The question of how to calculate IOL power in children has been an issue of debate among physicians for some time.
ParisThe question of how to calculate IOL power in children has been an issue of debate among physicians for some time.
Thomas Kohnen, MD, of the Johann Wolfgang-Goethe University, Frankfurt, Germany, attempted to provide some answers to this question in his presentation during a symposium on pediatric cataract surgery at the annual meeting of the European Society of Cataract and Refractive Surgeons.
Before Dr. Kohnen addressed the question of how to calculate IOL power in children, he reviewed four issues -- axial length growth, axial length measurement, IOL calculation formulas, and IOL positions -- as they pertain to calculating IOL power in children.
He pointed out the physiologic issues associated with children undergoing cataract surgery and supported his remarks with past clinical studies on children.
One important fact from the literature in regard to axial length growth is that pseudophakic eyes retard axial elongation. With children, physicians have to deal with short eyesbelow 20 mm at least in the early stage of the cataract formulation. This makes axial length and kerotometric measurements hard to obtain in children.
As for IOL calculation formulas, there are different generations of formulas. Dr. Kohnen said physicians need to work with the different formulas and look closely at the results derived from them. He prefers the third-generation formulas because better IOL calculations are established for short eyes.
IOL positioning in pediatric cataract surgery is also an important factor and Dr. Kohnen outlined the basic surgical techniques. He highly recommended the proper surgery technique for each patient.
What should be the refractive outcome after IOL implantation in the pediatric eye? Dr. Kohnen said there are really only two approaches: IOL power as an emmetropic approach or as a hyperopic approach.
The emmetropic approach has short-term results with good uncorrected visual acuity (UCVA) in the beginning. Dr. Kohnen warned that a myopic shift would occur over time. In the long-term, physicians may have to perform an IOL exchange, prescribe glasses for the high myopic child, or perform additional surgery.The hyperopic approach is Dr. Kohnen's preferred approach. The IOL lens calculations are done in regard to the age, depending on the implantation time.
"My preferred situation is to implant lenses between 1 or 2 years of age," Dr. Kohnen said. "Before this time, I leave the child aphakic, corrected with contact lenses, and later do the implantation."