Intraocular lens power requirements for humanitarian missions
Received 12 March 2009; received in revised form 30 April 2009; accepted 5 May 2009.
Purpose
To develop a generalized method to determine an optimum set of intraocular lens (IOL) powers for humanitarian missions.
Setting
Humanitarian missions to Central America, South America, and Southeast Asia.
Methods
Biometric data of adults who had cataract surgery on 2 humanitarian missions were reviewed, and the ideal emmetropic IOL power for each eye was calculated. Using statistical modeling, the number of extra IOLs required at each power to account for natural variation inherent in random population samples was calculated. To limit the total number of IOLs and maximize availability of suitable IOLs for each patient, a tolerance strategy for choosing IOL powers was developed and the ideal proportion of extra IOLs required at each power was empirically determined.
Results
Data of 103 patients were reviewed. The mean IOL power was 20.38 diopters (D) ± 2.32 (SD). Applying a tolerance strategy to accept IOLs with powers 0.5 D below or 1.0 D above the emmetropic IOL power, the number of extra IOLs required at each power was decreased to a fraction of the fourth root of the number of eyes anticipated to require that IOL power. The model predicted that with this strategy, fewer than 2% of all patients would be rejected due to lack of an IOL with a suitable power.
Conclusions
The spreadsheet-based IOL power prediction model calculated an ideal distribution of IOLs to order for humanitarian cataract surgery. It is generalizable to missions of any size and should help planners minimize costs while ensuring excellent refractive outcomes.
From the Ophthalmology Departments, Naval Medical Center San Diego (Lombard, McClatchey), San Diego, California, and Naval Hospital Newport (Borges), Newport, Rhode Island; Loma Linda University Medical Center (McClatchey), Loma Linda, California; Uniformed Services University of Health Sciences (McClatchey), Bethesda, Maryland, USA
Corresponding author: Peter N. Lombard, MD, 34800 Bob Wilson Drive, Suite 202, San Diego, California 92134, USA.
No author has a financial or proprietary interest in any material or method mentioned.
Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2009.
Prepared as part of Dr. Lombard's official duties. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the U.S. Government.
Electronic copies of the spreadsheet used in the study are available from the corresponding author.
ABSTRACT