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D. L. Chao, A. Shrivastava, D. Kim, H. Lin, K. Singh; Axial Length Does Not Correlate With Degree of Visual Field Loss in Myopic Chinese Individuals With Glaucomatous Appearing Optic Nerves. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4414.
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Myopia is endemic in Chinese populations throughout the world. We have previously described a group of young patients of Chinese ancestry who presented with optic nerve appearance and visual field loss suggestive of glaucoma but did not show progression characteristic of this disease for up to seven years. The purpose of this study was to assess whether or not greater axial length is a risk factor for visual field loss in patients presenting with this cluster of findings.
All patients of Chinese origin with characteristics of this previously described condition including myopia, tilted discs and glaucomatous visual field abnormalities followed by one practitioner (KS) were identified. Patients meeting the criteria for this condition who also had asymmetric visual field loss as defined by greater than 2 units of difference in mean deviation on Humphrey Automated Perimetry(Carl Zeiss Meditec, Dublin, CA) were offered enrollment into the study. All consenting subjects underwent axial length measurement in both eyes using a Zeiss IOL master(Carl Zeiss Meditec, Dublin, CA) and statistical analysis was performed to determine the relationship between axial length and the degree of visual field loss in each subject.
16 individuals (11 male and 5 female) met all entry criteria and consented to participation in the study. Tilted discs were found in 71.8%(23/32) of eyes, with cup/disc ratios ranging from 0.5-0.9. High myopia as defined by refractive error greater than 6 diopters was found in 75% (24/32) of eyes. In these eyes with discordant disease, longer axial length was not found to be a risk factor for greater visual field loss(p = 0.99, Freeman-Halton extension of the Fisher’s exact test). There was no correlation found between axial length and mean deviation on visual field testing(r= -0.07).
While myopia has been postulated to be a risk factor for glaucomatous optic nerve damage in this young Chinese population, we did not find greater axial length, one indicator of such myopia, to be a risk factor for greater visual field loss in eyes with asymmetric disease. While further study is indicated, these findings suggest that factors other than progressive lengthening of the eye play an important role in the process which leads to visual field loss in such individuals.
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