What does ‘Lazy Eye’ mean?

What does ‘Lazy Eye’ mean?


You probably have heard of amblyopia being referred to by its more generic name, lazy eye. Amblyopia describes the condition of an eye that does not develop its full potential or best possible visual acuity (resolution limit) commonly known as 20/20. Amblyopia is a visual disorder due to the eye and brain not working well together and develops at an early age in an eye that otherwise appears anatomically/physically normal. It is the most common cause of decreased vision in a single eye among children and younger adults and is estimated to affect 1 to 5% of the population. A person with amblyopia is unable to be eligible for certain professions, such as piloting or police officer. People with amblyopia have reduced binocular vision functioning, and therefore poorer depth perception. These individuals are also at risk to suffer traumatic eye injury in their dominant eye. The cause of amblyopia can be any condition that interferes with focusing during early childhood.

If amblyopia is not detected and treated at a young age, the brain will never be able to resolve a clear image in adulthood, causing permanent vision deficit. I often get asked if lasers or LASIK eye surgery can cure or solve this visual disorder. The answer is, unfortunately, no. The reason being that lazy eye is not a focusing problem, but rather a perception problem. Lasers cannot improve this neural deficit.


A lazy eye starts when one eye has significantly better focus than the other (i.e. anisometropia). Usually, one is more farsighted or has significant astigmatism while the other does not. This type of amblyopia is called refractive amblyopia and is usually the easiest to treat and least severe cause of amblyopia.

If your brain is receiving a blurred image (resulting in weak neural messaging) from one eye compared to the other, the resulting weak neural messaging is less able to stimulate the development of the visual cortex and its neural connections to the eye. This lack of neural development takes place in the back of the brain, the visual cortex, and more specifically within its ocular dominance columns.

If you have an eye that does not line up correctly with its counterpart, this is called a strabismus. It is a more debilitating cause of lazy eye when compared to anisometropia. Initially, a person with an acquired strabismus might see double (a.k.a. diplopia) and so the brain adapts its visual perception by blocking part of the image received from the deviated eye to suppress the diplopia. In a young person, this will result in strabismic amblyopia.

The last and most profound cause of a lazy or amblyopic eye results when part of the visual image is physically blocked from reaching the retina, such as what occurs when congenital cataracts or a low positioned upper eyelid (known as ptosis) are present. This is called deprivational amblyopia and results in very deep amblyopia or significant visual loss. As a result of this reality, their presence represents a near ocular emergency. Surgical intervention is urgently required to minimize the damage to the visual system.

Diagnosing Amblyopia

An optometrist will check to ensure the visual axis is unobstructed, that both eyes can focus equally well, and that each eye exhibits normal motility and are working in synchrony. Eye exams should begin at age 6 months, followed by yearly eye exams from age 3.


The most common way to treat a lazy eye is to force the brain to use it through patching the dominant eye. Of course, any refractive errors in the form of significant hyperopia, myopia or astigmatism be corrected to provide the brain with a focused retinal image, and therefore the strongest input to the brain’s visual cortex. If congenital cataracts or lid obstruction of the visual axis is present, urgent surgical correction is required as previously stated as the visual deprivation created by these obstructions are the strongest source of amblyopia.

Patching cannot be done all day, as the resulting interruption of binocular fusion is a detriment to normal binocular functioning and development in the young. Although it will be more difficult to see out of a weak eye, over time, vision should improve. While patching, video games are a great way of passing the time while providing visual stimulation. Playing sports, operating vehicles (such as bicycles or skateboards) and playing outdoors should be avoided due to safety concerns. Over the course of visual training, best corrected visual acuity and depth perception can be monitored to determine when the training should be reduced or stopped altogether. This may take weeks or even months to reach fruition. It is important to follow your doctor’s instructions carefully and come in for scheduled visits so that your optometrist can monitor the visual progress.

If you have a mild case of amblyopia, you may just have to use an eye drop called atropine. It blurs your strong eye so that you do not have to wear an eye patch.

Long-Term Outlook

Most patients can improve their vision with an early diagnosis of lazy eye. Intervention before the age of 9 or 10 is crucial in the prognosis or success rate of treatment. This is why it is vital for all children to have regular eye exams beginning as early as age 6 months with a trained eye care professional.

Dr. Sciberras, Mississauga’s Top Rated Pediatric Optometrist, and his staff are here to serve your family’s eye care and vision needs. Call us at 905-828-2282 to book your child’s comprehensive eye exam. Their future vision depends on it.

Dr. Jeff Sciberras, Optometrist

2019 Top Choice Optometry Clinic

2019 Top Rated Pediatric Optometrist

2019 Top Rated Optometrist