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J.C. Merriam, L. Zheng; The Relationship of Corneal Curvature and Axial Length in Adults . Invest. Ophthalmol. Vis. Sci. 2005;46(13):864.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine if corneal curvature is related to axial length in the adult human eye. Methods: This is a retrospective study of 1183 eyes of 761 patients, evaluated by a single surgeon for cataract surgery. The average age was 75, with a range of 38 to 99 years. Central corneal curvature was measured with a keratometer (Bausch and Lomb) 3 to 4 times; the mean keratometry value (K) was computed. Axial length (AL) was measured with ultrasound (Sonomed A–2000) 5 to 7 times, and the mean was calculated. The relationship between the K reading and axial length was established by linear fit. The distribution of axial lengths and K readings were also documented. Results: The average K was 43.57, with a range of 38.25 to 50. The average axial length was 24.04, with a range of 18.4 to 31.91. More than 90% of K values were between 40.5 and 46.5; and more than 90% of the axial lengths were between 22.5 and 26.5 mm. Axial length and corneal curvature are linearly related by: AL = 33.87 – 0.226K. The confidence interval for the slope is 0.06. The eyes were then subdivided into those that were spherical, or had predominantly vertical or horizontal corneal astigmatism prior to surgery. The relationship of axial length to mean corneal curvature was not significantly different in these three groups. Conclusions: This study of patients presenting with clinically significant cataract suggests that mean corneal curvature is related to axial length. As axial length increases, the cornea tends to become flatter.
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