Variations in central corneal thickness during the first year of contact lens wear

Variations in central corneal thickness during the first year of hard, hydrophilic or silicone lens wear are reported. The mean corneal swelling after 1/2,3 and 6 months was 4.7-3.0% in the first 2 groups (P less than 0.001 - P = 0.005), but only 1.3-0.8% in the latter group (P = 0.011 - 0.050). These differences were statistically significant (P less than 0.001 - P = 0.046) and are ascribed to a higher oxygen tension under the silicone lenses. An over-all reduction of corneal oedema was noted after 1/2 month (P = 0.025). One year after lens fitting a similar and not significant corneal swelling was found in the 3 lens groups. In addition to an initial 'osmotic' adaptation our results indicate that a further corneal adaptation to hard and hydrophilic lenses may take place between 6 and 12 months after lens fitting. Development of lens intolerance was not correlated to the degree of corneal oedema after 1/2 month of lens wear.