Identifying progression of subclinical keratoconus by serial topography analysis

We performed serial slit-lamp examinations and topography analysis on a patient whose initial topographic map suggested a diagnosis of keratoconus to us but which others interpreted as normal topography. Topography analysis documented cone progression during a two-year period. The initial map showed a cone apex power of 44.5 diopters located 2.1 mm inferior to the vertex normal. An oblong-shaped area of maximum power was surrounded by concentric bands of lower power. Corneal surface power ranged from 41.5 to 44.5 diopters. Two years later cone apex power increased to 51.0 diopters, and the patient developed a Fleischer's ring, Vogt's striae, and mild visual aberration. Our findings suggest the use of topography analysis systems in documenting subclinical cone progression. Topography systems may be a useful tool in the study of the true incidence and natural progression of subclinical keratoconus.