Purpose: To examine the relationship between central corneal thickness (CCT), scleral thickness (ST), refractive error, and axial length.
Methods: One hundred forty eyes of 140 patients with no previous history of intraocular surgery were enrolled. Axial length, CCT, and ST were measured ultrasonically. Radial ultrasound biomicroscopy (UBM) images were obtained by a single examiner scanning the temporal corneoscleral limbus. ST was measured independently on the UBM images by two masked observers at scleral spur (ST1) and 2.0 and 3.0 mm posterior to it (ST2 and ST3).
Results: Mean patient age was 57.0+/-15.7 (SD) years, and mean refractive error was -1.3+/-5.0 diopters. Intraclass correlation coefficients >0.75 indicated excellent agreement between the two observers for all ST measurements. There was a positive and significant correlation between CCT and ST1 (r=0.27, P=0.001) but not between CCT and ST2 (r=0.02, P=0.8), ST3 (r=0.06, P=0.5), refractive error (r=0.08, P=0.3), or axial length (r=0.07, P=0.4).
Conclusions: CCT correlates with ST only at the scleral spur and is unrelated to refractive error or axial length. This study does not support the hypothesis that a thin CCT is a surrogate marker for abnormal scleral or laminar thickness as an independent cause of increased glaucoma risk.