Ocular determinants of refractive error and its age- and sex-related variations in the Chinese American eye study

IMPORTANCE: Uncorrected refractive error (RE) is a leading cause of visual impairment, and variations in ocular anatomy determine RE. The unique ocular determinants of RE in Chinese American individuals have not been studied previously. OBJECTIVE: To report ocular determinants of RE in a Chinese American population 50 years and older in Monterey Park, California. DESIGN, SETTING, AND PARTICIPANTS: The Chinese American Eye Study, a population-based, cross-sectional study, was conducted from February 1, 2010, through October 31, 2013, in Monterey Park, with this particular data analysis performed from January 1 through December 31, 2016. This study included data from 4582 participants who underwent an eye examination to obtain axial length (AL), central corneal thickness, vitreous chamber depth (VCD), anterior chamber depth (ACD), lens thickness (LT), corneal power (CP), noncycloplegic subjective refraction, and lens nuclear opalescence (NOP) grading. Data from the right phakic eye of each participant were used. Multiple regression models (standardized regression coefficients [SRCs] and semipartial correlation coefficients squared [SPCCs2]) identified key determinants of RE. MAIN OUTCOMES AND MEASURES: Ocular determinants of RE. RESULTS: Among the 4071 participants eligible for analysis (1496 men [36.7%] and 2575 women [63.3%]; mean [SD] age, 60.5 [8.1] years), mean (SD) RE was -0.52 (2.95) diopters (D), with no sex-related difference. A hyperopic shift occurred in women from -0.62 (2.95) D at 50 to 59 years to 0.60 (1.62) D at 80 years or older and in men from -0.69 (3.00) D at 50 to 59 years to 0.40 (2.29) D at 80 years or older (P < .001 for both). Compared with men, women had shorter AL (mean [SD], 23.62 [1.34] vs 24.14 [1.27] mm; P = .006), shorter ACD (mean [SD], 3.33 [0.34] vs 3.44 [0.34] mm; P < .001), and steeper CP (mean [SD], 43.50 [1.52] vs 42.88 [1.45] D; P = .02), after adjusting for age and height. No sex differences were found in VCD, LT, and NOP after height adjustment. Compared with younger individuals, older individuals had shallower ACD, thicker LT, and more NOP compared with younger individuals (P < .001 for both), even after adjustment for height. Axial length was the strongest determinant of RE (SRC = -0.92; SPCC² = 0.55), followed by CP (SRC = -0.43; SPCC² = 0.15). When individual components of AL were evaluated, VCD had the greatest contributing effect (SRC = -0.99; SPCC² = 0.52), followed by CP (SRC = -0.47; SPCC² = 0.15) and LT (SRC = -0.29; SPCC² = 0.06). CONCLUSIONS AND RELEVANCE: These data suggest that Chinese American individuals have longer AL and greater contribution of AL to RE than do Latino and other Chinese populations. Future studies should explore risk factors for increased AL in Chinese Americans and potential interventions that may ultimately preventmyopia-related disease.