The effect of atigmatim and working ditance on optic nerve head image uing a Heidelberg Retina Tomograph canning laer ophthalmocope

PURPOE: To determine effect of atigmatim and working ditance on optic nerve head image in normal patient uing the Heidelberg Retina Tomograph. METHOD: The optic dik of 51 normal healthy ubject, aged 19 to 44 year, were imaged through dilated pupil. ubject with 0.75 DC or le of atigmatim were imaged without correction at a working ditance of 15 mm. They were then re-imaged with a cylindrical correction of +3.00 DC at 90 degree axi (n = 20). Naturally atigmatic ubject with more than 1.00 DC were imaged without correction and then re-imaged once thi wa neutralized with their appropriate pectacle precription (n = 15). The effect of working ditance were tudied uing ubject with 0.75 DC or le (n = 16). Two working ditance were ued, 15 and 25 mm. At each eion the mean of three topographic image were taken from which tandard deviation and parameter were recorded. Parameter analyzed included cup hape meaure, rim area, and inferior temporal rim volume. Z-profile full width at half maximum wa calculated from one image per ubject for each condition. REULT: No ignificant difference wa found in the meaured parameter of the optic dik for any atigmatic condition or change in working ditance (P > .05), (paired t tet). Both the tandard deviation of the mean topographic image and the Z-profile half-maximum width of the axial intenity profile were ignificantly greater with induced atigmatim of +3.00 DC (P value 0.3 and .00, repectively). CONCLUION: Optic dik parameter are not ignificantly affected by uncorrected atigmatim (up to 2.50 DC) or working ditance. The algorithm ued by the Heidelberg Retina Tomograph to generate topographic map i ufficiently robut that atigmatim up to 2.50 DC doe not require correction.