ABSTRACT
PURPOSE: Measuring corneal biomechanical properties may help detect keratoconus suspect corneas and eliminate the risk of ectasia after LASIK. METHODS: Data of 504 eyes separated into three groups were retrospectively reviewed: normal (n = 252), keratoconus suspect (n = 80), and keratoconus (n = 172). Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with an ocular biomechanics analyzer. RESULTS: Mean corneal hysteresis was 10.6 +/- 1.4 (SD) mm Hg in the normal group, compared with 10.0 +/- 1.6 mm Hg in the keratoconus suspect group and 8.1 +/- 1.4 mm Hg in the keratoconus group. The mean CRF was 10.6 +/- 1.6 mm Hg in the normal group compared with 9.7 +/- 1.7 in the keratoconus suspect group and 7.1 +/- 1.6 mm Hg in the keratoconus group. Mean CH and CRF were significantly different between the three groups (P < 0.001). CONCLUSIONS: CH and CRF alone cannot be used to identify keratoconus suspect corneas. Analyzing signal curves obtained with the biomechanics analyzer may provide additional valuable information for selecting qualified patients for refractive surgery.
Subject(s)
Cornea/physiopathology , Elasticity/physiology , Keratoconus/physiopathology , Pliability/physiology , Adult , Biomechanical Phenomena , Corneal Topography , Dilatation, Pathologic/diagnosis , Dilatation, Pathologic/physiopathology , Female , Humans , Intraocular Pressure , Keratoconus/diagnosis , Male , Retrospective StudiesABSTRACT
PURPOSE: To measure and compare total, corneal, and internal ocular aberrations using combined wavefront analysis and corneal topography in eyes with keratoconus and eyes with normal corneas. METHODS: This prospective study comprised eyes of patients with keratoconus and myopic patients seeking refractive surgery. Patients diagnosed with keratoconus and with a classification of "normal" or "keratoconus" on the NIDEK Corneal Navigator corneal disease screening software were selected for inclusion in this study. The normal group comprised eyes with a "normal" classification with 99% similarity. In the normal group, only one eye per patient was randomly selected based on a randomization schedule. Corneal, internal, and total wavefront measurements were provided by the NIDEK OPD-Scan II. RESULTS: One hundred eyes with keratoconus and 155 normal eyes were enrolled in the study. Statistically significant higher corneal and internal higher order aberrations were observed in the eyes with keratoconus (P<.05). However, an increase in ocular higher order aberrations proportional to corneal higher order aberrations was not observed in the keratoconus group. CONCLUSIONS: A compensatory effect of increased anterior corneal aberrations by internal aberrations in keratoconic eyes was present for some aberrations. The origin of this compensation and the optical mechanism behind it requires further study.
