Background: The onset of keratoconus usually coincides with adolescence, and may be associated with vernal conjunctivitis or other atopic conditions. In patients with vernal conjunctivitis, acute hydrops may be the presenting sign of keratoconus in pre-adolescence. Methods: Review of ophthalmic clinical manifestations of three children with presenting symptoms and signs of acute corneal hydrops associated with vernal conjunctivitis. Results: Three children, 5 to 11 years of age, presented with corneal hydrops associated with mild vernal conjunctivitis. In two of these children, vernal conjunctivitis was asymptomatic, and in one child the signs of vernal conjunctivitis appeared after the occurrence of hydrops. No other factors, including mechanical factors such as eye rubbing, were found to be related. Conclusions: The association of vernal conjunctivitis with keratoconus may contribute to the early occurrence of hydrops. Corneal hydrops in children may, therefore, indicate coexisting vernal conjunctivitis.