Wide Corneal Epithelial Mapping Using an Optical Coherence Tomography

Abstract

PURPOSE. To map the corneal epithelium using a map measuring 9 mm in diameter and view the effects of age, sex, and axial length. Additionally, we wanted to demonstrate the reproducibility of this technique. METHODS.We calculated the epithelial thickness in 220 individuals using an SD-OCT machine with the newly released commercially available algorithm. We included normal eyes with refractive errors between þ5 and À6 diopters (D). We excluded patients with an intraocular pressure of >22 mm Hg, history of cataract, previous ocular surgery, or disease and those with corneal pathology. Additionally, we excluded patients with evidence of systemic disease or pregnancy. Lastly, reproducibility was measured in 50 individuals. RESULTS.We found the center of the corneal epithelium to be thicker than the peripheral in all zones except the nasal (P ¼ 0.124). The superior quadrant was found to be the thinnest while the inferior was the thickest. Males had a thicker epithelium in all locations except the superior outer section (P ¼ 0.123). Three zones had a weak correlation with age: outer superior (P ¼ 0.039, R ¼ À0.152); outer temporal (P ¼ 0.042, R ¼ À0.150); and outer superior temporal (P ¼ 0.011, R ¼ À0.187). There was no significant relationship with the axial length. We found good to excellent reproducibility when using this technique in the central as well as the peripheral cornea.CONCLUSIONS. We provide a comprehensive study in healthy, normal eyes using a novel algorithm to map the corneal epithelium with a wide diameter. This study can be used as a reference for future research.

<p>Wide Stromal Mapping Using an Anterior Segment Optical Coherence Tomography</p>

“…3 Interestingly, we found the thinnest zone in our epithelial thickness profiles to be the superior zone; these were thicker as they approached the center. 4 This is the reversal of what we find in the stroma. All previous theories trying to explain the regional differences in epithelial thickness profiles focused on the outside environment or the measurement method.…”

“…In addition, the study adhered to the Declaration of Helsinki and was approved by the Ethics Committee of the Hospital. This study is an extension of our previous study measuring the corneal epithelium 4 and therefore some of the analysis presented here is similar.…”

Mapping of Corneal Layer Thicknesses With Polarization-Sensitive Optical Coherence Tomography Using a Conical Scan Pattern

“…Previous studies using various imaging modalities, like confocal microscopy, 34 VHF ultrasound, 35 and OCT, 12,15 found ET values varying from approximately 50 to 60 lm and an increase in thickness from superior to inferior, for which three possible reasons were described in the literature. First, friction forces due to blinking might ablate the epithelium.…”

“…The reproducibility of our ET measurements is comparable to that of commerciallyavailable devices. 15 It was lower in the outmost peripheral sectors, compared to the central sectors, which might be due to small misalignment between consecutive measurements of an eye and segmentation imperfections due to peripheral optical aberrations of the scanning lens. This applies to all segmented layers.…”

“…6 For more detailed studies on corneal diseases, measurement and imaging of individual corneal layers is required. Epithelial thickness (ET) measurements were described by various studies using custom built OCT 12,13 or commercial 14,15 devices. Most of these studies report an ET between 50 and 60 lm measured in a field of view (FoV) of up to 9 mm diameter.…”