Short-Term Deposition of PM Particles on Contact Lens Surfaces: Effect on Oxygen Permeability and Refractive Index.

PURPOSES

To identify the deposition of fine (≤2.5 μm diameter) particulate matter (PM) particles (PM) on contact lens surfaces and to investigate the effects of such deposition on the oxygen permeability (OP) and refractive index (RI) of contact lenses.

METHODS

A total of 36 contact lenses, including rigid gas permeable (RGP) lens and soft contact lens (SCL), were investigated. RGP lens (n=12) and SCL (n=12) (experimental group) were incubated in a PM solution for 24 h, after which PM-treated RGP lens (n=6) and SCL (n=6) were further washed for 1 h in phosphate-buffered saline (PBS). All lenses were examined by field emission scanning electron microscopy. OP and RI of all lenses were measured.

RESULTS

Average-sized PM particles deposited on RGP contact lens and SCL surfaces after immersion in the PM solution were 3.192 ± 1.637 and 2.158 ± 1.187/100 μm, respectively. On RGP lens surfaces, we observed both large (≥2.5 µm diameter) and small (PM) particles. PM particles were deposited in diffuse patterns, primarily along the honeycomb structural border of SCL, while no PM particles were found in the honeycomb hole of SCL surfaces. Washing in PBS removed the larger PM particles from RGP lens surfaces, but left copious amounts of PM particles. In contrast, nearly all PM particles were removed from SCL surfaces after PBS washing. OP values of RGP lens and SCL appeared to be unchanged by PM deposition. RI values increased in both RGP lens and SCL groups after PM deposition. However, these increases were not statistically significant, suggesting that PM deposition itself does not cause fluctuations in contact lens RI.

CONCLUSIONS

Deposition of PM particles on contact lens surfaces varies according to lens material. PM particles deposited on SCL, but only large particles on RGP surfaces were able to be removed by washing in PBS and did not appear to alter OP and RI of either lens type.