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What is the role of new technological advances in pediatric ophthalmology?
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New technologies and surgical techniques have always stepped timidly into pediatric ophthalmology.
No matter the degree of success, their role has remained conceptually questionable because, in the few published reports, indications are by rule ‘off-label,’ and studies neither multicentered nor prospective. Typically, rather, they are small series based on incomplete and inhomogeneous criteria, with a limited follow-up.
The scientific evidence upon which pediatric ophthalmologists rest for their choices only comes from adult-based studies, and specialists are well aware that the limitations and risks inherent to each new technique and technology should lead to an infinitely more cautious attitude when dealing with younger patients.
Indications
Pediatric refractive surgery has been at the center of a long-standing debate. Points at issue have included the limitation and definition of indications, as well as the acceptance of refractive surgery by pediatricians and pediatric ophthalmologists as an option that is primarily therapeutic. The functional and cosmetic aspects only pertain to the adult.
Furthermore, refractive surgery should never be considered as first-line treatment, but rather as an alternative option after other methods of optical correction have failed. We can offer it when spectacle correction is ineffective or impossible, such as in cases of amblyopic anisometropia, where only a partial correction is tolerated, and in cases of irregular or cloudy cornea. We can certainly try contact lenses first, but our attempts might be defeated by problems with manipulation, fitting, hygiene, child cooperation and the education of parents.
Which of the various surgical options is best indicated when we aim at preventing amblyopia, ensuring stereoscopic vision and at the same time respecting the anatomical structure of a developing eye? Photoablation poses the challenge of maintaining corneal transparency and biomechanics, as well as the problem of regression and stability of results. Phakic implants raise the issue of potential damage to the corneal endothelium, the iris and crystalline lens. Finally, multifocal IOLs can nowadays be considered in cases of congenital cataract, but power calculation, stability, and the inflammatory and fibrotic responses pose even greater problems in an infant’s eye. Caution is mandatory with any of these surgical options, since we know from adult surgery that LASIK carries the risk of secondary ectasia and PRK the risk of central haze.
We are aware of the potentially poor long-term outcomes of phakic implants in case of inaccurate sizing, and of how difficult it is to predict the success in terms of neuroadaptation and vision quality of multifocal IOLs. However, we cannot fail to acknowledge the great potential of these surgical techniques in preventing amblyopia, minimizing aniseikonia and rehabilitating binocular vision.
Establishing guidelines
For ethical and scientific reasons, we should in future years come to a definition of guidelines regarding modulation of scar tissue formation in pediatric eyes and find a consensus on nomograms for power and size of IOLs according to the specific characteristics of the developing eye. We should issue specific protocols for the application of diagnostic and surgical procedures to these patients. The topic of when to operate also remains controversial. Early surgery offers the advantage of preventing amblyopia and making the most of the powerful neuroplasticity of early age. On the other hand, later interventions — after 8 years of age — guarantee a better stability and a milder scarring response.
Although there is no consensus on acceptable strategies, it seems reasonable to do everything possible to maintain the integrity of a healthy cornea and to work on it only in cases of loss of transparency (PTK) or regularity (intrastromal rings). When remodeling is not possible and the cornea needs to be replaced, lamellar rather than full-thickness transplantation should be first-line.
The use of IOLs is somewhat less controversial, since they are a reversible procedure. Posterior chamber phakic implants are generally preferred, as they involve no risk for the corneal endothelium. Correct sizing is now more easily achieved with the aid of anterior segment optical coherence tomography technology. In case of cataract, and in presence of a healthy retina, normal pupil reactivity and capsular bag integrity, the multifocal option can now legitimately be considered. Piggy-back implants, toric and multifocal, are a further tool that has recently come into our armamentarium, offering the advantages of a secondary, adjustable technique.
Cross-linking is the one procedure on which consensus seems nowadays quite unanimous: Children younger than of 15 years, the age group in which keratoconus progresses more rapidly, are those who benefit most from the procedure. We still need to establish which of the available treatment modalities — conventional, trans-epithelial, flash, etc. — is better suited in this specific group. The answer can only come from controlled clinical trials, but ethical issues and the need for parental consent are limitations to studies in all branches of pediatric medicine.
Last but not least, an important role may be played in the future by the femtosecond laser for cataract surgery, thanks to the ability to perform a perfectly controlled anterior and posterior capsulotomy, thus allowing better centration and stability of intraocular implants.
The cover story in this issue focuses on the application of the latest technologies in pediatric ophthalmology. It should be able to demonstrate, through the experience of experts in the field, that new techniques and technologies, when used with caution and within appropriate limits, have a place of interest in the therapeutic armamentarium of those of us who take care of our most delicate and precious patients.
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- Béatrice Cochener, MD, PhD, is the chairperson of OSN Europe Editorial Board. She can be reached at Department of Ophthalmology, University of Brest, CHU Morvan - 5, Av. Foch, 29609 Brest Cedex, France; email: beatrice cochener-lamard@chu-brest.fr.
Disclosure: Cochener has no relevant financial disclosures.