Corneal stress test for extended wear.

OBJECTIVE

The relationship between overnight contact lens wear and infectious corneal ulcers has been widely reported. Corneal hypoxia during sleep with contact lenses is believed to be an important predisposing factor for infectious corneal ulcers. We designed a provocative test to identify corneas at risk for significant oxygen deprivation during extended wear.

METHODS

We measured the baseline corneal thickness of 161 eyes (82 patients). Extended wear soft lenses were then fit and pachymetry was repeated after 1 night of extended wear. Patients were instructed to continue extended wear for 6 additional nights.

RESULTS

Seventeen of 161 eyes could not continue extended wear for the full 7 nights. All failures were due to corneal decompensation. There were no failures in the group of 133 eyes with corneal swelling of 5% or less after 1 day of extended wear. All four eyes with swelling greater than 13% failed, while the failure rates for the 24 eyes with swelling between 6-13% was about 50%. The thicker hyperopic lenses produced the majority of failures.

CONCLUSIONS

Measuring corneal swelling after 1 night of extended wear may identify those corneas at risk for significant oxygen deprivation during overnight contact lens wear. Corneal swelling of 5% or less seems to indicate that the cornea can tolerate 7 nights of extended wear (significant to P < 0.001).