Changes in Ultraviolet Transmittance of Hydrogel and Silicone-Hydrogel Contact Lenses Induced by Wear

Development of corneal contact lens materials and current clinical application of contact lenses: A review

Unlike conventional glasses, corneal contact lenses (CLs) can directly contact the surface of the tear film through the application of biopolymer materials, to achieve therapeutic and cosmetic purposes. Since the advent of polymethylmethacrylate, a material that has gained widespread use and attention, statistically, there are now more than 150 × 106 people around the world who wear corneal contact lenses. However, the associated complications caused by the interaction of contact lenses with the ocular surface, tear film, endogenous and environmental microorganisms, and components of the solution affect nearly one-third of the wearer population. The application of corneal contact lenses in correcting vision and myopia control has been widely recognized. With the development of related materials, corneal contact lenses are applied to the treatment of ocular surface diseases, including corneal bandage lenses, drug-loaded corneal contact lenses, biosensors, and other new products, while minimizing the side effects associated with CL wear. This paper summarized the development history and material properties of CLs, focused on the current main clinical applications and mechanisms, as well as clarified the possible complications in wearing therapeutic contact lenses and the direction for improvement in the future.

Advanced morphological analysis of siloxane-hydrogel contact lenses

The purpose of this work is to provide a better understanding of three-dimensional (3-D) surface texture of siloxane-hydrogel contact lenses (CLs) using atomic force microscopy (AFM) and stereometric analysis. The 3-D surface texture characterization of unworn/worn siloxane-hydrogel CLs made of Filcon V (I FDA group) was performed with stereometric analysis. The atomic force microscopy (AFM) measurements of surface roughness and micromorphology of CLs were made using a Nanoscope V MultiMode (Bruker) in intermittent-contact mode, in air, on square areas of 5 × 5 μm. Stereometric study of 3-D surface texture was made according with ISO 25178-2:2012 for CL_rins (taken from the blister and rinsed with deionized water); CL_ss (preserved for 12 hr in saline solution and rinsed with deionized water); CL_worn-smooth (worn for 8 hr and presenting the smooth type morphology), and CL_worn-sharp (worn for 8 hr and presenting the sharp-type morphology). The 3-D surface texture of siloxane-hydrogel CLs was found to have specific morphological characteristics. Statistical parameters revealed local geometrical and morphological spatial structures at nanometer scale attributed to the specific interactions at the CLs surface. Before wear, the surface micromorphology of Filcon V CLs is regular with uniformly distributed microasperities and relatively small heights (Sq = 0.6 nm). After 12 hr in saline, it is found that the micromorphology changes relatively easily, but retaining the main morphological characteristics (Sq = 1.2 nm). After 8 hr of wear, there are two typical micromorphologies: smooth type, characterized by gutter structures and isolated microasperities (Sq = 2.5 nm), while the sharp type has an appearance with compactly arranged microasperities of hill type flanked by compactly arranged microregions of valley type (Sq = 2.2 nm). Surface statistical parameters allow manufacturers in developing the next generation of CLs with improved surface texture while improving biocompatibility and minimizing the impact of the material on corneal physiology. Furthermore, the micro-elastohydrodynamic lubrication due to surface texture at a nanometer scale between the back surface of the CL with the corneal surface and the front surface of the CL with the under-surface of the eyelid can be deeper and more nuanced to understand in light of modern tribological theories.

UV damage of the anterior ocular surface - microstructural evidence by in vivo confocal microscopy

PURPOSE

To evaluate and describe the microstructural changes at the ocular surface in response to habitual ocular sun exposure, correlate them with the UV protection habits and follow their dynamics using in vivo confocal microscopy(ICM).

METHODS

For a period of minimum 4 months 200 subjects (400 eyes), aged 28 ± 7.3 years, were recruited with the agreement that they will spend their summer exclusively in the region of the Black Sea coast at 43 °N latitude and will be examined before and after the summer. All subjects filled in a questionnaire about habitual UV protection and were examined clinically and by ICM.

RESULTS

Questionnaire results demonstrated that 83.5% (167 participants) of the subjects considered the sun dangerous for their eyes, but 78% (156 subjects) believed that there is danger exclusively during the summer period. Although no clinical changes were detected, microstructural analysis of the cornea demonstrated statistically significant (p = 0.021) decrease of the basal epithelial density - from 6167 ± 151 cells/mm² before to 5829 ± 168 cells/mm² after the summer period. Microstructural assessment of the conjunctiva demonstrated characteristic cystic lesions with dark centres and bright borders encountered in only 25 eyes(6%) before, and affecting 118 eyes(29.5%) after the summer. The total area of the cysts after the summer increased fivefold. Spearman analysis proved negative correlation between sun protection habits and number of cysts.

CONCLUSION

Summer sun exposure for one season leads to clinically undetectable, microstructural changes affecting the cornea, bulbar and palpebral conjunctiva with transient, but possibly cumulative nature.

Do UV-blocking Soft Contact Lenses Meet ANSI Z80.20 Criteria for UV Transmittance?

Purpose:

To compare ultraviolet (UV) ray transmission in four UV-blocking soft contact lenses with Z80.20 standards set by the American National Standards Institute (ANSI).

Methods:

Four soft contact lenses including Acuvue Oasys (Johnson & Johnson, Ireland), Acuvue 2 (Johnson & Johnson, Ireland), Zeiss CONTACT Day 30 (Zeiss, Germany), and Sauflon 55 UV (Sauflon, UK) were evaluated for UV transmission. One-way ANOVA testing was performed to compare mean values of UVA and UVB transmission for the contact lenses.

Results:

Acuvue Oasys, Acuvue 2, Zeiss CONTACT Day 30 and Sauflon 55 UV showed UV-B transmittance values of 0.24%, 1.46%, 10.37%, and 2.52%, respectively. Corresponding values for UV-A transmittance were 20.81%, 33.49%, 44.03% and 42.53%, respectively. One-way ANOVA showed a statistically significant difference among the tested contact lenses in terms of UV-B (P < 0.001) and UV-A (P < 0.001) transmission.

Conclusion:

Acuvue Oasys met the ANSI criteria for UV transmission and may thus be a good choice for eye and vision care specialists and contact lens wearers seeking UV protection.

Light transmission and ultraviolet protection of contact lenses under artificial illumination

PURPOSE

To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)).

METHODS

The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer.

RESULTS

Five of the nine soft CLs analysed state that they incorporate UV filters, but the other four do not specify anything in this regard. The spectral transmission of all the CLs studied is excellent in the visible region. The CLs with UV filters filter out this radiation more or less effectively. Xe lamps emit a part in the UV region. Incandescent, fluorescent and white LEDs do not emit at all in the UV.

CONCLUSIONS

Incorporating UV filters is important when the illumination is from a Xe lamp since this light source emits in the UV region. This, however, does not occur with incandescent and fluorescent lamps or white LEDs. The CLs that do incorporate UV filters meet all the standard requirements that the U.S. FDA (Food and Drug Administration) has for UV-blocking CLs Class II (OcularScience, CooperVision and Neolens), and AcuvueMoist and HydronActifresh400 even comply with the stricter Class I. The CLs without UV filters let UVA, UVB and even some UVC through.

The consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.