The Effects of Cheap Tinted Contact Lenses on Corneal Swelling and Ocular Surface Inflammation

Purpose: To evaluate the effects of cheap tinted contact lenses on corneal swelling and ocular surface inflammation, compared to hydrogel and silicone hydrogel contact lenses. Methods: Forty eyes of 20 New Zealand white rabbits were randomly assigned to 4 groups. Two types of tinted contact lenses, hydrogel lenses, and silicone hydrogel lenses were each applied to 10 rabbit eyes. Corneal thickness and tear lactate dehydrogenase (LDH) activity were measured at 1 and 4 days after contact lens wear, and the inflammation of ocular surface was scored at 4 days after contact lens wear. The internal surface of the cheap tinted lens was examined with a scanning electron microscope to compare the surface quality between the tinted and non-tinted area. Results: Although the corneal swelling of the silicone hydrogel lens group was significantly lower than the other 3 lens groups after contact lens wear (p0.1). Tear LDH activity at 1 and 4 days after contact lens wear showed no significant difference among the 4 groups (p>0.29). The scores of ocular surface inflammation in the 2 tinted contact lens groups were greater than the hydrogel and silicone hydrogel lens groups (p=0.03). The scanning electron microscope revealed the internal surface of the tinted area in the tinted contact lens was coarse and irregular though the surface of the non-tinted area was relatively smooth. Conclusions: Regarding corneal swelling and tear LDH activity, the cheap tinted contact lenses used in Korea were not significantly different from the common hydrogel contact lenses. However, tinted contact lenses showed a greater tendency to provoke ocular surface inflammation than other lenses. The coarse and irregular surface of the tinted area in the tinted contact lens appears to play a role in provoking severe ocular surface inflammation.