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Corneal refractive power and its associations with ocular and general parameters: the Central India Eye and Medical
Jost B Jonas1, Vinay Nangia, Ajit Sinha
1Suraj Eye Institute, Nagpur, India.
Purpose:
To investigate the normal distribution of corneal refractive power (CRP) and its associations with other ocular and systemic parameters in the Central Indian population.
Design:
Population-based study.
Participants:
The Central India Eye and Medical Study is a population-based study performed in a rural region of Central India. The study comprised 4711 subjects aged 30+ years.
Methods:
A detailed ophthalmic and medical examination was performed. Horizontal and vertical CRP were measured using a non-automatic keratometer.
Main Outcome Measures:
Corneal refractive power.
Results:
After excluding pseudophakic or aphakic eyes, keratometric measurements were available on 9024 eyes of 4617 study participants (98.0%) with a mean age of 49.1±13.2 years (range, 30-100 years) and a mean refractive error of -0.20±1.52 diopters (D). Mean horizontal CRP was 44.60±1.68 D (mean ± standard deviation; range, 36.5-52.0 D), and vertical CRP was 44.62±1.74 D (range, 37.75-52.0 D) with no significant difference between both parameters (P=0.27). In multivariate analysis, CRP was significantly (P < 0.001) associated with the systemic parameters of increasing age (P < 0.001), lower level of education (P=0.02), and lower body height (P < 0.001), and with the ocular parameters of thinner central corneal thickness (P < 0.001), deeper anterior chamber (P < 0.001), shorter axial length (P < 0.001), and myopic refractive error (P < 0.001). The results remained unchanged if eyes with CRP ≥48 D were excluded.
Conclusions:
Horizontal CRP increased with higher age, lower level of education, lower body height, thinner central cornea, deeper anterior chamber, shorter axial length, and myopic refractive error. The association with age may be of importance for refractive surgery. The association of a steeper cornea with a shorter body stature and a shorter axial length parallels an association between shorter body length and shorter axial length without association with refractive error. The association among steeper cornea, shorter body length, and lower educational level complements the association between shorter body length and lower educational level. The correlation between steeper cornea and deeper anterior chamber may be explained geometrically.
