Reliability of Corneal, Epithelial, and Stromal Thickness Mapping for a 9-mm Zone Using Spectral-Domain Optical Coherence Tomography

Abstract

Purpose To evaluate the reliability of spectral-domain optical coherence tomography (SD-OCT; RTVue XR; Optovue, Inc., Fremont, CA, USA) for thickness mapping of the entire cornea (CT), corneal epithelium (ET). and corneal stroma (ST) over a 9-mm zone in healthy eyes. We sought to develop reference values for different age groups and elucidate potential sex- and age-dependent characteristics of corneal sublayer pachymetry maps. Methods Three consecutive SD-OCT scans were obtained in 166 healthy right eyes (mean age = 50 ± 20 years). The thickness maps contain 25 sectors over a 9-mm diameter zone. To test measurement reliability, intraclass correlation coefficients (ICC), coefficients of variation (CoV), and within-subject standard deviations (WSSD) were calculated. Results CT, ET, and ST ICCs ranged from 0.961 to 0.998, 0.896 to 0.945, and 0.955 to 0.998, respectively. CoV values for CT, ET, and ST ranged between 0.3 and 1.5%, 1.6 and 4.2%, and 0.4 and 1.7%, respectively. WSSD ranged from 6 to 41, 4 to 8, and 7 to 46 µm, respectively. A negative correlation was found between age and ET (p < 0.05) but not between age and ST or CT. No gender-related differences in CT, ET, or ST were detected. CoV of CT, ET, and ST measurements showed a positive correlation with age in 28, 64, and 28% of the sectors, respectively. Conclusion SD-OCT is a rapid and noninvasive technique that provides excellent reliability for corneal sublayer thickness measurements over a 9-mm zone. The reliability of the ET measurement seems to be negatively affected by age. Peripheral CT and global ET thin with age.

Korneales Kollagen-Crosslinking (CXL) bei Hornhautektasie nach SMILE (Small Incision Lenticule Extraction)

“…To date, however, parameters of this type are too poorly understood; this means that further studies are necessary before reliable normative data are available. In recent years, OCT-based corneal epithelial mapping has emerged as a particularly promising diagnostic technique which could be useful not only for early detection or follow-up of keratoconus [1], but also for "form-fruste" keratoconus screening prior to keratorefractive surgery [20].…”

“…Verlaufskontrolle des Keratokonus [1], sondern insbesondere auch für das "Form Fruste" Keratokonus-Screening vor keratorefraktiven Eingriffen dienlich sein könnte. [20] In der Theorie existieren Vorteile der SMILE Methode gegenüber der LASIK in Bezug…”

“…Als besonders vielversprechendes diagnostisches Verfahren hat sich in den letzten Jahren das OCT-basierte korneale Epithel-Mapping etabliert, das nicht nur zur Früherkennung bzw. Verlaufskontrolle des Keratokonus 1 , sondern insbesondere auch für das „Form-fruste“-Keratokonus-Screening vor keratorefraktiven Eingriffen dienlich sein könnte 20 .…”

The Combined Utilization of Epithelial Thickness Mapping and Tomography in Keratorefractive Surgery Screening: One Imaging Modality is Not Sufficient

“…ETM has demonstrated impressive reproducibility, inter-device agreement and repeatability. [1][2][3][4][5] Research has demonstrated the value of these epithelial measurements and the significant role they can play in the preoperative screening of keratorefractive surgery candidates. [4][5][6][7][8][9][10] However, recent research has introduced nuances to our former understanding of the corneal epithelial resurfacing function upon which ETM interpretations are based.…”

“…In summary, ETM is an impressive and clinically valuable imaging tool that has been increasingly used in preoperative keratorefractive surgery screening due to its accuracy and precision in measuring epithelial thickness. [1][2][3]7,9,11,34 However, due to the limited information that epithelial thickness maps can provide, especially in the context of increasing awareness of keratoconic and corneal derivations from the traditional corneal resurfacing model, valuable tomographic parameters provided by other systems must be utilized in combination with ETM for optimal clinical decision making. [10][11][12][13]25 One imaging technology, the REVO NX (Optopol Technology, Zawiercie, Poland), is already moving in this direction and found to be effective in utilizing OCT scans to generate ETMs and other tomographic parameters from the same data points.…”