Abstract
Purpose :
To evaluate the reliability and repeatability of subfoveal choroidal thickness (ChT) measurements and determine sources of variability.
Methods :
Six eyes of 3 subjects (age 34±10.44yrs, sph -1.5±2.98D, cyl -1.85±1.23D) were imaged with Topcon Triton SS-OCT at baseline, immediately and 30min after the application of Synergeyes Duette hybrid multifocal contact lens (MFCL), which has the optical center made with rigid gas permeable material with a soft skirt. The foveal reference point was marked on the OCT and the choroidal borders were delineated by software, to extrapolate the average ChT of the central 1mm of the fovea. Image segmentation was evaluated for accurate delineation of the choroidal-scleral interface, and was manually adjusted if needed. The images were analyzed by a second examiner and intra-class correlation coefficient was calculated to determine the inter-examiner variability and repeatability. One-way ANOVA with repeated measures was conducted to evaluate the impact of lens wear on ChT.
Results :
Out of 18 images, 6 required manual adjustment, 3 of which were baseline without lenses. The inter-examiner difference of ChT was 9.76±17.74um and 29.03±20.03um (intra-class correlation coefficient 0.91 and 0.79) for all images and the 6 images that required manual adjustment respectively. Tilted images resulted in higher variability in manually determining foveal reference point (8.94±13.45 pixels, p=0.012) but did not result in a statistically significant difference in ChT measurement. The average baseline ChT were 283.44±25.47um, 266.36±29.24um and 266.69±32.73um at baseline, immediately after, and 30 min after the application of the lenses respectively. The difference of ChT measurements with and without the lenses was borderline significant (20.22±24.51um, p=0.09, intra-class correlation coefficient 0.77).
Conclusions :
Wearing contact lenses significantly increased the variability of ChT measurement hence a potential confounder for treatment-induced ChT changes. Future analysis for evaluating subtle choroidal thickness should have consistent comparison of baseline measurements with lens on to avoid such confounding. Additionally, manual adjustment of the choroidal-scleral interface is a major source of variability and subgroup analysis should be performed on images based on status of post-hoc adjustment to minimize the risk of bias due to arbitrary determination of the interfaces.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.