by Judy Prevost March 4, 2000
Age Related Macular Degeneration (ARMD) is the leading cause of severe vision loss in people over the age of 65. This can be caused by the growth of abnormal blood vessels and neovascularization under the macula, or in the center of the macula, leading to loss of central vision.
Subretinal choroidal neovascular membranes (SRN), when they grow under the center part of vision, can cause profound visual loss in patients with age-related macular degeneration, ocular histoplasmosis syndrome (OHS), or other idiopathic causes. These membranes are nothing more than scar tissue that is growing under the retina in an attempt to repair damage caused by one of these disorders. Subretinal membranes, being scar tissue, affect both the photoreceptors above them and the RPE cells below them as they age and mature, causing profound visual loss. In the early 1990's, researchers began looking at ways to remove these membranes in an attempt to improve vision in patients.
The purpose of submacular surgery is to remove subfoveal choroidal neovascularization (CNV), and other associated hemorrhage. The procedure was performed experimentally on many patients during the 1990's with mixed results. In 2002, the National Eye Institute (NEI) initiated multi-center submacular surgery trials (SST), the objective being to ascertain if submacular surgery to remove subfoveal CNV, as well as associated hemorrhage, would improve or stabilize vision compared to no surgery at all. In the November 2004 issue of the journal Ophthalmology, four of a total of six main result papers on the SST were published. The four papers addressed surgery for two groups of AMD patients.
In the first group, according to the NEI, surgery did not improve vision for half of 454 patients who had centrally located lesions that were not predominantly blood, when compared with half who did not receive surgery but did receive regular eye examinations. This finding confirmed a growing clinical impression among many retinal surgeons that submacular surgery is not helpful for these commonly-found lesions in AMD patients' eyes.
Surgery was also not beneficial for a second group of patients--those with more extensive bleeding under the retina. This second group involved 336 patients who were assigned randomly to either surgery or careful observation. Among these patients, vision had not stabilized or improved after two years in those who underwent surgery to remove lesions and associated blood (which was the primary test of the trials), when compared with patients with no surgery.