Effect of incubation in selected ophthalmic fluids on contact lenses

In a recent study published in the journal Materials, Polish researchers have analyzed the incubation effect of certain ophthalmic fluids on contact lenses.

To study: Influence of selected ophthalmic fluids on the wettability and hydration of hydrogel and silicone hydrogel contact lenses – in vitro study. Image Credit: Tatiana Kochkina/Shutterstock.com

Contact lenses and wearer discomfort

The majority of contact lens wearers complain of discomfort caused by dry eyes, which can be caused by factors such as protein adsorption or friction when blinking. Additionally, about half of contact lens wearers experience dry eye symptoms and 25% of eye patients stop wearing contact lenses due to dry eye complications. The need to improve the comfort of contact lenses is currently leading to the development of new optical materials used in the manufacture of lenses.

Different cases of liquid contact angle on surfaces specifying wettability: (a) high wettability, (b) medium wettability and (c) low wettability.

Different cases of liquid contact angle on surfaces specifying wettability: (a) high wettability, (b) average wettability, and (vs) low wettability. Image credit: Chwalik-Pilszyk, G et al., Materials

The aim of the current research was to see how contact lens solution (CLS) and hyaluronan eye drops affect the dehydration process and the surface properties of hydrogel and hyaluronan contact lenses. commercially available silicone hydrogel.

The dehydration process was calculated using the gravimetric method, and the dehydration rate and equilibrium water content (EWC) were also determined. Additionally, the surface free energy (SFE) was calculated by contact angle measurements, which determined the surface character of the materials.

Methodology

The researchers in the present study examined four commercial contact lens materials: hydrogel (Etafilcon A and Omafilcon A) as well as silicone hydrogel (Narafilcon A and Senofilcon A). All of the lenses used by the researchers had a back vertex power of 2.50 D to avoid the effect of variations in contact lens cross-section on dehydration studies. The researchers prepared all contact lens samples using the same protocol for optimal experimental conditions.

The researchers used tweezers to remove the contact lens from the storage solution, touching only the sides of the lens and being careful not to contaminate the material. After that, the samples were rinsed in saline solution and tested immediately or placed in the incubated contact lens solution to avoid degradation. After removing the contact lenses from the incubation solution, they were placed in a convex plastic holder. To replicate the eye conditions, the curvature of the contact lens was kept similar to the eye radius.

Wettability was determined using contact angle (CA) tests and SFE values ​​were also calculated. The measurements were made using an optical goniometer and software added with the sessile drop method.

Distribution of equilibrium water content values ​​as a function of time for Omafilcon A.

Distribution of equilibrium water content values ​​as a function of time for Omafilcon A. Image credit: Chwalik-Pilszyk, G et al., Materials

Results

Contact lenses incubated in eye drops (ED) showed the most significant changes in the dehydration profile. The most notable changes in CA properties were observed for contact lenses incubated in the ER, where sedimentation of water drops was impossible after incubation.

SFE analysis demonstrated higher values ​​for hydrogel contact lenses. Based on the Owens-Wendt method, the SFE ranged from 54.45 ± 6.56 to 58.09 ± 4.86 mJ/m2 for hydrogel contact lenses and 32.86 ±3.47 to 35.33± 6.56 mJ/m2 for silicone hydrogel contact lenses.

Additionally, incubation in all hydrogel contact lenses in the ER showed a reduction in SFE values, but the differences were statistically insignificant.

The Owens-Wendt, Wu, Neumann and Neumann-Kwok methods were used for SFE calculations by the researchers. The SFE values ​​calculated using all of these methods were similar; however, the values ​​obtained with the Wu method were higher than those calculated with the other models. In addition, the researchers also used Student’s t-test for two-group cases and one-way analysis of variance (ANOVA) to test hypotheses.

Water contact angle measurement for Narafilcon A.

Water contact angle measurement for Narafilcon A. Image credit: Chwalik-Pilszyk, G et al., Materials

conclusion

The results of the present study demonstrated how different ophthalmic fluids affect the dehydration, wettability, and surface properties of contact lenses. Additionally, differences in the molecular structure of the various materials studied by the researchers may explain the differences in contact lens dehydration profiles. A major limitation of the study is that the research examined the effects of a single contact lens solution and a single type of eye drop on lens properties.

Researchers combined SFE studies with dehydration studies to give the contact lens material a broad characterization. Additionally, SFE calculations were also useful as they could estimate the possibility of bacterial adhesion on contact lens surfaces.

Maintaining the wettability of contact lenses over a longer period of time is clinically essential to maintain ocular health and wearer comfort. Additionally, in vivo studies are needed to better understand the clinical impact of ophthalmic fluids on contact lens surface properties, wettability, and dehydration.

Future research should focus on examining SFE considering factors such as bacterial adhesion, oxygen permeability, and dehydration under different airflow and humidity conditions.

Source

Chwalik-Pilszyk, G.; Wis’niewska, A. Influence of selected ophthalmic fluids on the wettability and hydration of hydrogel and silicone hydrogel contact lenses – an in vitro study. Materials 2022, 15930. https://www.mdpi.com/1996-1944/15/3/930

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