Sherwin J. Isenberg and Leonard Apt
Approximately 500,000 children become blind worldwide each year. This figure represents one new case of pediatric blindness every minute. It has been estimated that today there are 1,400,000 blind children in the world,1 and many of these children will not survive beyond 2 years of age. While 1,000,000 are considered untreatable by current standards due to retinal dystrophy, microphthalmos, cortical blindness, and optic atrophy or hypoplasia, the remaining 400,000 cases are potentially treatable. The main avoidable causes are corneal scarring from infection or trauma (260,000), cataract (50,000), and retinopathy of prematurity (ROP; 40,000).2 Other treatable blinding conditions include amblyopia and uncorrected refractive error. Much of the data concerning causes of pediatric blindness in developing countries come from studies of children attending schools for the blind. This information may represent a bias, since data from children not attending these schools would not be included.
In developed areas, the main causes of pediatric blindness are ROP, perinatal hypoxic brain injury, optic nerve hypoplasia, inherited retinal dystrophies, congenital anomalies, cataract, and glaucoma. These disorders are largely not preventable, but some are treatable. Geographically, 90% of all pediatric blindness (1,300,000) occurs in developing countries with 24% in Africa, 20% in India, and 29% in the rest of Asia (Fig. 582-1). In these areas, the major causes of childhood blindness are vitamin A deficiency, trachoma, ophthalmia neonatorum, measles infection, harmful traditional medicines, and trauma. All these conditions are largely the result, directly or indirectly, of malnutrition, lack of sanitation, or infection, and most of these factors cause blindness primarily through corneal scarring. All of these conditions are preventable or treatable. Blindness in children due to uncorrected major refractive errors occurs in 0.6% to 2.6% of children in developing areas. In China, it is thought that nearly 6 millions children are visually impaired simply because they are in need of glasses that they may never receive.3
In some areas of the world, there are more specific localized causes of blindness. For example, in Brazil, endemic toxoplasmosis is very common and often results in bilateral macular scars with resultant legal blindness. In Uganda, rubella-related congenital cataract is frequently encountered. In Sri Lanka and many areas of the Middle East, genetic diseases resulting from consanguinity can often be found, explaining the relatively high prevalence of infantile glaucoma, retinal degenerations, and infantile cataract. In other locations, especially nontropical, semideveloped areas, the major etiologies of childhood blindness are similar to developed regions.
A contributing factor to worldwide childhood blindness is an inadequate number of pediatric ophthalmologists. General ophthalmologists may not want to operate on infants. In addition, anesthesiologists in these areas are often reluctant to anesthetize small infants. Thus, many children go untreated for ROP, cataracts, glaucoma, and treatable blinding disorders. For pediatric ophthalmologists, early infancy is often the most favorable period to surgically improve glaucoma, cataract, and structural defects. For example, in the People’s Republic of China, there are about 200,000 blind children (Fig. 582-2).4 Of them, 22.5% (45,000) have cataract, glaucoma, ROP, and uveitis and are thus potentially treatable. At least in China, the situation is improving with more advanced physician training and alteration of hospital policies regarding surgery on infants.
PREVENTION AND INTERVENTION
It may appear relatively easy to conceive strategies to combat blindness, since the causes are often single, identifiable, and uncomplicated. In regions with a high prevalence of rubella, vaccination would be beneficial. Yet, the price for a nationwide vaccination program is often too expensive to consider. Toxoplasmosis prevention is difficult in areas with a dense population and many pets. Discouraging consanguinity may be complicated by social and religious mores. In areas with inadequate numbers of professionals in the field, the proper training of pediatric ophthalmologists, nurses, and other health workers will reduce treatable blindness in the future, but there are financial, geographic, and access issues that make training new workers a challenge. The widespread distribution of vitamin A, especially where there is malnourishment, will greatly help to prevent corneal blindness, both primary blindness due to the deficiency and secondary blindness due to infection, as would better nutrition.
In developing countries, the most common treatable cause of pediatric blindness is infection. Antibiotics are often not an option due to lack of availability and relatively high cost. For use in developing countries, an antimicrobial agent would need to meet certain criteria, including effectiveness against bacteria and other microbes, safety, widespread availability, and ease of preparation. Importantly, it must not be expensive. Povidone-iodine meets these criteria. It is effective against all bacteria, viruses, and fungi in vitro (given enough contact time) and causes few allergic reactions. It is questionable whether true bacterial resistance to povidone-iodine even exists.5 It can be prepared from preexisting powders or solutions, which are available worldwide and are very cheap. In Kenya, a 5 mL bottle of the solution costs less than $0.10 to prepare.6 In addition, the povidone-iodine solution colors the eye brown for about 2 minutes, confirming proper administration.
FIGURE 582-1. Estimates of pediatric blindness by region. Top number = total number of blind children. Bottom number = number blind from avoidable causes. Below each set of numbers is the major cause of regional childhood blindness. ROP, retinopathy of prematurity.
Conjunctivitis can lead to keratitis and scarring. The first randomized controlled trial to investigate the use of povidone-iodine 1.25% ophthalmic solution was as effective as antibiotics for the treatment of bacterial conjunctivitis and was more effective against chlamydial conjunctivitis.7 More than 250,000 children are blind due to corneal infections with subsequent scarring. Corneal scarring in children begins with a compromised corneal surface produced by a number of possible causes, including trauma, trachoma, vitamin A deficiency, rubeola, ophthalmia neonatorum, and harmful traditional medications. Often, bacteria invade a compromised cornea, causing an ulcerative keratitis that subsequently scars. An appropriate antimicrobial medication could prevent or treat these maladies. Povidone-iodine 1.25% ophthalmic solution has been found to be as effective as topical antibiotics to treat this disorder.8
FIGURE 582-2. A musical band composed of students in a Chinese school for the blind.
Prevention of ophthalmia neonatorum has been practiced since the 19th century by administering prophylactic eyedrops immediately after birth. Initially, silver nitrate was used followed in more recent years by antibiotics such as erythromycin. Silver nitrate is no longer manufactured in the United States and other countries. Erythromycin and other antibiotics are often too expensive for use in developing countries. Povidone-iodine 2.5% ophthalmic solution has proven to be effective and very inexpensive and has few, if any, side effects. It is now being used in many developing areas to prevent ophthalmia neonatorum.
The World Health Organization (WHO) has advocated the SAFE strategy to combat trachoma:
S: Surgery for those at immediate risk of blindness, usually adults with trichiasis.
A: Antibiotic therapy to treat individual active cases and reduce the community reservoir of infection (usually children). WHO currently recommends mass drug administration if the prevalence of active trachoma among children under age 10 exceeds 10%. The most common reatment is either oral azithromycin or topical tetracycline.
F: Facial cleanliness and hygiene promotion to reduce transmission. Children with dirty faces are more likely to transmit trachoma if infected or to develop trachoma if they are not infected. Discharge from the eyes and nose attracts flies that can bring the infection or carry it to other people.
E: Environmental improvements to change living conditions in order to reduce the risk for trachoma transmission.
Education can be a powerful preventive tool. Instructing village healers not to apply “homemade” solutions to the eye can prevent corneal inflammation and scarring. Teaching families in trachoma-inflicted areas to have the children frequently wash their hands and faces will reduce the prevalence of trachoma. Since trauma is a frequent cause of reduced vision in children, having them wear ocular protection when engaging in contact sports or potentially injurious work would be beneficial. The latter is particularly true in developing countries where children are often engaged in outdoor farming activities.
Uncorrected major refractive errors can be addressed by having a local government provide visual acuity screening of children and offer spectacles, as necessary. This initiative can be expensive, but the increase in productivity of citizens who will see properly with eyeglasses should offset costs. The screening process also can uncover cases of cataracts, glaucoma, and other disorders.
The WHO has initiated the VISION 2020 program to address many of these prevention and treatment strategies.9 Hopefully, this concerted effort will decrease the tragedy of childhood blindness.