A characteristic optic disc appearance associated with myopia in subjects with Graves' ophthalmopathy and in subjects with primary open-angle glaucoma

Sei Yamazaki,¹ Rishu Inoue,² Toshikazu Tsuboi,³ Ai Kozaki,² Toshu Inoue,² Toyoko Inoue,² Yoichi Inoue<sup>2

1</sup>Yamazaki Eye Clinic, Shinagawa-ku, Tokyo, Japan; ²Olympia Eye Hospital, Shibuya-ku, Tokyo, Japan; ³Tsuboi Eye Clinic, Edogawa-ku, Tokyo, Japan

Purpose: To determine if qualitatively defining the appearance of optic disc change was a valid characteristic of myopia in subjects with Graves' ophthalmopathy (GO) or primary open-angle glaucoma (POAG).
Methods: We defined typical tilt appearance as the simultaneous presence of the following: an elliptical optic disc, a crescent, unequal sharpness of the cupping margin (horizontally), and nasally displaced vessels in the optic cup. Ninety-two eyes from 92 subjects each with GO or with POAG and no severe complications were included in the study after matching for spherical refractive errors. Using our definition of tilt appearance, two independent observers subjectively judged optic disc photographs. One observer repeated judgments in 70 randomly selected eyes and judgment reproducibility was assessed using kappa statistics. Tilt ratio was used as a quantitative parameter.
Results: The numbers of eyes judged as having a typical tilt appearance in the GO group and in the POAG group were 25 (27.2%) and 39 (42.4%), respectively, by one observer (P = 0.0297), and 12 (13%) and 44 (47.8%), respectively, by another observer (P < 0.0001). Intra- and interobserver reproducibility of tilt judgment were very good (kappa = 0.93) and good (kappa = 0.65), respectively. Tilt ratio did not significantly differ between the two groups. Analytical results including background factors were essentially the same for the two observers: multivariate logistic regression for one observer's judgment showed that the presence of the typical tilt appearance was associated with belonging to the glaucoma group (odds ratio [OR], 6.25; P = 0.0054), tilt ratio (OR per 0.01, 0.77; P < 0.0001), and spherical refractive error (OR per diopter, 0.80; P < 0.003).
Conclusion: The optic disc feature we designated as typical tilt was associated with myopia, and its frequency was higher in subjects with POAG compared to those with GO.

Keywords: glaucoma, myopia, tilted disc, qualitative definition, tilt ratio, Graves' ophthalmopathy