Relationship between the corneal surface and the anterior segment of the cornea: An Asian perspective

To determine the values for the anterior best-fit sphere (BFS) and posterior BFS in an Asian population using the Orbscan II (Bausch & Lomb) slit-scanning Placido disk corneal topographer.

Hospital-based refractive surgery center.

This prospective nonrandomized study comprised of 1 eye of 724 subjects. The eyes were measured with the Orbscan II. Default settings were used to generate relative elevation maps. Anterior BFS, posterior BFS, mean keratometry (K(mean)), spherical equivalent (SE), horizontal white-to-white size (WTW), and anterior chamber depth (ACD) were analyzed.

The mean spherical equivalent (SE) in the 724 eyes was -5.32 diopters (D) +/- 2.88 (SD). The anterior BFS and posterior BFS were normally distributed, with a mean of 43.05 +/- 1.37 D and 52.43 +/- 2.03 D, respectively. The regression equation of anterior BFS and posterior BFS was posterior BFS = 0.443 + 1.208 anterior BFS (r(2) = 0.667, P<.01). The ratio of posterior BFS to anterior BFS was 1.22 +/- 0.03. The anterior BFS was significantly correlated to posterior BFS (P<.01), K(mean) (P<.01), and horizontal WTW (P<.01) but not to SE (P = .28). The posterior BFS was significantly correlated to K(mean) (P<.01) and the horizontal WTW (P<.01) but not to SE (P = .70).

There was a close relationship between the various corneal parameters, which is significant in refractive surgery and intraocular lens calculation and design.