialist is required prior to procedure to ensure the device can have a benefit, as well as to determine eligibility (inadequate peripheral vision). Post-op visual training is required, as well.
One risk of this device includes the loss of corneal endothelial cells, which are essential for maintaining corneal clarity. The degree of this loss can be chronic (up to 5 percent per year). Major losses may have negative downstream effects, including corneal edema (swelling), decompensation (further loss of function), and ultimately a need for corneal transplant. 10 eyes in the above named study had corneal edema (unresolved), half of which resulted in corneal transplant. Calculated 5-year risks for adverse outcomes were calculated as follows: corneal edema (9.2 percent), corneal decompensation (6.8 percent) and corneal transplant (4.1).
Two post-approval studies are being carried out to further delineate risk, including a two-year follow up of the study’s initial two year cohort as well as a novel study of 770 newly enrolled subjects (focusing on endothelial cell density and related sequelae). Measures were also taken to ensure patients are informed of risks, including detailed labeling (manufacturer and FDA-generated) and an Acceptance of Risk and Informed Decision Agreement.