It is important to be able to accurately estimate the central corneal clearance when fitting scleral contact lenses. Tools available have intrinsic biases due to the angle of viewing, and therefore an idea of the amount of error in estimation will benefit the fitter.
To compare the accuracy of observers' ability to estimate scleral contact lens central corneal clearance (CCC) with biomicroscopy to measurements using slit-lamp imaging and anterior segment optical coherence tomography (AS-OCT).
In a Web-based survey with images of four scleral lens fits obtained with a slit-lamp video imaging system, participants were asked to estimate the CCC. Responses were compared with known values of CCC of these images determined with an image-processing program (digital CCC) and using the AS-OCT (AS-OCT CCC). Bland-Altman plots and concordance correlation coefficients were used to assess the agreement of CCC measured by the various methods.
Sixty-six participants were categorized for analysis based on the amount of experience with scleral lens fitting into novice, intermediate, or advanced fitters. Comparing the estimated CCC to the digital CCC, all three groups overestimated by an average of +27.3 ± 67.3 μm. The estimated CCC was highly correlated to the digital CCC (0.79, 0.92, and 0.94 for each group, respectively). Compared with the CCC measurements using AS-OCT, the three groups of participants overestimated by +103.3 μm and had high correlations (0.79, 0.93, and 0.94 for each group).
Results from this study validate the ability of contact lens practitioners to observe and estimate the CCC in scleral lens fittings through the use of biomicroscopic viewing. Increasing experience with scleral lens fitting does not improve the correlation with measured CCC from digital or the AS-OCT. However, the intermediate and advanced groups display significantly less inter-observer variability compared with the novice group.
Supplemental digital content is available in the text.
School of Optometry and Vision Science University of Waterloo, Waterloo Ontario, Canada (both authors) *firstname.lastname@example.org
Supplemental Digital Content: The appendix, available at http://links.lww.com/OPX/A328, includes the cases and questions that were posed with the online survey. The survey tool (SurveyMonkey) was used as all responses were anonymous, and the time taken to complete the survey is recorded.
Submitted: December 1, 2016
Accepted: November 5, 2017
Funding/Support: None of the authors have reported funding/support.
Conflict of Interest Disclosure: None of the authors have reported a conflict of interest.
Author Contributions and Acknowledgments: Conceptualization: DY; Data Curation: DY; Writing – Original Draft: DY; Formal Analysis: LS; Project Administration: LS; Supervision: LS; Writing – Review & Editing: LS.
The authors would like to thank Dr. Lacey Haines for her contribution to this project.
Supplemental Digital Content: Direct URL links are provided within the text.