Pachymetric mapping with Fourier-domain optical coherence tomography

Abstract

Purpose-To evaluate the repeatability of Fourier-domain optical coherence tomography (FD-OCT) pachymetric mapping and compare OCT central corneal thickness (CCT) measurements with those of ultrasound pachymetry and Orbscan II. Setting-DohenyEye Institute, University of Southern California, Los Angeles, CA Methods-An FD-OCT system (RTVue-CAM, Optovue Inc., Fremont, CA) was used to map the corneal thickness of fifty normal participants. The scans were centered on either the corneal vertex or pupil. The repeatability of central and pericentral map sectors were assessed by pooled standard deviation (SD). The CCT measured by OCT was compared with those measured by ultrasound and Orbscan II by paired t-test, Pearson correlation, and Bland-Altman analysis.Results-Pupil centration (SD: 1.3 μm central, 1.8-3.8 μm pericentral) provided better repeatability than vertex centration (1.7 μm central, 2.4-5.7 μm pericentral) in all sectors (P<0.035). The CCT measured by OCT, ultrasound, and Orbscan II (acoustic factor 0.92) was 536.9±27.0, 556.6±30.5, and 537.2±32.6 μm, respectively. The CCT measured by OCT was significantly thinner than ultrasound pachymetric readings (P=0.007, mean difference −19.7 μm, 95% limits of agreement -40.4 to 0.9 μm) but not those of Orbscan II (P=0.2637, mean difference -0.3 μm, 95% limits of agreement -24.0 to 23.5 μm). The OCT CCT correlated well with those of ultrasound and Orbscan II (Pearson r = 0.940 and 0.934, respectively).Conclusion-Pachymetric mapping with FD-OCT was highly repeatable. The repeatability was better with pupil-centered scans than with corneal vertex-centered scans. Ultrasound pachymetry, FD-OCT and Orbscan II should not be used interchangeably for the assessment of corneal thickness.

Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography

“…Several reports have showed repeatability and reproducibility results of various OCT systems for corneal pachymetry, which are summarized in Table 3 [4,22,24,40,41,[49][50][51][52]. Our results showed a CoR of less than 3.54 μm for normal subjects and 3.78 μm for post-LASIK patients within the central zone (0-2 mm) and the paracentral zone (2-5 mm) for corneal thickness repeatability and reproducibility.…”

“…However, only the vertex centration was used for image processing. Previous studies have found the difference between cornea vertex centration and pupil centration [22,62]. Whether one would be preferred or both should be combined in an automated algorithm needs to be investigated further.…”

“…These features make it possible to minimize the influence of eye movement during image acquisition and improve the repeatability of pachymetry measurements. Commercial SD-OCT instruments are available for corneal pachymetry [4,[22][23][24]. Most of these commercial SD-OCT systems are limited to a diameter of 6 mm or less for corneal pachymetry measurements [4,[22][23][24].…”

“…Commercial SD-OCT instruments are available for corneal pachymetry [4,[22][23][24]. Most of these commercial SD-OCT systems are limited to a diameter of 6 mm or less for corneal pachymetry measurements [4,[22][23][24]. However, a 6-mm-diameter imaging range may not be sufficient to image the peripheral cornea with diseases and surgery plans, such as pellucid and Terrien's marginal degeneration, Intacs implantation, and corneal cross-linking [24][25][26][27][28].…”

Anterior Eye Imaging with Optical Coherence Tomography

“…The first one is called spectrometer-based (or spectral-domain) OCT, in which the interferometric signal is detected by a spectrometer equipped with a high-speed line scan detector, such as a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) line camera. Spectrometer-based OCT systems capable of 6,700-310,000 axial scans per second were reported [14][15][16]. The second one is called swept-source OCT, which uses high-speed tunable lasers [17].…”