Distribution and Trends in Corneal Thickness Parameters in a Large Population-Based Multicenter Study of Young Chinese Adults.

Purpose: The purpose of this study was to characterize corneal thickness from multiple regions and determine accurate reference values in young adults for diagnosis and treatment.

Methods: This cross-sectional observational study was conducted from January 2008 through October 2016 using examiner-blinded clinical measurements and included 37,375 healthy eyes from young adults who exhibited normal corneal morphology, had no history of eye surgery or trauma, had stopped wearing soft contact lenses for ≥2 weeks (rigid contact lenses for ≥4 weeks), and had undergone topographies of both eyes on same day. Keratoconus and subclinical keratoconus were excluded. This multicenter study was conducted in four provinces of China: Tianjin, Shandong, Hubei, and Xinjiang.

Results: Central corneal, corneal vertex, and thinnest corneal thicknesses were higher in eyes from Hubei than other provinces. The left eye was thicker than the right in patients from Shandong, Tianjin, and Hubei, but not Xinjiang. Overall corneal thickness was higher in eyes from Hubei than from other provinces. Changing trend of the whole-cornea thickness in eyes from Xinjiang differed from eyes from other provinces. Trends in maximum and minimum axial for change of corneal thickness were similar between eyes from Hubei and Xinjiang and between Shandong and Tianjin.

Conclusions: Corneal thickness differs among eyes from different regions. Corneal thickness parameters are influenced by ethnicity and geographical location, as increasing proximity to the equator was related to increasing corneal thickness. Design of refractive surgery and diagnosis of related diseases in patients of a certain area should be based on reference values from its population.