Associations of biomechanical properties of the cornea with environmental and metabolic factors in an elderly population : the ALIENOR study

PURPOSE: The purpose of this study was to assess the associations of biomechanical properties of the cornea with metabolic and environmental factors in an elderly population. METHODS: The ALIENOR (Antioxydants, Lipides Essentiels, Nutrition, and Maladies OculaiRes) study is a population-based study. In 2009-2010, 624 subjects, aged 74 years or more, underwent an eye examination, including intraocular pressure (IOP), central corneal thickness (CCT), and biomechanical properties of the cornea measurements using the Ocular Response Analyzer. Socio-demographic, lifestyle, and medical history data were collected using standardized questionnaires. Mean lifetime ambient ultraviolet (UV) exposure was estimated using residential history and statistics of UV radiation at each location using the Eurosun UV database. RESULTS: Mean age was 82.2 ± 4.3 years. Mean corneal hysteresis (CH), corneal resistance factor (CRF), and CCT were 9.4 ± 1.9, 9.8 ± 1.9 mm Hg, and 551.6 ± 36.8 μm, respectively. In the multivariate analysis, CH and CRF values were significantly lower in subjects older than 80 years (-0.56; 95% confidence interval [CI]: -0.89;-0.24); P < 0.001 and -0.48; 95% CI: -0.75;-0.20; P < 0.001, respectively), in subjects having higher ambient UV exposure (-0.50; 95% CI: -0.88;-0.12; P < 0.01; and -0.46; 95% CI: -0.78;-0.13); P < 0.05, respectively), and in subjects with high plasma LDL cholesterol (CH: -0.46; 95% CI: -0.86;-0.03; P < 0.05; and CRF: -0.37; 95% CI: -0.72;-0.008; P < 0.05). Central corneal thickness was significantly higher in former smokers than in never smokers (+11.01; 95% CI: 0.48;21.55; P < 0.05) and was not significantly associated with age, ambient UV exposure, diabetes, or LDL cholesterol. CONCLUSIONS: Biomechanical properties of the cornea are modified by metabolic and lifetime environmental factors, especially UV exposure. The manner these factors may influence onset and progression of ocular diseases or IOP measurements need further investigation