Relationship between Eye Axial Length and Corneal Radius of Curvature

Introduction and goals: To study and determine the relationship between eye axial length and corneal radius of curvature, as the entire advancements in medicine have originated from basic studies. The goal of the research is to determine average size of different parts of body and their relationship.
Materials and methods: The research is a descriptive and analytical study. The statistics population consisted of 150,000 eyes in 150,000 patients (55% male, 45% female) who turned to Sadr Tehran Hospital during 2003 to 2013. The patients were examined by an optometrist (the researcher). The average age of men was 56.8 years (42-70) and the average age of women was 59.4 (43-75) years old. Patients with history of eyes surgery, glaucoma, impacts, surface eye diseases and contact lens users were excluded from the study. The anterior posterior length of eye and the corneal curvature of both eyes were checked by Coherent biometry (IOL.MASTER) in three to four repetitions by one optometrist, the research, and the measurements were made. The average of the measurement was then calculated. The relationship between the factors was assessed in linear form and was then studied and compared between the two genders. The SPSS-22 software was used for analyzing the data.
Findings: The mean average corneal curvature radius in men was 7.570mm in 7.00-8.18 range and in women, this number was 7.499mm in 6.79- 8.34 range. The mean length of anterior posterior length (axial length) in men was 23.79mm in 20.22-25.41 range and in women, it was 22.97mm in 21.51-25.62 range. By testing the data, it was shown that data had normal distribution and the following linear relation was found between the two parameters. In general state, AL=1.69 MidR+10.335, the value in women was AL=1.288MidR+13.32 and in men, it was AL=1.97MidR+0.38.
Discussion and Conclusion: By comparing the previous studies, it was showed that the axial length of Iranian population eyes, in this study, was shorter than Americans and South Koreans, longer than Indians and almost equal to Chinese. It was shown that as the cornea is more flat, the axial length of eye is higher; and in turn, as the axial length of eye is higher, the cornea tends to be more flat. In addition, the ratio of these changes was slightly bigger in men than women. This finding could be effective in improving precision of medical procedures in treating cataract, Keratoconus and refractive surgeries.

Keywords: Axial length; Corneal curvature radius; Biometry