The fact that a newborn can only see a blur up to 8 to 12 inches from its face is not commonly known. The newborns must be exposed to their surroundings to develop normal eyesight. The most crucial period for this exposure, first observed in newborn kittens, is within the first 3 months after the eyes open. The neural cell network in the brain’s visual cortex is relatively flimsy and highly plastic at birth, and it needs to be strengthened and refined through visual experiences. If the light entering the eye is partially or entirely blocked at birth, its connections in the brain die, resulting in permanent vision impairment, commonly referred to as a lazy eye (amblyopia). Lazy eye is reduced vision in one eye caused by abnormal visual development early in life. The weaker, or lazy, eye often wanders inward or outward. It generally develops from birth up to age 7 years and is the leading cause of decreased vision among children.
The eyes form an image of the surroundings and transmit it to the brain, to an area called the visual cortex that interprets and recognises various objects. In 1981, David Hubel and Torsten Wiesel won the Nobel Prize for physiology or medicine for their work on the immaturity and plasticity of vision at birth. The critical period for vision development in young children may extend up to the first 7 to 8 years. However, children lose the faculty of depth perception forever if they cannot simultaneously perceive objects from both eyes within the first 2 years of age. Early detection and intervention to remove any blocks in the path of light entering the eyes are thus of paramount importance in babies.
Of the 2.5 crore children born every year in India, 20,000-40,000 are born with cloudy crystalline lenses (cataracts) that impair light entering into their eyes. Congenital (present at birth or within the first year of life) and developmental cataracts are among the most common causes of childhood blindness.
A few years ago, Chandigarh-based expert Dr IS Jain and another group of experts from Madurai could not find any apparent cause of cataracts in half of the affected children. Interestingly, both found hereditary factors in nearly one-fourth of the cases. Dr Jagat Ram and Dr Jaspreet Sukhija, both from the PGI, believe that consanguineous marriages (between blood relatives who share a common ancestor) are the leading cause of hereditary cataracts that affect eyes.
Antenatal ultrasonography can discover opacities in the crystalline lens, which may not be apparent in newborns. Despite highly aggressive MMR (measles, mumps and rubella-German measles) vaccination campaigns for preventing these infections, nearly 15 per cent of Indian women of childbearing age remain susceptible to contracting rubella during pregnancy, with consequent congenital cataracts, deafness, heart anomalies and maldevelopment of several other organs. Before planning pregnancy, it is advisable for women to go for an MMR vaccine if not vaccinated earlier, at least four weeks prior to conception. Nearly 30 per cent cases of childhood cataracts, often occurring in one eye in school-going male children, result from eye injuries while playing.
While replacing the cataractous crystalline lens with an artificial intraocular lens implant (IOL) in adults is highly standardised and successful, it is a major challenge in newborns and infants. According to Dr Ram, who specialises in paediatric cataract surgery, there is no consensus on the optimal age for surgery. While some experts may wait until the child is at least 2 months old and is better able to withstand anaesthesia and surgery, others perform surgery as early as 28 days. The eye loses its ability to focus on objects after the surgical removal of the cataractous lens. In adults, an IOL can restore the lost power. There is a general agreement that children over 2 years can also have an IOL, but it remains controversial for children under 6 months. In children under 2, the IOL power calculation is highly inaccurate.
Dr Sukhija recently reported that if the size of the bag, critical for fixing the IOL, is small, it is safer to leave the eye without a lens (aphakia) or perform a bicapsular placement of the IOL. The aphakic eye’s power can be corrected with thick glasses or with a contact lens placed on the cornea as a temporary arrangement until an IOL implantation is done at a later age.
Infants who undergo surgery with IOL before the age of 6 months and especially those developing complications often require high myopic glasses by the age of 5, the change being less substantial in those corrected with thick glasses or contact lenses. While replacing contact lenses to adjust to the changing requirements of the eye is easy, the contact lenses are expensive, not readily available and require utmost care, posing a logistical challenge in low-income settings. Regardless, all children who undergo surgery require treatment to prevent a lazy eye and follow-up care for several years to monitor for any potential complications that may arise later.
Unfortunately, parents often stop bringing these children for follow-up after a few months of surgery.
Sheela Devi and colleagues from London University interviewed parents of nearly 750 children admitted to nine eye hospitals across India between 2015 and 2016. Most came from rural areas and belonged to low socio-economic strata. They noted staggering delays of 4 to 8 years in reporting for diagnosis and surgery. Recently, Dr Savleen and Dr Sukhija also noted a significant delay in the presentation and surgery of these children.
Early detection and treatment of childhood cataracts can prevent permanent vision impairment. A simple red reflex test, performed by paediatricians or ophthalmologists worldwide for decades, involves shining a direct ophthalmoscope light into each eye and comparing the reflected light from both eyes. This test can detect the presence of cataracts or any other visual disability. Although not highly sensitive, even at home, parents can use a mobile camera with a flash to take a picture of their toddler in a dark room, looking into the camera, seated at a distance of half a metre. A white, yellow, or black reflex, or a difference in the reflex between the two eyes, should prompt a visit to the ophthalmologist. While universal eye screening has been mandated in newborns in India since 2017, a simple red reflex test to detect common eye abnormalities in children is yet to catch up, losing the critical time to prevent permanent vision loss.
— The writer is Professor Emeritus, PGI, Chandigarh
