Corneal and Epithelial Thickness Mapping: Comparison of Enhanced Spectral-Domain- and Spectral-Domain-Optical Coherence Tomography

Abstract

Objective. To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes. Methods. 30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT. Results. The central and minimum ET obtained with both devices were correlated: central ET, r = 0.86, p < 0.05 ; minimum ET, r = 0.72, p < 0.05 . Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 μm on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, r = 0.994, p < 0.05 ; minimum CT, r = 0.995, p < 0.05 . SS-OCT tended to overestimate these figures by 11 and 14 μm on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT. Conclusion. SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.

Assessing progression limits in different grades of keratoconus from a novel perspective: precision of measurements of the corneal epithelium

“…Unexpectedly, the TRTs at the nasal and temporal points at 1 mm are higher than those at 3 mm regardless of the stage of KC. Georgeon et al [ 40 ] studied the reproducibility of ET provided by MS-39 in normal eyes and found that the superior regions usually showed poor reproducibility, which differed from the findings in our study. The altered morphology of the KC could lead to lower reproducibility.…”

“…After analysis, we attribute this to the irregularity of keratoconus, which would increase the uncertainty and difficulty of measurement. Moreover, the measurement error increases as the measuring point is further away from the corneal apex in our study, which is consistent with other studies [ 40 , 42 ]. This may be because the incident angle between the OCT probe beam and the corneal surface increases as the distance from the center of the cornea increases [ 40 ].…”

“…This means when the measurement error is greater than 3 µm, there is a possibility of clinical misdiagnosis in early KC diagnosis. Georgeon et al [ 40 ] proposed that MS-39 has high reproducibility in the measurement of TET for healthy people, with the S w value being 1.18 µm and the corresponding TRT (2.77S w ) was 3.27 µm. Li et al [ 43 ] obtained an acceptable S w value of 1.8 µm (TRT 4.97 µm) when evaluating the repeatability measurement for TET of KC.…”

Recombinant Human Nerve Growth Factor (Cenegermin)–Driven Corneal Wound Healing Process: An Evidence-Based Analysis

“…This instrument uses an 840-nm wavelength beam. We are aware that other specialized AS-OCTs by using a 1310-nm wavelength could be more performing (Georgeon et al, 2021). Anyway, RTVue-100 allowed us to detect detailed scans of the corneal healing process and its improvements over time.…”

Optical coherence tomography epithelial mapping for keratoconus screening

“…Regardless of the type of commercially available anterior-segment OCT strategy, studies have confirmed the excellent measurement repeatability and reproducibility of this imaging modality [13,14]. Recently, Kundu et al introduced an artificial intelligence-driven model for detecting early keratoconus.…”