Evaluation of Keratoconus in Asians: Role of Orbscan II and Tomey TMS-2 Corneal Topography

Abstract

To evaluate the corneal topographic patterns of Asian patients with keratoconus (KC). Prospective observational case-control study. Institutional. A total of 116 patients (both eyes included) with KC were recruited. The control group consisted of 70 laser in-situ keratomileusis (LASIK) candidates with myopia. Patients with previous ocular surgery and trauma were excluded. Corneal topography was performed using the Tomey KC screening system (Topographic Modeling System, software version 2.4.2J, Tomey Corp, Nagoya, Japan) and Orbscan II corneal topography system (Bausch & Lomb Surgical, Orbtek Inc, Salt Lake City, Utah, USA). Videokeratographic variables were analyzed and the eyes were grouped into KC, KC suspect, and control groups. The corneal topographic patterns of 196 eyes were analyzed. The topographic patterns displayed by Tomey (TMS-2N) and Orbscan II were similar. The majority of eyes with KC (71.2%) and KC suspect (70%) had asymmetric bowtie patterns. Thirteen indices of TMS-2N were analyzed and the means of the indices were found to be significantly higher in eyes in the KC group than the KC suspect group (P < .001). Fourteen indices of Orbscan II were analyzed. Eyes in the KC suspect group had higher mean posterior elevation (46 +/- 17 microm), 3 mm irregularity (2.44 +/- 1.36 diopters [D]), 5 mm irregularity (2.61 +/- 1.19 D) and had thinner corneas (mean 504.4 +/- 40.4 microm) than normal eyes (26 +/- 8 microm, 1.05 +/- 0.37 D, 1.38 +/- 0.39 D, and 554.0 +/- 25.0 microm, respectively). Corneal topography pattern recognition combined with quantitative diagnostic indices is useful for the screening and classification of KC with the Orbscan II being more sensitive in screening for KC than TMS-2N.