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Bifocals in kids: myopia, esophoria, esotropia may all be considerations
Contact Lenses and Eyewear
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For myopia and esophoria
Lynn A. Cyert, PhD, OD, FAAO: Based on the results of the Myopia Progression Study conducted by George Fulk, Donald Parker and me, some children with myopia and esophoria may be able to retard their myopia progression with a bifocal spectacle correction. Because the reduction in progression is based on the average response, it is impossible to predict what effect a bifocal lens might have for an individual child. All of the children in the study exhibited esophoria as well as myopia at their entrance into the study. As an added benefit, many of the esophoric children were more comfortable reading with the bifocal.
Our study does not address whether plus lenses for near wear (either as bifocals or single vision lenses) could prevent the initial development of myopia in a child not yet myopic, nor does it address the issue of a bifocal correction for children not exhibiting esophoria. However, because the median myopia progression in the experimental group during 30 months was 25% less than in the control group, some individuals may have benefited considerably from the bifocal prescription. Therefore, I would discuss with the parents of any esophoric child who had rapidly progressing myopia the possibility of bifocal lens wear in an effort to slow the myopia. If the appearance of a flat top bifocal were an issue, I would feel comfortable prescribing a progressive addition lens.
Other conditions for which I would consider prescribing a bifocal for children include esophoria, accommodative esotropia and intermittent or constant esotropia. Bifocals are appropriate for some binocular, oculomotor, accommodative and perceptual dysfunctions. I prefer not to prescribe bifocal lenses in children who are too young to walk. Bifocal lenses assume that “near” is also “down,” so the near vision demand of the patients must be considered in prescribing bifocals.
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Reference:
- Fulk GW, Cyert LA, Parker DE. A randomized trial of the effect of single-vision vs. bifocal lenses on myopia progression in children with esophoria. Optom Vis Sci. 2000;77:395-401.
Accommodative esotropia or convergence excess
Kelly A. Frantz, OD, FAAO, FCOVD: In general, I frequently recommend bifocal spectacles for children who have accommodative esotropia or convergence excess (with or without progressing myopia) and sometimes for those with accommodative insufficiency. Children with accommodative esotropia often are hyperopes who accept plus for distance, and sometimes this plus is sufficient, in single vision lenses, to eliminate their esotropia. However, if the esotropic angle is larger at nearpoint, a bifocal is quite useful to reduce or eliminate the esotropia.
My goal is to enable the patient to have fusion though the add. Even if there is no strabismus, bifocals are also indicated for convergence excess cases (symptomatic nearpoint esophoria with inadequate divergence ability). I attempt to eliminate the esophoria with the add, if possible.
In progressing myopes, if there is nearpoint esophoria, the literature supports prescribing bifocals as well. The rate of myopia progression may be slowed in some esophoric children treated with bifocals.
For accommodative insufficiency cases, a bifocal is one option for improving comfort, but I prefer to prescribe vision therapy if the patient and parent are suitably motivated. If prescribing bifocals, I aim to restore a normal accommodative lag through the add.
For preschool children, my preference is to use a flat-top 28 bifocal. I set segments high enough that the child cannot help but use them (at mid-pupil through age 5 years, then at the lower pupil border until about age 8). I like having a visible bifocal line because parents and teachers can monitor that the child is using the add appropriately. If the line becomes a cosmetic issue for older children, I prescribe progressive addition lenses with a rapid transition from distance to near power. I also recommend a separate pair of polycarbonate sports goggles without an add for use during sports/rough play.
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If it improves visual function
Michael J. Bartiss, OD, MD, FAAO, FAAP, FACS: There are primarily three circumstances in which I will prescribe bifocal lenses for children: if a bifocal results in improved visual acuity, visual functioning and/or binocular vision.
There is an obvious optical need for a near vision lens in aphakia and pseudophakia. In unilateral cases of pseudophakia, I will often prescribe a bifocal for the pseudophakic eye only, selecting an add with a focal length set for the child’s “Harmon distance” (distance from the elbow to the knuckle of the middle finger). This allows the most symmetric visual acuity at the reading distance, but maintains a wider range of near vision in the phakic eye.
I prescribe the full cycloplegic “plus correction” to all children with accommodative esotropia. If this straightens the eyes at distance, but the child is left with esotropia greater than 10 prism diopters (and does not fuse) at near, I will consider a bifocal if the addition of plus lenses (again set for the Harmon distance) produces binocular alignment and binocular fusion in free space. I use Janelli clips or a trial frame to determine this in the “dry” (non-cyclopleged) state before prescribing the bifocal.
If a patient has no significant hyperopic refractive error, but demonstrates a significant esodeviation at near that either produces functional visual problems or precludes binocular fusion, I will consider a bifocal (or single vision near lenses).
The amount of plus lens add I will prescribe is based on the near point refraction, accommodative function (accommodative lag determined by dynamic retinoscopy; binocular cross cylinder) as well as positive and negative relative accommodation. Again, the additional plus lens power must allow demonstrable binocular fusion/function to justify the prescription of bifocals. This makes much more sense to me than “shooting from the hip” and arbitrarily prescribing +2.50 or +3.00 adds. Not all children can or will cooperate enough to allow all of these data to be obtained, but if possible, it allows for a much more rational approach to bifocal prescription in children.
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