Correlation between central corneal thickness, scleral thickness and refractive error

Abstract

Abstract: : Purpose: To verify the relationship between central corneal thickness (CCT) and scleral thickness and to assess possible correlation between CCT, scleral thickness, refractive error and axial length. Methods: Ninety eyes of 90 consecutive patients without previous history of intraocular surgery were studied prospectively. CCT, axial length and scleral thickness were measured ultrasonically using pachymetry, A–scan and ultrasound biomicroscopy (UBM), respectively. The first two measurements were performed in the center of the cornea and the third on the temporal meridian of the eye at the scleral spur and at 2 and 3 mm posterior to it by one observer (CO). UBM measurements were independently obtained by the two observers (CT and CO), and both were masked to the data. The patients were allocated into groups according to spherical equivalent. Results: Mean age of the patients was 55.04 ± 15.11 years. Mean refractive error expressed as spherical equivalent was – 1.41 ± 4.85 diopters. Interobserver reproducibility was good, with CV of 3.1%, 4.9% and 5.1 % for scleral thickness at the scleral spur and at 2 and 3 mm posterior to it, respectively. There was a positive correlation between CCT and scleral thickness only at the scleral spur (r = 0.23, P = 0.028 for CT; r = 0.020, P = 0.047 for CO). CCT and scleral thickness did not correlate significantly with refractive error (P> 0.05), although there was a tendency for decreasing corneal thickness with increasing myopia. Nevertheless, an increasing myopic refractive error strongly correlated with an increasing axial length (r = –0.86, P< 0.0001). Conclusion: CCT correlates positively with scleral thickness only at the scleral spur. On the other hand, CCT and scleral thickness do not correlate with refractive error.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • sclera