Amblyopia (Lazy Eye)

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Young eyes need proper visual stimulation in order for mature vision to develop. For this to happen, both eyes need clear images of the world to focus on the retina and then be transmitted to the visual cortex of the brain. Amblyopia, also known as “lazy eye,” is a condition that occurs when vision in one eye is reduced, because the eye and the brain are not working together properly during critical periods of development. 

The visual cortex develops dramatically in babies and young children, and it continues to develop throughout the first decade of life. Anything that interferes with a normal image on the retina during this time can lead to amblyopia. Good eyesight needs a clear, focused image that is the same in both eyes. But if the two images are significantly different from one another, the brain cannot combine them, and the vision pathways won’t develop properly. This often leads to a permanent reduction in vision if not treated during the critical development period from birth to seven years of age. 

Amblyopia is the most widespread cause of reduced vision in children. It is estimated that three percent of children under six have some form of amblyopia. It has many causes but most often results from strabismus (crossed eyes) or when there is a large difference in the prescription between the two eyes.  It can also occur when something is interfering with the clarity of the various components of the eye such as a congenital cataract. 

Amblyopia is often without symptoms, although sometimes a child will close one eye or squint when focusing on an object. Since amblyopia often occurs in one eye and young children don’t know what optimal vision is like, most will not complain of any visual problems. Children that are old enough to vocalize may complain of eye fatigue or headaches. 

The key to restoring proper vision is through early diagnosis and treatment. Amblyopia can be treated fairly successfully between the ages of two and seven, but the success decreases with age. Because there are several causes of amblyopia, the method of treatment must match the problem. Treatment first involves correcting the underlying problem.  This often involves glasses for improved focusing or misalignment of the eyes, or possibly strabismus surgery to straighten the muscles in the eyes if non-surgical means are unsuccessful.

Following the correction of the underlying cause, treatment for amblyopia involves getting the child to use the weaker eye. In most cases, the ideal method is to place a patch over the stronger eye, thereby forcing the amblyopic eye to do all the work. Patching is an effective method that can significantly restore vision loss. Adhering to a strict patching schedule recommended by your eye care practitioner is essential for optimal results; it continues until the vision in the amblyopic eye can no longer be improved. Once the eye care practitioner confirms that vision is close to equal in both eyes, he or she may reduce the patching to part-time use or to alternating patching of both eyes. The entire process can last anywhere from a few weeks to months to years. It is important to watch closely for signs of recurrence once the patch treatment is discontinued. An alternative to patching is the use of atropine drops to blur the vision of the good eye in order to force the weaker one to work. 

Regular eye examinations are essential to prevent vision loss. It is relatively easy to overlook poor visual function in a young child, so routine testing of eyes is necessary before age three. Early detection of the problems that may lead to amblyopia can prevent it, and in most cases, treating amblyopia before the eyes are fully developed can reverse the condition. If not treated early enough, an amblyopic eye may never develop good vision and may even become functionally blind

Written by Trevor Miranda

Dr. Miranda was raised in Simcoe, Ontario and graduated from the University of Waterloo with his Doctorate of Optometry in 1995. Following graduation, he moved to beautiful Vancouver Island, where he continues to serve the eye care needs of the Cowichan Valley. Trevor is also an active member of the Third World Eye Care Society and has participated with other professionals to improve the vision of the less fortunate. Dr. Miranda was named Optometrist of the Year by the British Columbia Association of Optometrists in March 2015. This prestigious honour recognized Dr. Miranda’s commitment to providing every patient with exceptional care while mentoring optometrists across Canada. Outside the office, you will find Trevor enjoying hockey, coaching soccer, involved with the South Cowichan Rotary Club, and spending time with his wife Cheryl and their three children. Trevor looks forward to continuing to care for the eyes of the Cowichan Valley and welcomes new patients without a referral. Dr. Miranda is available for appointments in our Duncan and Cobble Hill.
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