Optical methods for measuring corneal topography: A review

Abstract

The cornea is the outermost surface of the eyeball; and has almost 70% of the eyes total refractive power, what makes it essential for the human vision process. However, some pathologies and refractive errors modify normal functions of the cornea, decreasing visual acuity along with the individual's quality of life. Thus, in the presence of ametropia, an appropriate diagnosis, treatment, and corrections of cornea's dimensions is vital. Nowadays, several methods to retrieve corneal topography are available. In this paper, the most relevant techniques in the field are presented.

Effect of the skew ray error on corneal topography using a cone topographer

“…Corneal topographers are traditionally based on the Placido disc which consists of a set of black and white rings placed alternately within a concave surface that is placed in front of the corneal surface. 1,2 The rings are projected onto the anterior corneal surface, the reflected light is collected by a positive lens and projected onto the detection plane of a camera. When the shape of the anterior corneal surface corresponds to a sphere and is also centered with respect to the topographer's axis, the image formed in the detection plane is a set of equally spaced bright and dark rings.…”

Null-screen based corneal topography using a smartphone

“…Devices for assessing the corneal surface are based on Placido disk, however, this method is inadequate in terms of accuracy in its reconstruction algorithms and edges segmentation [3][4][5] . Commercial corneal topography devices are based on a projection system (Placido disk).…”