PURPOSE To investigate the topography of the central and peripheral cornea in a group of young adult subjects with a range of normal refractive errors. METHODS Corneal topography data were acquired for 100 young adult subjects by a method that allows central and peripheral maps to be combined to produce one large, extended corneal topography map. This computer-based method involves matching t...

A forward ray tracing (FRT) model is presented to determine the exact image projection in a general corneal topography system. Consequently, the skew ray error in Placido-based topography is demonstrated. A quantitative analysis comparing FRT-based algorithms and Placido-based algorithms in reconstructing the front surface of the cornea shows that arc step algorithms are more sensitive to noise...

The corneal maps displayed on commercially available corneal topography instruments are really one-dimensional, defining quantities only along a meridian, and ignoring shape information along any other direction. Both axial and instantaneous power have the drawbacks that there is a singularity at the center data point on the videokeratograph axis, and the computed powers and appearance of the c...

standing of the eye’s refractive characteristics to a new level. It has changed our concepts for examining refraction in the same way that computerized corneal topography changed corneal surface measurement, which previously had been limited to the yardstick of keratometry. We now possess two, highly sensitive tools for the objective measurement of the eye—corneal topography and wavefront asses...

A system to measure the topography of the first optical surface of the human eye noninvasively by using a curvature sensor is described. The static corneal topography and the dynamic topography of the tear film can both be measured, and the topographies obtained are presented. The system makes possible the study of the dynamic aberrations introduced by the tear film to determine their contribut...

PURPOSE To compare central corneal thickness measurements and their reproducibility when taken by a rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit corneal topography/pachymetry. DESIGN Experimental study. PARTICIPANTS Seventy-four eyes of 64 subjects without ocular abnormalities other than cataract. METHODS Corneal thickness measurements were compared among the 3 me...

PURPOSE To evaluate changes in corneal topography indices after corneal collagen crosslinking (CXL) in patients with keratoconus and corneal ectasia and analyze associations of these changes with visual acuity. SETTING Cornea and refractive surgery subspecialty practice. DESIGN Prospective randomized controlled clinical trial. METHODS Corneal collagen crosslinking was performed in eyes wi...