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Orbscan, OCT can measure corneal thickness without contact lens removal
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Both noncontact scanning slit pachymetry and optical coherence tomography can be used to noninvasively measure central corneal thickness in contact lens wearers without removing the lenses, a study found.
Raul Martin, OD, and colleagues at the University of Valladolid, Spain, evaluated the utility of different imaging technologies for determining variations in corneal swelling during extended contact lens wear. The study included 20 participants with normal ocular health who were randomly fitted with high-Dk (lotrafilcon A) and low-Dk (etafilcon A) soft contact lenses for extended wear.
Investigators measured central corneal thickness (CCT) using ultrasonic pachymetry, noncontact scanning slit pachymetry (Orbscan II, Bausch & Lomb) and optical coherence tomography (OCT) 1 week before beginning lens use and during 1 week of continuous lens wear. They also measured CCT using Orbscan pachymetry and OCT while participants wore the lenses after 3 and 7 days of wear, according to the study.
Both Orbscan pachymetry and OCT had a high correlation with ultrasonic pachymetry. Also, Bland-Altman analysis showed high agreement and repeatable with Orbscan pachymetry and OCT both with and without contact lens removal, the authors reported.
"Both techniques allowed for measurement throughout the study period of the CCT differences induced by [contact lens] wear," they said.
Corneal swelling was significantly greater in eyes fitted with etafilcon A lenses compared with lotrafilcon A lenses, the authors noted.
The study is published in the July issue of Investigative Ophthalmology & Visual Science.