Morphology of the optic disc in the Tajimi Study population

To assess optic disc morphology and disc-fovea distance (DF)/mean disc diameter (DD) ratio and related factors in Japanese subjects in a population-based setting.

Digital fundus photographs obtained from 2634 subjects, comprising 87% of 3021 participants aged 40 years or older in the Tajimi Study, a population-based glaucoma survey, were analyzed planimetrically.

The disc size averaged 2.28 mm², the ovality (maximal/minimal disc diameter ratio) 1.12 and the DF/DD ratio 2.94. After adjusting for other systemic and ocular factors, the disc size was correlated with the spherical equivalent refraction (SE), the ovality and DF/DD ratio correlated negatively with the SE and disc size (P < 0.0001). These parameters did not differ significantly between 2095 ophthalmologically normal eyes and 58 eyes with open angle glaucoma (OAG). The angle of the long axis of the discs with ovality of >1.10 was between 91° and 120° in 53% of the subject eyes.

The reference data of disc morphology and DF/DD ratio in a Japanese population were obtained. SE showed significantly negative correlation with disc size, and disc size and SE showed significant negative correlation with ovality and DF/DD ratio. There was no significant difference between normal and OAG eyes evaluated by disc morphology and DF/DD ratio.