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Repeatability of corneal and epithelial thickness measurements with anterior segment optical coherence tomography in keratoconus

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First Author: M.Ziaei NEW ZEALAND

Co Author(s):    A. Gokul   Y. Li   C. McGhee   M. Ziaei           

Abstract Details

Purpose:

To investigate the repeatability in corneal thickness (CT) and epithelial thickness (ET) measurements using Spectral Domain Anterior Segment OCT (AS-OCT, REVO NX, Optopol) in patients with keratoconus, and examine the effect of corneal crosslinking (CXL), contact lens wear, and hydrops on repeatability.

Setting:

University of Auckland Cornea and External Eye Disease Tertiary Service.

Methods:

This prospective case series enrolled patients with keratoconus attending the corneal disease clinic from January 2019 to August 2019. Eyes with a history of severe dry eye disease, corneal oedema, ocular surgery other than CXL or trauma were excluded. Eyes were analyzed in four groups: eyes with no prior history of CXL, contact lens wear, or hydrops (Group A), eyes with a history of prior CXL (Group B), eyes with history of contact lens wear (Group C) and eyes with history of corneal hydrops (Group D). Repeatability of measurements was assessed using the intraclass correlation coefficient (ICC). 

Results:

In Group A, central corneal thickness was 472.18 ± 45.41µm, and the epithelium was found to be the thinnest in the inferior-temporal aspect at 51.79 ± 5.97µm and thickest at the superior-nasal aspect at 56.07 ± 5.70µm. In CT measurements, ICC was above 0.86, 0.83, 0.88, and 0.97 for all sectors in Groups A, B, C and D respectively. In ET measurements, ICC was above 0.82, 0.82, 0.77, and 0.67 for Groups A, B, C and D respectively. CXL and contact lens wear had no statistically significant impact on the repeatability, whereas hydrops significantly reduced the repeatability of ET measurements. 

Conclusions:

The REVO NX AS-OCT provides repeatable CT and ET measurements in the central and peripheral cornea in patients with keratoconus. Caution should be taken when using REVO NX for ET measurements in eyes with a history of corneal hydrops, as these patients were found to have significantly more variable measurements. Despite potential effects of CXL on corneal haze, repeatability of CT and ET in CXL eyes were not affected. History of contact lens wear did not affect the repeatability of CT or ET. The REVO NX can be a useful device in the diagnosis and surveillance of patients with keratoconus.

Financial Disclosure:

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