Comparison of keratometry data using handheld and table-mounted instruments in healthy adults

To compare keratometry data between the handheld Retinomax K-plus 3 and the table-mounted IOLMaster 700.

Healthy adult volunteers were prospectively recruited to the study. All participants underwent 3 consecutive keratometry measurements using the Retinomax K-plus 3 and a single biometry assessment using the IOLMaster 700. Differences between the Retinomax K-plus 3 and the IOLMaster 700 were assessed using Wilcoxon test for paired samples, Spearman correlation, Bland-Altman and mountain plots.

Twenty-eight healthy subjects with a median age of 37 years (interquartile range (IQR) 28-44 years) were included in the study. The median mean keratometry (mean K) reading was higher using the Retinomax K-plus 3 (44.04D; IQR 42.96-45.61D) compared to the IOLMaster 700 (43.78D; IQR 43.22-44.90D, p < 0.01), with a mean difference of 0.18D (95% confidence interval (CI) 0.11-0.23D). Mean K readings were highly correlated between the 2 devices (r = 0.995, p < 0.01). Bland-Altman plots showed 95% limits of agreement between -0.14D and 0.49D. Frequency histogram of mean K reading differences between the Retinomax K-plus 3 and the IOLMaster 700 showed that 56% of cases were between ± 0.2D, 93% of cases were between ± 0.4D and all cases were between ± 0.5D. Mean corneal astigmatism measurement was higher using the Retinomax K-plus 3 (1.01 ± 0.40D) compared to the IOLMaster 700 (0.77 ± 0.36D), with a mean difference of 0.23 ± 0.37D (p < 0.01) between the devices.

A good agreement exists between the Retinomax K-plus 3 and the IOLMaster 700 regarding keratometry readings. This enables cataract surgeons to safely use the Retinomax K-plus 3 device when indicated.