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EW GLAUCOMA 32 by Matt Young EyeWorld Contributing Editor Foveal contrast sensitivity affected by glaucoma Could contrast sensitivity testing help detect glaucoma earlier? I n contrast to conventional wis- dom, new research finds that sharp central vision is signifi- cantly decreased by glaucoma. The research, published in Jan- uary in Archives of Ophthalmology, found significantly lower foveal con- trast sensitivity in both photopic and mesopic conditions in eyes with glaucoma. "The maintenance of good vi- sual acuity until late in the disease and the absence of characteristic central visual field defects lead to the belief that the fovea remains un- affected in the early stages of the dis- ease," reported co-lead study author Hani Levkovitch-Verbin, M.D., Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Is- rael. "However, the density of gan- glion cells is 10-fold greater at the fovea than the density at 25 degrees eccentricity and 100-fold greater than at the farther periphery, an ef- fect that enables substantial redun- dancy at the fovea to overcome the early loss in the glaucomatous process, sparing normal foveal func- tion." Just because the fovea is still in good working order doesn't mean it's not affected. "The CS [contrast sensitivity] testing methods used in this study detected damage in cen- tral vision despite good acuity," Dr. Levkovitch-Verbin noted. A factual basis for foveal damage Dr. Levkovitch-Verbin analyzed 35 eyes with glaucoma, age-matched against 23 control eyes with visual acuity of 20/30 or better. The glaucoma group included eyes with primary open-angle glaucoma (15 eyes), exfoliation glaucoma (six eyes), chronic angle- closure glaucoma (five eyes), nor- mal-tension glaucoma (three eyes), and suspected glaucoma (six eyes). "Contrast sensitivity was examined by means of two comput- erized psychophysical tests," Dr. Levkovitch-Verbin reported. "The transient method included the pres- entation of a target in a temporal, two-alternative, forced-choice procedure, and the static method involved four forced-choice proce- dures." Using the transient method, re- searchers found significant differ- ences between the glaucoma and control groups at all special frequen- cies (SFs) under both photopic and mesopic conditions. Researchers also uncovered significant differences using the static method. "We used the common SF (6.0 cpd) that was used in both the static and transient methods to compare CS between different glaucoma categories and the controls," Dr. Levkovitch-Verbin reported. "There was a trend of decreasing CS with in- creasing severity of glaucoma. Pa- tients with severe glaucoma had significantly decreased CS compared with controls using the static or the transient photopic SF of 6.0 cpd." Previous research has indicated that glaucoma affects contrast sensi- tivity, but this is one of the first re- ports to indicate an impact on the fovea itself. "Our results are consistent with previous studies but add psy- chophysical evidence that foveal functions are affected in glaucoma, February 2011 May 2011 said. "Specifically, they had IOP of less than or equal to 21 mm Hg at diagnosis." Investigators also found that oral contraceptive use played a role. "Use of oral contraceptives for 5 or more years was associated with an increased risk of POAG overall," Dr. Pasquale said. Estrogen connection? Results substantiated what investiga- tors had suspected. "We have felt for some time now that circulating es- trogen levels are important in POAG pathogenesis in women," Dr. Pasquale said. "I suspected we'd find some relations, albeit modest, be- tween female reproductive factors and POAG." Dr. Pasquale theorized estrogen levels likewise play a role in the long-term oral contraceptive con- nection. "Oral contraceptives blunt the mid-cycle surge in estrogen me- diated by luteinizing hormone and follicle stimulating hormone," he said. "Ocular structures, including the optic nerve, are sensitive to the physiologic ebb and flow of estrogen in the normal menstrual cycle." He thinks that perhaps the disruption of the ebb and flow alters an impor- tant physiologic mechanism that puts women at risk for glaucoma. "This is pure speculation and more research is needed to confirm the connection between oral contracep- tive use and POAG," Dr. Pasquale said. Investigators hope that practi- tioners keep reproductive factors in mind when examining female pa- tients for POAG. "The bulk of emerging research supports a role of declining estrogen in the pathogene- sis of POAG," Dr. Pasquale said. "When an ophthalmologist sees a perimenopausal female patient with a glaucoma-like disc, even if the intraocular pressure is in the normal range, he should perform a glaucoma workup." Unfortunately, there are currently no specific rec- ommendations regarding how to manage glaucoma in light of these findings. As of yet, there are also no recommendations available on con- traceptive use. "No lifestyle recom- mendations regarding use of oral contraceptives can be made based on this data," Dr. Pasquale said. Going forward, investigators plan to study whether there are in- teractions between attributes of fe- male reproductive health and genetic profile in POAG. "We hope such work will lead to biochemical pathways that are important in POAG pathogenesis," Dr. Pasquale said. EW Editors' note: Dr. Pasquale has no fi- nancial interests related to his com- ments. Contact information Pasquale: Louis_Pasquale@meei.harvard.edu Reproductive continued from page 31 Contraceptive use and age of menstrual onset can have a bearing on a woman's glaucoma risk Source: National Eye Institute, National Institutes of Health A scene as it might be viewed by a person with glaucoma. A new study found that central vision is significantly decreased by the disease Source: National Eye Institute, National Institutes of Health 30-33 Glaucoma_EW May 2011-DL_Layout 1 5/2/11 2:08 PM Page 32

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