Repeatability, Reproducibility and Comparison of Cirrus OCT, RTVue OCT, MS-39 OCT, and Insight 100 VHFDU

Repeatability and Reproducibility of Carl Zeiss Meditec Cirrus HD OCT 5000, Optovue RTVue OCT, CSO MS-39 OCT and ArcScan Insight 100 Very High-frequency Digital Ultrasound and Comparison Between Devices

The purpose of this study is to evaluate the repeatability and reproducibility of corneal, epithelial, and LASIK flap thickness using the Carl Zeiss Meditec Cirrus HD OCT 5000, Optovue RTVue OCT, CSO MS-39 OCT, and ArcScan Insight 100 very high-frequency digital ultrasound arc-scanner.

Very high-frequency (VHF) digital ultrasound was first used in 1993 to obtain images and measure the thickness of the cornea (the window at the front of the eye) and the layers within the cornea, such as the epithelium (the layer of skin on the surface of the cornea). A commercially available instrument, known as the Artemis, has been used in routine clinical practice since 2001. The ArcScan Insight 100 VHF digital ultrasound scanner is an updated version, which obtained CE mark in 2016.

Optical coherence tomography (OCT) is another method of measuring the thickness of the cornea and the corneal epithelium. OCT has been used for measuring corneal thickness since 1997 and the technology had evolved to also measure epithelial thickness since 2012. There are currently three OCT scanners capable of measuring epithelial thickness; Carl Zeiss Meditec Cirrus HD OCT 5000, Optovue RTVue OCT, CSO MS-39 OCT.

The aim of the study is to establish the repeatability (i.e. the variability in measurements taken by a single examiner during a single visit) and reproducibility (i.e. the variability in measurements taken in the same conditions between two examiners) for each of the four devices for measuring corneal thickness and epithelial thickness.

Inclusion Criteria:

Only patients who are medically suitable for corneal laser refractive surgery can be included in the study.

As general inclusion criteria the following aspects are defined:

• Subjects should be 21 years of age or older.
• Contact lens wearers must stop wearing their contact lenses at least four weeks per decade of wear before baseline measurements in case of hard contact lenses and one week before baseline measurements in case of soft contact lenses.
• Patient will be able to understand the patient information and willing to sign an informed consent.

For the normal eye populations:

• Eyes with no ocular pathology
• Eyes with no previous ocular or corneal surgery

For the post-op eye populations:

• Eyes between 3 and 9 months after LASIK or SMILE

Exclusion Criteria:

• Previous ocular or corneal surgery (for normal eyes)
• Patient not being able to tolerate local or topical anesthesia
• Patient has active conjunctivitis or any active ocular infection or inflammation
• Patient has a corneal ulcer
• Patient has an open wound on the corneal epithelium
• Patient has compromised epithelium (e.g. ≥Grade 3 superficial punctate keratitis)
• Pregnancy