Direct measurement of the ciliary sulcus diameter using optical coherence tomography: Inter‐rater variability

Abstract

Aims/Purpose: To develop a method for measuring the exact dimensions of the ciliary sulcus in order to improve the predictability of accommodative intraocular lens sizing.Methods: Patients scheduled for cataract surgery have been pre‐operatively examined with the anterior segment optical coherence tomographer (AS‐OCT) CASIA2 (Tomey, Nagoya, Japan). Optimized scan protocols were defined to improve the image quality of the ciliary structures. The horizontal scan from 0° to 180° was taken to represent the space where a sulcus‐fixated accommodative intraocular lens (IOL), whose diameter must agree with that of the ciliary sulcus, may be placed. The images were corrected for the optical distortion induced by the cornea's refraction. The sulcus‐to‐sulcus (STS) size as well as the depth of the sulcus plane (SPD) was measured using the integrated software calliper by two independent raters. Inter‐rater variability and correlation were evaluated. In addition, STS measurements were compared to other ocular diameter measures, such as angle‐to‐angle (ATA) and anterior chamber width (ACW). Data were analysed by means of correlation coefficient R2 and Bland–Altmann analysis.Results: 55 eyes of 28 patients were included in the study. The optimized scan protocols improved overall image quality and subjective visibility of ciliary anatomy compared to the default protocol. STS ranged from 10.66 mm to 12.89 mm, ACW from 10.76 mm to 12.74 mm and ATA from 10.69 to 12.46 mm. SPD ranged from 3.73 mm to 5.0 mm, while ATA depth was between 2.74 mm and 3.95 mm. Readings of both raters were highly correlated (R2 > 0.98). Manual readings of STS correlated poorly with automated ACW and ATA measurements (R2 < 0.66). The mean difference was 0.018 mm for STS and −0.011 mm for SPD. The levels of agreement were within [−0.109; +0.145] mm for STS and [−0.112; +0.091] mm for SPD.Conclusions: Despite the absorption of light by the iris pigment, the infrared light from the AS‐OCT is able to penetrate the posterior chamber to some degree. Therefore, the new AS‐OCT method for sulcus‐to‐sulcus and ciliary dimensions measurements seems to be feasible, reliable and is less bothersome for the patients compared to ultrasound bio‐microscopy. This approach could be useful for sulcus fixated accommodative IOLs and for sizing determination of posterior chamber phakic IOLs.