The multicenter study, which is published in the November issue of Ophthalmology, was the work of Dr Emily Y Chew, Deputy Director, Division of Epidemiology and Clinical Applications at the National Eye Institute (NEI), in Bethesda, Maryland, and colleagues.
AMD is a progressive eye condition that according to the Macular Degeneration Partnership affects some 15 million Americans and millions more people around the world. It attacks the macula of the eye, where our vision is at its sharpest.
Although AMD rarely leads to complete blindness, people with the disease increasingly see only at the periphery of their vision, with the centremost part becoming dimmer and dimmer until it looks just like a black hole. There are two types of AMD, a "wet" form called neovascular AMD and a "dry" form called central geographic atrophy. There is no cure for either type, but new treatments are available for the wet form.
A cataract is a condition where the lens of the eye, that sits behind the pupil inside the eye and helps to focus what we look at onto the retina, becomes cloudy, thus impairing vision. Most cataracts are age-related and very common in older people. According to the NEI, more than half of all Americans aged 80 and over either have a cataract or have had cataract surgery.
The proportion of Americans with age-related AMD is expected to rise in line with an ageing population, similarly more and more people will develop cataracts, and if untreated, both AMD and cataracts can lead to blindness.
For this study, which is thought to be the first to use an adequate number of advanced AMD patients, Chew and colleagues used data from the multicenter, prospective Age-Related Eye Disease Study (AREDS), funded by the National Eye Institute (NEI).
AREDS was primarily set up to look at the effects of high-dose vitamin and mineral supplements on cataract and AMD.
Chew, who led the study, told the press that:
"Earlier epidemiology had suggested cataract surgery might worsen AMD, so the data from the AREDS cohort study were evaluated to answer this important question."
The researchers evaluated the visual acuity (sharpness) of 1,939 eyes from 1,244 patients in various stages of AMD after they had undergone cataract surgery.
They found that:
- On average, visual acuity improved after cataract surgery in patients with AMD ranging from mild to advanced.
- The best improvement in visual acuity was in patients whose vision was worse than 20/40 before surgery.
- There was no difference in improvement between patients with wet and dry AMD.
- About 12 months later, improvement in visual acuity remained statistically significant in 865 eyes that were available for follow-up.
- High doses of vitamin C, vitamin E, and beta-carotene did not affect the development or progression of cataract.
- But when these vitamins were combined with zinc, there was a 25 per cent reduction in the risk of progression to advanced AMD over the 5 years of the study.
"On average, participants with varying severity of AMD benefited from cataract surgery with an increase in visual acuity postoperatively. This average gain in visual acuity persisted for at least 18 months."
"Visual Acuity Outcomes after Cataract Surgery in Patients with Age-Related Macular Degeneration: Age-Related Eye Disease Study Report No. 27."
Farzin Forooghian, Elvira Agrón, Traci E. Clemons, Frederick L. Ferris, Emily Y. Chew, AREDS Research Group
Ophthalmology, Volume 116, Issue 11, Pages 2093-2100 (November 2009)
Source: American Academy of Ophthalmology. AMD.org, NEI.
Written by: Catharine Paddock, PhD