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The etiology of refractive changes at high altitude after radial keratotomy. Hypoxia versus hypobaria
R K Winkle1, T H Mader, V C Parmley
1Ophthalmology Service, Madigan Army Medical Center, Tacoma, Washington 98431-5000, USA.
Objective:
Refractive changes at high altitude that occur after radial keratotomy (RK) may be caused by hypoxia or hypobaria.
Design:
A prospective study was performed to evaluate the effects of hypoxia on RK and non-RK corneas.
Participants:
There were 20 RK and 20 control eyes.
Intervention:
These eyes were subjected to ocular surface hypoxia using an air-tight goggle system at sea level for 2 hours.
Main Outcome Measures:
Keratometry, cycloplegic refraction, and pachymetry were evaluated using repeated measures analysis of variance.
Results:
A significant hyperopic shift (P < 0.0001) and corneal flattening (P < 0.0013) occurred in all subjects with RK compared with those of control subjects. Corneal thickening occurred symmetrically in both groups.
Conclusions:
These results suggest that refractive changes in subjects with RK occur at high altitude as a direct result of corneal hypoxia.
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