Researchers in Australia assessed central choroidal thickness in a large sample of young adults with the aim of establishing a normative reference profile and exploring its association with best-corrected visual acuity (BCVA). Age and axial length were the most notable predictors of central macular choroidal thickness. There was a significant association between worse BCVA and thinner choroids below a threshold of 300μm, raising the possibility that choroidal thickness could be predictive of visual function.

The study recruited 741 young adults (19 to 30 years) who underwent a comprehensive ophthalmic examination. The median central macular choroidal thickness of young adults was 370μm. The choroid was thickest at the superior, inferior and central macular regions (370µm to 373μm), and thinnest nasally at the outer macular region (256μm). The study associated decreased central macular choroidal thickness with younger age, female sex, non-Caucasian ethnicities and myopia.

There was a significant association between better BCVA and increased central macular choroidal thickness after adjusting for age, sex, ethnicity and ocular measures. This relationship was only apparent in eyes with central macular choroidal thickness measurements less than 300μm and absent in eyes with measurements greater than that value. The researchers believe that choroidal thickness may no longer be important in achieving a better VA when this threshold is reached.

“Given the choroid’s critical role in maintaining retinal integrity, its thickness may be a predictor of VA, and even future visual impairment,” the study’s authors wrote in their paper on the study.