PARAPAPILLARY GAMMA AND DELTA ZONES IN HIGH MYOPIA

To examine parapapillary zones gamma and delta in highly myopic eyes.

The retrospective observational study included patients attending the Tokyo high myopia clinics. Fundus photographs were morphometrically examined.

The study population included 600 eyes (304 individuals) with a mean age of 62.7 ± 14.3 years (range: 13-90 years) and mean axial length of 29.6 ± 2.2 mm (range: 23.2-35.4 mm). In multivariate analysis (regression coefficient r:0.90), larger horizontal gamma zone diameter was correlated with wider delta zone diameter (P < 0.001; standardized regression coefficient beta: 0.81), higher ratio of vertical-to-horizontal disk diameter (P < 0.001; beta: 0.10), shorter fovea-outer gamma zone border distance (P < 0.001; beta: -0.19), longer disk-fovea distance (P < 0.001; beta: 0.18), and higher count of chorioretinal atrophic lesions (P < 0.001; beta: 0.07). Longer horizontal delta zone width was correlated with longer horizontal gamma zone diameter (P < 0.001; beta: 1.00), longer horizontal disk diameter (P < 0.001; beta: 0.15), shorter disk-fovea distance (P < 0.001; beta: -0.19), longer fovea-outer gamma zone border distance (P < 0.001; beta: 0.19), and smaller diameter of the largest chorioretinal lesion (P = 0.03; beta: -0.04). Longer width of both zones together was associated with longer horizontal disk diameter (P < 0.001; beta: 0.31), higher ratio of vertical-to-horizontal disk diameter (P = 0.001; beta: 0.18), longer disk-fovea distance (P < 0.001; beta: 0.19), shorter fovea-outer gamma zone border distance (P < 0.001; beta: -0.18), higher number of chorioretinal lesions (P < 0.001; beta: 0.30), and longer vertical distance between the superior and inferior temporal arterial arcade (P = 0.001; beta: 0.13).

Larger gamma and delta zones were correlated with larger optic disk and more marked vertical optic disk rotation, longer disk-fovea distance, higher number of chorioretinal lesions, and longer temporal vascular arcade diameter. Parapapillary gamma and delta zones may develop before chorioretinal lesions develop and enlarge.