Size and position of the optic disc crescent in a white European population with myopia

Significance: One of the first clinically observed changes in the retina with progressing myopia is in the form of optic disc crescents. If such a change is predictive of myopia progression, it could aid in myopia management interventions to target those at greatest risk of progression and subsequent ocular morbidity. Purpose: To investigate the type, dimension and appearance of optic disc crescents and how they relate to the level of myopia. Methods: Retrospective data collection analysing retinal photographs of healthy children and adults with a refractive error of ≤−0.50 D sphere and astigmatism ≤2.00 D. Crescent location, maximum crescent width and vertical disc diameter were measured from retinal images of right eyes only. Results: Four-hundred eyes with a mean spherical error (SER) of −0.50 to −14.00 D (aged 7–81 years) were included (83.5% exhibited a discernible crescent). Mean (SD) maximum crescent width was 0.24 (0.24) mm. Univariate analysis showed a significant correlation between crescent width and age (r = 0.26, p < 0.001). SER was correlated with crescent width when controlling for age (r = −0.45, p < 0.001) and to the ratio of crescent width to vertical disc diameter (r = −0.43, p < 0.001). Temporal crescents were the most frequently observed (74%), followed by inferior temporal crescents (17%). One-way between-groups analysis of variance showed a significant difference between crescent locations (F = 5.2, p < 0.001). Post-hoc analysis revealed significant differences in SER between those with no crescent versus an inferior-temporal crescent, as well as differences between those with temporal versus inferior-temporal crescents. Other crescent locations did not differ significantly in the level of myopia. Participants not exhibiting a crescent had the lowest level of myopia (mean [SD] −3.03 [1.97)] D), while those with inferior temporal crescents had a mean (SD) SER of −5.01 (2.37) D. Conclusion: In this white European population, higher levels of SER were associated with increasing crescent size. Eyes with inferior temporally located crescents were more myopic.