Document Detail

The effect of altitude on radial keratotomy.
MedLine Citation:
PMID:  9587844     Owner:  NLM     Status:  MEDLINE    
The authors analyzed refractive results of patients who underwent radial keratotomy (RK) at sea level and high altitude and evaluated the effects of the altitude. A total of 102 eyes undergoing RK procedures performed in two clinical centers having different altitude were analyzed. The results compared between subjects who had undergone RK at sea level (Istanbul/Turkey) and at an altitude of 5750 feet (Van/Turkey) were compared. Subjects were 19-42 years old with myopia from -4.00 to -12.00 diopters (D). The average preoperative spherical equivalent cycloplegic refractions (SECR) were -8.01 +/- 1.86 D and -6.99 +/- 2.15 D in the Istanbul and Van groups, respectively. These were divided into subgroups according to myopia degree and number of incisions and optic zone size. The RK procedures were performed by the same surgeon with diamond blade in standard Russian style. The average changes in SECR were 5.09 +/- 1.29 D and 6.50 +/- 2.24 D in subjects who had undergone RK at sea level and at 5750 feet, respectively. There was a significant difference between the subgroups (P < 0.0002). This difference was especially higher in the high myopia subgroups. Additionally, we obtained a partial relation between increase of RK incision number and SECR change at high altitude but not at sea level. No notable regression and progression were seen in the 3 months of follow-up at high altitude. These results support hypotheses suggesting both corneal hypoxic expansion in the area of RK incisions, which may lead to central corneal flattening, and barometric pressure directly altering corneal shape, which is responsible for the hyperopic shift induced by altitude. Ophthalmologists performing RK surgery at high altitude had better consider redesigning their RK nomograms in light of these findings. However, when the nomogram used at sea level was used at high altitude, the subjects became hyperopic.
S Simşek; A Demirok; A Cinal; T Yaşar; O F Yilmaz
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Publication Detail:
Type:  Clinical Trial; Comparative Study; Journal Article; Multicenter Study    
Journal Detail:
Title:  Japanese journal of ophthalmology     Volume:  42     ISSN:  0021-5155     ISO Abbreviation:  Jpn. J. Ophthalmol.     Publication Date:    1998 Mar-Apr
Date Detail:
Created Date:  1998-07-13     Completed Date:  1998-07-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0044652     Medline TA:  Jpn J Ophthalmol     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  119-23     Citation Subset:  IM    
Department of Ophthalmology, Yüzüncü Yil University, Medical Faculty, Van, Turkey.
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MeSH Terms
Cornea / physiopathology,  surgery*
Follow-Up Studies
Keratotomy, Radial*
Myopia / physiopathology,  surgery*
Postoperative Period
Refraction, Ocular

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