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At Issue: pediatric IOL myopic shift
At Issue posed the following question to a panel of experts: “When implanting pediatric IOL, do you plan for a myopic shift; how and why?”
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Recognizing shift is crucial
Suqin Guo, MD: I do plan for the myopic shift when implanting IOLs in pediatric patients, especially in young children. It has been the experience of our pediatric ophthalmology service, which includes Anthony R. Caputo, MD, and Rudolph S. Wagner, MD, that myopic shift after pediatric IOLs is real. However, the shift may or may not be significantly different from the natural curve of physiological change in refraction in phakic children (from hyperopia to emmetropia or myopia).
Recognizing the myopic shift is crucial in choosing the proper power of IOLs in children. From our experience, the myopic shift is multifactorial, depending on the patient’s age, axial length and refractive error of fellow eye at time of the IOL implant.
The increase in axial length can cause approximately 3 D of myopic shift in refraction, whereas a 1-mm change in corneal curvature leads to only a 1 D change in refraction. The closer the axial length to that of an adult level at time of the IOL implantation, the smaller the myopic shift. Our experience agrees with most studies in the literature. The axial length in majority of children will reach adult level between 4 to 6 years of age. By then, the myopic shift becomes less significant.
The patient’s age at the time of the IOL implant is another important factor. The younger the children are, the more significant and more variable the myopic shift occurs. The significant myopic shift in younger children is most likely influenced by the increases of axial length and decrease of corneal curvature with age. Match of refractive error with fellow eye in children with unilateral cataract should also be considered to minimize postoperative anisometropia or amblyopia.
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Consider long-term result
Scott E. Olitsky, MD: The overwhelming cause for poor vision following cataract surgery in children continues to be untreated or uncorrectable amblyopia. While some surgeons choose an implant power that takes into consideration the expected myopic shift that will occur as the child grows, I believe the introduction of any potential obstacle to successful visual rehabilitation in a visually immature child may serve to increase the risk of a poor result.
When deciding on an implant power, I aim to make the child emmetropic or slightly myopic. A small degree of postop myopia will allow most young children to function well at both distance and near activities even without glasses or bifocals while patching. It will make their visual development less dependent on wearing corrective lenses.
Making a young child hyperopic in hopes of having them become emmetropic later in life will make them dependent on glasses and bifocals at all times. If the child is not compliant with their spectacles, they will most likely develop significant amblyopia even if they can be successfully patched. This will be even truer in the very young patient, who will need to be made more hyperopic and be less likely to wear bifocals well for near activities.
Of course, making a very young child myopic will most likely make them significantly nearsighted later in life. However, the older child is much more likely to wear his or her glasses or contact lens when, or if, this occurs at an age when amblyopia treatment is less likely to be needed.
In addition, refractive surgery is available for the teenager who seeks this option. In the end, a child who is myopic but has good correctable vision has a far better outcome than the one who “grows to” emmetropia but was a failure in their amblyopia treatment and will forever have poor vision in the treated eye.
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Sliding scale found reliable
Roberto Warman, MD: To answer this question, it is necessary to consider several factors, of which probably the most important is the age at which the IOL will be implanted.
A significant number of pediatric ophthalmologists do not advise placing IOLs before the age of 2 due to the difficulty with calculating the myopic shift. Several studies are trying to predict the myopic shift, with conflicting results. The underlying denominator is the great variability and exceptions with big swings that cannot be anticipated.
I prefer not to implant IOLs for pediatric aphakia before 2 years of age as a standard rule, but I have done some between 1 and 2 years, in which case I tend to leave room for approximately 3 to 4 D of myopic shift. I would leave 4 D between 12 and 18 months and 3 D between 18 and 24 months of age. Between 2 and 3 I allow 2 D and between 3 and 4, 1 D. After that age I do not take the myopic shift significantly into consideration. I calculate for plano until the age of 7 years.
I do not have any long-term study to support this sliding scale, but I have found it to be reasonably reliable. I do expect occasional surprises.
Another consideration is the size of the eye and avoiding implants on significant microphthalmia. Considerations are more important in the accurate measurement of the keratometric readings and the axial length than on the myopic shift.
I have been very successful throughout many years fitting infant patients with aphakic soft contact lenses. If I find myself with some higher refractive errors, I would not hesitate in placing a soft contact lens postop and see how the refraction modifies in the following years.
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