Document Detail

Errors of residual stromal thickness estimation in LASIK.
MedLine Citation:
PMID:  18435333     Owner:  NLM     Status:  MEDLINE    
BACKGROUND AND OBJECTIVE: To investigate inaccuracy and variability in residual stromal thickness estimation in LASIK by pachymetry and measurements of corneal thickness, flap thickness, and ablation depth. PATIENTS AND METHODS: In 73 eyes of 37 patients, preoperative and postoperative corneal thicknesses were obtained with slit-scanning elevation topography and the ultrasound pachymeter. LASIK was performed and corneal flaps were created with a microkeratome. Flap thickness and ablation depth (expected and achieved) were calculated. Residual stromal thickness estimation error was analyzed. RESULTS: The mean preoperative corneal thicknesses were 559.58 +/- 23.47 and 554.92 +/- 29.95 microm for the ultrasound pachymeter and slit-scanning elevation topography, respectively. Measurement differences ranged from -36 to 30 microm. With the pachymeter, calculated mean flap thickness was 139.58 +/- 17.59 microm. With this device, predicted ablation depth differed from achieved depth by 20% or more in approximately one-third (30.14%) of treated patients; ablation differences ranged from 10.0% to 19.99% in 37% of patients and 1.00% to 9.99% in 31.5% of patients. CONCLUSION: Imprecision of microkeratome cuts, preoperative corneal pachymetry, and laser ablation depth have a significant impact on the inaccuracy of residual stromal thickness prediction. Especially in patients with borderline corneal thickness, intraoperative pachymetry measurements and a residual stromal thickness higher than the safety margin of 250 microm are recommended to minimize iatrogenic ectasia.
Huey-Chuan Cheng; Yen-Tung Chen; Shu-I Yeh; Chi-Wang Yau
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Ophthalmic surgery, lasers & imaging : the official journal of the International Society for Imaging in the Eye     Volume:  39     ISSN:  1542-8877     ISO Abbreviation:  Ophthalmic Surg Lasers Imaging     Publication Date:    2008 Mar-Apr
Date Detail:
Created Date:  2008-04-25     Completed Date:  2008-04-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101155780     Medline TA:  Ophthalmic Surg Lasers Imaging     Country:  United States    
Other Details:
Languages:  eng     Pagination:  107-13     Citation Subset:  IM    
Department of Ophthalmology, Mackay Memorial Hospital, Taipei, Taiwan.
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MeSH Terms
Body Weights and Measures
Corneal Stroma / pathology*,  ultrasonography
Keratomileusis, Laser In Situ / methods*
Microscopy, Acoustic
Middle Aged
Myopia / surgery*
Prospective Studies
Reproducibility of Results
Surgical Flaps / pathology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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