Characterization of the external limbus on corneoscleral topography with ultrawide-field optical coherence tomography

Clara Llorens-Quintana; Yan Li; Siyu Chen; James G Fujimoto; David Huang

doi:10.1016/j.clae.2023.102065

Characterization of the external limbus on corneoscleral topography with ultrawide-field optical coherence tomography

Cont Lens Anterior Eye. 2023 Dec;46(6):102065. doi: 10.1016/j.clae.2023.102065. Epub 2023 Oct 11.

Authors

Clara Llorens-Quintana¹, Yan Li¹, Siyu Chen¹, James G Fujimoto², David Huang³

Affiliations

¹ Casey Eye Institute and Department of Ophthalmology, Oregon Health and Science University, Portland, OR, USA.
² Massachusetts Institute of Technology, Cambridge, MA, USA.
³ Casey Eye Institute and Department of Ophthalmology, Oregon Health and Science University, Portland, OR, USA. Electronic address: huangd@ohsu.edu.

PMID: 37827941
PMCID: PMC10842492 (available on 2024-12-01)
DOI: 10.1016/j.clae.2023.102065

Abstract

Purpose: To present a new method for 3-dimensional external limbal demarcation on corneoscleral topography derived from optical coherence tomography (OCT). Limbal shape is investigated and compared to other landmarks.

Methods: Images from the anterior segment were obtained with a ultrawide-field (20 mm) OCT. An automated algorithm was developed to demarcate the topographic limbus based on the transition from corneal to scleral curvature. The internal limbus was manually identified as the scleral spur on the OCT images. The external topographic limbus was fit with a circle on a plane. Ellipticity and ovality were defined by the lateral limbal deviation from the best-fit circle. Toricity was defined by the axial deviation from the best-fit plane. Repeatability was assessed by the within-subject standard deviation from two repeated measurements. For comparison, the white-to-white (WTW) diameter was obtained from Pentacam HR.

Results: 18 eyes from 11 subjects were analyzed. The topographic limbal diameter was 12.16 ± 0.68 mm (mean ± standard deviation) horizontally and 11.18 ± 0.65 mm vertically. The repeatability for the topographic limbal diameter was 0.054 mm. The internal and WTW horizontal limbal diameters were significantly smaller (linear mixed-effects model (GLMM), p <.017). The vertical internal limbal diameter was significantly larger (GLMM p <.05). The topographic limbus had significant ellipticity (0.25 ± 0.13 mm, wider horizontally, repeatability of 0.07 mm) and toricity (0.15 ± 0.08 mm, flatter horizontally, repeatability of 0.10 mm). Low coefficients of determination were found for the topographical limbus with the internal limbus (R²=0.021 and R²=0.039, for horizontal and vertical diameters respectively) and with the WTW (R²=0.146 for the horizontal diameter).

Conclusion: The proposed method to demarcate the 3D external topographical limbus is repeatable. The topographic limbal shape and size cannot be accurately derived from WTW nor internal limbus measures. This new technology may improve the process of scleral lens fitting.

Keywords: Anterior segment optical coherence tomography; Corneoscleral topography; Limbus; White-to-white.

MeSH terms

Algorithms
Cornea
Corneal Topography / methods
Humans
Limbus Corneae* / diagnostic imaging
Sclera / diagnostic imaging
Tomography, Optical Coherence* / methods

Abstract

MeSH terms

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