Unraveling the Macular Mystery in GlaucomaDana Blumberg, MD, MPH and patient.
Traditionally, ophthalmologists who treat glaucoma have not paid a significant amount of attention to the macula, the tiny portion of the retina responsible for focusing central vision in the eye. It has long been accepted that glaucoma is a disorder of the peripheral vision and that damage to the central visual field only takes place late in the disease process. Despite this, Assistant Professor of Ophthalmology Dana Blumberg, MD, MPH, frequently hears her glaucoma patients report difficulty with low contrast, glare from bright lights, and difficulty adjusting to the dark. These tasks are all related to central visual function, which presumably should not be impacted until late in the disease course. “These findings are hard to explain using the traditional model of glaucoma damage,” Dr. Blumberg says.
Several years ago, she reached out to Donald Hood, PhD, James F. Bender Professor of Psychology and Professor of Ophthalmic Science (in Ophthalmology), whose work has been pivotal in recognizing that the macula is impaired much earlier on in glaucoma progression than was previously thought. In collaboration with Dr. Hood, she hypothesized that damage to the macula helped explain many of the visual complaints of glaucoma patients that could not be otherwise explained.
“The 24-2 visual field test that has classically been used in diagnosing glaucoma is not sensitive for detecting changes in the macula,” explains Dr. Blumberg. “Traditional visual field testing has also correlated poorly with patients’ self-reported visual function and ability to perform activities of daily living.”
Visual field testing of the macula, on the other hand, strongly correlates with patients’ self-reported visual function, as Dr. Blumberg and her colleagues have recently demonstrated in several published articles. “We also found that patients who report disproportionate levels of difficulty with daily visual function compared to the findings from their standard glaucoma visual field testing almost always have macular damage that previously went undetected,” she says. “In other words, if your day-to-day vision is much worse than your 24-2 visual field test results might suggest, the odds are very good that you also have macular damage.”
Certain specific visual complaints, in particular, point to macular damage. “For example, complaints related to luminance—difficulty adapting to changes in light level, like going into a dark movie theater or experiencing glare on a sunny day at the beach—are commonly reported by glaucoma patients who also have damage to the macula,” Dr. Blumberg says.
Dr. Blumberg and her colleagues will be testing these hypotheses in an innovative prospective study that will explore whether glaucoma patients with macular damage have diminished contrast sensitivity, impaired vision with glare testing, and difficulty with adaptation to the dark. These associations have never been explored before.
“If we can better understand how patterns of macular damage affect patients’ vision, ophthalmologists could start looking for these patterns earlier in the disease course and could target treatment toward the macula if it proves to be involved,” she says. “If we could align early changes in the macula with these specific visual dysfunctions, we may have the missing piece in terms of understanding glaucomatous functional visual loss. Not every patient with glaucoma experiences damage in the macula, but those who do seem to experience more visual disability.”
The encouraging results of the pilot studies speak to Dr. Blumberg’s skills as both a clinician and a scientist. She explains that the foundation for this research came from carefully listening to each patient and studying their examination findings. “I am grateful to several patients who were able to articulate their visual difficulties. Were it not for these patients, the idea for this study may not have happened.”