Pediatric cataracts can occur in one eye (unilateral) or both eyes (bilateral). They can be complete or partial and can be present at birth or occur sometime after birth. In contrast to adults, cataracts in children present a special
challenge, since early visual rehabilitation is critical to prevent irreversible amblyopia. Up until the late 1980s, many ophthalmologists would not even attempt surgery on unilateral congenital cataracts because of the poor prognosis. With new knowledge in the treatment of congenital cataracts and improved surgical and clinical management, visual prognosis has improved. Now ophthalmologists operate as early as the first week of life and fit patients with contact lenses within a day or two after surgery.
However, even with the best of care, there is still a chance that the affected eye(s) may not be visually rehabilitated. Children born with cataracts are also at risk for developing glaucoma, strabismus, nystagmus, and poor stereopsis, further complicating successful outcomes. In most cases, it is the willpower and resolve of the parents or caregivers to follow post-operative management that determines visual success for the child.
Acquired Cataracts
It is important to remember that some visually significant cataracts assumed to be congenital may have been partial during the critical period are not amblyogenic at birth. Even nuclear cataracts can be partial at birth and later progress to become visually significant. Patients with acquired progressive cataracts have less amblyopia and a much better visual prognosis than patients with cataracts that cover the visual axis since birth. This is why progressive cataracts have a relatively good prognosis, even when surgery is performed after the critical period of visual development.
Unilateral Cataracts
Unilateral infantile cataracts are rarely caused by a systemic disease, except in some cases of intrauterine infections such as rubella. Approximately 20-30% of rubella cataracts are unilateral. The work-up for a unilateral congenital cataract should include a full ophthalmic examination. Generally, monocular congenital cataracts have a relatively good prognosis if surgery and optical correction is provided by two months of age. Despite the improved visual acuity results in infants receiving early surgery for monocular congenital cataracts, the prognosis for obtaining binocular fusion has been poor. Binocular fusion is possible, but only if visual rehabilitation is established early, and occlusion therapy for amblyopia is limited to part-time patching. A number of clinical studies show that binocular fusion and good visual acuity is obtainable in patients with unilateral congenital cataracts if there is early visual rehabilitation and limited part-time occlusion therapy during the first few months of life.
Bilateral cataracts are often inherited, and recent genetic studies have isolated chromosomal abnormalities associated with many types of cataracts. Approximately 5 to 10% of bilateral cataracts are associated with a systemic disorder. The work-up for bilateral congenital or infantile cataracts should include a careful pediatric examination and special tests. Laboratory work-up is not necessary if the cataracts can be definitely defined as hereditary without other systemic abnormalities.
Dense bilateral congenital cataracts require urgent surgery and visual rehabilitation because, if left untreated past two months of age, almost all patients develop sensory nystagmus and have a poor visual prognosis with vision usually in the range of 20/100 to 20/200. Thus, the window of opportunity for bilateral congenital cataracts is similar to that of monocular congenital cataracts, with best results obtained when surgery and visual rehabilitation are instituted prior to two months of age. It is important to note that once sensory nystagmus occurs, the visual prognosis is poor, with most children achieving vision of 20/100 or worse. Since many of these children with bilateral cataracts and sensory nystagmus will be legally blind, it is critical that bilateral cataracts be treated with utmost urgency so that visual rehabilitation occurs early, during the first few weeks of life. In general, bilateral cataracts operated prior to two months of age have a good visual prognosis with approximately 80% achieving vision of 20/50 or better.
Bilateral Patching for Congenital Cataracts
The ideal treatment of a visually significant unilateral or bilateral congenital cataract is immediate removal of the
cataract with instantaneous correction of the aphakia. Unfortunately, this is usually not obtainable. Time is required to place the patient on a surgery schedule, obtain medical consultations, and to allow for postoperative recovery before fitting the contact lens. This process of establishing a clear retinal image after identification of the congenital cataract can require three weeks for unilateral cataracts and longer for bilateral cases. During the critical period of visual development, even one to two weeks of a blurred retinal image can worsen the amblyopia.
A method for preventing the amblyogenic effect of a blurred retinal image is to completely eliminate all light in both eyes with bilateral light occlusion or dark rearing. The length of time bilateral occlusion can be safely given remains unknown. Previous studies indicate that it appears bilateral patching of a neonate can be safely done for at least two weeks. To prevent amblyopia, light occlusion must be bilateral and total. Monocular patching causes monocular amblyopia of the occluded eye, and bilateral diffuse light from incomplete occlusion causes bilateral amblyopia. Therefore, it is important that the patch actually occludes essentially all light when performing bilateral patching. Bilateral patches are worn full-time and are only removed if the infant is asleep in a completely darkened room. It is interesting to note that young infants with ocular opacities (like cataracts) do not appear to mind total light occlusion and, in fact, tolerate the bilateral patching extremely well.
The role of bilateral patching in patients with congenital cataracts remains controversial. Bilateral patching should be used in infants with unilateral or bilateral congenital cataracts as a temporary measure to prevent amblyopia until a clear retinal image can be established in both eyes. Because bilateral patching extends the critical period of visual development, only visually immature infants should be patched; that is, those under four months of age. In general, bilateral patching should not be continued longer than two weeks unless absolutely necessary, as the effects of long-term total light occlusion in humans have not been well defined. Bilateral patching is not recommended in cases of unilateral congenital cataracts if the visual prognosis is poor, such as in patients with significant macular or optic nerve problems. It does not make sense to delay visual development of the "good eye" if there is no chance for central vision in the eye with the cataract.
Partial Cataracts
When a child presents with a partial cataract, it is often difficult to determine whether this cataract is truly visually significant. Clinical evaluation should be tailored to the child’s age and ability to cooperate with visual acuity testing. Because of the difficulty in examining young children, the decision of whether or not to operate should be based on a compilation of multiple findings, rather than an individual test. Most often, partial cataracts at birth are not significant enough to interfere in the normal visual development. Small, partial cataracts of less than 3mm or peri-central cataracts can be managed with observation. These patients are usually followed for many years before surgery is necessary. In some cases, the cataract never worsens and patients go through life with the cataract intact. If the opacity is such that an examination determines that visual development will not occur during the first few months of life, then vision will be poor if surgery is not performed immediately and vision is rehabilitated through contact lenses or spectacles. If a patient with a cataract has straight eyes, this indicates that the cataract was only partially obstructing the visual axis during the critical period of visual development, and there is usually a relatively good visual prognosis.
Management of Pediatric Cataracts
Amblyopia is the most common cause of poor vision associated with congenital and infantile cataracts. A unilateral or bilateral blurred retinal image during this critical period will result in irreversible amblyopia. Most authorities now agree that visually significant unilateral or bilateral congenital cataracts should be removed and appropriate correction provided as soon as possible, ideally during the first week of life. Very early visual rehabilitation can result in good visual acuity and fusion with stereopsis, even in patients with unilateral congenital cataracts. Newborn nursery screening of every neonate with the red reflex test is essential in order to identify congenital cataracts before irreversible amblyopia occurs.
The earlier the onset and the longer the duration of the cataract, the worse the prognosis. Acquired cataracts have a much better prognosis for visual acuity and binocular function than congenital cataracts. Visual rehabilitation of patients with truly congenital cataracts necessitates aggressive occlusion therapy, and virtually all patients will have strabismus and lack binocular fusion. Children with bilateral cataracts and sensory nystagmus generally have a poor visual prognosis, but, in some cases, even late surgery can damp the nystagmus and significantly improve visual acuity.
Intraocular Lens (IOL) Implantation
The management of pediatric aphakia depends on many factors including the age of the child, the family situation, and the state of the cornea. Dr. Wright currently recommends considering IOL implantation in patients who are one year or older, and IOL implantation is the procedure of choice in children 2 years and older. With the very young infants under 1 year of age, the use of intraocular lenses is not recommended, and the patient remains aphakic. This means that the infant is without a lens inside the eye because the cataract lens is removed but not replaced.
Contact Lenses
The use of aphakic contact lenses continue to be the treatment of choice for congenital cataracts in neonates, while an IOL is preferred for children over one year of age. These lenses must be fit as soon as the patient heals from the cataract surgery. It requires a serious commitment on the part of the parent or guardians to insert and remove the lenses on a regular basis and make sure the child is not without correction during any waking hours.
Aphakic spectacles continue to be useful in children who are contact lens intolerant or as back-up to contact lenses in patients with bilateral aphakia. Aphakic spectacles are not the treatment of choice for infants with unilateral or bilateral aphakia, as infants do not tolerate spectacles well and they require a clear retinal image 100% of the time to stimulate visual development. Because unilateral aphakic spectacles disrupt binocular fusion, this treatment should not be used on children with binocular fusion potential.
However, unilateral aphakic spectacles and patching of the good eye can be used to improve vision in children with strabismus and no binocular function. It is important to use a high index of refraction lens to diminish the weight and size of the aphakic spectacle lenses.
