Relationship between corneal edema and topography.

We found that corneal edema can occur without significant concomitant changes in central and peripheral corneal topography. We examined the relationship between corneal edema and corneal topography in 10 subjects with normal ocular examinations. Baseline pachymetry and topographic measurements for both eyes of each patient were obtained. The right eye of each subject was exposed to an anoxic environment for 2 hours using a nitrogen chamber goggle. The left eye served as control. Optical pachymetry and computerized corneal topographic measurements were taken for both eyes immediately after removal of the nitrogen chamber goggle. All corneas exposed to the nitrogen chamber were thickened in all areas after removal of goggles. Average percent thickening per area was: 16.4% centrally, 6.3% nasally, 6.0% temporally, 6.3% superiorly, and 9.2% inferiorly. Corneas exposed to the nitrogen chamber demonstrated no significant topographic changes, except in the nasal area where the corneal power lessened. Furthermore, there was no significant correlation between corneal thickening in any area measured and changes in corneal topography. Control corneas did not thicken or demonstrate significant topographic changes.