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Clara Llorens Quintana, Siyu Chen, JUNHONG Lin, James G Fujimoto, Yan Li, David Huang; Anterior topographic limbal demarcation with ultrawide-field OCT. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1195 – A0195.
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© ARVO (1962-2015); The Authors (2016-present)
To develop an automatic method to find the external limbal transitions points between the cornea and the sclera based on anterior topography obtained from ultrawide-field anterior segment optical coherence (OCT) images.
An ultrahigh-speed (325 kHz) ultrawide-field swept-source OCT prototype was used to obtain corneo-scleral (CS) images of the left and right eyes from four subjects. The imaging depth range is 15.5 mm with an axial resolution of 12.2 µm (in air). The scan pattern consisted of 16 radial scans of 20 mm width. This scan pattern was centered on the pupil and repeated three times consecutively in each acquisition. The CS profile, segmented from the OCT cross-sectional images, was corrected for the field distortion inherent to the OCT scans. For each meridian, the second central moment of the OCT signal was projected to obtain a radial profile on which the anterior CS junction [DH1] and pupil can be identified by sharp transitions. The anterior corneal surface inside the CS junction was fitted with a 4th degree polynomial and the anterior conjunctival surface over the sclera outside the CS junction was fit with a 2nd degree polynomial. The external limbus was identified as the point where these best-fit corneal and scleral surfaces intersected. The external [DH2] limbal positions from the 16 meridians were combined and modelled with a best-fit ellipse.
The average ± standard deviation radial distance from the pupil center to the limbal transition was 6.16 ± 0.24 mm. Further, the limbus was modeled with an ellipse which average ± standard deviation minor and major axes of 11.87 ± 0.70 mm and 13.01 ± 0.48 mm, respectively.
Ultra-fast swept-source OCT provides high-resolution CS images. Using the central moment of the OCT signal, the CS transition and the pupil can be identified automatically. The external limbus defined by the shape of the anterior surface is different to the WTW distance and therefore an automatic method, as the one proposed, would be more suitable to define the external limbus which is needed for scleral lens fitting.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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