Bilateral congenital cataract is the most common cause of treatable childhood blindness. Prompt surgery must be performed in cases with dense congenital cataract. If nystagmus has developed, the amblyopia is unfortunately irreversible. Nuclear cataract is usually present at birth and is nonprogressive (Figure 1), whereas lamellar cataract usually develops later and is progressive (Figure 2).
In infants with bilateral cataracts, performing surgery in both eyes in one surgical intervention is advantageous. In older children, amblyopia does not develop as quickly, and it is possible to perform two separate surgeries, months apart. In the developed world, most surgeries in children are performed during general narcosis. In developing countries with scare resources, an effective form of narcosis called neurolept anesthesia—a combination of ketamine, atropine, and benzodiazepine—is given intravenously, followed by a peribulbar injection of anesthesia.
During cataract surgery in children, creating a long sclerocorneal tunnel avoids anterior synechia formation to the wound. A high-viscosity ocular viscosurgical device (OVD) is preferable, because the anterior chamber is often shallow and has high vitreous pressure. For a small pupil, a common occurrence in eyes with congenital cataract, flexible iris retractors may be helpful. If the cataract is very dense and grey, staining the anterior capsule with dye makes the anterior capsulorrhexis easier and safer to perform. The dye is administered with a blunt syringe under the OVD and just above the anterior capsule and painted on the capsule with the end of the syringe. A small amount of dye is needed, and just the capsule is stained. Remember to keep the small amount of dye it away from the corneal endothelium, because the dye affects the density and cell viability.
PREEXISTING POSTERIOR CAPSULE DEFECT
When implanting an IOL, the anterior capsulorrhexis should be round, smaller than the optic, and placed in the center of the capsule. Corticocleaving hydrodissection must be performed with caution, or in some cases (eg, eyes with preexisting weakness or defect in the posterior capsule, eyes after trauma), avoided altogether.
A preexisting posterior capsule defect in cases with congenital cataract is a challenge to the surgeon, and it is important to detect before the surgery.1 This developmental disorder is more common in Asia than in Europe. Cataract associated with posterior lenticonus or posterior lentiglobus is usually unilateral, and the posterior capsule is thin and fragile. Therefore, perform hydrodissection with great caution. In most cases, it is possible to remove the nucleus and cortex with I/A. In the presence of very dense nuclear cataracts, and when white calcified parts are lodged in the nucleus, however, ultrasound is needed. AquaLase liquefaction (Alcon Laboratories, Inc., Fort Worth, Texas) with a warm-water stream is useful to remove these dense cataracts. It is important to remove all lens material to minimize postoperative inflammation, which is pronounced in the youngest patients. To reduce opacification of the visual axis after surgery, removal of most lens epithelial cells is important, however, it is almost impossible with the techniques routinely used today.
POSTERIOR CONTINUOUS CAPSULORRHEXIS
To diminish posterior capsule opacification in children, perform a posterior capsulorrhexis. High-viscosity OVD is injected to fill the capsular bag, and a posterior continuous capsulorrhexis is performed with a cystotome and completed with forceps by frequently grasping and regrasping the flap. The posterior capsule is thinner than the anterior; it is not as elastic. Fibrotic parts may be found in the posterior capsule, making tearing impossible. Scissors must be used. It is wise to look for persistent fetal vasculatures, particularly in unilateral cases with posterior cataract.
Persistent hyaloid artery adheres to the posterior aspect of the lens and optic disc. If present, it should be cut with fine scissors. Sometimes, the vessel contains blood, but cautery is seldomly indicated. With this method, it is possible to implant an IOL into the capsular bag. Capsular fixation is preferred over ciliary sulcus placement, because complications such as pupillary capture and IOL decentration are more common with ciliary sulcus fixation.
PRESCHOOL-AGE CHILDREN
An anterior vitectomy should be performed in preschool-age children to diminish visual axis opacification.2 Performed through the main incision, the OVD is left in the anterior part of the eye after IOL implantation, and the IOL is moved with the second instrument. A dry anterior vitrectomy is preferred. When the anterior vitreous is removed, the lens epithelial cells most often cannot grow on the remaining vitreous.
Another surgical technique involves performing an optic capture; the IOL is then pressed through the posterior capsulorrhexis, while the haptics remain in the bag. Optic capture—in the anterior and posterior capsulorrhexis—is a great technique, providing a good centration of the IOL. Good centration is necessary in cases after trauma or an incomplete capsulorrhexis. This technique may not fully prevent the formation of after-cataract, however.
Optic capture through the anterior capsule may also be performed when the IOL is implanted in the sulcus for better IOL centration. Optic capture is hard or impossible to perform with the single-piece IOL, because the haptics are not angulated.
The sclera is soft and elastic in children, and a self-sealing incision is hard to achieve in most cases; use of a long tunnel may help. Thus, the incision should be closed with a running or horizontal 10-0 nylon or thin vicryl suture. Iridectomy is not necessary in these eyes, not even if they are left aphakic.
To avoid endophthalmitis, prophylactic antibiotics are usually recommended. Perioperatively, 1 mg of cefuroxime in 0.1 mL saline 0.9% is injected into the anterior chamber. This regimen effectively prevents gram-positive bacteria, which is by far the most common bacteria.
Antiinflammatory treatment should start early after surgery, and a perioperative subconjunctival injection of 2 mg steroid (Betapred; Swedish Orphan, Stockholm, Sweden) is recommended after surgery, at least in the youngest patients.
Postoperatively, a child's eye may react with more inflammation than the adult eye, particularly in darkly pigmented eyes. Systemic treatment with glucocorticoids is indicated in children with uveitis. Start topical treatment with dexamethasone 0.1% immediately following surgery. In the newborn, treatment should be intense, starting with eight to 10 times daily and tapering over 2 months to 3 months. In the youngest eyes and in eyes with dark-brown irides, mydriatic drops are administered for several weeks after surgery.
POSTSURGICAL PATCHING
The use of a protective patch is not necessary after surgery, although I have not seen any disadvantages with this regimen. On the contrary, the child immediately starts amblyopia treatment, and parents are very pleased that they are able to establish visual interaction with the child soon after surgery.
At what age is it safe to implant an IOL? Today, with modern techniques and IOLs, it is perfectly safe and acceptable to carry out a primary IOL implantation from the age of 1 year, even in both eyes simultaneously. Personally, I conduct bilateral implants in infants as young as 2 months to 4 months old. Regardless of age, I implant an IOL in almost all children if the cataract is unilateral, even though there is no available IOL that really fits the small newborn eye.
Aiming for close to emmetropia at surgery is most appropriate, because of the threat of amblyopia in unilateral cases. The remaining hyperopia may be corrected with contact lenses. In bilateral cases, the goal is to start with hypermetropia in childhood that will convert into adulthood emmetropia.
What IOL do you implant? This is another important question. A foldable acrylic hydrophobic IOL implanted in the young eye allows fewer complications and has, at least in the developed world, replaced the PMMA IOL. The PMMA IOL is still the most commonly used IOL in developing countries; it is the cheapest. A yellow-filter IOL that removes harmful blue light is probably most advantageous for the pigment epithelium and the retina in the pediatric eye.
COMMON COMPLICATIONS
Opacification of the visual axis is the most common complication found after cataract surgery in children, particularly in the youngest patients. Even when a posterior capsulorrhexis and a dry anterior vitrectomy are performed, lens epithelial cell growth—on the vitreous surface or on the back of the optic—may be found several months after surgery (Figure 3). An IOL implanted in the bag will decrease or prevent formation of Soemmering's ring, but it is then easier for the epithelial cells to migrate from the periphery to the center of the pupil. After-cataract with membrane formation is an unsolved problem in infants after IOL implantation, and sometimes several interventions are needed. A promising device to fight visual axis opacification in children is the perfect capsule (Figure 4). A sealed system is created, and the empty lens capsule bag can be rinsed with an antimetabolite, such as 5 fluorouracil.3
Secondary glaucoma is a common complication and the most sight-threatening. The highest incidence is found in infants younger than 2 months who underwent surgery. Eyes with small corneal size, nuclear cataract, or persistent fetal vasculature are at greatest risk. IOL implantation into the capsular bag seems to inhibit the development of secondary glaucoma. Postoperative inflammation is also an important factor.4
It is important to remember that when cataract surgery has been performed during the first months of life, intraocular pressure and optic nerves require life-long control.
Visual outcome following cataract surgery depends on (1) the age of onset, (2) whether the cataract is uni- or bilateral, (3) the type of cataract, (4) preexisting ocular abnormalities or diseases, (5) complications following the surgery, and (6) the outcome of amblyopia treatment. Late onset of the cataract, as in developmental or traumatic cataracts, is an important factor and has better visual prognosis than dense congenital cataract. Good visual outcome is also often found in bilateral congenital cases, if the surgery has been performed before the age of 2 months to 3 months and no serious complications have occurred.
Charlotta Zetterström, MD, PhD, is a Professor at the UllevÂl University Hospital, University of Oslo, in Norway. Dr. Zetterström states that she has no financial interest in the products or companies mentioned. She may be reached at charlotta.zetterstrom@medisin.uio.no.
Up Front | Mar 2007
Update on Pediatric Cataract Surgery
Lifelong control of intraocular pressure and the optic nerve are necessary when cataract surgery is performed during the first months of life.
Charlotta Zetterström, MD, PhD
