Reprinted from American Journal of Ophthalmology (ML FIakV> MEO.A)O. 2462 Vol. 107, No. 2, February 15, 1989 Large Optic Disks in the Marshallese Population 401845 James M. Maisel, M.D., Caryn S. Pearlstein, M.D., William H. Adams, M.D., and Peter M. Heotis, M.P.S. On routine examination, asymptomatic pa- tients from the Marshall Islands were noted to have large optic disks associated with high cup/disk ratios and normal intraocular pressure. We retrospectively analyzed color fundus photographs of 54 eyes and 22 eyes of 15 patients had optic disks greater than 2.10 mm, or megalopapilla. Of 36 patients with cup/disk ratios exceeding 0.6, 31 (86%) had visual acuities of better than or equal to 20/30. The optic nerve rim and disk areas varied directly as did disk and cup diameters. Three large disks with an 18-year photographic follow-up showed no change. Optic disk characteristics can vary widely among genetically isolated populations. DURING ROUTINE ophthalmologic examination of a Micronesian population in the Republic of the Marshall Islands, a striking numberof patients were noted to have large optic disks. These disks were associated with high cup/disk ratios without increased intraocular pressures, other disk anomalies, or any other ocular complaints.' This Pacific atoll population, which may be considered genetically isolated, demonstrates a large number of people with megalopapilla. Fundus photographs were obtained on a group of patients noted to have high cup/disk ratios as well as on a randomly selected group of control patients. We performed a masked Accepted for publication Oct. 14, 1988. From the Department of Ophthalmology, School of Medicine, State University of New York at Stony Brook, Stony Brook, New York (Drs. Maisel and Pearlstein) and the Medical Department, Brookhaven National Laboratories, Upton, New York (Drs. Adams and Heotis). This project was supported in part by the U.S. Deparment of Energy under Contract No. DE-AC0Q276CHO00016. Accordingly, the U.S. Governmentretains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution or allow others to do so for U.S. Government purposes. Reprint requests to James M. Maisel, M.D., 400 S. Oyster Bay Rd., Suite 305, Hicksville, NY 11801-3516. retrospective analysis of the fundus photographs in order to demonstrate that the optic disks that appeared on ophthalmoscopic examination to have high cup/disk ratios were actually larger than those optic disks judged clinically normal on ophthalmoscopy. Subjects and Methods The population examined consisted of 141 adults native to the Marshall Islands. Some had a history of radiation exposure in 1954, andit is to provide diagnosis and care of radiationrelated illness that complete physical examinations are performed annually.” However, many unexposed patients are also examined. All examinees receive ophthalmologic evaluation, including slit-lamp examination, biennially. Visual acuities are measured with a Snellen chart at 20 feet. For this study there was noselection based on age, sex, previous radiation exposure, consanguinity, or ocular complaints or findings. The ocular examination was performed by an ophthalmologist (J.M.M.} who was part of the Brookhaven National Laboratory medical team. He completed a standardized examination form for each patient as well as performed the fundus photography. All patients thought to have abnormally large disks or high cup/disk ratios underwent fundus photography, as did many patients with normal disks who served as controls. Fundus photographs were taken in a total of 63 patients. The photographs were given to a masked observer (C.S.P.) for analysis. Color slides of the optic nerve head taken with a fundus camera were projected onto the screen of a slide viewer. Using a ruler, meas- urements were madedirectly from the projected image. Black and white photographsof the optic disks of three patients were available from 1967, and measurements madedirectly from these photographs were compared to those of 1985. OAMERICAN JOURNAL OF OPHTHALMOLOGY 107:145-150, FEBRUARY, 1989 sULZog| 145