THE SIGNIFICANCE OF DRY EYE SIGNS ON PREOPERATIVE KERATOMETRY MEASUREMENTS IN PATIENTS SCHEDULED FOR CATARACT SURGERY

The primary objective of this study was to assess whether the variability in anterior keratometry measurements from three different optical biometers were higher in patients with dry eyes compared to patients with non-dry eyes. The secondary objective was to investigate which separate signs of dry eyes affected the biometric measurements.

This study was conducted as part of a broader prospective interventional randomized controlled clinical trial consisting of two arms, with data collected in one private eye clinic in Haugesund, Norway. Study subjects were recruited from among patients scheduled for cataract surgery. 

After dry eye diagnostics were performed according to DEWS II (signs only) subjects were divided sign of dry eye (SDE) positive and negative groups. To investigate variability, we performed two keratometry measurements for each subject with three different optical biometers: Anterion (OCT optical biometer), Eyestar (combined OCT and reflection based optical biometer), and Lenstar (reflection based optical biometer).  

One hundred and thirty-one subjects were available for analysis. The variability of astigmatism was significantly higher for subjects with hyperosmolarity compared to normal eyes for the Lenstar, as were the percentage of eyes with variability of astigmatism greater than 0.25 D. The percentages of eyes with variability of average K greater than 0.25 D were higher for subjects with non-invasive keratography break-up time < 10 seconds (NIKBUT positive) compared to normal eyes for the Lenstar.

Utilizing the diagnostic criteria combined according to DEWS II (signs only) revealed no statistically significant differences in variability of keratometry measurements for any of the three optical devices.

However, for the separate signs of dry eyes there were statistically significantly greater variability of keratometry measurements both in eyes with hyperosmolarity or instability of the tear film with the Lenstar biometer. These findings suggests that in some dry eye subjects, keratometry measurements (and therefore refractive precision) from reflection based optical biometers like Lenstar should be used with caution when planning cataract surgery.