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Elmira Baghdasaryan, Kenneth Marion, Tudor Tepelus, Srinivas R. Sadda, Hugo Y Hsu; Evaluation of Corneal Epithelial Thickness in Healthy Eyes using Spectral-Domain OCT. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3847.
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To evaluate regional variations in corneal epithelial thickness (CET) in healthy eyes using spectral domain optical coherence tomography (SD-OCT).
36 healthy eyes of 18 subjects (10 M, 8 F) were prospectively imaged using the Cirrus HD-OCT with the pachymetry scan protocol. Scans were repeated twice to average the measurements. The average CET was assessed within 4 pre-defined corneal zones consisting of concentric rings centered on the center of the cornea (0-2 mm, 2-5 mm, 5-7 mm, and 7-9 mm) and compared using one-way ANOVA. The average corneal thickness (CT) was quantified within three concentric rings (0-2 mm, 2-5 mm, and 5-7 mm) using the Cirrus Review Software. In addition, within the 2-5mm and 5-7mm rings, the CET was assessed and compared within specific regions: superior (S), inferior (I), superonasal (SN), and inferotemporal (IT). The difference between S and I (S – I), and SN and IT (SN – IT) were computed and compared between males and females.
The mean age of subjects was 32 ± 5.2 years. The average CET was 48.3, 47.1, 46.1, and 45.8 µm in the 4 concentric zones (0-2, 2-5, 5-7, and 7-9mm), respectively (p-value < 0.001). The average CT was 533.5, 551 and 579.5 µm in the three CT concentric zones (0-2, 2-5, and 5-7mm), respectively (p-value < 0.001). Of note, there was no statistically significant correlation between CET and CT in any of the measured zones (p-value > 0.05). Males had thicker corneas than females in each of the three CT zones (p-value < 0.05), but the CET did not differ significantly between males and females in these same 3 zones (p-value > 0.05). CET regional difference values (2-5mm ring) for S-I and SN-IT between males and females were -2.3 µm vs. -0.4 µm (p-value = 0.05), and -1.15 µm vs. 0.9 µm (p-value = 0.04), respectively. In the 5-7 mm zone, CET regional difference values (S-I and SN-IT) for males and females were -3.9 µm vs -0.9 µm, p-value = 0.05 and -1.4 µm vs. -0.3 µm, p-value = 0.3, respectively.
OCT-based analysis of the corneal epithelium reveals that it is thinner in the periphery, whereas the total cornea is thicker. While the total corneal thickness appears to be influenced by gender, the CET is generally not, though the superior corneal CET tends to be thinner in males. These regional and gender-based variations in corneal thickness may need to be considered when assessing corneal and epithelial alterations in disease.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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