The challenge of childhood cataract blindness

Childhood blindness remains a cause of great concern globally despite large advances in the field of ophthalmology in the past few decades. Childhood visual impairment and blindness are due to preventable causes in most cases1. With over 1.4 million children blind throughout the world, low vision that can significantly hinder activities of daily living is present in over 17.5 million1. Cataract forms a large share of the preventable blindness with the latest WHO estimates (2010) ranging above 200,000 cases world over2. Developing countries like India and China form the epicenter of the problem with more than 20 per cent of their population visually impaired1. High percentages are also reported from Africa (15%) and Eastern Mediterranean Region (EMR)12. These figures are likely underestimating the actual numbers because many children with multiple disabilities may go unreported. Economic burden and years of productive life lost due to untreated paediatric cataract clearly favours urgent attention to this challenge123.

The best way to address a problem is to delve into the root cause: There are numerous lacunae in the understanding of aetio-pathogenesis of infantile/developmental cataract34. While certain causes of cataract in children are well-documented, including perinatal and intrauterine infections, many cases may go without a definite aetiological diagnosis3. Childhood cataract is associated with genetic56, metabolic7 and acquired causes, such as trauma8, retinopathy of prematurity (ROP)4, enzyme defects9 and idiopathic. Drug-induced cataracts due to steroids are also common in this age group. Certain genetic defects are associated with abnormal lenticular shape/position needing surgical management including entities like spherophakia10 and lenticonus11. Mutations in crystallin and connexin genes have been identified as putative causes of cataract in children. Genetic polymorphisms may be associated with increased incidence of cataract, some of which are yet to be identified46.

The patients are hidden in the community - we need to identify them: There is often a delay in the diagnosis of paediatric cataract that compounds the problem2. Delayed treatment is associated with permanent visual impairment even after adequate specialized care due to development of severe amblyopia. Vigorous case-search and prompt referral are areas that need to be strengthened if we desire to tackle the problem successfully112. Thorough visual acuity assessment using specialized charts, pupillary reaction, strabismus and ocular motility must be done. Slit-lamp biomicroscopy is the best method to evaluate lenticular opacities and study the morphology of cataract4. Intraocular pressure measurement is a must to rule out congenital glaucoma which can frequently co-exist. Fundus examination is performed by indirect ophthalmoscopy after pupillary dilation to rule out posterior segment pathology. Detailed evaluation of family history, features of congenital rubella syndrome, metabolic diseases and survey of enzyme defects must follow if clinical symptoms suggest.

The biggest challenge in paediatric cataract surgery is gearing up for the next challenge: Though there have been tremendous changes with the ushering of technology in the field of ophthalmology but the task of managing childhood cataract remains difficult, fraught with potential complications at every stage313. Presently, the modern technique of phacoaspiration with posterior chamber intraocular lens implantation in the capsular bag is the preferred technique to manage paediatric cataract34131415. This has replaced older techniques of lensectomy and extracapsular cataract surgery. Ultrasound B-scan rules out posterior segment pathology in children with dense cataracts. Calculation of intraocular lens (IOL) power is a subject in itself with more than a dozen guidelines available in literature313141516. Popular guidelines include those laid down by Dahan and Drusedau16, where an under-correction is performed keeping in mind the future growth of the eye.

A child's eye is different from those of an adult in many more ways than one: Unlike for adult cataracts, there is a sense of urgency in the management of childhood cataracts, especially unilateral cases given the poor prognosis associated with delayed surgery341415. Certain attributes such as low scleral rigidity, highly elastic anterior capsule and increased vitreous pressure contribute to surgical difficulty. Hence, interventions may be limited to dedicated, specialized centers17. Phacoaspiration in children is performed using automated systems under controlled parameters. Specialized Ophthalmic Viscosurgical Devices (OVDs) are used, viz. 1.4 per cent sodium hyaluronate to maintain the integrity of anterior chamber intraoperatively. After continuous curvilinear capsulorhexis (CCC), cortical aspiration is performed1415. In young children aged 1 month to 6 years, posterior capsulotomy is done as a primary procedure with limited anterior vitrectomy to minimize the risk of posterior capsular opacification (PCO) and further interventions18. The current preferred practice to manage surgical aphakia is to place posterior chamber IOL in children to achieve optimal visual rehabilitation3414151619. Extensive studies have proven that hydrophobic acrylic IOLs perform the best with lesser complication rates compared to older IOLs3141520.

Cornerstone of successful paediatric cataract surgery is the post-operative management: Post-operative care in children is highly specialized as paediatric eyes are susceptible to high levels of inflammation18. High dose steroids are required topically combined with antibiotic therapy. Complicated cases of uveitis and trauma may benefit from intraocular depot steroids like dexamethasone implants21. Visual axis obscuration (VAO) can occur in the post-operative period due to formation of PCO or other IOL-related complications like tilt, decentration or subluxation/dislocation18. Maintaining a clear visual axis by managing VAO and prompt institution of occlusion therapy are sine-quo-none for achieving optimal amblyopia therapy.

The future holds promise: Futuristic approach includes surgery with newer IOL designs including multifocal IOLs in children22, bag-in-the-lens IOL23, use of newer synthetic suture materials, better vitrectomy devices, innovative instruments like plasma blade, maneuvers like optic capture and array of more efficacious drugs to control inflammation348131519. Benchmarks for post-operative outcomes after paediatric cataract surgery have risen and presently, the focus is on achieving highest grades of binocularity, stereopsis and contrast sensitivity along with emmetropia22.

With increasing evidence of genetic polymorphisms responsible for cataract, genetic counselling is probably going to play an important role in the management of these patients in the future24. Identification of mutations responsible for early cataractogenesis can help formulate guidelines regarding genetic counselling and prenatal diagnosis in the future24. It may become possible to identify cataract very early and intervene before damage is done.

To conclude, the future of paediatric cataract management is exciting. It is the need of the hour to take cognizance of this challenge and the rewards will be truly gratifying.