The Dundee University Scottish Keratoconus study: demographics, corneal signs, associated diseases, and eye rubbing

Aim: To investigate and correlate the corneal, refractive, topographic and familial characteristics of a large cohort with keratoconus. Methods: Prospective observational study of 200 consecutive patients presenting with keratoconus during the 4year-period 1997-2000. Subjects were examined at enrolment and at a final review. Data were collected on demographic characteristics, referral route, symptoms, refractive correction, eye rubbing, family history, medical history, slit-lamp biomicroscopic corneal signs, and computerized corneal topography. Results: Mean age at enrolment was 30.9 ± 10.4 (range, 12.2-72) years (N = 200, 62.5% male, 93% white Caucasian) with a 5% family history of keratoconus. Atopic diseases included asthma (23%), eczema (14%), and hay fever (30%). Only 9% wore contact lenses before referral. Mean follow-up was 1004 days ± 282 (range, 390-1335) and 9.7 ± 8.9 (range, 1.1-60) years from diagnosis. The mean simulated K1 corneal power at enrolment was 51.74 ± 5.36 (range, 42.59-67.32) D and 88.5% exhibited bilateral keratoconus. Fifty-three (15%) topographically confirmed cones exhibited no clinical corneal signs at presentation. At enrollment, 56% had a pachymetry <0.480 mm increasing to 77% at final review. Forty-eight percent of subjects reported significant eye rubbing and there was a highly statistically significant difference (two sample t-test P = 0.018) between keratoconus and control groups. TMS-2 axial corneal power was strongly associated with corneal scarring and age at diagnosis. The size of the scarring effect was 2.2D (95% confidence interval (CI) 1.34, 3.06). Conclusions: This study provides an overview of a large population with keratoconus highlighting presenting features and clinical and topographic progression over a 4 year-period.