OPTIC DISC SHAPE, CORNEAL ASTIGMATISM, AND AMBLYOPIA

Objective: The cornea and the optic disc form the anteroposterior open ing of the sclera. This study evaluated whether an abnormal shape of t he optic disc is associated with an abnormal configuration of the corn ea measured as corneal astigmatism. Design, The study design was a cro ss-sectional one. Participants: The study included 882 subjects (430 w omen, 452 men) with a mean age of 45.9 +/- 13.6 years (mean I standard deviation; range, 8-87 years) and a mean refractive error of -1.09 +/ - 2.76 diopters (range, -21.0 diopters to +7.0 diopters). Intervention : Corneal astigmatism was determined by keratometry, and the optic dis c was analyzed morphometrically by planimetric evaluation of optic dis c photographs. Main Outcome Measures: Corneal astigmatism ratio of min imal-to-maximal disc diameter, and optic disc form factor were measure d. Results: The amount of corneal astigmatism was significantly (P < 0 .001) correlated with an increasingly elongated optic disc shape. Corn eal astigmatism was significantly (P < 0.01) higher in eyes with tilte d discs, It was significantly (P = 0.006) smaller in eyes with an almo st circular disc shape. Amblyopia was significantly (P < 0.05) associa ted with an elongated optic disc shape and high corneal astigmatism Th e axis of corneal astigmatism was correlated with the orientation of t he longest disc diameter. The optic disc was significantly (P < 0.05; chi-square test) more often horizontally oval in eyes with a steeper h orizontal corneal meridian than in eyes with a steeper vertical cornea l meridian. Correspondingly, the disc was significantly (P < 0.05) mor e often vertically oval in eyes with a sleeper vertical corneal meridi an than in eyes with a steeper horizontal corneal meridian. Conclusion s: An abnormal optic disc shape is significantly correlated with corne al astigmatism. Especially in young children, if an abnormal optic dis c shape is found on routine ophthalmoscopy, refractometry should be pe rformed to rule out corneal astigmatism and to prevent amblyopia. The direction of the longest optic disc diameter can indicate the axis of corneal astigmatism.