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Every minute of the day a child is born blind or acquires blindness, with most cases of blindness occurring in developing nations.1 The excess in prevalence of childhood blindness in the poorest regions of the world is caused by many factors. Vitamin A deficiency and measles lead to corneal scarring; inadequate vaccination programmes result in high rates of congenital rubella and acquired rubeola; and inadequate treatment programmes allow manageable disorders such as congenital glaucoma and retinopathy of prematurity to damage vision. Many of these causes of blindness could be avoided or treated with proper resources.
One of the most common and avoidable causes of blindness in children in the developing world is cataract.2 Experience of treating childhood cataract in the United States is illuminating in this regard. Cataract ranked as a leading cause of childhood blindness in the USA 40 years ago,3 but with modern surgical techniques, improved diagnostic programmes, and rubella vaccination programmes cataract is now an uncommon cause of childhood blindness. Unfortunately, superimposing successful cataract management programmes from well to do regions onto poor regions is not so simple. The task of surgical and postoperative management of aphakia is particularly daunting. Glasses are easily lost and contact lens use is virtually impossible, leaving aphakic children with blurred vision during a critical period of visual development.
In this month's issue of the BJO (p 267), Yorston and colleagues report their experience using intraocular lenses for childhood cataract in east Africa, where cataracts rank as the leading cause of paediatric blindness. The majority of children (76%) were blind preceding surgery, and 42% had “sensory” nystagmus. With implantation of an intraocular lens (IOL) at the time of surgery, 44% had visual acuity of 6/18 or better and 91% had corrected acuity of 6/60 or better. The authors had success with several types of IOL and with capsular or sulcus fixation. The results of this study allow new optimism for those who manage paediatric cataract in poor regions of the world. For those practising in developed regions, there are important and cautionary lessons as well.
The first note of caution is sounded by the occurrence of severe fibrinous uveitis in 30% of cases, with sulcusor capsular placement of the IOL. In five children this resulted in a fibrinous membrane that required further surgery. Distorted pupils also occurred in a few children and may have been caused by uveitis. Since follow up in this study was short (3 months in most cases), we do not know the long term ramifications of severe uveitis. In a developing region, uveitis seems a reasonable risk when no aphakia management option other than an IOL is available. In a developed region where contact lenses and glasses are an option, an incidence of 30% is alarming.
A second lesson comes from the group's experience with amblyopia. Children operated before the age of 2 were more likely to have amblyopia, presumably because their cataracts were visually significant during a critical period of visual development. Esotropia was also more likely to occur in the younger children with cataracts. Successful surgical management loses much of its significance if amblyopia is not managed properly. It is not enough to provide expert surgical care to young children. An understanding of the diagnosis and management of amblyopia is equally important.
Biometry was an important aid to surgery in this study. When used, it nearly halved the postoperative refractive error, on average. Most patients were left with hyperopia, which showed a trend towards emmetropisation with time. But if replacement of glasses and contact lenses is a priority in developing regions, the argument could be made that amblyopia would be better avoided if the patient were left emmetropic or even slightly myopic. Then the child would have a usable focal distance, thereby ensuring better visual development without correction.
Intraoperative management often included removal of the posterior capsule and sulcus placement of the IOL, in this study. Postoperative management of the posterior capsule is problematic for a number of reasons in any region of the world: the young, awake child's posterior capsule may pose a formidable laser target; posterior capsule opacification often includes thickening, requiring higher laser energy; and posterior capsule scarring may recur, necessitating additional treatment.
The authors' experience teaches us an important lesson in neurophysiology. In most children where nystagmus had developed as a result of cataracts, it disappeared after treatment. The developing ocular motor system acquires nystagmus as the result of inadequate afferent input in early childhood, but well timed removal of the sensory defect evidently allows recovery and steady visual fixation. In regions where direct ophthalmoscopy is unavailable, or when cataracts are developmental and not easily identified, nystagmus might be a useful marker of ocular defects. Prompt correction of the defect will promote ocular motor stability, a sign of vision rehabilitation.
The future of any society is its children. The renewed goals of the World Health Organization (WHO) to improve the care of children with blindness and vision impairment is especially prescient, since childhood blindness almost equals adult blindness when measured in blind years of life.1 Childhood blindness significantly shortens life expectancy and imposes an enormous economic, psychological, and social hardship on its victims. The results reported in this month's issue of the BJO truly have global implications for children. For those caring for children in underdeveloped regions where glasses and contact lenses are not available, IOLs seem a reasonable option, but an option not without risk. And for those caring for children in developed regions, surgeons should carefully consider the side effects of IOLs reported in this study.
Supported by NEI grant 00384.