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Myopia and Glaucoma: Sorting out the Diagnosis

Myopia and Glaucoma: Sorting out the Diagnosis

Clinical Update

GLAUCOMA and : Sorting Out the Diagnosis

by miriam karmel, contributing writer interviewing simon k. law, md, shan c. lin, md, and kuldev singh, md, mph

s it glaucoma? Or is it a condi- Myopia +/- Glaucoma tion that looks like glaucoma? Ophthalmologists assessing 1 2 patients with high myopia often face this diagnostic dilemma. I“High myopes may not have glaucoma, but the presentation looks like glauco- ma. Or they may have glaucoma, and we are not sure,” said Simon K. Law, MD, at the Jules Stein Eye Institute. These questions take on special ur- gency in light of what appears to be an almost epidemic explosion of myopia, particularly in Chinese populations appearance of two highly myopic patients: (1) diagnosed with glau- (see “The Chinese Connection”). coma; (2) without glaucoma. The link between myopia and glau- coma has been explored for nearly a How Myopes Are Different and determine whether or not those century.1 A number of studies, includ- Optic nerve findings. The presenta- who are diagnosed with myopia and ing the Blue Mountains Eye Study and tion in these challenging cases is glaucoma follow a course similar to the Beijing Eye Study, have found that anything but classic. For starters, the the classic presentation of primary the risk of glaucoma appears to in- optic nerve may look different from open-angle glaucoma [POAG],” said crease in persons with high myopia (6 the characteristic glaucomatous op- Dr. Singh. D or more).2,3 Recently, Kuldev Singh, tic nerves that clinicians have been He explained that classic untreated MD, MPH, at Stanford University, and trained to identify. “We call them POAG often presents with an arcuate Shan C. Lin, MD, at the University of ‘funny-looking’ optic nerves,” Dr. Lin defect in one hemifield, California, San Francisco, reported a said (Figs. 1 and 2). followed by similar loss in the other similar association in a U.S. popula- Dr. Law put it this way: “The dif- hemifield, split fixation, and ultimate- tion.4 Dr. Law added that patients with ficulty with diagnosis is because the ly—in those with severe disease—loss mild myopia appear to follow a course optic nerve looks abnormal, and we of all vision. Dr. Singh hypothesized similar to those without myopia. base diagnosis on the optic nerve. But that myopia may be associated with While they acknowledge the link the nerves [in myopes] sometimes regional damage to an optic nerve, between myopia and glaucoma, Drs. look different from nonmyopic pa- sometimes the superior or inferior Law, Singh, and Lin are among a group tients. And the pressure may not be too rim, with relative sparing of the other of glaucoma experts who ask: How do high. They may even have visual field half of the nerve. “While such asym- you distinguish patients with myopia defects, but [these] don’t progress or metry between the superior and infe- and glaucoma from those who have progress differently. So we have a di- rior nerve bundles is characteristic of myopia-related visual field defects that agnosis problem and then a following most patients with glaucoma, those may mimic glaucoma—but are not problem.” with myopia may perhaps be less likely destined to show progression charac- Visual field defects and progres- to follow the same progressive POAG

simon k. law, md teristic of glaucoma? sion. “A focus of our research is to try pattern, where the other half of the

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3A 3B ily when the pressure is lowered after . • Watch out for former high myopes, that is, patients whose myopia was reduced or eliminated by . Even though their refractive status has been improved by a kera- torefractive procedure, their elongated eye structure and optic nerve status remain unchanged. Ask these patients if they have had TILTED DISCS. (3A) Right and (3B) left optic nerves of highly myopic Chinese man LASIK. Because that procedure thins with bilateral tilted discs and peripapillary atrophy (double arrows). At presentation, the , IOP measurements may be he had a dense superior field defect on the right and an early arcuate defect on the artifactually low. There are no good right and was being treated with antihypertensive eyedrops. During five years of fol- nomograms to tell how much the pres- low-up and continuing topical treatment, the field defects remained stable. sure will change, and the change is not linear. These patients should be fol- nerve and corresponding visual field who are suspected of having, or are lowed carefully. ultimately become damaged.” diagnosed with, glaucoma. Code these post-LASIK patients as Dr. Singh reported observing • Follow the nerve; you still have to “high-risk glaucoma suspects.” this phenomenon in young Chinese rely on it. Take pictures of the optic Dr. Lin noted several points to con- myopes who presented with steep- nerve to document its appearance sider in deciding whether to initiate edged visual field defects and com- over time. If you see changes, then you treatment. monly had “normal” intraocular pres- know for sure that the glaucoma is • Treat each case differently, taking sure (IOP). This presentation resulted progressing. into account family history, degree in a diagnosis of POAG or glaucoma • Remember that visual field change of visual field defect, and your own suspect.5 Although these eyes may isn’t always the result of glaucoma but comfort level with following versus show extension of existing defects, may represent other types of optic treating. they appear to less commonly exhibit nerve damage. For example, nerves • A large proportion of high myopes new field defects in the opposite hemi- that tilt inferiorly (Fig. 3) may have truly have glaucoma. If you’re not sure, field in later years. Still, he cautioned visual field defects at the top hemi- you may want to treat it as if it’s glau- that this observation needs further field. Other visual field defects may be coma if the visual field defect is severe study. In the meantime, Dr. Singh caused by myopic retinal degeneration, or very close to fixation. said that not all progression should be not glaucoma. • Drugs for treating glaucoma have a considered equally significant. “There • Be mindful of the pressure. Eyes relatively safe systemic side effect pro- is greater concern when patients show with high myopia may be less able to file, so it’s reasonable to err on the side new field defects corresponding to tolerate IOP fluctuations than other of caution and treat. regions of the optic nerve previously eyes: They have a longer , thinner • Recognize when the visual field pat- considered healthy.” lamina cribrosa, and thinner scleral tern does not follow the typical pattern wall with different elasticity. An IOP of glaucoma. For example, in myopic Pearls From the Experts increase may be sufficient to cause atrophy of the , the visual field Dr. Singh warned against “lumping damage in the posterior pole without usually doesn’t respect the horizontal everyone into one POAG category and causing abnormal corneal IOP readings. meridian. In , in glaucoma, treating them exactly the same.” For In addition, because of the myopic when there is focal damage to the op- example, a 36-year-old myope with eye’s elongated or ellipsoid shape, its tic disc, it usually does not cross the a tilted optic nerve and a visual field posterior wall may be stretched more horizonal meridian. If it crosses that defect who is labeled as having POAG than the nonmyopic eye’s as IOP in- midline, or is isolated in the periphery, may have a very different disease than creases, making the optic nerve more it may not be glaucoma. But the physi- the 80-year-old nonmyope who carries susceptible to damage. cian must bear in mind that there are the same diagnosis, he said. • Be cautious about doing glaucoma no hard-and-fast rules for these diffi- Here is advice from the experts on surgery. People with high myopia have cult diagnoses. how to assess and manage patients a greater chance of hypotony maculop- Dr. Singh cautioned against always with high myopia and “funny-look- athy after surgery, particularly young treating these patients aggressively. ing” optic nerves. high myopes, who have a thinner, less • Avoid filtration surgery, if possible. Dr. Law offered his recommenda- rigid scleral wall. In such patients, While I’m happy to treat with topical

tions for following myopic patients the scleral wall tends to collapse eas- glaucoma , which are rela- Doshi A et al. . 2007;114(3): 472-479.

36 november 2013 Glaucoma tively safe, one should be cautious in setting a very low IOP goal at presenta- The Chinese Connection tion, particularly in those with mild disease without a documented rate of The growing interest in the role of myopia as a risk factor for glaucoma has been prior progression. In these patients, fueled by a startling increase in myopia, particularly in Chinese populations. For early filtration surgery to achieve such example, a study of 5,060 Chinese university students in Shanghai found that 95.5 goals not attained by medications may percent of the students were nearsighted (defined in this study as –0.5 or worse), 1 not be warranted. and 19.5 percent had high myopia. • Don’t assume that moderate field City life. The phenomenon, said Dr. Lin, appears related to rapid urbanization. loss in a young patient confirms rapid “Environment appears to play a role,” he said. Children who once spent much time recent progression unless you have old outdoors playing or doing farm chores are now spending time indoors studying and 2 data to confirm such a course. reading. Yet they need bright sunlight for normal development. “Your mother was • Progression of disease while under right. If you read too much, you’ll become nearsighted. Except it now appears that treatment with medications and the confounding factor is spending time outside.” does not always justify Dr. Singh noted that the sudden increase is occurring in certain populations, par- filtration surgery. Given the inherent ticularly Chinese, where myopia has been historically uncommon. “There has been a risks involved, surgery is most appro- refractive shift in Chinese populations from hyperopia and short eyes to myopia and priate in patients in whom the location longer eyes. This is most evident in urban areas, where this shift has occurred with a and rate of progression suggest a sig- concomitant increase in open-angle versus angle-closure glaucoma.” nificant risk of the patient becoming Consider the overall clinical picture. This phenomenon is more than a matter of symptomatic from the disease. statistical interest. While some Chinese glaucoma patients are destined for poor outcomes that require glaucoma filtration surgery, Dr. Singh believes that there is a More Data Needed subset at risk of overtreatment. Perhaps these patients are destined to follow a very Dr. Law wants to compare the progres- different course than young African-Americans presenting with equally severe visual sion of glaucoma in high myopes with field loss, though often in the setting of high IOP. that in patients who don’t have high Further studies, said Dr. Singh, may determine whether it is appropriate to con- myopia. He is seeking answers to the ceptualize a diagnostic subcategory under “glaucoma suspect.” One possibility: following questions: Are there differ- “Chinese myopia-related suspicious for glaucoma.” ent risk factors for progression in these groups? What is the influence of pa- 1 Sun J et al. Invest Ophthalmol Vis Sci. 2012;53(12):7405-7509. tient characteristics—higher or lower 2 Wu PC et al. Ophthalmology. 2013;120(5):1074. pressure, more myopia, Asian versus Caucasian? 1 Knapp A. Arch Ophthalmol. 1926;55(1):35- service at Stanford Medical School, Stanford, Dr. Lin agreed that there are many 37. Calif. Financial disclosure: Is a consultant to unanswered questions, boiling down 2 Mitchell P et al. Ophthalmology. 1999; Alcon, Allergan, Ivantis, Santen, Sucampo, to who is most likely to progress—and, 106(10):2010-2015. and Transcend. thus, who really needs treatment. “In 3 Xu L et al. Ophthalmology. 2007;114(2): the past, there wasn’t quite the need, 216-220. but the recent explosion of myopia 4 Qui M et al. Invest Ophthalmol Vis Sci. More at the Meeting 2013;54(1):830-835. breeds necessity,” he said. “We need Learn more about prospective data to say how likely per- 5 Doshi A et al. Ophthalmology. 2007;114(3): solving the diagnostic son X is to get glaucoma. There may 472-479. challenges presented by be racial differences. We haven’t done high myopes during Sec- the study targeting this specific risk Simon K. Law, MD, is clinical professor of tion 1, “Diagnostic Tests factor.” health sciences at Jules Stein Eye Institute, in Glaucoma,” at Glaucoma Subspe- In the meantime, as Dr. Singh University of California, Los Angeles. Finan- cialty Day, Saturday, Nov. 16. From noted, “We don’t have a crystal ball on cial disclosure: Has received speaker’s fees from these patients. We don’t know if they Alcon, Allergan, and Tissue Bank Interna- 8:38 to 8:54 a.m., join Felipe A. behave as classic glaucoma patients, tional. Medeiros, MD, Ki Ho Park, MD, PhD, so unless you think vision is immedi- Shan C. Lin, MD, is professor of clinical oph- and Nathan M. Radcliffe, MD, as they ately threatened, it’s best to avoid early thalmology and codirector of the glaucoma ser- provide their perspectives on the case filtration surgery. It’s best to initially vice at University of California, San Francisco. of a highly myopic patient, including follow these patients more conserva- Financial disclosure: Is on the advisory boards considerations for appropriate moni- tively, using safe medications whenever of Alcon, Allergan, Merck, and Sucampo. toring of such patients and the role of necessary. One often has the luxury of Kuldev Singh, MD, MPH, is professor of corneal biomechanics. time.” n ophthalmology and director of the glaucoma

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