This prospective study investigated the anatomic basis for variation in angle closure prevalence across ethnicities. It found that corneal vault may account for the shallower anterior chambers of Chinese subjects relative to Caucasians.
Researchers used OCT to compare the anterior segment biometric parameters of Caucasians, American Chinese, and Southern and Northern mainland Chinese subjects. The cohorts were matched for age and gender and each had roughly 120 subjects.
To reflect lens vault, the authors developed a novel anterior segment parameter, corneal arc depth - which is the perpendicular distance from the corneal endothelium apex to the interscleral spur line. Using corneal arc depth as the parameter, Chinese subjects had less vaulted corneas than Caucasians.
Additionally, multiple linear regression found that in Chinese subjects corneal arc depth tended to be smaller in females than in males after controlling for confounders, such as age and axial length. The authors posit that corneas of Chinese females allow less underdome capacity for the anterior chamber along both axial length and ISS line dimensions. This is a likely cause of crowded anterior chamber, as well as higher risk for angle closure in Chinese females.
Although no interethnic difference was detected in terms of lens vault mean values, Chinese subjects appeared to have greater increments of lens vault per decade of age increase than Caucasians, suggesting the contribution of lens vault to a crowded anterior chamber could be more prominent in older Chinese than in Caucasians of the same age.
In the Chinese cohort, females and older subjects tended to have smaller anterior chamber depth, anterior chamber width and corneal arc depth. The more anteriorly located lens under a less vaulted cornea in Chinese females compared with Chinese males may account for the higher risk of angle closure in this subpopulation. The authors write that the shallower anterior chamber in Chinese subjects is likely due to their shorter corneal arc depth.