Case report: Tear film and wettability of daily disposable contact lenses

Contact lens wettability is an important issue for patients and practitioners has an impact on comfort and visual performance.

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Abstract

Objectives: Contact lens wettability is an important issue for patients and practitioners as it has an impact on comfort and visual performance. In vivo wettability can be assessed by various means and evaluating the use of the point spread function (PSF) as a surrogate for lens wettability presents one option that may have advantages over other methods of assessment. One of the functions of the HD Analyser instrument is to record PSFs over 20 seconds to derive the objective scatter index (OSI). The aim of this paper is to explore the feasibility of using this instrument to evaluate in vivo contact lens wettability.

Methods: The OSI was measured in one subject wearing six different daily disposable contact lens materials in one eye on different days. Measurements were performed 5 minutes after application of the contact lens and again 3 hours later. For the purpose of comparison, the OSI data were fitted with trend lines.

Results: The slopes and intercepts of the trend lines vary considerably between contact lens materials and between the measurement after insertion and 3 hours later, suggesting this instrument is capable of detecting differences in wettability with hydrogel and silicone hydrogel contact lens materials. Whereas a low slope indicates only minimal tear film evaporation over the 20-second recording period, a steep slope describes more rapid tear film evaporation.

Conclusions: The data suggest that the OSI as derived from the HD Analyser instrument is capable of detecting differences in wettability with different contact lens materials. The HD Analyser might be a helpful tool supporting practitioners in selecting the most appropriate contact lens material for a patient. 

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