Diagnosis of cataracts

A critical first step in the optimal management of pediatric cataracts is early recognition of the problem. Diagnosis is often first made by family members or primary care physicians who notice a white or partially white pupil in one or both eyes (leukocoria). Careful examination of the red reflex of both eyes using a direct ophthalmoscope (Bruckner test) can usually detect even the most minor of lens opacities. Asymmetry of the red reflex in a child of any age should raise concern for cataract or other ocular abnormalities and warrants prompt referral to an ophthalmologist. Strabismus (usually in unilateral cases) or nystagmus (usually in bilateral cases) may also be the presenting sign of childhood cataracts. The onset of nystagmus is generally considered a poor prognostic sign for achieving good visual outcomes.28

Careful evaluation of the medical and family history of patients with childhood cataracts, along with evaluation of the opacity and other associated ocular and systemic abnormalities, can often lead the clinician to elicit the etiology. If other dysmorphic features are present, consultation with a geneticist should be considered. When the etiology cannot be determined, further laboratory testing may be indicated. In the case of unilateral cataracts, TORCHS titers (IgM) and Venereal disease Research Laboratory (VDRL) for syphilis is all that is generally necessary. If bilateral, urine should be tested for reducing substances (after milk-feeding). Additional optional testing includes calcium and phosphorus levels, red cell galactokinase level, and urine for amino acids.4,5

Management/treatment of cataracts

Visual significance

Determination of the visual significance of a particular lens opacity is an important step to help guide treatment. In neonates, this evaluation can at times be especially challenging. Streak retinoscopy and view of the ocular fundus using a direct ophthalmoscope can give the ophthalmologist a good sense of the visual significance. Careful examination of the particular characteristics and morphology of the

cataract is also important. In general, opacities in the visual axis >3 mm can be assumed to be significant. Posterior opacities and confluent opacities (without intervening clear zones) also tend to be more visually significant. If surgical intervention is deemed necessary in a neonate, timing of such intervention is critical to help maximize visual outcomes. When possible, this

should take place before 6 weeks of age in unilateral cases and 8 weeks if bilateral.29,30

Surgery should occur even earlier when possible. Such early intervention can lead to good visual acuities and binocular function.31

In older preverbal children, careful assessment of fixation preference and other visual behaviors can be a reliable indicator of visual deficits. The use of special tests, such as pattern visually evoked potentials and the preferential looking test (Teller acuity cards), may be effective tools to help determine levels of reduced vision and are especially useful in determining interocular differences in vision.

In verbal children, acuity can be accurately assessed using various optotypes (Allen figures, tumbling E chart, HOTV matching, or Snellen letters). There still remains the challenge, however, of determining at what level of visual deficit is surgery indicated. Most would agree that cataracts causing a reduction in visual acuity beyond 20/70 require surgery.5 Some feel that vision of 20/50 or less is a more appropriate cutoff for surgical intervention.32

Opacities that are not visually significant can usually be carefully observed over time to monitor for signs of progression or development of amblyopia. Anisometropia (difference in refractive error) is common and should be corrected optically with glasses or contacts. In some cases, amblyopia from anisometropia may be more significant than the cataract itself. Aggressive treatment of the anisometropic amblyopia is indicated prior to considering cataract surgery in these instances. Opacities that are only mildly visually significant can often be managed conservatively. If unilateral or asymmetric, patching the better eye, in addition to optical correction, can be effective at preventing or treating amblyopia.

Surgery

Surgical management of pediatric cataracts differs significantly from that of senile cataracts. Senile cataracts generally have a hard nucleus that requires phacoemulsification (ultrasonic removal) or an extracapsular (manual expression) technique to remove. Pediatric cataracts, in contrast, are much softer and can be removed by aspiration either with vitrectomy instrumentation (allowing aspiration and cutting of any fibrotic lens material) or with aspiration instrumentation only. The surgical technique may involve a posterior approach (from behind the lens) through the pars plana, or an anterior

approach (in front of the lens) through the limbus or clear cornea. The anterior approach has become the preferred method of most pediatric ophthalmologists.5,33

The central portion of the anterior capsule is first removed and the lens material is then aspirated. If an intraocular lens (IOL) is to be inserted, it is then placed in the capsular bag (126–133). Currently, foldable acrylic IOLs are preferred by most surgeons, but rigid polymethylmethacrylate (PMMA) lenses are also used. Foldable silicone IOLs are rarely used in the pediatric population.34

The long-term safety of placing an IOL has become increasingly well established. However, the earliest age at which to begin implanting IOLs has not. The decision of whether to place an IOL is controversial in children under 2 years of age, and especially in the first few months of life. Some surgeons advocate IOL placement in nearly all cases, whereas others believe the youngest patients should initially be left aphakic and treated with contact lenses or aphakic spectacles. The primary concerns for IOL placement in infants are increased postoperative inflammation, increased risk of needing one or more reoperations, and difficulty in calculating the ideal IOL power to implant due to the dramatic lens power changes that occur over the first year of life.

If left intact, opacification of the posterior capsule after lensectomy occurs in nearly all pediatric patients (134). The decision whether to remove the central posterior capsule and perform anterior vitrectomy at the same time as the initial cataract surgery is also age dependent and somewhat controversial. Experts currently recommend performing primary posterior capsulotomy with anterior vitrectomy in most patients under 5 years of age and consider this an optional step in older patients. A secondary posterior capsulotomy may be performed with the use of a slit-lamp mounted YAG laser if the patient is able to cooperate with the procedure. However, up to one-third will close

spontaneously if performed in children under 6 years, forming a secondary membrane.33 A traditional surgical posterior capsulotomy with anterior vitrectomy may also be performed if the opacification is too dense or if the patient is uncooperative with the YAG laser procedure.

Aphakia

Aphakic eyes are generally extremely hyperopic and require optical correction. In most cases, infantile aphakia is best treated with contact lenses. They should be placed as soon as possible postoperatively and almost always within the first week. The lens power should overcorrect infants by +1.00 to +3.00 diopters to create clear near vision. Once the natural lens of an eye is removed, accommodation is lost. Therefore, bifocal spectacles are used over the contacts after the age of 2–4 years. Bilateral aphakic spectacles can also be used in contact lens intolerant children or as a backup to contacts (135). Unilateral aphakia should not be managed with spectacles unless there is no binocular fusion potential. This is because the magnification caused by unilateral aphakic spectacles creates unequal retinal image sizes and disrupts binocular fusion. In these cases, extensive patching of the sound eye is often necessary to promote proper visual development in the aphakic eye.

135 Aphakic spectacles on a 5-year-old who underwent bilateral lensectomies for autosomal dominant lens subluxation.

136 Patching of the better seeing left eye in the same patient from Figure 135.

Pseudophakia

Even when an IOL is placed (either at the time of initial surgery, or secondarily), additional optical correction is usually required. This is because postoperatively there is generally residual hyperopia with or without astigmatism. Eyes are frequently deliberately left with a variable amount of hyperopia due to the anticipated myopic shift which occurs as the eye continues to grow throughout development. Several reports have been published establishing the ideal amount of residual

hyperopia to target, based on the specific age at which the IOL is placed.35–37 Depending on

the age and level of cooperation of the child, the additional optical correction may be achieved by the use of either spectacles or contact lenses. If tolerated, spectacles are the ideal choice since they allow for the use of bifocals, which are necessary for attaining both near and distance optical correction. Some experts recommend aiming for emmetropia in the case of unilateral cataracts even in very young children.5 This recommendation is based on the premise that the success rate of amblyopia treatment is higher in an emmetropic eye than in one that requires additional optical correction early on. Multifocal IOLs have been used on a limited basis in an attempt to eliminate the need for lifelong bifocal spectacle dependence. Additional studies are necessary to establish better their role in the pediatric population.

Amblyopia

Once proper optical correction has been achieved, patching constitutes the mainstay of amblyopia treatment. In unilateral (or bilateral asymmetric) congenital cataracts, the degree of amblyopia is highly dependent on the severity of lens opacity and the age at which the lens is removed. Patching regimens may vary with both age and level of amblyopia (136). Recommendations may be as little as 1–2 hours per day or as much as 50% or more of the waking hours. Visual development continues throughout childhood until approximately age

8–9 years and the risk of amblyopia continues through that age as well.5,38 It is not

uncommon to maintain some level of patching until children reach this age in order to achieve and maintain maximal visual potential. In the case of acquired cataracts, amblyopia may not be as severe, but is dependent on the duration and degree of opacity. In the case of equal bilateral amblyopia, appropriate optical correction may be all that is required. If visual acuity is equal, patching is generally not recommended unless strabismus is present, in which case strabismus surgery is often required.