Although cataract surgery for adults is a routine procedure around the world, the same cannot be said for pediatric cataract. Surgery in children can be complex and challenging, not simply, of course, because cataracts obscure the image received by the retina but because the retinal deprivation retards the development of the visual pathway, possibly leading to an intractable form of amblyopia.
Worldwide, cataracts are one of the most important causes of blindness in children and one of the most preventable causes of lifelong visual impairment. Visual loss from untreated cataract is uncommon in Western countries but is still problematic in some developing nations.
A Chilean Cohort
One ophthalmologist on the front lines of research into the cause of congenital cataracts is J. Bronwyn Bateman, MD, a geneticist and professor of ophthalmology at the University of Colorado in Denver. Over the past 15 years, Dr. Bateman has studied more than 50 large, multigenerational families in Latin America to isolate the genetic causes of cataracts and to catalog their characteristics. Through this work she identified a new locus for autosomal dominant cataract on chromosome 19. Most recently, she has been interested in the clinical variability of cataracts among a cohort of Chilean families that manifests pediatric cataracts inherited in an autosomal dominant pattern.
Same mutation, various presentations. In a paper soon to be published in the American Journal of Medical Genetics, Dr. Bateman and her colleagues studied 28 individuals from four generations of a Chilean family with a high incidence of congenital cataracts. Thirteen of the family members had cataracts caused by mutations in the CRYAA crystalline lens gene, but clinically the cataracts varied widely and exhibited some novel features. “What we were seeing was enormous variability in the clinical features of the cataracts, including the age at diagnosis, the natural history of the cataract and how it affected the development of vision,” Dr. Bateman said. “When you have a large family with hereditary cataracts, such as those we worked with in Chile, you can trace the polymorphic DNA markers through the family and see which markers are inherited with the cataract.”
Grateful Patients and Patient Chickens
Although many had limited economic resources, Dr. Bateman’s patients in Chile were often willing to travel for several hours to meet with her. “The patients I’ve worked with in Chile are very concerned about the reasons why people have this disease. As well as wanting to help their family members, they want to help society by participating in this research project.”
Dr. Bateman, who speaks Spanish, got to know some of the Chilean families quite well through her work. “Often they would have a family reunion while they met with us.”
On one recent trip involving the families’ blood samples, she tangled with the Chilean police. Dr. Bateman had arrived at the local airport in Concepción, where she was doing her research, to take a flight to Santiago to meet with ophthalmologists there. In her carry-on bag she had the blood specimens of the families she had been working with in Concepción. When the airport officials heard of blood in her luggage, they told her the specimens would need to travel in the luggage compartment rather than under her seat. Concerned that the tubes might rupture, Dr. Bateman instead decided to take the local bus to Santiago—a five-hour trip. As she sat holding the blood samples, the man sitting next to her held a chicken. “He was very nice,” Dr. Bateman said. “He helped me with my Spanish verb conjugations!”
Some of the Chilean patients have not had their cataracts removed, although the surgery is provided free of charge in Chile. “Many of the families are very poor. Although some are treated with cataract extraction, a lot of them are afraid of the surgery and don’t want to undergo it,” said Fernando Barria, MD. Dr. Barria is an assistant professor of ophthalmology at the Universidad de Concepción and is on the ophthalmology staff at the Hospital Clinico Regional de Concepción Guillermo Grant Benavente. “But often, when the family members see the results of these surgeries, those who had been unwilling before decide to have the surgery,” he said.
When to wait, when to act. Dr. Bateman noted that resolution of infantile cataracts often depends on individual characteristics of the patient. “If the cataract is particularly dense and obstructs vision, then you want to surgically remove it early in life,” she said. However, she said that some people with hereditary cataracts can do quite well without surgery. Some patients she met in Chile did not have their cataracts removed until the age of 30.
Underlying systemic disease? Congenital cataracts can be unilateral or bilateral. “When bilateral, an examination of the parents may help determine if the cataracts are genetic,” said M. Edward Wilson Jr., MD, professor and chairman of ophthalmology at the Medical University of South Carolina in Charleston. Dr. Wilson practices pediatric ophthalmology with an emphasis on cataract. “It’s important to look for a cause if the cataracts are bilateral because if the cause is metabolic, then other specialists may need to be called in to treat the underlying disease,” he said.
Dr. Bateman explained that cataract surgery for children is quite different from that for adults. Although cataract extraction can be done when a child is several weeks old, she said, “You have to take into account how the eye and the vision will develop as the child ages in deciding when to do surgery,” she said.
Dr. Wilson agreed. In kids, he said, the eye is still growing. As the eye becomes longer front to back, the lens changes its shape to adapt. “However, when we remove the lens, that natural progression disappears, and we have to decide if we will make the eye farsighted, so that as it grows the child will have as near-to-normal vision as possible, or instead fix the eye with the proper lens at a young age, and anticipate that the child will become nearsighted as he or she gets older—a problem that will need to be corrected later with lenses,” he said. Put another way, removing the lens will leave a refractive error and surgically induced presbyopia. “So we want to think carefully before we create premature presbyopia. Often whether we do cataract surgery will depend on the amount of visual trouble the child is having with the cataract. A mild cataract may not be worth sacrificing accommodation,” Dr. Wilson said.
How to avoid amblyopia. If the patient has a cataract in only one eye and already has severe amblyopia, the most pressing need might be to rehabilitate the eye right away. In this case, the best choice, again, might be a lens with the proper correction, anticipating nearsightedness later on, Dr. Wilson said. “However, if the cataract is in both eyes and there’s no amblyopia, we might decide to have the child be somewhat farsighted. It’s all a question of whether you want to have thicker glasses now to avoid thicker glasses later,” he said.
Dr. Wilson noted that some infantile cataracts worsen over time and some don’t. If the cataract is a dense nuclear opacity present at birth, surgery is best done at 4 to 6 weeks of age, he said. “If you delay longer there may be more amblyopia, which will become more and more difficult to reverse over time,” he said. However, lamellar cortical cataracts, which are also often genetic, tend to appear after birth and progress more slowly, he said.
How to manage the surgery. The treatment of cataracts in children is more serious than in adults because children have to be put under general anesthesia for cataract surgery. So the timing for cataract removal in a child is often an issue that needs to be analyzed and discussed with the parents.
Dr. Wilson said that while adult cataracts are usually hard and brittle, those in children are often soft and gummy. “So they can be removed with aspiration alone,” he said. “Another major difference in children is the way we handle the posterior capsule. In children from birth to about 6 years of age, I perform a primary posterior capsulectomy and anterior vitrectomy. My preferred method is to first place the IOL in the capsular bag with the posterior capsule intact. I then remove the viscoelastic from the eye. With the irrigation cannula remaining in the anterior chamber, I make a single microvitreoretinal stab incision through the pars plana and place the vitrectomy hand piece through the incision. I remove the central 4.5 mm of posterior capsule with the vitrector and then perform enough of a vitrectomy so that cells that grow out from the equator of the remaining lens capsule cannot use the childhood vitreous face as a scaffolding. This approach is needed, at times, even in older children who have a posterior capsular plaque or those who will not cooperate for a YAG laser capsulotomy, or those older children whose YAG capsulotomy closes spontaneously after it is successfully opened.”
The cataract of the future. “Understanding the genes that cause these cataracts can help reduce blindness in children,” Dr. Bateman said. “It may even be helpful, one day, in predicting who will get age-related cataracts.” None of the physicians interviewed report financial interests related to this story.