The probability of glaucoma leading to blindness in at least 1 eye fell almost 50% for patients in Olmsted County, Minnesota, who were diagnosed during 1981 to 2000 compared with patients diagnosed during 1965 to 1980, according to an article published online October 28 in Ophthalmology.
The older the patient is at glaucoma diagnosis, however, the greater the risk for progression to blindness, the researchers report.
Mehrdad Malihi, MD, from the Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, and colleagues analyzed medical records of open-angle glaucoma (OAG) incidences of patients in the most recent group through the end of 2009.
The researchers identified 294 patients who received a new OAG diagnosis during the earlier period. Their mean age was 66.7 years ±13.1 years. In the latter period, the investigators identified 563 patients with a new OAG diagnoses , with a mean age at diagnosis of 65.2 ± 15.3 years. The mean follow-up time for the earlier group was 15.0 ± 8.0 years and 11.2 ± 6.7 years for the latter group.
The researchers found that the probability of OAG-related blindness in at least 1 eye decreased from 25.8% (95% confidence interval [CI], 18.5% - 32.5%) for patients in the first period to 13.5% (95% CI, 8.8% - 17.9%) for patients in the second period (P = .01). Incidence of blindness within 10 years of diagnosis decreased from 8.7 per 100,000 (95% CI, 5.9 - 11.5) for patients during the earlier period to 5.5% (95% CI, 3.9 - 7.2) for patients in the latter period (P = .02).
"The reason we did the study was because in the previous study there was a very high rate of blindness and there have been a lot of changes in practice and a lot of changes in diagnostic techniques and tools, and all of those we know help individual patients, but we didn't know if it actually helped populations," senior author Arthur J. Sit, MD, associate professor of ophthalmology at the Mayo Clinic College of Medicine, told Medscape Medical News.
"We're excited in that this [study] actually showed that we're making a difference to the population in general, but there's still a long way to go," he continued.
The researchers also found that older the age at diagnosis was associated with an increased risk for progression to blindness (P = .001), although sex was not a risk factor. "The older you are at diagnosis presumably correlates to advanced disease and the more likely you are to go blind," Dr. Sit said.
Effect on Practice Today
"In terms of how this is going to affect today's practice, [the study] definitely brings up a good point regarding the higher age at diagnosis," Lucy Q. Shen, MD, an ophthalmologist and glaucoma expert at the Massachusetts Eye and Ear Infirmary and instructor of ophthalmology at Harvard Medical School in Boston, told Medscape Medical News.
"Even though the awareness has been raised, there are still many patients who are unaware that they have this condition," she continued. A need exists for educating not just the glaucoma specialists but also optometrists, general ophthalmologists, and some of the primary care physicians for whom "awareness needs to be there to have these patients screened earlier for this disease.
"Also," she added, "it is important to inform patients to have their family members screened. They don't often realize that the risk for siblings to develop OAG is actually much higher than for the general population."
Even though reduction of intraocular pressure remains the only treatment for glaucoma, the researchers note, reliance on it as a diagnostic factor has decreased as the field has developed better methods for observing changes in the optic disc and retinal nerve fiber layer.
"I think we have done a pretty good job over the past 20 years of treating the patients who actually get into our clinic, but we clearly haven't picked up all the patients who are diagnosed at a late stage," Dr. Sit said. "Over this 45-year period, probably the biggest change has been in medication. Getting into the 1990s, a number of new medications were coming along, including the prostaglandin analogs and alpha agonists. I think there has been a real explosion of the number of medications that are available. Surgeries, interestingly, haven't changed a lot during that time."
"One of the things that they didn't mention that could be potentially a confounding factor is that maybe patients of the 1960s were blind from other diseases that became treatable over time, such as cataracts or macular degeneration, which are much more treatable now than they were that many years ago," Dr. Shen said.
"It's [also] hard to know how many of the patients in the study went blind from the treatment, because some of the glaucoma surgeries can cause vision loss," she said. "Some of the complications are reversible, others may not always be reversible. Now that we're developing more minimally invasive, safer options to treat the disease, at least hopefully we are preventing vision loss from the treatment as well.
The researchers analyzed data from the Rochester Epidemiology Project, which has tracked the entire population of Olmsted County over multiple decades and is considered well-suited to assessing longitudinal trends in this population. However, generalization to other populations may be limited because the study population is almost all white.
The Minnesota population may also be more compliant than others, Dr. Shen said. "There is still a significant patient population [that is not] as aware and concerned about their condition. Often we catch them when it's already too late. One of the problems with glaucoma is that people don't know that they're going blind until it really starts to affect their central vision, and at that point it's very difficult to stop it from getting worse."
The authors and Dr. Shen have disclosed no relevant financial relationships.
Ophthalmology. Published online October 28, 2013. Abstract
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Cite this: Fewer Cases of Glaucoma Now Progressing to Blindness - Medscape - Nov 06, 2013.