BMC Ophthalmology · 8 authors, 4 centres
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This cohort study of 2,546 university employees in Iran found a keratoconus prevalence of 0.98%. A family history of keratoconus (OR 21.00) and elevated serum LDL ≥110 mg/dL (OR 3.00) were significant risk factors, supporting an inflammatory and oxidative stress component in the disease. Despite worse best-corrected visual acuity in keratoconus subjects, no cases met the WHO definition of visual impairment, likely due to access to treatment.
**Background:** Keratoconus (KCN) is a bilateral progressive corneal ectasia causing visual impairment. Its prevalence varies globally (0.04%–4.0%) and is influenced by genetic and environmental factors. Oxidative stress is implicated in KCN pathogenesis, and biomarkers such as elevated LDL, low HDL, hyperglycemia, and high BMI are associated with oxidative stress. This study aimed to determine KCN prevalence and evaluate associations with oxidative stress biomarkers in a cohort of university employees in Shiraz, Iran.
**Methods:** A total of 2,546 participants (mean age 40.35 ± 6.70 years; 46% male) were recruited from 2019–2020 as part of the SUMS Employees’ Health cohort study (a branch of the PERSIAN national cohort). All participants underwent objective refraction (auto-refractometer and retinoscopy), subjective refraction, and biomicroscopy. Suspected KCN cases were confirmed with Pentacam imaging using predefined topographic criteria: zonal Kmax-3 mm >48 D, ART-max <339, IS-value >1.4, and BAD-D >1.6. KCN diagnosis required clinical signs plus two or more abnormal Pentacam parameters. Blood samples were collected after fasting to measure glucose, LDL, HDL, and triglycerides. Visual impairment was defined as best-corrected visual acuity (BCVA) worse than 0.5 logMAR. Univariate and multivariable logistic regression were performed.
**Key Results:** The prevalence of KCN in at least one eye was 0.98% (95% CI: 0.6%–1.4%), with 24 cases identified (12 male, 12 female; p=0.58 for sex difference). Twenty-one cases were bilateral, three unilateral. Mean BCVA was significantly worse in KCN subjects (0.06 ± 0.1 logMAR) vs. non-KCN subjects (0.01 ± 0.07 logMAR; p<0.001). Spherical equivalent was −4.00 ± 3.10 D in KCN vs. −0.70 ± 1.50 D in non-KCN (p<0.001). No KCN subject met the WHO definition of visual impairment (BCVA >0.5 logMAR). In multivariable regression, family history of KCN was the strongest risk factor (OR 21.00, 95% CI: 9.00–48.00, p<0.001). Elevated LDL ≥110 mg/dL was also significant (OR 3.00, 95% CI: 1.20–6.40, p=0.01). Age, sex, education level, BMI ≥30, glucose ≥100 mg/dL, HDL ≤40 mg/dL, and triglycerides ≥150 mg/dL were not significant. Mean LDL was significantly higher in KCN subjects (110.48 ± 19.53 mg/dL) vs. non-KCN subjects (99.73 ± 23.55 mg/dL; p=0.01).
**Clinical Implications:** This study confirms that family history is a major risk factor for keratoconus, with a 21-fold increased odds. The novel finding of elevated LDL as an independent risk factor (three-fold increased odds) supports an inflammatory and oxidative stress component in KCN pathogenesis. The absence of visual impairment among KCN subjects likely reflects good access to treatment (including cross-linking and keratoplasty) in this educated, employed population. These findings suggest that lipid profile assessment may be relevant in KCN evaluation and that further investigation into inflammatory pathways could open avenues for dietary or pharmacological interventions. Limitations include the lack of universal Pentacam screening (possibly missing mild or forme fruste cases) and restriction to university employees, which may limit generalizability.