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Estimating pediatric IOL power from aphakic refraction as accurate as calculation with biometry
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Estimating IOL power for aphakic children using refraction alone with an arbitrary keratometry value may be as accurate as calculations based on biometry, according to a study.
Arif O. Khan, MD, and Abdulrahman AlGaeed, BSc, COT, of King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia, compared the two IOL power calculation methods in a retrospective study of 50 eyes in 30 children. The mean age of the patients was 7.9 years. An Alcon MA60BM IOL was implanted in the ciliary sulcus in all cases.
IOL powers were determined with the Holladay formula using two methods. Using an assumed keratometry value of 44 D and an axial length estimated from the aphakic refraction, the researchers estimated a mean IOL power of 25.81 D. This was similar to the mean IOL power of 26.35 D calculated using actual biometry measurements (P = .11), according to the study authors.
The actual pseudophakic refractions achieved after IOL placement in the sulcus differed significantly from the refractions predicted by each calculation method (P < .001). But the values predicted by the estimation method seemed closer to the actual pseudophakic refractions (average difference of 1.48 D), than the values predicted by the calculation methods (average difference of 1.8 D), the authors said.
"Both techniques are prone to measurement error in eyes of children with aphakia, largely because of inaccuracies in axial length determination," the authors said. However, the estimation method can be useful, particularly if biometry is not available, they said.
The study is published in the December issue of the British Journal of Ophthalmology.