Prevalence of keratoconus and subclinical keratoconus in subjects with two or more diopters (D) of astigmatism using pentacam derived parameters

Abstract

Keratoconus is a common progressive asymmetric, bilateral, ectatic corneal disorder that arises due to biomechanical and structural defects in organization of corneal collagen. It is characterized by axial protrusion of cornea and thinning of corneal stroma which deforms the shape of cornea leading to myopia and irregular astigmatism with decreased vision. This is a prospective cross-sectional study. All the patients within age group of 8-45 years who attended Outpatient Department of a Tertiary Care Hospital, Ajmer, with signs and symptoms of keratoconus or with astigmatism ≥2D with no previous history of ocular trauma or surgery were evaluated and a complete ophthalmic examination was done including the best corrected visual acuity, retinoscopy, slit lamp biomicroscopy and fundus examination and the findings were recorded. Only subjects with no other signs and symptoms of other ocular pathology were included. 334 eyes (167 subjects) were included in this study and among 334 eyes, 291 eyes had ≥2 D Astigmatism, 152/167 (91.02%) right and 139/167 (83.23%) left eyes. Mean age of the patients was 19.6±9.09 years ranging from 8 to 45 years. 50.3% of study subjects were females and 49.7% were males. Overall, in both eyes, prevalence of astigmatism was found to be 73.88%, FFKCN was 10.31% and KCN was found 15.81% among the study population having ≥2 D astigmatism. Patients with astigmatism of ≥2D who attend outdoor clinics should be evaluated with corneal tomography for early diagnosis, even if visual acuity is not significantly affected. Pentacam gives a more accurate diagnosis than corneal topography devices used conventionally, particularly in keratoconus suspicious eyes.