Implantable miniature telescope: lessons learned

The Implantable Miniature Telescope (IMT) is a telescopic prosthesis that, combined with the optics of the cornea, constitutes an intraocular magnifying system. It is indicated for use in patients with stable, nonfoveal sparing, bilateral, stable, age-related macular degeneration (end-stage) with associated scotomas. The telescope prosthesis is implanted in only one of the patient's eyes. In this way, the implanted eye provides improved visual acuity, and the nonimplanted eye continues to provide peripheral vision for ambulation. Two hundred seventeen patients with end-stage AMD were enrolled in a prospective, multicenter, open-label trial (IMT-002) beginning in 2003. The implanted eye was the worse eye for most patients based on a selection rule set by the U.S. Food and Drug Administration (FDA) protocol; however, in most cases (90%), visual acuity improvement goals were met with the device. This report will retrospectively look at 2 selected patients implanted at the Emory Eye Center in Atlanta as part of that trial to derive lessons for subject and eye selection criteria.

Two cases were selected to represent patients' levels of functional success and satisfaction. Determination of their visual and functional outcome at 1-year postimplantation was based on best-corrected visual acuity and the National Eye Institute Visual Functioning Questionnaire 25-Item quality-of-life survey. Four years after implantation, 1 patient continued to use the telescope prosthesis eye for all visual activities; the other patient did not perceive any benefit from the device and continued to primarily use the fellow nonimplanted eye. The benefit of the telescopic prosthesis was most likely accounted for by the level of visual acuity in both eyes postimplantation and eye dominance.

Proper eye selection chosen for implantation with the telescope prosthesis appears to be an important if not critical factor in determining patient satisfaction for visual processing and functional success. Based on the author's experience with the IMT, optometrists can aid the multidisciplinary team by preoperatively determining which eye, if implanted, offers the optimal potential functional benefit for appropriate candidates.