Corneal Biomechanics in Unilateral Keratoconus and Fellow Eyes with a Scheimpflug-based Tonometer.

SIGNIFICANCE: Before the appearance of evident keratoconus, corneal biomechanical changes may be detectable. Here, these properties are analyzed to detect any difference that could help in the early recognition of keratoconus to allow patients to benefit from early treatments and to avoid refractive procedures in these corneas. PURPOSE: The purpose of this study was to compare corneal biomechanical characteristics as determined by Corvis Scheimpflug Technology tonometry between normal eyes and asymmetric keratoconic eyes. METHODS: Retrospective data from normal eyes (n = 100), keratoconic eyes (n = 18), and their topographically normal fellow eyes (n = 18) were analyzed. Differences in the variables among the groups were determined. For the parameters that showed significant differences, the receiver operating characteristic curve and the area under the curve (AUC) were used to assess the diagnostic accuracy of each variable. The optimal cutoff points were determined when comparing normal and fellow eyes. Also, a new linear combination of variables was performed to obtain better discriminative values. RESULTS: The following variables differed significantly between normal and fellow eyes: length of the flattened cornea in the second applanation, peak distance, curvature radius at highest concavity, and central corneal thickness. When each variable was independently considered, AUCs, sensitivity, and specificity were insufficiently high for good discrimination between the two groups. However, using a linear combination of variables, an optimal cutoff point (0.157) was obtained with an AUC of 0.78, sensitivity of 0.84, and specificity of 0.69. CONCLUSIONS: A best predictive linear combination of corneal biomechanical variables was tested including diameter of the flattened cornea in the second applanation and central corneal thickness. This combination was considered as the best in terms of its prediction capacity, simplicity and clinical application. This formula may be useful in clinical practice to discriminate between normal eyes and incipient keratoconus.

Small Incision Lenticule Extraction (SMILE) as Re-treatment for a Thick LASIK Flap.

PURPOSE: To report the case of a residual refractive error after LASIK for moderate myopia successfully re-treated several years later using the small incision lenticule extraction (SMILE) technique. METHODS: Case report. RESULTS: Following LASIK, the patient showed a central flap thickness of 269 microns, whereas residual stromal bed thickness under the flap was 210 microns. SMILE was performed within the flap. In this less invasive surgical procedure, the residual stromal bed is not manipulated and ablation is conducted on the existing flap. At 6 months of follow-up, visual and anatomical outcomes were satisfactory. Uncorrected distance visual acuity was 20/20 and refractive error was +0.75 -0.50 × 30°. CONCLUSIONS: In selected patients with a thick flap and thin residual stromal bed after LASIK, SMILE as re-treatment may be a good option. [J Refract Surg. 2016;32(10):718-720.].