The second Thursday of every October is internationally celebrated as ‘World Sight Day’ to draw attention to blindness and vision impairment. This year, it is being celebrated on 14 October, the key theme being #LoveYourEyes.
Let us all take this opportunity to know more about the ‘lazy eye’ disease, a potential cause of vision impairment and permanent eyesight loss affecting the younger generation.
Lazy eye (amblyopia) is reduced vision in one eye caused by abnormal visual development early in life.
In India, the condition affects about 1.1 percent of children between 5-15 years of life.
In light of the above facts, it is important to raise awareness about amblyopia among the general public, especially parents of young children, to enable early diagnosis and management of the condition.
Amblyopia generally develops from birth up to the age of 7 years.
Lazy eye rarely affects both eyes.
Early diagnosis and treatment can help prevent this condition. The eye with the poorer vision can be corrected with glasses, contact lenses, patching therapy or surgery, as indicated.
Recent evidence suggests the condition to be a leading cause of vision impairment globally too, with a reported prevalence of 1.44 percent.
Data further predicts a rising burden of amblyopia from about 99.2 million in 2019 to 175.2 million by 2030 and 221.9 million by 2040.
Causes
Lazy eye develops because of abnormal visual experience early in life that changes the nerve pathways between the retina and the brain. With time, the brain suppresses the inputs from the weaker eye, eventually leading to visual impairment.
The child relies on the stronger eye for vision.
The common causes of this abnormal nerve pathway development can be attributed to :
The difference in sharpness of vision between the eyes (refractive)
A significant difference between the prescriptions in each eye – often due to farsightedness, sometimes near- sightedness, or uneven curvature of the eye (astigmatism) – can result in lazy eye. Glasses/ contact lens should be prescribed as early as possible to correct these refractive errors.
Muscle imbalance (strabismus amblyopia)
Another common cause of lazy eye is an imbalance in the muscles that position the eyes (squinting eyes). This imbalance can cause the eyes to cross in or turn out, and prevent them from working together.
Deprivation of light
...due to a problem in one eye, such as cloudy lens (cataract), cloudy cornea, or drooping of eyelid, can prohibit clear vision in that eye. These then require urgent treatment to prevent permanent vision loss. It is often the cause of severe type of amblyopia.
Screening for Lazy Eye
One of the challenges in establishing a diagnosis is that young children cannot understand and report the problem themselves, and lazy eyes cannot be detected without an eye test.
It is thus, important for every child to undergo regular and complete eye examination between 3 and 5 years of age.
A vision check is particularly important in children with a positive family history of eye conditions, such as childhood cataract, crossed eyes, etc.
Parents should be looking out for symptoms, such as squinting, head tilting, the child having trouble telling how far or near an object is, abnormal eye movements, such as an eye that moves inward or outward or eyes that do not work in synchronization.
Management
The most common treatment modalities may include:
● Corrective glasses or lenses to correct near-sightedness, farsightedness or blurred vision.
● Eye patch over the eye with good vision so as to stimulate the weaker eye.
● Surgery in case of droopy eyelids, squint or cataracts.
Lazy eye disease can be prevented from developing and stopped from getting worse causing permanent vision loss through early diagnosis and treatment.
The lazy eye does not resolve on its own unless treated.
Young children are recommended to undergo eye examination through the early developmental years to establish an early diagnosis.
(Dr Jyoti Shetty is an Ophthalmology Consultant at Manipal Hospitals, Bengaluru.)
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