Screening for Keratoconus in a High-Risk Adolescent Population

Purpose To estimate the prevalence of keratoconus (KC) in a majority-Emirati adolescent population and to demonstrate the feasibility of screening using a dual Scheimpflug and Placido imaging device. Methods Adolescent subjects from two secondary schools in Abu Dhabi, UAE underwent corneal imaging with the Galilei tomographer (Ziemer Ophthalmic Systems AG, Port, Switzerland). The prevalence of KC and KC suspects was determined using a combination of both subjective and objective criteria. Objective criteria included these KC indices: percent probability of keratoconus, inferior-superior index, asphericity asymmetry index, maximum keratometry and thinnest pachymetry. Subjective pattern analysis was performed by four experienced cornea specialists. Subjects were classified by each cornea specialist into three groups: normal, KC and KC suspect. The final classification was made by group reconciliation of cases where disagreement was present. Inter-observer agreement was assessed with the kappa statistic. Results A total of 839 eyes of 420 students between 10 and 19 years of age underwent corneal tomography. After the exclusion of 251 eyes due to insufficient scan quality based on internal instrument-derived standards, 588 eyes of 339 subjects were included in the analysis. The prevalence of KC and KC suspect was estimated to be 2.7% (95% CI [1.2%, 5.0%]) and 19.8% (95% CI [15.7%, 24.4%]), respectively. There was a strong inter-observer agreement between examiners' classification of the subjects' KC status (kappa = 0.84). Conclusion KC is highly prevalent in Emirati adolescents. Screening secondary school students for keratoconus appears to be feasible and may be indicated in this population to improve early detection and intervention.