Repeatability of pachymetry and thinnest point localization using a fourier-domain optical coherence tomographer

To evaluate the repeatability of pachymetry measures at six distinct locations using a Fourier-domain optical coherence tomographer. The location of the thinnest point was also described using vector analysis, and repeatability of the localization of the thinnest point was calculated.

The right eye of 25 healthy subjects had 3 images of their right cornea captured using the pachymetry protocol and anterior segment lens of a commercially available Fourier-domain optical coherence tomographer (RTVue-100, Optovue, Fremont, CA). The first two images were used to quantify repeatability in the central (2 mm) and paracentral (2-5 mm) cornea. Cartesian coordinates representing the location of the thinnest point were used to determine the mean location in relation to the central cornea.

Mean central thickness was 536.8 ± 31.1 μm, and the mean minimum thickness was 526.4 ± 33.1 μm. The thickest paracentral zone was the superior cornea and the thinnest was the temporal cornea. Intraclass correlation values ranged between 0.969 and 0.996, and the mean coefficient of repeatability was 1.74% across all locations evaluated. The thinnest point was located in the inferior temporal region in 80% of eyes and was an average distance of 1.01 mm from the corneal apex, subtending an angle of 26.7° from the horizontal.

The RTVue-100 provides a highly repeatable measure of corneal thickness at various locations. The instrument is capable of describing and consistently duplicating the location of the thinnest point of the cornea; however, further comparative work with other clinical imaging modalities is required.