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Refractive changes at extreme altitude after radial keratotomy
1Ophthalmology Service, Madigan Army Medical Center, Tacoma, Washington 98431, USA.
American Journal of Ophthalmology
|June 1, 1995
Summary
High altitude exposure caused significant hyperopic shifts in corneas after radial keratotomy. This suggests the cornea adjusts to changing oxygen levels, impacting refractive error.
Area of Science:
- Ophthalmology
- Corneal Surgery
- High-Altitude Physiology
Background:
- Radial keratotomy (RK) is a refractive surgical procedure to correct myopia.
- Corneal physiology can be affected by environmental factors, including oxygen levels.
Purpose of the Study:
- To investigate the impact of high altitude on corneas previously treated with radial keratotomy.
- To compare refractive and keratometric changes in RK corneas versus normal corneas at varying altitudes.
Main Methods:
- Four RK corneas and four normal corneas were studied.
- Measurements included visual acuity, cycloplegic refraction, keratometry, and intraocular pressure.
- Corneas were exposed to sea level, 12,000 ft, and 17,000 ft for 24 hours.
Main Results:
- RK corneas showed a significant hyperopic shift in spherical equivalence at altitude compared to controls (P < .0001).
- Average spherical equivalent change was +1.03 D at 12,000 ft and +1.94 D at 17,000 ft.
- Keratometry values significantly decreased at altitude in RK corneas (P < .0001), with average changes of -0.59 D and -1.75 D at 12,000 ft and 17,000 ft, respectively.
Conclusions:
- Hypoxic corneal expansion at RK incision sites may cause central flattening and a hyperopic shift.
- RK corneas demonstrate adaptive changes to environmental oxygen concentrations over 24 hours.
- Further research is needed to confirm the exact cause of high-altitude hyperopic shift.