Expert Interview - Glaucoma Risk Factors With Andrew G. Iwach, MD

How much is your management of glaucoma governed by risk factors?

Dr. Iwach: Glaucoma is complicated. To start, glaucoma really encompasses many different entities. Different types of glaucoma have different rates of progression; sometimes we know the etiology, sometimes we don’t. When looking at risk factors, one has to discern the type of glaucoma to be sure risk factors are applied appropriately.

Many larger studies focus on open-angle glaucoma. They have started the process of quantifying the known risk factors: IOP, age, race and cup-to-disk ratio, etc. One has to take these aggregate risk profiles and apply them appropriately to a given patient, because we treat individuals, not means or averages. When I see patients, I factor in the aggregate data concerning how patients with certain characteristics fare and, together with clinical acumen, customize a treatment plan for a particular patient.

When considering risk factors, we also need to step back and think of the patient’s overall health. One cannot predict how long a patient will live. Ophthalmologists, as physicians, are uniquely qualified to assess health. One can’t predict how long a patient will live, but we need to look beyond the eye itself.

For example, a younger patient with a compromised optic nerve and a long life expectancy will likely require preservation of vision longer than will someone who is much older or who has end-stage cancer. We must customize our treatment recommendations accordingly. Risk factors do not dictate recommendations, but they can help guide us. And what really counts is not just the eye, but the patient.

What risk factors have had the biggest impact on you and your patients?

Dr. Iwach: Before talking about the role of any particular risk factor, I would ask: How accurate are the risk factor assessments? How appropriate are these risk factors for this patient?

IOP is the common denominator in glaucoma and is the only modifiable risk factor. Yet our measurements of IOP are far from perfect. Our understanding of the importance of central cornea thickness is increasing.

Family history is another significant factor, yet our information is often incomplete or inaccurate. Some patients may initially report a family history of glaucoma; however, after further investigation, it may turn out to be another eye disease, such as macular degeneration. Rather than glaucoma, we might find ocular hypertension with no field damage and no ocular changes. Even when glaucoma is confirmed, more detail can be helpful, such as timing and extent of optic nerve damage.

One of the most effective screening tools for glaucoma is having family members with the disease talk to other family members about being screened. Family get-togethers, such as those around the holidays, are a great time for those with glaucoma to mention their disease to their families. They can be giving a great gift of sight.

Finally, cup-to-disc ratio may be another risk factor with glaucoma. We know that on a strictly geometric basis, we need to account for optic nerve head diameter variation, which affects the perceived cup-to-disc ratio. A large ratio may simply result from a larger than average diameter. Of more concern are eyes with smaller than average nerve head diameters, which may lead to delayed diagnosis.

We need to acknowledge the limitations of the data, and this is where clinical acumen is important. We do have newer technology and tools to help us sort out these apparent inconsistencies. So again, looking at risk factors can be helpful, but one needs to accept the limitations and apply them appropriately.

Will our perception of the importance of risk factors change over the next 20 years?

Dr. Iwach: Absolutely. The indices we have now are helpful, but we need better biomarkers. Technology is advancing to improve our ability to image structures at a more refined level, to not only detect the disease, but detect subtle progression. Although we rely heavily on IOP measurements, at this time during a typical exam we are obtaining only a snapshot, a narrow slice of data. The patient will come in to the clinic a few times a year, and we obtain 3 to 5 seconds of data per visit, typically only with the patient sitting upright. From these isolated data points we extrapolate to make major treatment decisions, such as adding medication or recommending laser treatment or even surgery. Several groups are actively pursuing IOP sensors, some of which are even implantable. Someday, when we discuss risk factors, our information will be derived from a much more robust data set.

So, we have made a lot of progress in the last 20 years. I’m very optimistic that in the not-too-distant future we will have better diagnostic tools that will help us better understand the anatomy and dynamics of glaucoma. Ultimately, this should make us more efficient and smarter clinicians, who know better if, when and how aggressively to treat patients.

What were some of the insights from the recent Los Angeles Latina Eye Study?

Dr. Iwach: No ethnic group is immune to glaucoma. With that said, good data show a higher incidence of glaucoma in the African American population and a higher risk of narrow-angle glaucoma in Asian populations.¹ The Los Angeles Latino Eye Study highlights the fact that Latinos are also at high risk.² This study found that 64% of Latinos in Los Angeles are not aware of their condition. This is yet another study confirming that many patients remain undiagnosed. The Los Angeles Latino Eye Study shows us that we need to continue our efforts to screen for visual impairment and eye disease. Earlier diagnosis can prevent unnecessary vision loss.

So how is your message getting to the public?

Dr. Iwach: The American Academy of Ophthalmology’s Get Eye Smart program (www.geteyesmart.org) is geared to the public to alert them to the importance of good eye health and regular eye exams. As a part of that, the Academy’s Eye-Smart—EyeCheck campaign raises awareness of the impact of eye diseases and visual impairment. This program offers free screenings and referrals, is building a national inventory of community eye screenings, and is testing and tracking a new screening approach that checks for visual impairment rather than individual diseases. The campaign is being emphasized in the Latino community initially and will be expanded from there.

What are the risk factors for failure of glaucoma surgery, and what can we do to mitigate them?

Dr. Iwach: We do have some great drugs as well as some very good laser treatments. Fortunately, most patients will respond adequately to a combination of these, but not all. At the moment, despite its limitations, many feel that trabeculectomy is the gold standard. Unfortunately, our newer glaucoma surgeries, although promising, also have limitations.

When we speak of failure of glaucoma surgery we usually address this topic from the surgeon’s perspective. We need to expand this discussion and incorporate what the patient perceives.

Just telling patients they might have glaucoma can adversely affect quality of life—they can start fearing vision loss. Many patients with glaucoma are asymptomatic despite having a vision-threatening disease. In an effort to maintain vision in the long run, you may operate on a patient whose vision is fine for all practical purposes and cause immediate symptoms from “successful” filtering surgery, including visual distortions, decreased acuity and ocular discomfort. Longer term, those filtering blebs may get infected, potentially leading to loss of the eye. Thus, accurately determining the need for surgery and the optimal timing is critical.

References

The Eye Diseases Prevalence Research Group. Arch Ophthalmol. 2004;122:532–538.
Francis BA, et al. Invest Ophthalmol Vis Sci. 2011;52:6257–6264.
American Academy of Ophthalmology Web site. EyeSmart. www.geteyesmart.org. Accessed December 6, 2011.

Full references are available at www.OSNSupersite.com. Click on Education Lab