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. 2014 May 20;9(5):e97962.
doi: 10.1371/journal.pone.0097962. eCollection 2014.

Vertical and horizontal corneal epithelial thickness profile using ultra-high resolution and long scan depth optical coherence tomography

Shuangqing Wu  1 , Aizhu Tao  2 , Hong Jiang  3 , Zhe Xu  2 , Victor Perez  3 , Jianhua Wang  3
Affiliations

Vertical and horizontal corneal epithelial thickness profile using ultra-high resolution and long scan depth optical coherence tomography

Shuangqing Wu et al. PLoS One. .

Abstract

Purpose: To determine the vertical and horizontal thickness profiles of the corneal epithelium in vivo using ultra-long scan depth and ultra-high resolution spectral domain optical coherence tomography (SD-OCT).

Methods: A SD-OCT was developed with an axial resolution of ∼ 3.3 µm in tissue and an extended scan depth. Forty-two eyes of 21 subjects were imaged twice. The entire horizontal and vertical corneal epithelial thickness profiles were evaluated. The coefficient of repeatability (CoR) and intraclass correlation (ICC) of the tests and interobserver variability were analyzed.

Results: The full width of the horizontal epithelium was detected, whereas part of the superior epithelium was not shown for the covered super eyelid. The mean central epithelial corneal thickness was 52.0 ± 3.2 µm for the first measurement and 52.3 ± 3.4 µm for the second measurement (P>.05). In the central zone (0-3.0 mm), the paracentral zones (3.0-6.0 mm) and the peripheral zones (6.0-10.0 mm), the mean epithelial thickness ranged from 51 to 53 µm, 52 to 57 µm, and 58 to 72 µm, respectively. There was no difference between the two tests at both meridians and in the right and left eyes (P>.05). The ICCs of the two tests ranged from 0.70 to 0.97 and the CoRs ranged from 2.5 µm to 7.8 µm from the center to the periphery, corresponding to 5.6% to 10.6% (CoR%). The ICCs of the two observers ranged from 0.72 to 0.93 and the CoRs ranged from 4.5 µm to 10.4 µm from the center to the periphery, corresponding to 8.7% to 15.2% (CoR%).

Conclusions: This study demonstrated good repeatability of ultra-high resolution and long scan depth SD-OCT to evaluate the entire thickness profiles of the corneal epithelium. The epithelial thickness increases from the center toward the limbus.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Representative images of the corneal epithelium with ultra-long and ultra-high resolution SD-OCT.
(A) The horizontal corneal epithelial thickness image. (B, C) The entire corneal epithelial layer could be distinguished. (D) In the vertical corneal epithelial thickness image, part of the superior cornea was covered by the eyelid, and the tear menisci could be observed clearly (Bar  = 250 µm).
Figure 2
Figure 2. Repeated two tests for the corneal epithelial thickness profiles.
There was no significant difference between the repeated Test 1(white bar) and Test 2 (gray bar) with ultra-long and ultra-high resolution SD-OCT in horizontal or vertical meridian in the bilateral eyes (P>.05).
Figure 3
Figure 3. Comparison of corneal epithelial thickness in the bilateral eyes in horizontal and vertical meridian.
The horizontal and vertical profiles with ultra-long and ultra-high resolution SD-OCT showed no significant differences between the right eyes and the mirrored left eyes (P>.05). The temporal and nasal corneal epithelial thickness increased symmetrically, and the inferior corneal epithelial thickness increased more rapidly than the superior ones. T: temporal; N: nasal; I: inferior; S: superior.
Figure 4
Figure 4. Coefficients of repeatability (CoR) of the horizontal and vertical corneal epithelial thickness profiles.
The average CoR of the horizontal and vertical corneal epithelial thickness profiles of the bilateral eyes with ultra-long and ultra-high resolution SD-OCT.
Figure 5
Figure 5. Intraclass correlation coefficients (ICC) of the horizontal and vertical corneal epithelial thickness profiles.
The average ICC of the horizontal and vertical corneal epithelial thickness profiles of the bilateral eyes with ultra-long and ultra-high resolution SD-OCT.
Figure 6
Figure 6. Coefficients of repeatability (CoR) and intraclass correlation coefficients (ICC) between two observers.
The horizontal images of the right eyes (n = 21) in the first examination were analyzed by two observers to test the interobserver variability.
See this image and copyright information in PMC

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