Refractive changes caused by hypoxia after laser in situ keratomileusis surgery.

OBJECTIVE

To determine whether hypoxia induces refractive changes in subjects who have had laser in situ keratomileusis (LASIK) refractive surgery.

METHODS

Prospective paired eye clinical trial.

METHODS

There were 20 LASIK subjects (40 eyes) and 20 myopic non-LASIK controls (40 eyes).

METHODS

Each subject had one eye exposed to ocular surface hypoxia (humidified nitrogen) by use of an airtight goggle system at sea level for 2 hours. The other eye was simultaneously exposed to humidified, compressed air (21% oxygen) with the same airtight goggle system.

METHODS

Keratometry, cycloplegic refraction, and pachymetry were compared before and after exposure by use of repeated measures analysis of variance.

RESULTS

A significant myopic shift (P: < 0.01) occurred in LASIK corneas exposed to hypoxia compared with myopic control subjects. A significant increase in corneal thickening occurred symmetrically in both LASIK and control subjects exposed to hypoxia. There was a trend toward corneal steepening (keratometry) in LASIK subjects, but this was not statistically significant.

CONCLUSIONS

These results suggest that ocular surface hypoxia induces a myopic shift in LASIK subjects.