A person with a lazy eye or amblyopia develops poor or blurred images in the affected eye.
A lazy eye develops when the image in one eye is blurred and in the other is clear. When both of these images travel to the brain, the brain ignores the blurred image and only focuses on the clear one. Thus, the neurons in the amblyopic eye progressively become weaker and the eye loses vision.
It is estimated that almost 10 million people are affected with amblyopia or lazy eye in the United States.
Why does lazy eye lead to blindness?
Lazy eye is one of the most common ophthalmic disorders in children.
- Early diagnosis (in people younger than six years) and treatment are a must to improve the vision.
- The crucial developments of the eye occur in childhood based on the response to visual stimuli.
- The visual pathway from the eye to the brain for the formation of an image completely develops by the age of seven years.
During this stage, if there is sensory deprivation or if the brain receives a poor image, the developmental process of the visual pathway is slowed or stopped. This results in impaired vision in one or both eyes.
The importance of early diagnosis of a lazy eye is that vision can be recovered. If treatment is administered after the vital stage of visual development, then the treatment would not be beneficial because the development process is complete.
If the sensory input or the picture quality is restored, development begins rapidly in the first two or three years. Eventually, the pace of the development slows down and completes by the age of seven years.
Even though visual problems due to a lazy eye or amblyopia begin in childhood, they can persist throughout adulthood, exacerbating symptoms if left untreated. Children with untreated amblyopia may develop persistent vision loss before reaching adulthood.
5 signs of lazy eye
- Irritated because of a lazy eye:
- The child stresses, squints, rubs, or closes one eye to see properly.
- The child cannot form a proper image with the lazy eye or cannot see the bright sun, so may attempt to cover it to see properly. This is the first notable sign of a lazy eye.
- Head tilt: The head may be tilted to one side while watching TV or trying to play catches so that the healthy eye can have a better view of the TV or the ball to make a successful catch.
- Difficulty reading or doing math:
- The child may find it difficult to read. They must exert extra concentration effort, which can lead to exhaustion and decreased concentration when reading.
- A lazy eye can make reading difficult, especially when the text gets smaller in higher grade level books.
- If a math problem is presented in a tabulated form, the child with a lazy eye may not perceive the numbers clearly due to fuzzy vision. This affects their ability to answer math problems correctly. Because the child tries too much to concentrate, they may not grasp the work at hand or the problem-solving approach.
- Reduced motor skills:
- Lazy eye symptoms, such as impaired binocular synchronization and depth perception, can lead to a loss of fine motor abilities, such as using scissors or tying shoelaces.
- Binocular coordination is required for clear depth perception and other fine motor skills, including legible handwriting. Binocular coordination, however, is impaired by a lazy eye.
- It can be difficult to stay on the line when writing if one does not have great fine motor skills. If the child consistently writes above or below the line, this indicates that the eyes may be out of sync.
- Attention difficulties:
- Though the child may appear to have a problem with attention, a lazy eye may cause focusing issues during activities that need extended visual focus.
- As a result, the child fails to concentrate during visually oriented tasks, which could be a sign of poor focusing abilities or a lazy eye.
3 types of lazy eye
- Strabismic amblyopia:
- The most prevalent cause of amblyopia is squint or strabismus.
- Strabismus is the misalignment of the eyes, where one of the eyes or both eyes may face outward or inward.
- To avoid double vision caused by misaligned eyes, the brain disregards visual input from the misaligned eye, resulting in amblyopia in that eye.
- Refractive amblyopia:
- Despite perfect eye alignment, amblyopia can be induced by uneven refractive defects in the two eyes.
- One eye has considerable uncorrected nearsightedness or farsightedness while the other does not, or one eye may have considerable astigmatism (blurring of the vision caused by improper curvature of the eye) while the other does not.
- In such instances, the brain depends on the eye with better vision or the lowest uncorrected refractive error and tunes out the blurred vision from the other eye, resulting in amblyopia.
- Deprivation amblyopia: Something prevents light from entering and focusing in the child’s eye. In the absence of visual stimuli, the vision pathway will not be developed making the eye a lazy eye, which may include:
- Congenital cataracts must be treated as soon as possible for proper visual development.
- Eyes with ptosis or droopy eyelids block the vision of the child, leading to amblyopia.
- Any damage caused to the eye that reduces the vision may lead to a lazy eye, such as injury, corneal ulcer, surgery to the cornea, and glaucoma.
4 risk factors of lazy eye
The following factors have been linked to an increased incidence of a lazy eye:
- Premature childbirth
- Small for gestation age baby
- Developmental impairments, such as congenital cataracts and autism spectral disorder
- A family history of lazy eye or myopia
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How is lazy eye diagnosed?
The parents and close associates must pay attention to the behavior of the child and observe for signs that indicate difficulty seeing or concentrating. If one or both parents have myopia, it is essential to screen the child for visual issues when they turn three years old.
Bring such changes to the notice of an ophthalmologist to determine the root cause.
- Visual acuity test: If the child is old enough and can speak or read, the doctor may use an alphabet chart to perform visual tests to establish if the child's distance vision is normal.
- Differential occlusion test: During this exam, the doctor alternatively covers the child's right and left eyes with a patch to assess the reaction. Children who cannot see properly out of one eye grow irritated when the healthy eye is covered.
- Retinoscopy enables doctors to reliably examine the child’s vision regardless of their level of cooperation or ability to talk. The purpose is to detect whether the child has refractive errors, such as farsightedness, nearsightedness, or astigmatism.
- During this examination, the ophthalmologist will use a retinoscope, which is a device that shines a beam of light into the child's eyes.
- The doctor then studies how the retina reflects the light as the beam moves across the eye. The reflection from the retina tells the doctor where light is focused in the eye and what type of refractive defect exists.
- The doctor will next place different power lenses in front of the eye until the light is appropriately focused and reflected and the refractive error is rectified. The strength of the lens required to concentrate light in the eye allows the doctor to decide what sort of eyeglass prescription the child may require.
- Prism test: The ophthalmologist may use a prism-shaped tool to assess the degree of eye misalignment called strabismus. The prism bends the stream of light that the doctor shines into the eye, allowing the doctor to determine the degree of misalignment. The test can help doctors to understand if the child prefers one eye over the other when prompted to look at an object.
During clinical examination, the visual fields may be normal because the healthy eye compensates with good vision; the person may even have normal color vision. Microscopical abnormalities may be found in the retina, lateral geniculate bodies, and visual cortex in the bad eye.
The doctor takes thorough medical history including all the signs and developmental behavior of the child and family history to make the diagnosis.
4 treatment options for a lazy eye
Amblyopia treatment forces the brain to focus on images of the amblyopic or weaker eye to improve vision in that eye. This is accomplished through:
- Glasses: When amblyopia is caused by severe refractive defects or anisometropia (both eyes have different refractive power, making one eye see better than the other), glasses or contact lenses are used. Glasses aid in the transmission of clear, focused images to the brain, which teaches it to turn on the weaker eye. This enables the brain to coordinate the function of the eyes and acquire proper vision.
- Eye patches: Many children with amblyopia must wear an eye patch over their stronger or unaffected eye. The patch is worn for two to six hours per day while the child is awake and for several months or years depending on the condition. The patch makes the eye with poor vision better by forcing the brain to receive blurred images and reprogramming the affected neurons.
- There are two types of eye patches:
- One that acts like a band-aid and is applied directly to the eye
- A cotton patch that fits securely over one lens for children who wear glasses
- It can be difficult to ensure that a child wears an eye patch. However, most children adjust well, and the patch simply becomes a part of their daily routine. A new or exciting toy, a trip to the park or simply playing outside might assist children to forget about the eye patch.
- There are two types of eye patches:
- Atropine drops: Some children refuse to wear eye patches. Atropine drops may be used in certain instances. Atropine drops momentarily blur vision in the strong eye, forcing the brain to recognize the images seen by the weaker eye.
- Surgery to the muscles may be required in cases when:
- The muscles that cause the eye to wander are either loosened or tightened during surgery. This type of surgery does not normally necessitate an overnight hospital stay.
There could be no symptoms of visual impairment. Therefore, it is critical to get yearly vision screenings done during toddlerhood and preschool years to identify abnormalities before a kid reaches visual maturity.
Advance treatment methods use computer programs, which can help older children and adults with long-stranded lazy eyes. These programs promote brain changes that increase visual acuity and contrast sensitivity.
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Boyd K. Amblyopia: What Is Lazy Eye? American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/amblyopia-lazy-eye
Stanford Health Care. Lazy Eye. https://stanfordhealthcare.org/medical-conditions/eyes-and-vision/lazy-eye.html
National Institutes of Health. Amblyopia (Lazy Eye). https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/amblyopia-lazy-eye
Johnson S. What Is a Lazy Eye? Healthline. https://www.healthline.com/health/lazy-eye
Mayo Clinic. Lazy eye (amblyopia). https://www.mayoclinic.org/diseases-conditions/lazy-eye/symptoms-causes/syc-20352391
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