A diagnostic scale combining corneal epithelial mapping with Fourier-domain OCT and certain patient factors offers a novel, objective method for identifying and potentially determining the severity of dry eye disease.
Study design
This single center, prospective, comparative study assessed the corneal epithelial thickness of 59 patients (118 eyes) with dry eye disease and 55 controls (110 eyes). Epithelial thickness was measured with a 9 mm scan using the RTVue XR 100 Avanti Fourier-domain OCT (Optovue, Fremont, USA). Dry eye disease was defined according to the DEWS II: symptoms of dryness (Ocular Surface Disease Index) and the presence of at least one ocular surface disorder (non-invasive tear break-up time and Oxford scale ocular surface staining). T-test comparisons and univariate receiver operating curve calculations were used to define the accuracy of OCT epithelial mapping in discriminating healthy eyes from eyes with dry eye disease. Multivariate analyses using artificial intelligence (random forest), logistic regression, and bootstrapping identified other factors (e.g., gender, age, etc.) that could help improve the diagnostic performance of OCT epithelial mapping.
Outcomes
Eyes in the dry-eye–disease group had thinner epithelium compared to those in the control group, regardless of location. Superior intermediate epithelial thickness was the best marker for diagnosing dry eye disease (ROC: 0.87, best cut-off value: 50 μm), and the difference between the inferior and superior peripheral zones was most effective at grading severity. Incorporating superior epithelial thickness in zone 2, the difference between superior and inferior epithelial thickness in peripheral zone 3, age, gender, use of glaucoma drops for at least 3 months, and the presence of blepharitis yielded a multivariate model that had a sensitivity of 86% and a specificity of 91% for diagnosing dry eye disease, even without an ophthalmological examination. OCT epithelial thickness parameters contributed the most predictive value to the model.
Limitations
Epithelial mapping includes the tear film, which may affect the measured epithelial thickness, but the investigators found no significant difference between maps taken immediately after blinking and 10 seconds after blinking. Tear film osmolarity and objective meibomian dysfunction were not included in the diagnostic model. This study did not evaluate changes to epithelial parameters with dry-eye–disease treatment (but the authors suggest that epithelial thickness improves with treatment). The sample size was limited, and the patient population was from a university hospital.
Clinical significance
It may be possible to accurately screen for dry eye disease in the community using a diagnostic scale that integrates non-invasive corneal epithelial mapping with Fourier-domain OCT, age, gender, use of glaucoma drops, and blepharitis. Severity of dry eye disease may also be quantifiable with epithelial mapping.
Financial Disclosures: Dr. Christopher Sales discloses a financial relationship with Network Medical Review (Patents/Royalty).