ABSTRACT:- AIM :- To determine the problems related with Amblyopia OBJECTIVE :-To review and establish the problems of Amblyopia.
INTRODUCTION:- Amblyopia is reduced visual acuity in one or both eyes in the absence of any demonstrable abnormality of the visual pathway. With Amblyopia,the brain suppress one of these images and this negatively impacts a person’s binocular vision .It is not immediately resolved by the correction of refractive error. The amblyopia eye must have the most accurate optical correction possible .
Because of high amounts of nearsightedness and ,farsightedness and ,astigmatism and the presence of a constant eye turn,the brain has suppressed the information in that eye and this suppression negatively impacts the development of clear vision.Amblyopia is a reduction in best-corrected visual acuity that cannot be accounted for by any structural abnormality, either in the eye or in the visual pathways (i.e., a pathway or tract of optic nerves and fibers that transmits a visual image from the eye to the brain).
A commonly-used term for this condition is “lazy eye.” A “lazy eye” refers to an amblyopic eye, not an eye that is misaligned (i.e., an eye that does not point or look in the same direction as the other eye). In some cases, however, amblyopia may be the result of a misaligned eye, or severe amblyopia may cause a misaligned eye.
In addition to a reduction in visual acuity in one or both eyes individuals with amblyopia will not be able to use both eyes together well. As a result, they may have poor depth perception.Normal vision develops during the first few years of life. At birth, infants have very poor vision, however as they use their eyes the vision improves because the vision centres in the brain are developing.
If infants are not able to use their eyes for various reasons the vision centres do not develop properly and the vision is decreased despite normal appearance of the structures of the eyes.The common cause is that the refractive error in one or both eyes that is it cannot be corrected early in childhood resulting in poor development of the visual function in the affected eye or eyes. This is called refractive amblyopia.Another common cause is strabismus or eye misalignment.
This is known as strabismic.Rarely there will be a structural anomaly that impairs the visual function like a droopy eyelid or opacity in the visual axis like cataract or corneal scar. This is called deprivation amblyopia.MATERIALS AND METHODS:-A total of 60 articles were identified through the database searches. An additional 10 articles were identified through a recent HTA publication and two systematic reviews on amblyopia screening and treatment. These articles were not identified because the publication was in a journal that was not included in the search engines used (ie, articles were published in journals not found on Medline). After the removal of duplicates, a total of 49 articles were applicable for this review. Every article identified was checked by one reviewer (JC) and subjected to a pre-determine inclusion/exclusion criteria.
Articles were rejected at title if they were not related to the subject area and rejected at abstract if they were in a non-English publication or not pertinent to the research question Letters, reviews, and editorials describing other studies reporting implications of amblyopia were excluded. Where abstracts were ambiguous, the article was obtained. A further seven articles were rejected at full paper stage. These were found to be review papers, summaries of other studies, or contained no data to inform the research question.A total of 35 articles were included in the review.
DISCUSSION;-Amblyopia is a childhood problem that happens when one eye is weaker than the other (1). The brain chooses to take in images from the stronger eye and ignore images from the weaker eye. This means that the child uses the strong eye more than the weak eye. If the weak eye doesn’t have to work, it isn’t able to develop good vision.
This leads to poor vision in the weaker eye(2). Amblyopia usually affects only one eye.The problem starts between birth and about age 7 (3).The Child will not be aware of whether he or she is using only one eye. Ignoring the images from the weak eye is an automatic response (4).Amblyopia can result from any condition that prevents the eye from focusing clearly (5). Amblyopia can be caused by the misalignment of the two eyes—a condition called strabismus. With strabismus, the eyes may cross in (esotropia) or turn out (exotropia).
Occasionally, amblyopia is caused by a clouding of the front part of the eye, a condition called cataract(6).A common cause of amblyopia will be the inability of one eye to focus as well as the other one. Amblyopia can occur when one eye is more nearsighted, more farsighted, or has more astigmatism(7). These terms refer to the ability of the eye to focus light on the retina.
Farsightedness, or hyperopia, occurs when the distance from the front to the back of the eye is too short(8). Eyes that are farsighted tend to be focused better at a distance but have more difficulty focusing on near objects(9).Nearsightedness, or myopia, occurs when the eye is too long from front to back. Eyes with nearsightedness tend to focus better on the near objects. Eyes with astigmatism have difficulty focusing on far and near objects because of their irregular shape(10).Amblyopia is derived from the Greek word for “blunt or dull sight.
“(11). The loss of sight can occur in childhood. The brain depends on receiving simultaneous clear focused images from both eyes for the visual pathways to develop properly(12).
Because of difficulty in producing a single image when looking with both eyes, the person with amblyopia elects to see with only one eye to see one image. The lazy eye, if deprived of visual input for sufficient time, will lose sight, and the child will become functionally blind because of a lack of visual cortex development(13). This problem may be associated with an eye that is deviated in any direction–in, out, up, or down–a condition known as strabismus.
However, strabismus is not necessarily a cause of amblyopia. In addition, the use of only one eye may not be apparent unless screening is conducted(14).In 2002, the American Academy of Pediatrics (AAP) issued a statement regarding the use of photoscreening, a vision screening technique, as a method of identification of children with visual problems(15). The AAP reaffirmed this position in August 2008. All children should be screened for risk factors associated with amblyopia. The prevalence of amblyopia is thought to be 1% to 4%.
13 However, almost 80% of children in preschool never get screened(16). With only 21% of children being screened, there is a very real possibility that a lot of children with visual problems are not being identified(16). The difficult to screen population such as the very young and developmentally delayed are at even greater risk for not being screened for preventable visual loss or treatable visual conditions(17). The AAP recommends se of a photoscreening method that would facilitate screening in all children. Salcido and colleagues found photoscreening more efficient than traditional screening in a group of 3- and 4-year-old children. A U.S.
preventive task force recommended that photoscreening was able to identify amblyogenic factors, such as significant refractory error, strabismus, and media opacities but not amblyopia (18).Amblyopia may occur in children when there is aberrant or contradictory information coming from a retina(19).The brain will selectively inhibit development of the cortical cells receiving the aberrant input. Just like cells everywhere else in the nervous system, the cells of the occipital lobe need to be stimulated to function(20).If the cells are not stimulated, the connections and organization of the cells will be affected.
This may occur if a child has a strabismus severe enough that a double image is created(21). The brain will shut off the signal from the deviant eye. Cells in the occipital cortex receiving signals from this eye will be deprived of stimulation and will not develop. Although the globe, the retina and the nerve pathways may be functional, the occipital lobe cannot interpret the signal they carry(22).Symptoms• Decreased vision in one or both eyes• Strabismus (misaligned eyes)• Poor depth perception(23) It is not easy to recognize amblyopia.
Unlike adults, a child is usually unaware if one of his or her eyes has reduced vision(23). Unless the child has a misaligned eye or other obvious external abnormality, there is often no way for parents to tell that something is wrong(24). In addition, it is difficult to measure vision in very young children at an age in which treatment is most effective(25). A positive family history of strabismus, amblyopia, or media opacities would increase the risk of amblyopia in the child.
Children who have conditions that increase the risk of strabismus, anisometropia, or media opacities (ex. Down syndrome) would also be at increased risk for the development of amblyopia(25). The risk of developing amblyopia, from a condition that is known to cause amblyopia, diminshes as the child approaches 8-10 years of age(26). The depth of amblyopia is typically less severe the older the child is at the time of onset of the amblyogenic factor(27).Amblyopia is a developmental problem in the brain, not any intrinsic, organic neurological problem in the eyeball (although organic problems can lead to amblyopia which can continue to exist after the organic problem has resolved by medical intervention) (28).The part of the brain receiving images from the affected eye is not stimulated properly and does not develop to its full visual potential.
This has been confirmed by direct brain examination(29).”The maximum “critical period” in humans is from birth to two years old(30).Reliance on parental history for some information and on assessments by general medical examiners (rather than ophthalmologists) raises the possibility of misclassification of amblyopia(31).However, visually impairing disease is rare in childhood, and amblyopia is the most likely cause of unilateral reduced acuity despite optical correction. Thus, most people with amblyopia were probably correctly classified, and they also probably account for most “cases.
“(32). This is supported by our prevalence of 1.2% for residual amblyopia at a threshold of 6/18 or worse, which is consistent with previous reports(33).The 1958 birth cohort is a representative population, studied longitudinally, ensuring that visual status was known before measurement of a range of important outcomes. This confers important advantages for studying the functional consequences of amblyopia; the size of the population studied was sufficient to detect even modest associations, for key outcomes, where they exist(34).
Extensive psychophysical and neurophysiological work has elegantly delineated clear deficits in specific components of vision, such as contrast sensitivity, that occur in amblyopia(35). Our findings fail to identify their “real life” functional correlates(36). For example, the reading speed of people with amblyopia may be measurably slower but may nevertheless, on average, be adequate for educational or occupational purposes(37).
Experimental work will remain the foundation for advancing understanding of visual development and the pathophysiology of amblyopia, but its value to decisions about screening needs to be enhanced by considering the impact of specific visual abnormalities on everyday activities, as well as the degree to which these are permanently reversed by treatment(38).In children >6 years old, the presence of motor fusion affects whether to treat or continue to treat, and the risk of causing potentially troublesome diplopia(39). If good motor fusion is present, certain cases can be occluded after the usual 7–8 year cut-off(40). If motor fusion is poor or absent, warn parents to stop occlusion if diplopia occurs.. Readily appreciated diplopia indicates weak fusion or less dense suppression and occlusion should be avoided to reduce the risk of subsequent diplopia(41).Amblyopia is usually corrected by making the child use their weaker eye(42).
This can be done by putting a patch over the child’s stronger eye. Another way is to make vision blurry in the stronger eye using eye drops(43). Or the child may wear eyeglasses with a lens that blurs vision in that eye.It can take several weeks to several months for vision to get stronger in the weaker eye.
Once the child has better vision in that eye, he or she may need to wear an eye patch part-time for a few years(44).This helps keep their vision strong.In some cases, the ophthalmologist will recommend surgery to correct certain eye problems causing amblyopia(45). After surgery, the child may need to keep wearing a patch or otherwise cover the strong eye until his or her vision improves(46).It is possible to prevent vision loss from amblyopia.
But treatment only works if your child only uses the weaker eye to see(47). Children do not like to have their stronger eye patched or blurred(48). However, you need to help your child do what is best for them(49).CONCLUSION Scientific research shows that treatment for children with amblyopia is not easy to implement.
It can be stressful for both children and parents, especially when it involves wearing patches.DrPatch’s own research indicates that children wear an attractive patch more willingly and thus participate more readily in a patching treatment program. We can assume that children who wear patches that they want to wear are less likely to suffer the distress normally associated with patching.With the variety of attractive alternatives to the traditional medicinal-looking patch, eye care professionals may now offer patching treatment programs that are more likely to be carried out to a successful conclusion.