Author: Vanessa Mora
Editor: Daisy Li
Overview
Amblyopia, also known as lazy eye, is a form of visual impairment where there is a decrease in vision resulting from abnormal visual development in infancy to early childhood (Blair et al., 2020). Amblyopia ranges from mild vision loss (20/25) to legal blindness (20/200 and worse); the brain focuses on one eye more than the other and hence leads to its blindness unless the child or young adult receives proper treatment (Chen & Cotter, 2016). Amblyopia may be extremely dangerous since it involves eye symptoms that are hard to detect during infancy (Holmes & Clarke, 2006).
What Causes Amblyopia?
Amblyopia develops because of abnormal visual stimulation and a large difference in the prescription between the two eyes. Other eye diseases such as cataracts, droopy eyelids, corneal opacity, hemorrhage, strabismus (crossed eyes), astigmatism, and a combination of these factors may lead to amblyopia. (Blair et al., 2020).
Symptoms
Some common signs and symptoms of Amblyopia include:
- Abnormal eye movements (eye wanders inward or outward),
- Eye strain,
- Headaches,
- Head tilting,
- Reduced contrast sensitivity,
- Reduced visual resolution,
- Spatial distortion,
- Squinting, eye shutting (Chen & Cotter, 2016)
If left untreated, Amblyopia may lead to permanent vision loss (Blair et al., 2020).
Risk Factors
Risk factors that increase the likelihood of acquiring amblyopia include:
- Family history of amblyopia,
- Muscle imbalance of the neck,
- Unequal prescriptions between both eyes,
- Premature birth,
- Farsighted, or nearsightedness (Birch, 2013).
How does the Doctor know it’s Amblyopia?
Physical examination is performed by acquiring the child’s medical history, eye history, pupil examination and inspection of the eyelids; a physician may decide to conduct further tests to determine if the patient may suffer from Amblyopia (Bradfield, 2013).
For infants and children, a lighted magnifying device is used to detect other eye diseases in the back of the eye that may contribute to amblyopia and allows them to assess the ability of the patient to follow a moving object (Bradfield, 2013).
Physicians may also place an adhesive patch on the eye with good vision. If the patient has consistent non-cooperativity or discomfort it may hint towards amblyopia (Jefferis & Connor, 2015).
The physician may also perform visual testing for children 3 years or older with an eye chart based test. The charts are held at a proper testing distance of 10 or 20 feet. If their vision is very low in either eye (20/32), the patient may be referred to a pediatric ophthalmologist (Bradfield, 2013).
Types of Amblyopia
- Anisometric amblyopia
It is the most frequent type of amblyopia, caused by unequal focus and refractive power between the two eyes. This results in one eye getting a clearer image than the other, and amblyopia in the eye with poor image quality (Zagui, 2019).
- Deprivation amblyopia
It is the most severe form of amblyopia, caused by other eye diseases that impact vision such as cataracts, droopy eyelids, corneal opacity and hemorrhage during early development. If the eye has physical problems that impact vision, amblyopia may develop (Zagui, 2019).
- Isoametropic amblyopia
Occurs when both eyes have trouble focusing and there is a high but equal refractive error in each eye. This results in both eyes developing amblyopia (Zagui, 2019).
- Strabismic amblyopia
Occurs when one eye turns inwards, outwards, upwards, downwards, and is not straight. When this occurs the brain will start to ignore that eye and vision will drop and develop amblyopia (Zagui, 2019).
- Reverse amblyopia
Occurs when there is overpatching the non-amblyopic eye (good eye) when treating amblyopia (Zagui, 2019).
Treatment Protocol
It is important to treat amblyopia as soon as possible in childhood (Jefferis & Connor, 2015). Your physician might recommend the following:
Eyepatch: Patients may wear an eyepatch over the good eye ( non-amblyopic eye) for a couple of hours during the day to force reliance on the affected eye (amblyopic eye) (Jefferis & Connor, 2015).
Eyedrops: Eye drops called Atropine are an alternative form of patching (Tailor & Greenwood, 2016).The drops are used in the good eye (non-amblyopic eye). They cause blurry vision in order to force reliance on the affected eye (amblyopic eye) (Birch, 2013).
Routine Eye examination: Children with amblyopia, that also have other associated eye diseases may be prescribed routine eye examination as priority treatment. If there is no gain in vision after 3 months, eyedrops or eye patch treatment will be performed (Jefferis & Connor, 2015).
Vision Therapy: Visual activities such as coloring,video games, reading, card games and other crafts may be performed during the treatment program while the patient is wearing red/green glasses which allows both eyes to work together to treat aspects of visual function such as accommodation, eye movements/fixation, eye tracking and eye-hand coordination (Lyon et al., 2013).
References
Birch, E. E. (2013). Amblyopia and binocular vision. Progress in Retinal and Eye Research, 33, 67-84. DOI: 10.1016/j.preteyeres.2012.11.001.
Blair, K., Cibis, G., & Gulani, A. C. (2020). Amblyopia. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK430890/.
Chen, Angela M, and Susan A Cotter. “The Amblyopia Treatment Studies: Implications for Clinical Practice.” Advances in ophthalmology and optometry vol. 1,1 (2016): 287-305. DOI: 10.1016/j.yaoo.2016.03.007.
Holmes, J. M., & Clarke, M. P. (2006). Amblyopia. The Lancet, 367(9519), 1343-1351. DOI: 10.1016/S0140-6736(06)68581-4.
Jefferis, J. M., Connor, A. J., & Clarke, M. P. (2015). Amblyopia. Bmj, 351. DOI: 10.1136/bmj.h5811.
Lyon, D. W., Hopkins, K., Chu, R. H., Tamkins, S. M., Cotter, S. A., Melia, B. M., Holmes, J. M., Repka, M. X., Wheeler, D. T., Sala, N. A., Dumas, J., Silbert, D. I., & Pediatric Eye Disease Investigator Group. (2013). Feasibility of a clinical trial of vision therapy for treatment of amblyopia. Optometry and vision science : official publication of the American Academy of Optometry, 90(5), 475–481.
Tailor, V., Bossi, M., Greenwood, J. A., & Dahlmann-Noor, A. (2016). Childhood amblyopia: current management and new trends. British medical bulletin, 119(1), 75–86. DOI: 10.1093/bmb/ldw030.
Zagui, R. (2019). Amblyopia: Types, diagnosis, treatment, and new perspectives. American Academy of Ophthalmology. Retrieved from https://www.aao.org/disease-review/types-of-amblyopia.
