Contraction of corneal wounds as the incisions heal may account for changes in corneal topography after radial keratotomy; such contractility of avascular corneal wounds has been demonstrated in vitro. Using a cat model of radial keratotomy, we demonstrated in vivo contractility of radial keratotomy incisions. In eight eyes of adult female cats, four-incision radial keratotomies were performed, producing central corneal flattening. After 3 and 8 days, serotonin (1 mg/mL) was applied. On day 3, application of topical serotonin resulted in corneal steepening (P < .0001); serotonin produced no topographic changes when applied on day 8 and had no effect on normal unoperated corneas. Vehicle produced no change in corneal curvature before or at any time after radial keratotomy. Fluorescence microscopy revealed cells with myofibroblastic differentiation at the incisions. These data suggest that cells with contractile abilities play a role in determining corneal topography after radial keratotomy.