Optical Coherence Tomography and Biometry in High Myopia with Tilted Disc

Purpose. The purpose of this study was to compare retinal thickness and biometric parameters between highly myopic eyes with and without tilted optic discs. Methods. A total of 60 eyes from 60 highly myopic individuals (defined as a mean spherical equivalent refraction of -6.00 D or greater and axial length >= 26 mm) underwent detailed ophthalmic examination. Twenty-one eyes (13 females and 8 males; mean age: 29 +/- 7 years) with tilted optic discs were recruited and compared with 39 eyes (23 females and 16 males; mean age: 28 +/- 6 years) of control subjects without tilted optic discs using spectral domain optical coherence tomography (OCT) and the Lenstar biometer. Disc ovality was assessed using the ratio of minimum to maximum disc diameter (index of tilt). A ratio of <= 0.80 was considered as a tilted optic disc. Results. There were no significant differences in biometric parameters between two groups. However, myopia in the tilted disc group was significantly greater compared to the non-tilted group (-8.82 +/- 1.58 D vs. -7.84 +/- 1.22 D, p = 0.01). Comparison of OCT sectoral macular nerve fiber layer measurements between groups showed significant differences in inner ring thicknesses for the nasal (p = 0.01), inferior (p < 0.001), and temporal (p = 0.04) quadrants. A significant difference was also seen in outer ring macular nerve fiber layer thickness for the temporal quadrant (p = 0.03). No significant differences were demonstrated in optic disc peripapillary retinal nerve fiber layer (RNFL) thickness between the two groups. Conclusions. Mean spherical equivalent refractive error is strongly correlated with optic disc tilt; however, other biometric factors are independent of tilt. Structural examination of the eye using OCT can be employed to differentiate between eyes with tilted optic discs and those with normal discs. Peripapillary RNFL appears to be unaffected by tilted discs.