Seasonal variations in anterior segment angle parameters in myopes and emmetropes.

Clinical Relevance: Seasonal variations are known to occur in a range of ocular parameters and in conditions including refractive error and glaucoma. It is of clinical importance to know if seasonal changes also occur in anterior segment angle parameters, given that they can influence these conditions.

Background: The study aimed to examine the seasonal variations in anterior segment angle parameters in healthy young adults.

Methods: Twenty-three emmetropic participants with a mean age of 26.17 ± 4.43 years and 22 myopic participants with a mean age of 27.27 ± 4.47 years completed four seasons of data collection. Anterior segment angle parameters were measured using swept-source anterior segment optical coherence tomography. Intraocular pressure (IOP) and objective refraction were also measured. Repeated-measures analysis of variance was used to determine the effect of season and refractive error on the various ocular parameters.

Results: A significant main effect of season was found for the majority of anterior segment angle parameters, including the angle opening distance at 500 and 750 µm from the scleral spur ( = 0.02,  = 0.006, respectively), angle recess area at 500 and 750 µm from the scleral spur (both  = 0.002), and trabecular iris space area at 500 and 750 µm from the scleral ( = 0.02,  = 0.008, respectively). However, measures of anterior chamber depth and trabecular iris angle did not exhibit statistically significant seasonal variations (all  > 0.05). A significant main effect of season was also found for the changes in IOP ( = 0.004) and objective refraction ( < 0.001). There was no season by refractive group interaction for any anterior segment angle parameter or IOP (all  > 0.05).

Conclusion: There is a small but significant seasonal changes in the anterior segment angle parameters, refractive error, and IOP in healthy young adult males, in which the anterior segment angle dimensions are narrower, the IOP is higher, and the refraction is more myopic during winter.