Independent Validation and Verification of Keratograph for Measuring Tear Meniscus Height in Ocular Surface Disease Patients
Purpose
To determine the validity and reliability of the tear meniscus height (TMH) measurements obtained by the novel OCULUS Keratograph 5M.
Methods
Sixty-five participants (24 male, 41 female; 111 eyes) were recruited prospectively over 9 months and classified into two groups. Group-A consisted of 81 eyes clinically diagnosed with ocular surface disease of patients aged 64.1 ± 13.6 years. Group-B included 30 normal control eyes of subjects aged 34.8 ± 10.5 years. Automated TMH values generated by the OCULUS Keratograph 5M (Wetzlar, Germany) at 3 points along the lid margin (central, nasal, and temporal). For comparison, fluorescein was used to stain the tear lake and TMH was manually graded based on images captured using the integrated cobalt blue light within the OCULUS. Measurements of central and average TMH (mean of three points) were compared for validity against fluorescein TMH readings. Data were analyzed using MedCalc 19.0 (Ostend, Belgium).
Results
Standard fluorescein TMH readings confirmed lower TMH values in ocular surface diseased eyes as compared to controls (0.24 mm versus 0.4 mm, r = 0.2, p < 0.001). However, mean readings for automated central TMH and average TMH for group-A were found to be significantly higher than group-B (0.39 and 0.43 mm versus 0.27 and 0.32 mm respectively, r = 0.1, p < 0.001). No correlation was found between TMH measurements obtained by the automated mode of the OCULUS Keratograph 5M and TMH obtained manually by fluorescein staining in all eyes from both groups examined (r = 0.08, P < 0.001).
Conclusion
The OCULUS Keratograph 5M is able to provide automated TMH values without the use of fluorescein and cobalt blue light. However, the automated TMH values are higher in eyes with ocular surface disease than in normal control eyes. Measurements are not interchangeable with standard fluorescein TMH measurements, and it may not be a valid and reliable diagnostic tool for ocular surface disease.