Biometric Determinants of Epithelial Thickness Profile Across a Wide Range of Refractive Errors

Corneal Epithelial Thickness Mapping in Healthy Population Corneas Using MS-39 Anterior Segment Optical Coherence Tomography

Purpose

The corneal epithelium is the outermost layer of the cornea. It plays a vital role in both normal and pathological conditions of the eye surface and serves as a protective layer. This study aimed to evaluate corneal epithelial thickness (ET) and create a normative database of corneal ET for pediatric and adult age groups using MS-39 AS-OCT.

Patients and Methods

This is a cross-sectional multi-center study conducted among the Saudi population.

Results

A total of 268 eyes of 268 patients were analyzed (male 50.7% vs female 49.3%). 53.8% were pediatric age group. Higher mean values of central, paracentral, and peripheral were associated with the adult age group except for superior paracentral, temporal peripheral, and nasal peripheral. Male patients had higher mean values of central, paracentral, and peripheral in each quadrant, except for inferior peripheral. There was a significant correlation between inferior, superior, nasal, and temporal in both paracentral and peripheral. No significant correlations were observed between the spherical equivalent and epithelial thickness map.

Conclusion

The study found sex differences, with females generally having lower ET values than males, and older age having higher values than children.

Blepharoptosis and corneal epithelial thickness alterations, is there any relation?

BACKGROUND

To compare the epithelial thickness map of ptotic eyes of blepharoptosis patients with contralateral non- ptotic eyes.

METHODS

Unilateral blepharoptosis patients were enrolled consecutively. Patients were underwent full ophthalmologic examination and their demographic data such as age and gender and specific ptosis findings e.g. the cause and duration, MRD-1, and levator palpebralis superioris function were registered. Anterior segment imaging for epithelial thickness measurements was done using the Avanti RTVue-XR platform. The corneal epithelial thickness maps of ptotic and non-ptotic eyes were compared.

RESULTS

44 patients with unilateral blepharoptosis were included in the study. 27 (61.4%) of them were female and 17 (38.6%) cases were male. The mean of the patients' ages was 24.40 ± 15.16 years. Ptotic eyes had significantly thinner superior (p = 0.000), superior-temporal (p = 0.000) and superior-nasal (p = 0.005) sectors of the cornea and slightly thicker corneal epithelium (CE) in the inferior-nasal sector. The correlation of difference of superior-inferior CE was evaluated with different parameters including patient's age (p = 0.457), type of blepharoptosis (p = 0.786), duration of blepharoptosis (p = 0.477) and MRD1 (p = 0.248), but no correlation was found.

CONCLUSIONS

This study revealed that lid position in blepharoptosis may have effects on the corneal epithelial thickness map. Because of the lower position of upper eyelid, a thinning effect on superior corneal sectors may happen.

Corneal Epithelial Thickness Mapping: A Major Review

The corneal epithelium (CE) is the outermost layer of the cornea with constant turnover, relative stability, remarkable plasticity, and compensatory properties to mask alterations in the underlying stroma. The advent of quantitative imaging modalities capable of producing epithelial thickness mapping (ETM) has made it possible to characterize better the different patterns of epithelial remodeling. In this comprehensive synthesis, we reviewed all available data on ETM with different methods, including very high-frequency ultrasound (VHF-US) and spectral-domain optical coherence tomography (SD-OCT) in normal individuals, corneal or systemic diseases, and corneal surgical scenarios. We excluded OCT studies that manually measured the corneal epithelial thickness (CET) (e.g., by digital calipers) or the CE (e.g., by confocal scanning or handheld pachymeters). A comparison of different CET measuring technologies and devices capable of producing thickness maps is provided. Normative data on CET and the possible effects of gender, aging, diurnal changes, refraction, and intraocular pressure are discussed. We also reviewed ETM data in several corneal disorders, including keratoconus, corneal dystrophies, recurrent epithelial erosion, herpes keratitis, keratoplasty, bullous keratopathy, carcinoma in situ, pterygium, and limbal stem cell deficiency. The available data on the potential role of ETM in indicating refractive surgeries, planning the procedure, and assessing postoperative changes are reviewed. Alterations in ETM in systemic and ocular conditions such as eyelid abnormalities and dry eye disease and the effects of contact lenses, topical medications, and cataract surgery on the ETM profile are discussed.

Impact of Corneal Toricity on the Distribution of Corneal Epithelial Thickness

PURPOSE

To investigate the impact of corneal toricity on the distribution characteristics of corneal epithelial thickness (CET).

METHODS

A total of 330 eyes in 330 healthy participants were included in this study. They were divided into two groups based on the median of the corneal toricity value: low-toricity group (corneal toricity < 1.50 diopters) and high-toricity group (corneal toricity ≥ 1.50 diopters). The CET within a 9-mm-diameter area of the central cornea was obtained using optical coherence tomography. The difference of CET value between flat and steep meridians (F-S CET) was defined to evaluate the CET distribution. The F-S CET between the two groups was compared, and the correlations between F-S CET and the corneal toricity were analyzed.

RESULTS

The CET was thinner in the superior-peripheral area than in other areas. A slight intergroup difference was noted in terms of the F-S CET at the paracentral (0.11 ± 0.93 vs 0.32 ± 0.92, P = .038), midperipheral (0.45 ± 0.78 vs 0.77 ± 0.89, P = .001), and peripheral (3.11 ± 2.18 vs 4.10 ± 2.38, P < .001) zone. In each zone, the difference in F-S CET between the two groups was less than 1 μm. As the area expanded, the F-S CET continued to increase (F = 850.303, P < .001). A weak correlation was observed between F-S CET and corneal toricity (r = 0.103 to 0.240); however, this correlation was not significant in the paracentral zone. Covariance analysis demonstrated that F-S CET was slightly correlated with age, refractive state, and intraocular pressure.

CONCLUSIONS

The corneal toricity did not significantly affect the distribution of the corneal epithelium in normal corneas. [J Refract Surg. 2023;39(7):482-490.].