by Dan Roberts
Originally published on MDSupport, updated March 2005
Since March 2000, an experimental study (“Transpupillary Thermotherapy of Occult Subfoveal Choroidal Neovascular Membrane,” or TTT4CNV”) has been underway using transpupillary thermotherapy (TTT) for the treatment of the occult form of age-related macular degeneration (AMD). The therapy utilizes a low dose of infrared laser light without the accompaniment of therapeutic drugs and with no damage to surrounding tissue.
In findings published in October 1999 in the American Journal of Ophthalmology, a clinical study showed that TTT was effective in improving or stabilizing vision in 75% of treated eyes, and decreasing subretinal fluid in 94%.
On October 22, 2004, Iridex Corporation announced disappointing results to the American Academy of Ophthalmology meeting in New Orleans. 47 percent of 303 study subjects avoided modest or severe vision loss after two years, compared with 43 percent in those who received a sham treatment: results which are not statistically significant.
On February 25, 2005, however, the company announced a significant clinical benefit in a subset of patients with wet age-related macular degeneration (AMD) who were treated with TTT. The results showed that in a subgroup of patients with baseline visual acuity of 20/100 or worse, 22% of treated eyes improved vision by one or more lines compared with none of the eyes in the untreated control group. Furthermore, at 18 months, there was a 2 line benefit in preserving vision in this subgroup when compared to sham treated eyes. Specifically, TTT treated eyes, on average, lost 2 lines of visual acuity, while sham treated eyes lost 4 lines. Both of these findings were statistically significant.
AMD is a progressive eye disease that damages the central vision, which affects the ability to read, recognize faces, and drive a vehicle. Of the millions of people world wide with AMD, 90% have the Dry form. The remaining 10% have the Wet type, the more severe of the two. Wet MD can be manifested in two ways: classic neo-vascularization (seen), or occult neo-vascularization (hidden). Over 70% of people with Wet MD have the occult type, and this is the group that is targeted for TTT clinical trials.
The TTT4CNV Clinical Trial is a multi-center, prospective, double-masked, placebo-controlled clinical trial conducted at 22 centers in the United States. These latest results were reported at The Macula Society Meeting in Key Biscayne, Florida by Dr. Elias Reichel, Study Chairman of the TTT4CNV Clinical Trial and Associate Professor of Ophthalmology at the New England Eye Center, Tufts University School of Medicine.