Purpose: It is hypothesized that an unstable tear film would affect the quality and repeatability of optical coherence tomography angiography (OCTA). Therefore, OCTA repeatability according to tear break-up time (TBUT) was compared.
Methods: The 3 × 3 OCTA was performed twice and, the eyes were divided into 3 groups according to the TBUT (Group 1: TBUT ≤ 5 seconds, 43 eyes; Group 2: 5 seconds < TBUT ≤ 10 seconds, 35 eyes; Group 3: TBUT > 10 seconds, 34 eyes). The intraclass correlation coefficient, coefficient of variation, and test-retest SD were calculated and compared.
Results: The signal strengths of OCTA were 9.1 ± 1.2, 9.5 ± 0.8, and 9.5 ± 0.8 in each group from Groups 1, 2, and 3, respectively, which showed significant difference (P = 0.049). The intraclass correlation coefficient of vessel density were 0.733, 0.840, and 0.974 in Groups 1 to 3, respectively, and the values increased in the order of Groups 1, 2, and 3. The coefficient of variation were 6.41 ± 6.09, 3.29 ± 2.22, and 1.30 ± 1.17, and the test-retest SD were 0.83 ± 0.70, 0.47 ± 0.31, and 0.19 ± 0.17 in Groups 1, 2, and 3, respectively. The coefficient of variation and test-retest SD values decreased in the order of Groups 1, 2, and 3, and showed a significant difference (all, P < 0.05).
Conclusion: The repeatability of OCTA tended to decrease with a shorter TBUT. When the TBUT is <5 seconds, care must be taken to interpret the OCTA results correctly.