Long-term effects of tear film component deposition on the surface and optical properties of two different orthokeratology lenses.

PURPOSE: To understand the effects of long-term deposition of tear film components on the surface and optical properties of orthokeratology (ortho-k) lenses, two different lenses, Brighten 22 and Optimum Extra, were tested here. METHODS: Ortho-k lenses were immersed in artificial tears and cleaned with a commercial care solution repeatedly for up to 90 days. Both the daily and accumulated lysozyme deposition amounts using an Enzyme-Linked ImmunoSorbent Assay were then analyzed. The base curve, central thickness, power, and transmission of visible light, ultraviolet A, and ultraviolet B were analyzed before and after repeated tear film component deposition procedures. The surface roughness using atomic force microscopy was observed and an energy dispersive spectrometer was used to analyze the composition of the deposits. RESULTS: The highest levels of lysozyme were adsorbed on both lens materials during the first four days of the procedure and became saturated by day 6. For both lens materials, contamination on the lenses was easily observed by day 30, and the degree of surface roughness was higher. The transmission levels of different light spectrums were reduced showing that the optical characteristics of both lenses were also affected. CONCLUSIONS: The results provide in vitro evidence that lysozyme could not be completely removed from orthokeratology lenses. Both surface and optical properties were affected by the deposition of tear film components. However, only one commercial multipurpose care solution was used to clean the lens in this study when the main ingredient was a surfactant, and the results might be different when other care regimens with other key ingredients are used. In addition, whether tear film component deposition might result in increased risks of infection or corneal abrasion will require further investigation.

The Effect of Different Cleaning Methods on Protein Deposition and Optical Characteristics of Orthokeratology Lenses.

Orthokeratology lenses are commonly used for myopia control, especially in children. Tear lipids and proteins are immediately adsorbed when the lens is put on the cornea, and protein deposition may cause discomfort or infection. Therefore, we established an in vitro protein deposition analysis by mimicking the current cleaning methods for orthokeratology lens wearers for both short-term and long-term period. The results showed that the amounts of tear proteins accumulated daily and achieved a balance after 14 days when the lens was rubbed to clean or not. Protein deposition also affected the optical characteristics of the lens regardless of cleaning methods. Our results provided an in vitro analysis for protein deposition on the lens, and they may provide a potential effective method for developing care solutions or methods that can more effectively remove tear components from orthokeratology lenses.