Use of Corneal Topography to Assess Tear Film and Meibography in Ocular Surface Disease
To use the novel OCULUS K5M Keratograph to acquire images for the assessment of tear meniscus height, tear break up time, and meibography. To compare the reliability and validity of these measurements in healthy eyes and those affected by ocular surface disease.
Three-hundred forty two eyes were imaged by the OCULUS K5M keratograph including 90 normal control eyes and 252 eyes affected by dry eye syndrome and/or meibomian gland disease. Automated features of the device were tested on all eyes: Tear Meniscus Height (TMH) and Non Invasive Keratograph Break-Up Time (NIKBUT). For comparison, fluorescein staining of the tear film with cobalt blue light was used to assess standard TMH and TBUT with traditional methods. Meibography evaluation using two unique manual methods for quantification of the distribution of meibomian glands as well as glandular dropout area are described.
Standard fluorescein TMH and TBUT values were lower in OSD eyes as compared to controls (0.2 vs. 0.4 mm, p < 0.001 and 6.1 vs. 9.4 seconds, p < 0.001 respectively) and correlated negatively with OSDI scores (r = -0.79, p < 0.001). There is no correlation between TMH and TBUT measurements generated by automated versus standard methodology (r = 0.08, p < 0.01); automated values do no correlate with OSDI values (r = 0.08, p < 0.05, and r = -0.02, p < 0.001 respectively). Meibomian gland distribution and dropout area quantify different but complimentary characteristics of meibography (intra-class correlation coefficient = 0.99). Both manual methods of meibography quantification showed high intra-grader and inter-graders reproducibility.
The Oculus K5M keratography is able to provide quantification of TMH, NIKBUT, and meibomian gland density, without the use of fluorescein, cobalt blue light or external image software. However, machine generated TMH and NIKBUT values feature high discrepancies from measurements derived by traditional methods. The instrument generates infrared images of the tarsal conjunctiva that are useful for quantification of meibomian gland characteristics.