Eyeworld

EW GLAUCOMA 100 March 2016 by Tony Realini, MD, MPH said, "with 46% of NTG eyes and 23% of high tension open-angle glaucoma eyes manifesting one or more disc hemorrhages. This sug- gests that there is a specific subpop- ulation of glaucoma patients who are at risk for disc hemorrhages. The higher prevalence of disc hemor- rhages in NTG versus HTG suggests the possibility that NTG eyes have a higher susceptibility of small blood vessels to rupture." Is sleep apnea an unrecognized risk factor? The ongoing search for risk factors in glaucoma has recently revealed a new potential factor: obstructive sleep apnea. "There is a very strong connec- tion between obstructive sleep apnea and normal tension glaucoma," said Robert Ritch, MD, New York. "Risk factors for developing NTG in Japan and Korea are in- creasing intraocular pressure (IOP), myopia, and advancing age," Dr. Park said. "In Korea, additional risk factors include male gender, system- ic hypertension, and not being over- weight. In younger people—those under age 40—additional risk factors include high fasting blood glucose and low HDL cholesterol." "Based on a study conducted in the United States, risk factors for progression of NTG include disc hemorrhage, female gender, and a history of migraine headaches," he added. Disc hemorrhages have long been considered an ominous sign of progression in NTG. "Longitudinal detection of disc hemorrhages in open-angle glauco- ma plateaus after 5 years," Dr. Park and Hispanics. Although estimates vary widely between studies, taken together, epidemiologic studies sug- gest that throughout the world, NTG represents perhaps 50% or more of all open-angle glaucoma." "The more we look, the more we find," Dr. Park said. "Retinal nerve fiber layer photography and optical coherence tomography (OCT) can detect normal tension glaucoma and its progression before the visual field changes." Who is at risk for NTG? The risk factors for both the devel- opment of normal tension glauco- ma and its progression have been evaluated in many studies. Most of these come from east Asian coun- tries, where NTG is most prevalent and most easily studied. O ver the past 2 decades, numerous epidemiologic studies have revealed that normal tension glaucoma (NTG) represents a much higher proportion of all open-angle glaucoma than previously thought. These studies have also demonstrat- ed significant regional variation in the prevalence of NTG. This was the focus of one of the glau- coma sessions at the 2016 World Ophthalmology Congress (WOC) in Guadalajara, Mexico. "In Japan, 92% of open-angle glaucoma is NTG," said Ki Ho Park, MD, Seoul, Korea. "In Korea, it is 95% according to a recent study from the Korea National Health and Nutrition Examination Survey." Makoto Araie, MD, Tokyo, agreed. "The prevalence of NTG is particularly high in eastern Asians Normal tension glaucoma: Who gets it and who goes blind? A disc hemorrhage in an NTG case Source: Tetsuya Yamamoto, MD A case with early NTG. At the 7:00 region of disc margin, there are disc hemorrhages and wedge-shaped retinal nerve fiber layer defects (darker colored compared to the adjacent area) extending to periphery. However, the visual field test result by standard automated perimetry was within normal limits, which means there is a time gap between the structural and functional abnormality. Source: Ki Ho Park, MD

• Cover