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Jonathan Crews, Lance Kugler; Epidemiology of the predominance of noncorneal ocular regular astigmatism (ORA) compared to anterior corneal astigmatism.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2721.
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To evaluate the predominance of noncorneal ocular residual astigmatism vs. anterior corneal astigmatism of patients based on gender, age groups (18-29, 30-44, 45+) and race from a single Midwestern ophthalmology private practice.
The records of dominant eyes of patients who received LASIK consults and preoperative evaluation during the period from 11/2012 to 11/2013 were retrospectively analyzed to obtain ocular residual astigmatism and manifest refraction astigmatism. The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. The ratio of ORA to preoperative refractive cylinder (R) was determined in order to differentiate predominantly anterior corneal astigmatism (ORA/R ratio <1.0) from eyes with predominantly noncorneal ocular residual astigmatism (ORA/R ratio >1.0). These values were then analyzed by gender, race (black, white, Asian), and age groups (18-29, 30-44, 45+ years of age).
The study evaluated 175 eyes of 175 patients. The average ORA/R ratio of the entire patient population was found to be 1.1. The average ORA/R ratio of males and females was found to be 0.98 (n=95) and 1.27 (n=80). The average ORA/R ratio of whites, blacks and Asians was found to be 1.08 (n=166), 1.5 (n=7), and 1.52 (n=2). The average ORA/R ratio of the three different age groups was found to be 1.16 for 18-29 (n=50), 1.03 for 30-44 (n=79), and 1.16 for 45+ (n=46) years of age.
There is a significant difference in the ORA/R ratio between males and females, where males have a predominantly anterior corneal astigmatism whereas females have a predominantly ocular residual astigmatism. The is a significant difference in the ORA/R ratio between white and non-white patients, where white patients have a smaller predominance of ocular residual astigmatism whereas non-white patients is much larger. There also appears to be a bimodal distribution of ocular residual astigmatism from the age group data, where younger and older patients (18-29 and 45+ years of age) have a larger predominance of ORA, whereas the middle-aged patients (30-44 years of age) is much smaller.
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