Hydrogel contact lens binding induced by contact lens rewetting drops

To investigate alterations in prelens tear film (PLTF), contact lens (CL), and postlens tear film (PoLTF) thicknesses and contact lens movement associated with boric acid-containing rewetting drops.

This was a single-center, randomized, double-masked clinical trial. Following etafilcon A lens application, baseline lens movement and interferometric measures (PLTF, CL, PoLTF thicknesses) were captured. A randomly assigned drop (either a low or high boric acid-containing drops) was applied to both eyes, followed immediately by lens movement and interferometric measures. After a 2-h washout period (spectacle wear), subjects returned for testing with the alternative drop. Statistical analyses addressed pre- to postdrop changes in lens movement and PLTF, CL, and PoLTF thickness.

The presence of a drop alone lead to substantial decreases in contact lens movement (general reduction of 0.45 mm), but the reduction was not related to drop type. The presence of a drop led to an increase in PLTF thickness (approximately 0.14 microm), again regardless of the drop type. Both the general presence of a rewetting drop and drop type lead to an increase in CL center thickness (lower boric acid drop = 0.31 microm and higher boric acid drop = 1.13 microm). Both the general presence of a rewetting drop and the drop type lead to a significant decrease in PoLTF thickness, whereby the lower boric acid drop lead to a decrease of 0.28 mum and the higher boric acid drop lead to a decrease of 0.73 microm.

Boric acid-containing rewetting drops were shown to be associated with a significant reduction in lens movement with a concurrent increase in lens center thickness and reduction in PoLTF thickness. The higher boric acid-containing drop was associated with more substantial increases in lens center thickness and decreases in PoLTF thickness.