Retinoscopy as a Screening Tool for Keratoconus

PURPOSE: To investigate the validity and reliability of retinoscopy in screening for keratoconus using the rotating Pentacam Scheimpflug camera as the gold standard comparison. METHODS: Patients between the ages of 10 and 30 years who were referred to the outpatient clinic with keratoconus, keratoconus suspect, reduced vision, eye discomfort or frequent change of glasses, or for refraction or refractive surgery, were screened by two independent and masked retinoscopists for the presence of scissoring reflex. Patients then underwent vision testing, slit lamp examination, and Pentacam imaging. A diagnosis of keratoconus by Pentacam was made if the final D index in the Belin and Ambrosio Display was ≥2.69. The results of retinoscopy and Pentacam examinations were compared to assess the validity and reliability of the test. RESULTS: A total of 123 patients (67 male patients and 45 female patients) with a mean age of 21 years ±5.6 (range 10-30 years) comprising 245 eyes were included. There were 87 eyes with keratoconus, and using the Amsler-Krumeich classification, 67.8%, 26.4%, 2.3%, and 3.4% of the eyes had stage I, II, III, and IV, respectively. Sensitivity, specificity, positive predictive value, and negative predictive value of retinoscopy were 97.7%, 79.9%, 70.8%, and 98.4%, respectively. The area under the curve was 0.88 (95% confidence interval, 0.83-0.92). There was excellent agreement between the 2 retinoscopists (Cohen's kappa value 0.84). CONCLUSIONS: Retinoscopy appears to be a very sensitive and reliable test for detecting keratoconus including early disease. Such a test may be implemented in population-based screening programs for keratoconus.