The Impact of Dry Eye Disease before and after cataract surgery

Abstract

The outcomes of modern cataract surgery are generally very good. About 80% of patients achieve the intended refractive precision within 0.5 diopters. Only a few patients experience refractive errors of more than 0.75 or 1.0 diopters, which may be a considerable source of dissatisfaction for these patients. Especially when patients choose advanced IOLs to amend refractive errors. Dry eye disease (DED) is one factor that can result in an undesired refractive outcome when using a reflection-based keratometry. Additionally, cataract surgery can contribute to or worsen dry eye conditions post-surgery. The main aim of this thesis was to investigate whether dry eyes could affect the outcome of cataract surgery. Our first and second studies aimed to determine whether the variability of keratometry was affected by dry eyes and if dry eye treatment could improve this variability and, consequently, improve refractive precision. The results showed that subjects with either instability (reduced break-up time) or hyperosmolarity of the tear film had a statistically significantly higher mean variability of keratometry or proportions of outliers (difference > 0.25 D) when measured with reflection-based keratometry. There was no statistically significant difference in the variability of keratometry for patients with the combined signs of DED from baseline to the time of cataract surgery. There were no statistically significant differences in refractive predictability for dry eye subjects (treated with artificial tears or untreated) versus non-dry eye subjects. The aim of our third study was to explore differences in osmolarity between the two eyes as a diagnostic criterion for dry eye disease (DEWS II recommendations). Chi-square analyses were performed to compare this criterion to other criteria for DED. The results revealed that the inter-eye difference did not correlate with any other dry eye tests, suggesting that an intereye difference of 8 mOsmol/L is not a useful cut-off for diagnosing dry eyes. In the fourth and the last of our studies, we aimed to evaluate the effects of preservative-free NSAIDs, corticosteroids, and trehalose/hyaluronic acid eye drops versus NSAIDS and corticosteroids with preservative benzalkonium chloride for patients with dry eyes and nondry eyes after cataract surgery. We discovered that subjects with dry eyes before surgery (signs and symptoms) improved six weeks after cataract surgery. The effect of the steroids could explain this improvement. In contrast, subjects without dry eyes became worse. We concluded that preservative-free eye drops and artificial tears had no beneficial effects. Our research in the first study found that the signs of hyperosmolarity and instability of the tear film associated with DED can affect reflection-based keratometry, potentially affecting refractive precision. However, the combined criteria of DED appear to be insufficient to assess if patients are at risk for uncertain keratometry measurements. Our results showed that lubrication and preservative-free eye drops are insufficient to improve refractive predictability. Further research on different DED treatments is required. However, we suggest that patients with reduced break-up time should have repeated biometric measurements and that IOL calculations can be based on averaged keratometry. An inter-eye difference in osmolarity of more than 8 mOsmol/L seems unsuitable for diagnosing DED and requires re-evaluation (third study). Finally, our fourth study found no positive effects of preservative-free eye drops and twoweek treatment with lubricants in a cohort of patients scheduled for cataract surgery.