Pediatric Aphakia : A Team Approach Ophthalmic Rehabilitation

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Author: Dr. Sanjeev Bhattarai

Assistant Professor, Department of Ophthalmology, 
Maharajgunj Medical Campus, Institute of Medicine, 
Maharajgunj, Kathmandu, Nepal.

Contact Number: 9841509323.

**Disclaimer: Views expressed in the submitted article are my own and not an official position of the institution or any funder.
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Review Article

Abstract:

Management of aphakia and timely rehabilitation is very important to preserve the ability to see clearly. Only about 50% of eyes with unilateral infantile cataract will develop vision of better than 20/200. Amblyopia is usually common with unilateral infantile cataract. The age at which the treatments for pediatric aphakia initiated is important as the recent studies show that earlier treatment would provide a better visual outcome .In both unilateral and bilateral aphakia constant monitoring is necessary to prevent the onset of amblyopia, strabismus, nystagmus and other aphakia related complications later in life. The optical correction of monocular aphakia in children is a challenge mainly due to diplopia and aniseikonia. In a case with monocular aphakia, contact lens is the best option immediately after the postoperative period to avoid stimulus deprivation amblyopia. The suitable contact lens options include Silicone hydrogel, Silicone elastomer and rigid gas permeable lenses.

For the maintenance of good corneal health, the contact lens material should be of deposit resistant and high DK value.  Aphakic spectacles are still satisfactory and are alternative means of optical correction in bilateral aphakia. But during spectacles dispensing, frame and lens selection with consideration of curve variation factor is crucial. The intra ocular lenses (IOLs) are the preferred options for correcting aphakia in older children after infancy. If aphakia is associated with amblyopia, it should be carried out with patching of the phakic eye along with suitable optical correction placed in aphakic eye. Strabismus is more common in a large number of infants with unilateral cataract. In such cases surgery is delayed until the misalignment between the visual axes is stable and the visual acuity has been optimized. With advancement of technologies, good vision and binocularity may be attained nowadays in great percentage of children following the removal of congenital cataracts.

Key Words: Amblyopia, Aphakia, Congenital cataract, Contact lenses, Infant, Pediatric, Silicone elastomer.

Introduction

Aphakia indicates an ocular condition in which the crystalline lens is absent. It may be congenital but usually it is due to surgical removal of a cataract. An aphakic patient has no accommodative power and typically has high hypermetropia. The main symptom includes focussing difficulties at near and distance objects and faded colour appearance. According to World Health Organization,  pediatric cataracts and subsequently aphakia either unilateral or bilateral are relatively common and  among most treatable causes of childhood blindness In pediatric population the common causes for aphakia are eye injuries, genetics, metabolic disorders, radiation, drugs, retinopathy of prematurity, intrauterine infection in mother etc. The major clinical findings include monocular or binocular lack of crystalline lenses, irregularity of pupil as an unexpected consequence after surgery, opacified peripheral capsular ring, occasional heterochromia of iris, esodeviation or exodeviation particularly in longstanding untreated cases, hyperphoria on the aphakic eye, dissociated vertical deviation, nystagmus and ocular torticollis etc (1, 2).

Examination: Clinical investigation begins with patient’s history. Examination include Objective and Subjective refraction if possible, Kerato-refraction by handheld autokeratorefractometer, Cover uncover test, Hirschberg and Krimsky’s prismatic test, Fixation testing for amblyopia, Ultrasonic axial length measurement, Slit lamp and Fundus examination.(3).

Differential diagnosis:  It includes Anisometropia, Congenital esotropia, congenital lens dislocation, Lens coloboma and Nystagmus. Among them, defective development (coloboma) or even dislocation of lens may mimic that there might be an absence of crystalline lens in the pupillary area. Similarly esotropia and anisometropia with nystagmus might occur due to high hypermetropia as like in pediatric aphakia (4).

Background and Rehabilitation

In children, the eye is still growing and due to aphakia, there will be high hyperopia with some amount of astigmatism. Good postoperative care requires highly motivated parents and coordinated care from ophthalmologists/optometrists. The leading cause of reduced vision in children following cataract surgery is amblyopia which may develop as a consequence of visual deprivation, anisometropia or strabismus. The prognosis will be poor in some infants with unilateral congenital cataract due to delay in treatment or due to poor compliance with contact lens wear or patching therapy. The visual outcome for eyes with infantile onset cataracts depends on factors such as the age at which surgical treatment and visual rehabilitation is initiated and whether the cataracts are unilateral or bilateral. The visual prognosis for bilateral infantile aphakia is much better than for unilateral aphakia due to nearly normal binocular interaction in the bilateral condition. The presence of nystagmus either unilaterally or bilaterally indicates that the vision is affected significantly. The aniseikonia in unilateral aphakia during spectacle wear is around 25% and it is reduced to about 5% in contact lens wear and even 0-2 % in intra ocular lenses (4,3).

Besides contact lenses and IOL implantation, spectacles correction to some extent can help in optical management and rehabilitation of pediatric aphakia. Several authors (5, 6, 7) have mentioned about this modality too when contacts lenses or IOLs can not be applied due to poor compliances or due to contradictions or complications. Proper frame and lens selection, provision of near addition segment along with inter pupillary distance measurement and accurate placement is the vital factors for successful spectacle wear. For children frame should be larger, round in shape, sturdy construction with deep grooves so that lenses are well fitted there. The frame should closely match the eye size and be of non allergic plastic materials. Since the aphakic spectacles and lenses are heavier, nose pads should be larger to minimize scars on the nose. The temple design should be either riding bow or tied with string round the head. The lens selected should be of high index plastics with low weight and good impact resistance. The spectacles should be fitted close to the eye with optimum vertex distance to reduce magnification effect.

A study done by Aasuri et al.(8) to evaluate the performance of Silicone elastomer lenses in pediatric eyes with aphakia suggested that  these lenses are safe ,provide satisfactory optical correction and are easy to handle. They had fitted Silsoft lenses (Elastofilcon A) of Bausch and Lomb Company. All the patients were advised for one week extended wear for six months and lenses were replaced for change of power, lens loss and deposits or damage.  Similar findings were reported in the study of Russell et al. (9) in which a cohort of infants with unilateral aphakia wore contact lenses successfully with relatively few adverse events. In this study, the visual acuity outcomes were identical independent of the contact lens materials or modality but RGP lenses needed replacement more often than a Silicone elastomer lenses. In both lens user groups, the median recorded visual acuity was + 0.80 Log MAR at one year of age. Based on these findings, Russell et al. concluded that with the advancement of techniques, excellent visual results could be obtained with early surgical treatment along with optical correction with a contact lens and patching therapy of the fellow eye.

The American Academy of Pediatrics (10) recommends that the babies with cataracts should have surgery when they are about a month old. Surgery should be done earlier because their eyes and visual milestones develop very quickly. Immediately after the surgery, they will need glasses or special contact lenses to be worn in an extended wear basis. According to the recommendations, babies can receive an artificial lens implant once they are about a year old.  Surgery for older children after one year involves removing the cataractous lens and implanting an artificial lens immediately. In all cases, timely and prompt follow up is very essential as children can develop aphakic complications like glaucoma, retinal detachment and vitreous detachment. American Academy of Pediatrics’ recommendations are in  close harmony with  those from Repka M.X.(11)where the author  pointed  out that the visual rehabilitation of children with unilateral cataract requires a use of contact lenses or an intraocular lenses for the best results with good prognosis for binocularity. For bilateral cataracts, either contact lenses or IOLs or even aphakic glasses can be used for visual rehabilitation post surgery. Amblyopia therapy along with optical correction in unilateral aphakia needs to be continuous from the time of surgery until at least 8 years of age.

A scientific review article from Richard G Lindsay and Jessica T Chi (12) on uses of various designs of contact lenses in the management of infantile aphakia reported that the visual outcomes for infants 18 months or younger with cataracts when detected earlier along with prompt surgical removal might have a successful rehabilitation with contact lenses. Such aphakic cases would have a better visual prognosis. However, during contact lens fitting and assessment proper knowledge about the ocular parameters like corneal curvature and diameter, refractive error of both normal and phakic eyes during the neonatal period and infancy is essential. Though they are cheaper, soft hydrogel lens have a disadvantage when compared to other designs of contact lens as it cause corneal hypoxia due to low oxygen permeability (DK).  The article by Lindsay and Chi also reported that, although better visual outcomes are obtained in bilateral aphakic cases, unilateral infantile cataract if operated earlier and further managed with contact lens can achieve visual acuity better than 6/12.Unfortunately there is a wide variation in visual outcomes in some cases of unilateral infantile cataract ending up with vision of less than 6/60 despite proper management. Alternative to contact lens for correcting aphakia is an intra ocular lens (IOL) in older children, which is means for administering a permanent correction. However, there are some demerits of IOLs in infantile eyes. Infant’s eyes require a small diameter IOL which may lead to refractive issues later in adult life leading to myopic shift. In all conditions of pediatric aphakia, IOLs can not be inserted due to various contradictions like uveitis, corneal endothelial dystrophies, uncontrolled glaucoma or due to developing age factor. The main challenge is due to changes in refraction in the growing eye along with the rapid growth and development of the eye ball. The most critical period for development of the visual system is up to age of two years and the overall development reaches to adult level by the age of six to seven years. Considering the growing eye, IOL can be implanted which has long term safety with no routine care and maintenance unlike contact lenses or even aphakic spectacles. Other possible risks might be posterior capsular opacification, corneal endothelial cell loss and uveitis which should be closely monitored.

The role of Optometrist, Orthoptician and vision therapist is very crucial in the rehabilitation of pediatric aphakia. According to Lindsay and Chi, if a child has developed amblyopia or strabismus  before or after cataract surgery, the child needs amblyopia therapy in the form of patching or penalization with atropine. Both might be equally effective for the treatment of amblyopia (12). But the prognosis of patching therapy is limited as the child gets older. In both modality of treatment care should be given such that the normal eye should not get occlusion amblyopia during the therapy. Most aphakic children will require some patching until about eight years of age. However atropine penalization is not an option if the infant is bilaterally aphakic due to the absence of accommodation in both eyes. Strabismus is more common in a large number of infants with unilateral cataract (12). In such cases, amblyopia therapy is initiated first to increase the quality of vision in the amblyopic eye, giving more opportunity for the retinal images to be fused with some degree of binocularity. Generally, strabismus is delayed until the misalignment between the visual axes is stable and the visual acuity of the amblyopic eye has been optimized. But in case with a relatively large magnitude of esotropia, strabismus surgery may be performed earlier to facilitate contact lens wear so that the cornea is a bit far from nasal canthus. Usually in cases of large esotropia, contact lens is more likely to be dislodged from the eye particularly when the direction of gaze is nasal and lens irritation may be greater due to the lens rubbing against the nasal canthus. The importance of amblyopia therapy should be explained well to the child’s parents for their proper compliance. The infant’s ocular health including IOP should be monitored closely to prevent risk of glaucoma and occlusion amblyopia of sound eye.

The article by Scott R. Lambert (13) reports on amblyopia therapy after unilateral or bilateral cataract surgery in children. Amblyopia is one of the leading causes of reduced vision in aphakic children. Amblyopia might be developed due to visual deprivation, anisometropia or strabismus. Lambert further suggested that progressive patching regimens may help to preserve the binocularity of children following unilateral cataract surgery. Even excellent visual outcomes could also be achieved in children with bilateral congenital cataract if cataract surgery and optical corrections are initiated prior to the onset of nystagmus. Again constant monitoring is necessary to treat and prevent amblyopia and other aphakia related complications.

Regarding management of pediatric aphakia, Jagat Ram and Jaspreet Sukhija  in their book Pediatric Cataract Management (14) highlighted the role of proper refractive correction and lattest new design IOLs for its corrective modalities. The new designs IOLs include hydrogel, silicone and foldable acrylics. Refractive correction should be done as soon as inflammation subsides and prescription based on the age of the child should be given in the form of bifocal lenses or contact lenses in aphakic eye along with patching therapy in the sound eye. The IOLs should be of better visco elastic materials with appropriate size and design. Their view is also supported from a research article from Kirti Singh and Sonal Dangda (15) in which the authors recommended that management of aphakic children is critical and timely rehabilitation is very important to preserve the vision. Contact lenses both soft and rigid gas permeable could be extremely effective means of visual rehabilitation in aphakic children with compliance of wear and follow up being most important to achieve and maintain good visual acuity gain. They advised that for unilateral aphakes during the interim period while waiting for a secondary IOL to be implanted, the contact lenses remain the only effective option prevent stimulus deprivation amblyopia.

Conclusion:  The management of infantile aphakia has improved dramatically over recent years. Early cataract detection and prompt surgical management at the appropriate time along with advances in contact lens fitting technologies and availabilities have greatly contributed for the good visual prognosis in children. The best optical device in a case of monocular aphakia is contact lenses along with occlusion of the normal eye. But for bilateral aphakia, spectacles are alternative optical correction despite poor cosmesis and compliance. While the contact lens management in infantile aphakia is very challenging, it is rewarding too as the optical benefits to the patients are immeasurable.

Photo mero eye

Author: Dr. Sanjeev Bhattarai

Assistant Professor, Department of Ophthalmology, 
Maharajgunj Medical Campus, Institute of Medicine, 
Maharajgunj, Kathmandu, Nepal.

Contact Number: 9841509323.

References:

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