Corneal Epithelium Metrics Provide Insight Into Ocular Surface Disorders

Corneal epithelial thickness mapping may aid in the diagnosis of ocular surface diseases involving the corneal epithelium.

Epithelial map pattern recognition combined with quantitative analysis of corneal epithelial thickness (ET) can aid in diagnosis of ocular surface disorders (OSDs), according to research published in Cornea. The technology can also help differential diagnoses, the report shows.

Researchers conducted a retrospective comparative study to assess the role of ET mapping  via spectral domain optical coherence tomography (OCT) in the diagnosis of OSDs involving the corneal epithelium in a real-world setting.

They used records of a consecutive series of patients with a confirmed OSD diagnosis involving the corneal epithelium and on OCT assessment as well as records of patients with normal eyes on OCT assessment (control group). Spectral domain OCT with epithelial mapping was conducted in the central 6 mm. 

The primary outcome measures included ET map classification (normal, doughnut, spoke-wheel, localized/diffuse, and thinning/thickening patterns) and ET measurements (minimum, maximum, and standard deviation). The researchers also used receiver-operating curves to determine a quantitative threshold to distinguish pathological and normal corneas. They also calculated the sensitivity and specificity of classification and quantitative data using all eyes to determine whether corneas with a given corneal disorder could be distinguished from other conditions.

A total of 303 eyes with an OSD and 55 normal eyes of 55 patients were included in the study. The mean patient age in the control group was 38±16 years (range, 18-86 years). Among patients with OSDs, 135 eyes were keratoconus (patient mean age, 35±13 years; range, 11-79); 56 eyes had limbal stem cell deficiency (LSCD; patient mean age, 46 ± 16 years; range, 16-75); 55 eyes had epithelial basement membrane corneal dystrophy (EBMD; patient mean age, 58±14 years; range, 26-85); 21 eyes had dry eye (patient mean age, 57±15 years; range, 30-76); 10 eyes had a pterygium (patient mean age, 66±14 years; range, 45-84); 15 eyes had trachoma (patient mean age, 72±10 years; range, 58-88); and 11 eyes had in situ carcinoma (patient mean age, 70±12 years; range, 50-88).

Full agreement between 3 readers for classification of was obtained in 75.4% to 99.4% of cases. The main features among OSDs were a doughnut pattern (sensitivity/specificity=56/94%) and max-min ET of 13 μm or thicker (84/43%) for keratoconus eyes, a spoke-wheel pattern (66/98%) and max-min ET of 14 μm or thicker (91/59%) for LSCD eyes, an inferior thickening pattern (55/92%), and central ET thicker than 56 μm (53/81%) for EBMD eyes, a superior thinning pattern (67/88%) and minimal ET of 44 μm or thinner (86/48%) eyes with dry eye, a nasal thickening pattern (100/86%) and nasal ET of 56 μm or thicker (80/71%) for eyes with a pterygium, and max ET thicker than 60 μm (91/60%) and ET SD thicker than 5 μm (100/58%) for eyes with in situ carcinoma.

“Our proposed diagnosis method is highly objective because pattern classification was found to be repeatable among different observers, and ET data and statistics are provided by the SD-OCT device,” researchers report. “Deep learning analysis of big data could lead to the fully automated diagnosis of these disorders.”

Limitations of the study included the retrospective design, small sample sizes for some OSDs, the limited 6 mm diameter size of the thickness map, no grading of severity for certain OSDs, and potential selection bias by use of only high-quality OCT images.

Reference

Levy A, Georgeon C, Knoeri J, et al. Corneal epithelial thickness mapping in the diagnosis of ocular surface disorders involving the corneal epithelium: a comparative study Published online March 31, 2022. Cornea. doi:10.1097/ICO.0000000000003012