OBJECTIVE: To compare the axial length derived from a formula incorporating corneal dimensions with the results obtained by A-scan biometry. METHODS: This is a nonrandomized comparative study of patients from the outpatient department of a tertiary-care academic medical institution who were screened for cataract surgery. Corneal diameter and slope were measured with a Vernier no. 6 caliper and axial length determined using Ophthasonic A-Scan III machine. Computed axial lengths were arrived at using a formula incorporating corneal diameter and slope. The mean difference of measured and computed axial lengths were statistically analyzed using paired t test and general linear model tests. RESULTS: A total of 105 eyes (96 patients) were included in the study. The mean difference between computed and measured axial lengths was not statistically significant (p=0.64 for computed axial length< 22.00 mm, p=0.11 for computed axial length of 22.00 to 22.99, p=0.81 for computed axial length of 23.00 to 23.99, and p=0.03 for computed axial length ? 24.00 mm). CONCLUSION: Axial length measured with an A-scan can be reliably approximated by using Surrells formula based on corneal length measurements.
Human ; BIOMETRY ; CORNEA ; LENSES, INTRAOCULAR ; AXIAL LENGTH, EYE