Approvable telescope advances

November 15, 2009

An investigational telescope implant has been given an 8-0 approvable vote by the FDA advisory panel.

Although the FDA panel unanimously recommended approval for patients with end-stage age-related macular degeneration (AMD), the panel members suggested that the device be approved with conditions related to endothelial cell loss rates associated with the implantation procedure. However, the visual acuity (VA) and quality of life outcomes give this visually challenged patient population another option to achieve functional vision, said Kathryn Colby, MD, PhD.

The telescopic device, which is implanted in one eye of a patient, has two high-power wide-angle lenses encased in a glass cylinder. This is placed on a polymethylmethacrylic carrier plate to be implanted in the capsular bag. The device magnifies the image (the central vision) seen by the patient and effectively decreases the relative size of the scotoma in a patient with AMD at the expense of decreased peripheral vision in that eye, said Dr. Colby She is assistant professor of ophthalmology, Harvard Medical School, and attending surgeon, Cornea Service, Massachusetts Eye and Ear Infirmary, Boston.

Efficacy endpoints

The primary efficacy endpoint of that study was that 50% of the patients had to achieve a two or more-line increase in the best-corrected VA (BCVA) 12 months after implantation. The secondary efficacy endpoint included the results of questionnaires, such as the National Eye Institute VFQ-25 questionnaire, that measured the subjective effects of implantation of the device on the patients' ability to perform activities of daily living.

The primary safety endpoints were a loss of fewer than two lines of VA in less than 10% of patients 12 months after implantation and a loss of endothelial cells that was less than 17% at that time point.

"The efficacy endpoints were easily met," Dr. Colby said. "In actuality, 67% of patients achieved an increase in BCVA of three or more lines as well as in their abilities to perform their daily activities. Regarding the safety endpoints, only 7% of patients lost VA at 12 months, but the benchmark for endothelial cell loss was not reached."

The BCVA improved in these patients from a range of BCVA of 20/80 to 20/800 preoperatively (mean, 20/320). The mean improvement was three lines of vision; 67% achieved three or more lines, 80% achieved two or more lines, and 12% achieved six lines or more.

The only sticking point in the approval process, the endothelial cell loss, was a mean 25% loss at 12 months in these patients. Dr. Colby said that a subgroup analysis of VA outcomes based on surgeon discipline showed a difference in the loss of endothelial cells.

"The surgeons who were cornea-trained met the FDA benchmark for an endothelial cell loss below 17%, but the trial protocol was not restricted only to cornea surgeons," she said.

Dr. Colby also discussed that when the FDA monitored the endothelial cell loss over time, the cell counts stabilized at 12 months after implantation of the telescope and did not progress over and above the normally expected cell loss.

Surgical modifications are a potential way to improve the outcomes with this technology. After evaluating surgical videos and surgical techniques, Dr. Colby and several other investigators were able to describe the optimal surgical technique for safe implantation of this device. These surgical pearls would be integrated into a surgeon training program based on the documents submitted for the FDA panel meeting, she said.

"Implantation of this device represents a real advance for patients with end-stage AMD who have limited options to improve their VA effectively," Dr. Colby concluded.