Keratoconus in Thai population - a cross-sectional hospital-based study

Background: Studies in the epidemiology of keratoconus are limited in Southeast Asia. A study on the prevalence and characteristics of keratoconus in the Thai population could give a general idea of its impact. Objectives: To study keratoconus prevalence in patients seeking refractive surgery and analyze the characteristics of keratoconus. Methods: Medical records from April 2015 to August 2018 were retrospectively reviewed. Keratoconus and keratoconus suspect prevalence in patients seeking laser vision correction were calculated. The characteristics of keratoconus patients were reviewed. The Amsler-Krumeich classification was used to determine the stages. Topographically, the types of cones were categorized into oval, nipple, pellucid marginal degeneration (PMD)-like, and astigmatic types. Results: Keratoconus and keratoconus suspect prevalence were 1.66% and 0.68%, respectively. Out of the affected patients, 73.8% were male. The mean age at diagnosis was 25.25 +/- 8.35 years. The presenting symptoms were blurred vision (87%) and itching (47%). Stage 1 was predominant, found in 39% of patients (followed by stages 2, 4, and 3, respectively). Ocular findings comprised the Munson sign (14.63%), the Rizutti sign (6.94%), Fleischer ring (28.14%), Vogt striae (24.95%), corneal scar (8.63%), prominent corneal nerve (2.81%), and corneal staining (7.69%). Mean uncorrected visual acuity (logarithm of the minimum angle of resolution [logMAR]) was 0.88 +/- 0.64. Mean corrected visual acuity (logMAR) was 0.40 +/- 0.49. Mean Q-value was -0.92 +/- 0.63. The thinnest pachymetry was 459.39 +/- 56.96 microns. The mean keratometry was 49.7 +/- 6.64 diopters. Topographically, the types of cones were oval (57%), astigmatic (33%), PMD-like (5%), and nipple type (4%). Conclusions: Keratoconus prevalence among Thai patients seeking refractive surgery was 1.66%. Most patients were male and presented with the disease at a mild bilateral stage in their second decade of life.