|Geographic atrophy (GA) is considered late stage dry age related macular degeneration.|
Atrophy is the the wasting away or the deterioration of cells or systems. You usually hear these words in association with muscle atrophy - which is the loss of muscles due to lack of use or exercise.
However, in the case of our macula - the center of the retina responsible for our straight ahead, sharp detailed vision - the cone cells waste away due to lack of oxygen and nutrients and the inability to get rid of built up waste products. Here is a picture of geographic atrophy from the National Eye Institute.
Credit: National Eye Institute, NIH Ref#: EDA23
Dry or atrophic macular degeneration (AMD) is identified by three macular degeneration stages. AMD is a progressive eye disease. Each eye may be in a different stage.
Advanced AMD is the last stage of this progressive retinal disease. This late stage, or advanced AMD, is identified by:
√ Circular patches of partial or complete depigmentation of one of the layers of the retina, the retinal pigment epithelium. (RPE).
√ Usually there is exposure of another layer of tissue, the choroidal blood vessels
These changes in the RPE may stabilize or they may progress. "Degeneration of RPE cells leads to the death of rods and codes. What an eye doctor sees in a dilated eye exam in a patient with GA is like a continent of atrophy surrounded by a sea of retina. The continent appears different from the surrounding retina because of the loss of the pigmented RPE cells. Areas of geographic atrophy look whiter than the surrounding retina."
Janet Sunness, M. D. and head of Hoover Low Vision Services at the Greater Baltimore Medical Center
The area of atrophy will determine the amount of vision loss.
Dr. Michael A. Samuel, a retina specialist and author of Macular Degeneration: A Complete Guide for Patients and Their Families,describes geographic atrophy as, "the end stage of dry AMD, where central vision is lost."
This loss of our straight ahead vision is called a central scotoma - it is a gray or black spot that appears in the center of one's vision.
Other vision changes involve:
1. Reading slower
The speed of reading drops as GA progresses
2. Require more light
Difficulty seeing in low light conditions
3. Require more magnification
"Forty percent of people with GA require print to be twice as large after 2 years of worsening," says Dr. Sunness.
The most common risk factors for geographic atrophy include:
1. Chronic inflammation
Dr. Sunness states that "more than half of patients with GA in one eye develop GA in the other eye."
There are several AMD clinical trials that are investigating new ways to treat advanced AMD.
1) Antibiotics to Treat Geographic Atrophy
The National Eye Institute is looking to see if a common antibiotic, minocycline, will help those with geographic atrophy. (GA).
Dry macular degeneration has a slower progression of central vision loss due to the degeneration and loss of the retinal pigment epithelial (RPE) cells and photoreceptors in the macula.
According to the description from ClinicalTrials.gov, "While the etiology of GA is not completely understood, inflammatory processes involving the activation of resident immune cells of the retina called microglia is likely to contribute. Minocycline inhibits the activation of microglia which produce inflammatory factors implicated in GA development. The objective of this study is to investigate the safety and possible efficacy of oral minocycline in patients with GA."
Forty participants who have GA in one or both eyes will be enrolled in the study. A 100 mg dose of minocycline will be taken twice daily for 36 months. To find out more about this study visit:
2) Safety and Efficacy Assessment Treatment Trials of Emixustat Hydrochloride
The stated purpose of this clinical trial that is ongoing but not recruiting new participants is, " to determine if emixustat hydrochloride (ACU-4429) reduces the rate of progression of geographic atrophy compared to placebo in subjects with dry age-related macular degeneration."
This double blind placebo controlled study recruited 508 patients with geographic atrophy due to dry age-related macular degeneration. The drug, emixustat is a once-daily oral medication. According to Acucela, the sponsor of the study, "Emixustat has been shown to play a critical role in slowing the profession of multiple retinal degenerative diseases in animal models, including GA secondary to AMD."
Patients were divided into four groups and randomized to receive varying amounts of the drug - 2.5 mg, 5 mg, 10 mg or placebo.
The investigators will be evaluating the rate of change of the total are of the GA lesion and changes in visual acuity scores as well as the number of participants who develop wet macular degeneration in the study eye. The last patient recently completed the treatment period of 24 months. Study results are expected to be published in the next several months.
3) Sirolimus to Treat Geographic Atrophy Associated With Age-Related Macular Degeneration
This study is in Bethesda, Maryland.
Inflammation may play a role in the pathogenesis of GA. Sirolimus inhibits the production, signaling and activity of many inflammatory factors relevant to the development of GA. Therefore, the objective of this study is to investigate the safety and possible efficacy of multiple sirolimus subconjunctival injections in participants with bilateral GA.
4) Safety and Efficacy of Brimonidine Intravitreal Implant in Patients With GA Due to Age-Related Macular Degeneration (AMD)
This study is in Abiline, Texas.
It is a "stage 1 patient-masked, dose-escalation, safety evaluation of brimonidine intravitreal implant. Patients will receive implant in one eye and "sham" treatment (meaning no treatment) in the fellow eye. Stage 2 will begin after 1 month of safety has been evaluated for Stage 1. Stage 2 is a randomized, double-masked, dose-response, sham-controlled evaluation of the safety and efficacy of brimonidine intravitreal implant in patients with GA from age-related macular degeneration."