Purpose: To detect the incidence of keratoconus by videography in patients with vernal keratoconjunctivitis (VKC) and to evaluate the clinical characteristics of VKC associated with keratoconus.
Design: a prospective, cross-sectional (prevalence) study.
Participants: Eighty-two consecutive subjects with the diagnosis of VKC.
Methods: Both eyes of VKC subjects were investigated by videokeratography in comparison with slit-lamp biomicroscopy and keratometry. To detect keratoconus, corneal topography maps were examined with modified Robinowitz-McDonnell test.
Main outcome measures: In this test, maps with central corneal power greater than 47.2 diopters and/or the inferosuperior asymmetry value greater than 1.4 were considered to have a keratoconus pattern. The findings of VKC were also recorded,
Results: The distribution of clinical forms of VKC were as follows: 46.34% mixed, 43.90% palpebral, and 9.76% limbal types. Twenty-six (31.7%) of 82 subjects had complications with keratopathy such as pseudo-genontoxon, punctate keratitis, and shield ulcer. Forty-four eyes (26.8%) were detected as keratoconus by quantitative evaluation of videokeratography maps. 14 eyes (8.5%) by biomicroscopy, and 30 eyes (18.3%) by keratometry. The increased incidence of keratoconus was associated with male gender, long-standing disease, mixed and palpebral forms, and advanced corneal lesions.
Conclusions: The higher incidence of keratoconus in our study compared with the previous reports may result from early detection of mild keratoconus by interpretation of color-coded videokeratographic maps with a sensitive quantitative method.