Multifocal intraocular lenses in children
2001; Elsevier BV; Volume: 108; Issue: 8 Linguagem: Inglês
10.1016/s0161-6420(01)00670-4
ISSN1549-4713
Autores Tópico(s)Ocular Infections and Treatments
ResumoWhen a child has a cataract, the surgeon is faced with an imposing assortment of therapeutic dilemmas, none of which has been addressed adequately with long-term studies. Should an intraocular lens (IOL) be placed? Are foldable lenses appropriate? Should the posterior capsule be opened at the time of surgery? For pediatric patients, the information is sparse, but the result of our treatment decisions could stand for 80 years or more. Although the surgical procedure itself can be technically difficult with small and unforgiving eyes, surgery is usually the easy part. Patients may not cooperate for examination or treatment. Postoperative inflammation can be intense. Amblyopia is common, and therapy must be maintained for years. To optimize acuity at both distance and near, bifocals usually must be fitted. With Food and Drug Administration approval of the Allergan Medical Optics Array multifocal IOL (Allergan, Irvine, California), (for use in adult patients),1Steinert R.F Visual outcomes with multifocal intraocular lenses.Curr Opin Ophthalmol. 2000; 11 ([review]): 12-21Crossref PubMed Scopus (42) Google Scholar, 2Javitt J.C Steinert R.F Cataract extraction with multifocal intraocular lens implantation a multinational clinical trial evaluating clinical, functional, and quality-of-life outcomes.Ophthalmology. 2000; 107: 2040-2048Abstract Full Text Full Text PDF PubMed Scopus (260) Google Scholar we are faced with new choices. Could insertion of an IOL that provides built-in “bifocal” capability decrease the severity of amblyopia? Will the near power of the multifocal optics give the surgeon the option of intentionally undercorrecting patients, using the “add” for distance correction in childhood and thereby avoiding high myopia in adulthood? In this issue, Jacobi et al3Jacobi PC, Dietlein TS, Konen W. Multifocal intraocular lens implantation in pediatric cataract surgery. Ophthalmology 2001;108:1375–80.Google Scholar report on their experience implanting multifocal IOLs in 35 eyes of 26 pediatric patients aged 2 to 14 years. They suggest that for children, multifocal IOLs are a viable alternative to the standard monofocal IOL. However, this study has limitations. The reported benefit of improved stereopsis may come from improved acuity. Data on spectacle dependence and subjective satisfaction are not helpful when obtained from children, who will understate their symptoms in the hope of avoiding glasses. The average follow-up of 27 months (range, 12–58 months) was good for adults but is not sufficient for pediatric patients. There are several questions that must be considered before multifocal IOLs are implanted in children outside of research protocols. These include centration problems, IOL power calculations, the use of silicone IOLs, the amblyopiagenic effect of multiple overlapping images and decreased contrast, and the tolerability of glare. Is the child’s eye an appropriate environment for an IOL that requires precise centration and a round, central pupil for optimal function? In Jacobi et al’s study,3Jacobi PC, Dietlein TS, Konen W. Multifocal intraocular lens implantation in pediatric cataract surgery. Ophthalmology 2001;108:1375–80.Google Scholar 6 of 35 eyes experienced decentration severe enough to require another operation. Posterior synechiae developed in 54% of eyes. When these problems occur, they may convert the multifocal IOL to an effectively monofocal implant by obscuring the lens periphery or may impair image formation and exaggerate glare and contrast problems. Furthermore, just 1 diopter (D) of uncorrected corneal astigmatism may impair image formation in a multifocal system.4Ravalico G Parentin F Baccara F Effect of astigmatism on multifocal intraocular lenses.J Cataract Refract Surg. 1999; 25: 804-807Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar Selection of the proper IOL power is difficult in the pediatric age group. The younger the patient, the more difficult it is to predict the growth of the eye and the final refraction in adulthood.5McClatchey S.K Dahan E Maselli E et al.A comparison of the rate of refractive growth in pediatric aphakic and pseudophakic eyes.Ophthalmology. 2000; 107: 118-122Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar Yet to benefit from multifocal optics, the postoperative distance refraction should be very close to emmetropia. An IOL may give emmetropia for only a few years of childhood because of subsequent ocular growth. Unless spectacles are worn routinely, there will be either a transient benefit during childhood or the child will have to wait until adulthood (or undergo a secondary refractive procedure) to benefit from multifocal optics. An intentionally undercorrected child using the multifocal add for distant focus will require glasses for near work. The Allergan Medical Optics Array lens has a silicone optic. Most published experience with IOLs in children is with polymethyl methacrylate or foldable acrylic lenses. A study of silicone IOLs in children performed by Pavlovic et al6Pavlovic S Jacobi F.K Graef M Jacobi K.W Silicone intraocular lens implantation in children preliminary results.J Cataract Refract Surg. 2000; 26: 88-95Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar included only eight eyes of seven patients. No short-term complications occurred, but that study did not address long-term safety. How these silicone lenses will fare over a period of decades rather than years remains unknown. When an eye is out of focus, the perceived image is better than the actual physical image that falls on the retina.7Parsa CF, Ellis FJ, Guyton DL. Photographic reproduction of out-of-focus and distorted ocular imagery. Vision Res 2001;41:1489–99.Google Scholar This enhancement has been attributed to neural processing. Such processing of blurred images may be a learned skill, relying on the prior experience of seeing properly focused, high contrast images at least some of the time. The Array lens allocates 50% of light for distant focus, 13% for intermediate, and 37% for near. This can be thought of as producing three images of any object: one focused and two larger, superimposed, blurred “fringe” images. The adult brain then presumably selects the “good” image, and the two blurred fringe images are discounted. But can a developing eye and brain make such a distinction between the good, sharp image and the bad, blurred images? If not, the multiple images from a multifocal lens may prove to be an even stronger amblyopiagenic stimulus than ordinary optical defocus alone. Will the decreased contrast sensitivity of the multifocal design at all distances8Featherston K.A Bloomfield J.R Lang A.J et al.Driving simulation study bilateral Array multifocal versus bilateral AMO monofocal intraocular lenses.J Cataract Refract Surg. 1999; 25: 1254-1262Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar contribute to amblyopia in this age group? Amblyopic eyes already show poor performance in low-contrast environments.9Simmers A.J Gray L.S McGraw P.V Winn B Functional visual loss in amblyopia and the effect of occlusion therapy.Invest Ophthalmol Vis Sci. 1999; 40: 2859-2871PubMed Google Scholar Thus, there is a theoretical risk that any advantage of multifocal optics could be negated by decreased contrast sensitivity. In a primate study of the amblyopiagenic effects of unilateral diffusing lenses, even the weakest diffusing lens caused amblyopia.10Smith 3rd, E.L Hung L.F Harwerth R.S The degree of image degradation and the depth of amblyopia.Invest Ophthalmol Vis Sci. 2000; 41: 3775-3781PubMed Google Scholar Although the amount of contrast reduction induced by a multifocal IOL may not be large, it may nevertheless induce a corresponding degree of amblyopia. A monkey model of unilateral cataract has been used to compare multifocal IOLs with monofocal IOLs.11Lambert S.R Fernandes A Drews-Botsch C Boothe R.G Multifocal versus monofocal correction of neonatal monocular aphakia.J Pediatr Ophthalmol Strabismus. 1994; 31: 195-201PubMed Google Scholar, 12Boothe R.G Louden T Aiyer A et al.Visual outcome after contact lens and intraocular lens correction of neonatal monocular aphakia in monkeys.Invest Ophthalmol Vis Sci. 2000; 41: 110-119PubMed Google Scholar However, the acuity methods used were not sensitive for detecting amblyopia. Any cooperative effect of bilaterally inserted multifocal IOLs13Arens B Freudenthaler N Quentin C.D Binocular function after bilateral implantation of monofocal and refractive multifocal intraocular lenses.J Cataract Refract Surg. 1999; 25: 399-404Abstract Full Text PDF PubMed Scopus (50) Google Scholar may not be relevant in children with subnormal binocular vision. Glare is a recognized drawback of the multifocal design.1Steinert R.F Visual outcomes with multifocal intraocular lenses.Curr Opin Ophthalmol. 2000; 11 ([review]): 12-21Crossref PubMed Scopus (42) Google Scholar In Jacobi et al’s study,3Jacobi PC, Dietlein TS, Konen W. Multifocal intraocular lens implantation in pediatric cataract surgery. Ophthalmology 2001;108:1375–80.Google Scholar 16 of the 24 patients were deemed old enough to report on symptoms of glare, but children are unreliable in their ability to report symptoms. It will be years before we know whether the optical aberrations inherent to a multifocal IOL are severe enough to cause these patients more symptoms than have been described in adult populations to date. What is the best choice of IOL in children who are considered candidates for IOL insertion? A monofocal polymethyl methacrylate lens remains the best-studied lens with a long record of safety. Foldable acrylic lenses have a good, but shorter, track record. The smaller incision with the attendant increase in wound integrity and decrease in postoperative inflammation probably tilt the risk-to-benefit ratio in favor of the foldable lens. Until the multifocal design is shown to prevent or at least not promote amblyopia, caution should be used when considering the insertion of multifocal IOLs in children outside of research protocols, especially in children at risk for amblyopia. Caution should also be observed when using these lenses in traumatic cataract, because traumatized eyes are most likely to experience lens decentration or pupillary abnormalities after surgery, converting the potential advantage of multifocal optics into a liability.
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