Axial Length to Corneal Radius of Curvature Ratio and Refractive Errors

Farsi     جستجوی اساتید     ورود اساتید     سایت اصلی دانشگاه علوم پزشکی شاهرود     Farsi    
Dr Mohammad Hassan Emamian

Axial Length to Corneal Radius of Curvature Ratio and Refractive Errors


Journal name:
Year: 2013
Volum: 8
Pages: 220-226


Purpose: To determine the distribution of axial length (AL) to corneal radius of curvature
(CRC) ratio and to evaluate its association with refractive errors in an Iranian population.
Methods: In this cross sectional study, multistage cluster sampling was used to select
subjects 40-64 years of age residing in Shahroud, northern Iran. All subjects underwent
manifest and cycloplegic refraction, and biometry using the Allegro Biograph (WaveLight
AG, Erlangen, Germany). Individuals with a history of intraocular surgery, extensive
pterygia and ocular trauma were excluded.
Results: Of a total of 6,311 patients, 5190 (82.2%) participated in the study. We excluded
247 patients to adhere with study criteria and 132 patients due to missing data. Mean
AL/CRC was 3.034 [95% confidence interval (CI), 3.031–3.037]. AL/CRC was 3.028 and
3.042 in female and male subjects, respectively (P<0.001). The R2
coefficients between
spherical equivalent (SE) refractive error and AL/CRC, AL, CRC, lens thickness, and
anterior chamber depth were 0.607, 0.351, 0.012, 0.038, and 0.091, respectively. Linear
regression showed a 12.1 diopter (D) shift towards myopia with every 1 unit increase
in AL/CRC (P<0.001). Mean AL/CRC was 3.472 among myopes with SE less than
-5.0D; this value decreased linearly and was as low as 2.690 among hyperopes with
SE more than 5.0D. R2
coefficients for AL/CRC with spherical and cylindrical power
were 0.560 and 0.071, respectively.
Conclusions: Minimal changes in AL/CRC lead to large changes in refractive error.
The correlation between refractive errors was significantly stronger with the AL/CRC
ratio than with AL and CRC alone

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