The Effect of Tear Film Stability on Variability of Posterior Corneal Curvature Readings with a Swept-Source Optical...

To investigate the IOLMaster 700 variability of posterior curvature readings in relation to ocular surface parameters.

Eligible cataract patients underwent two consecutive IOLMaster 700 exams and ocular surface assessments including non-invasive and fluorescein tear film break-up time (NIKBUT first and average, FBUT) during one preoperative visit. Intradevice repeatability was assessed based on within-subject standard deviation (Sw), test-retest variability (TRT), and intraclass correlation coefficient (ICC). The device composite standard deviation (SD) for biometric data, anterior corneal radii (R, R1, R2) and posterior corneal radii (PR, PR1, PR2) were analyzed in relation to ocular surface indices. Subgroup analysis evaluated the effect of FBUT on repeatability of trimmed-mean astigmatism vectors.

One hundred eyes of 67 patients were evaluated. Posterior keratometric indices had lower ICCs than anterior indices. The TRT for R and PR was 0.01 and 0.09 mm, respectively. The mean PR composite-SD was significantly higher than mean R composite-SD (34.49 vs 2.55 μm, respectively, p < 0.001, t-test). The mean R1 composite-SD was negatively correlated with FBUT (ρ = -0.35, p < 0.001). The mean PR composite-SD was not correlated with ocular surface parameters. A trend towards increasing PR composite-SD with age was observed, approaching statistical significance. Subgroup analysis showed no statistically significant differences for repeat astigmatism vectors in relation to FBUT.

The OCT-based posterior curvature readings show greater variability than the telecentric anterior keratometry. Unlike anterior corneal measurements, posterior corneal readings variability was not linked to tear film parameters.