This article reviews current thoughts regarding pediatric refractive surgery. This encompasses current trends in adult refractive surgery, differences between adult and pediatric refractive surgery, and future possibilities for refractive technology for the pediatric population.
Key points
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Pediatric refractive surgery has different indications than adult refractive surgery.
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Refractive surgery is for children who are failing with cognitive or visual development because of refractive error.
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There are many surgical options for pediatric refractive surgery patients.
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Challenges with pediatric refractive surgery include logistics, patient cooperation, anesthesia, high refractive errors, and amblyopia.
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Pediatric refractive surgery includes off-label treatments.
Introduction
Refractive surgery, or surgery to eliminate the need for eyeglasses or contact lenses, has become a common and well-accepted elective surgery across the world. Adult refractive surgery is an environment with rapidly changing technology, techniques, and vast advances over the past 40 years. With greater experience of refractive surgery in the adult population, the pediatric community has begun to show special interest in using these techniques to help a new population of patients. As pediatric clinicians proceed into the realm of refractive surgery, additional challenges, adaptations, and concerns about this emerging practice arise. Careful consideration of the unique aspects of visual development combined with lessons learned during the history of adult refractive surgery are joined to offer children novel and effective therapies for treating select conditions.
Historical perspective
Modern refractive surgery started in 1950 with Columbian ophthalmologist Jose Barraquer and his development of an instrument to create a corneal flap for the purpose of correcting refractive errors termed “keratomileusis.” In 1974 radial keratotomy, which consists of making radial partial-thickness cuts in the cornea, was introduced by Svyatoslav Fyodorov for the treatment of myopia. Excimer laser was first proposed for the treatment of corneal refractive errors by US ophthalmologist Stephen Trokel in 1983. Laser technology evolved rapidly and photorefractive keratectomy (PRK) was first performed on humans in the mid-1980s by Theo Seiler. As a melding of PRK and Barraquer’s early thoughts on keratomileusis, laser-assisted in situ keratomileusis (LASIK) was first performed in 1990 by Lucio Burrato and Ioannis Pallikaris.
When the first lasers were introduced the obvious initial candidates for treatment were those with large, often debilitating refractive errors. After initial success with the treatment of high refractive errors, clinicians began to note complications with haze, excessive corneal thinning, and scarring in some patients. Researchers began to look for alternative technology for the treatment of high refractive errors and reserved laser technology for low-to-moderate refractive errors.
The first phakic intraocular lens (PIOL) was implanted in 1990 for the treatment of high myopia. This surgery placed the PIOL in the anterior chamber without disruption of the crystalline lens. Further studies have shown that the PIOL technologies provided excellent optical outcomes in patients with high refractive errors. Because this technology is more invasive than surface refractive procedures, risks include endothelial cell damage, cataract formation, risk for retinal detachment, and the generally increased risk of intraocular surgery.
Another treatment modality that has evolved for large refractive errors is lensectomy with or without implantation of a low-power or plano IOL. This technique, termed “refractive lens exchange,” has been used for patients with large refractive errors and adult patients desiring multifocal IOLs to treat presbyopia and refractive error in one procedure ( Boxes 1 and 2 ).
1950 – Keratomileusis
1974 – Radial keratotomy to treat myopia
1983 – PRK using an excimer laser
1990 – LASIK using an excimer laser
1990 – PIOL
LASIK
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A thin flap is created in the anterior cornea with a blade or laser
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The flap is reflected and the excimer laser is used to reshape the tissue beneath the flap
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The flap is then replaced and seals in place without sutures
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PRK
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The epithelium is manually removed from the surface of the cornea
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The excimer laser is used to reshape the surface of the cornea
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The epithelium heals over the following 3 to 4 days
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PIOL
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Surgically implanted device
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Natural lens remains intact
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Can treat high myopia
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Refractive lens exchange
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Surgical removal of the natural lens
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Placement of intraocular lens
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Results in loss of accommodation
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Can treat high hyperopia or myopia
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Refractive surgery procedures today in adults
Low-to-moderate Myopia and Low Hyperopia
After determination that the patient is a suitable candidate for refractive surgery (adequate corneal thickness, normal corneal architecture, absence of other pathology, realistic expectations, and stability of current refractive error) most of these low-to-moderate myopes and hyperopes are excellent excimer laser candidates. Generally, laser correction (either LASIK or PRK) is the procedure of choice for refractions ranging from approximately +3.00 diopter (D) to −8.00 D, depending on many factors identified in the preoperative visit. This is the range where the author finds maximization of refractive outcomes, stability, and patient satisfaction with excimer laser surgery.
High Myopia
Decisions about treatment options for moderate-to-high myopia often hinge on age and refractive error. In young patients with greater than −8.00 D of myopia, laser treatments are sometimes an option when the patient has adequate corneal thickness. If there is concern about corneal thickness, young patients with myopia are often better candidates for PIOL implantation.
Moderate-to-high Hyperopia
Because there is no PIOL approved by the Food and Drug Administration for the treatment of hyperopia, patients with hyperopia have more limited surgical options. Excimer laser treatments are most effective up to +4.00 D. The discrepancy between the limits for hyperopic and myopic treatment results from the relative ease in flattening the central cornea (myopic treatment) as contrasted with the difficulty in achieving a satisfactory optical result with steepening the central cornea (hyperopic treatment). Patients with hyperopia outside the range of excimer laser treatments have the option of a refractive lens exchange with IOL implantation.
Excimer lasers and PIOLs are not approved for use in the pediatric population. All of these treatments are available in the United States but are used on an off-label basis in children. A thorough discussion of the risks, benefits, and off-label nature of these treatments is necessary when planning for pediatric refractive surgery ( Box 3 ).
Low-to-moderate myopia and low hyperopia
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+3.00 to −8.00 D
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If adequate corneal thickness, absence of risk factors
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PRK or LASIK
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High myopia
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PIOL
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Refractive lens exchange with or without IOL
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Moderate-to-high hyperopia
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Refractive lens exchange
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Challenges of pediatric refractive surgery
As in most aspects of medicine, children are not just small adults when considering refractive surgery. There are many unique challenges that arise when considering refractive surgery for the pediatric population. Paramount in the discussion of pediatric refractive surgery is the understanding of the fundamental difference between pediatric and adult indications for refractive surgery. Pediatric ophthalmologists must be conscientious of safety concerns, but we cannot be so conservative that we prevent the pediatric population from benefiting from new technology. It has only been 30 to 35 years that pediatric ophthalmologists have routinely inserted an IOL after removing a cataract. Before this children with unilateral cataracts could only be corrected with a contact lens, and cases of bilateral cataracts were treated with very thick aphakic glasses or contact lenses. Visual rehabilitation was much less successful with such limited options, and contact lens complications in very young children are frequent. Through the work of forward-thinking pediatric ophthalmologists, children undergoing cataract surgery now have similar options as adults. Refractive surgery must be evaluated carefully as a potential option for a small segment of the pediatric population faced with specific vision problems.
Indications for Treatment
Adult refractive surgery is performed to eliminate the need for eyeglasses and contact lenses. It is an elective procedure that adults choose to reduce hassle with eyeglasses and contacts and simplify their lives. Pediatric refractive surgery is not ever an option simply to reduce the inconvenience of eyeglasses and contact lenses. It is only considered in cases where visual development or overall cognitive development is at risk because of the presence of an untreated refractive error. There are two primary conditions that are most commonly treated with pediatric refractive surgery: anisometropic amblyopia and bilateral high refractive error with neurodevelopmental disability.
Anisometropia occurs when the refractive error is very different between the two eyes. This can occur because of an underlying problem with one of the eyes (eg, glaucoma or myelinated nerve fiber layer) or can occur spontaneously. Depending on the degree of anisometropia, amblyopia may develop because of a poor retinal image from the eye with the higher refractive error. When this occurs, the first-line treatment is refractive correction with eyeglasses or contact lenses and then the use of an occlusive patch to treat the amblyopia. Most patients respond favorably to this treatment and the amblyopia reverses. When the vision is no longer at risk, the child wears eyeglasses or contact lenses until they become an adult. At this point they can choose to have elective refractive surgery. If the vision fails to respond to refractive correction and occlusive therapy, whether from poor compliance or primary failure to respond, then refractive surgery is considered.
The other condition that has been addressed with pediatric refractive surgery is bilateral high refractive error with poor compliance with refractive correction. Most infants are born hyperopic and shift toward emmetropia (no refractive error). Around the age of 7 to 9 years a certain percentage of children continue to shift and become myopic. There are genetic and environmental factors that are implicated in the progression of myopia. Myopia is mainly caused by axial growth of the eye. Currently, there is no way to predict which children will become myopic, how myopic they will be, and when the myopia will stop progressing. There are some general hereditary and environmental risk factors that are widely accepted. For example, children with at least one myopic parent are two to four times more likely to become myopic than a child whose parents are not myopic. Myopia is much more prevalent in Chinese populations. This may be related to genetics and the prolonged school day and intensive reading to which Asian school age children are exposed. Animal experiments support the theory that prolonged reading can precipitate a myopic shift in populations at risk for myopia. In a large prevalence study (refractive error study in children [RESC]) 55% of 15-year-old girls in rural China were myopic compared with 3% in Nepal.
Regardless of what causes severe myopia, there is no known prevention at this time; therefore, we must concentrate on refractive correction to help normal visual development. Most children with bilateral high refractive error take to wearing eyeglasses or contact lenses very rapidly and enjoy the clear vision provided by their correction. Most children who refuse their refractive correction have concurrent neurodevelopmental disorders including autism, brain injury, or genetic disorder. The stimulation of having eyeglasses on their face is often too bothersome to enjoy the benefits of clear vision. These children immediately remove their eyeglasses and in most cases do not allow the insertion of contact lenses. Children with mild refractive error, either hyperopic or myopic, can function well without correction and do not need refractive surgery. When the refractive error is greater than 3 to 4 D, then refractive surgery is considered.
A secondary factor in this process is the timing of treatment. Visual development can occur up until the age of 7 to 9 years. Amblyopia that goes untreated past this point, and sometimes even younger, is very difficult if not impossible to reverse. Children with anisometropic amblyopia or bilateral high refractive errors should be identified; conservatively treated; and if treatment failure occurs, referred for surgery before reaching this age. Even after age 9, there is still the possibility for reversing a small amount of amblyopia, but effects are greater at a younger age ( Box 4 ).
