EQUIVALENCE OF LIPID LAYER PATTERNS OBTAINED FROM TWO DIFFERENT INTERFEROMETERS AND GRADED WITH TWO SCALES

Purpose : Observation of lipid layer characteristics by interferometric methods is well established, however, it is not clear if different instruments and grading scales are equivalent. This study evaluated the lipid layer patterns obtained by the Keratograph 5M (Oculus) and the DR1a interferometer (Kowa) and compared the Guillon and Yokoi grading scales. Methods : Thirty young adults (22.4 ± 2.5 years; 15 females) completed the Dry Eye Questionnaire (DEQ-5). Tear meniscus height (TMH) and non-invasive break up time (NIKBUT) were assessed (Keratograph 5M). Lipid layer interference patterns measured with the Keratograph 5M and DR1a interferometer (LLP-K5 and LLP-DR1a-g) were subjectively rated using the Guillon scheme. Moreover, as Kowa recommends the Yokoi scheme, this was also used to grade DR1a images (LLP-DR1a-y). Results : Participants with a mean DEQ-5 of 6.60 ± 3.32 presented a TMH of 0.24 ± 0.07 mm and a NIKBUT of 8.53 ± 4.19 s. LLP-K5, LLP-DR1a-guillon and LLP-DR1a-yokoi were 3.50 ± 1.40, 3.55 ± 1.39 and 2.45 ± 1.05, respectively. Lipid layer interference patterns between instruments as evaluated with the Guillon scheme were strongly correlated (ρ=+0.596, p=0.006). Yokoi and Guillon grades of DR1a lipid layer patterns were related (ρ=+0.788, p<0.001). However, only the LLP-DR1a-y showed an association with NIKBUT (ρ=+0.471, p=0.036). No other correlations between LLP and other tear film parameters were found. Conclusions : Tear lipid patterns between interferometers appear similar and grading with either the Guillon or Yokoi seems equivalent.