What is it?
- The term anisometropia comes from four Greek words ‘œan’ that means not, ‘œiso’that means same, ‘œmetr’ meaning measure, and ‘œops’ for eye, so as a whole it basically means ‘œnot having the same measurement of vision.’
- Medically, anisometropic amblyopia is defined as the condition where the two eyes do not have equal refractive power. It may be that the eyes may be in different states of hyperopia or farsightedness, myopia or nearsightedness or antimetropia at the extreme wherein one eye is hyperopic and the other one is myopic. The eyes having unequal refractive states would cause it to have an unequal rotation which could lead to diplopia and asthenopia.
- Binocular Vision: Normally, when a person looks at a thing, the image falls on the retina. The retina is located at the back of the eye and the image seen should be about the same size and shape with that of the other eye. The image perceived through both eyes is what is called binocular vision. A person having a good binocular vision would see images in about the same size or if any difference is seen it would be less than 0.5%. But people affected with anisometropic amblyopia would have a poor binocular vision and would see things differently up to about 20%. Because one eye would have an image larger than the other eye, it would result to a blurry image.
- Amblyopia or sometimes called lazy eye is an abnormality characterized by poor vision caused by structural disproportion. An otherwise physically normal eye can have problems in transmitting visual image to the brain and an estimated one to five percent of the population is said to be affected of the condition. However, in case of anisometropic amblyopia, the eyes may appear physically normal and some eye examinations have to be done first in order to finally diagnose the condition.
- Development of Vision: It is normal for newborn babies to have poor vision, but it improves rapidly in the next few weeks and months as the eye and brain connection develops in reaction to the child’s early visual experience. The eye and the brain needs to work together in order to produce vision. Light pass through the eye and sends nerve signals to the brain, and in order to develop normal visual and an excellent high-resolution vision, a clear and focus image is required. Anisometropic amblyopia happens during the critical and most active visual development period which is during the few months from birth until six to years of a child’s life. There is an interruption in the normal visual development and an improper visual motivation during the early childhood years resulting to anisometropic amblyopia.
Causes of Anisometropic Amblyopia
Anisometropic amblyopia is caused by anisometropia, a condition wherein one eye is weaker than the other because of an unequal refractive error. It means that the lens of one eye and its other optical parts could not properly focus on an image causing the brain to get a blurred vision. In effect, one eye becomes dominant and the child will eventually suppress the area of the brain that is hooked up to the blurred eye. The same part that is suppressed will only mature up to the level that it has been stimulated and thus, visual development will be damaged. The longer the blurred vision exists and the greater the image look blur, the worse anisometropic amblyopia becomes.
Treating Anisometropic Amblyopia
- Anisometropia amblyopia is a condition that affects infants and children and their development of binocular vision with the large inconsistency in clarity of the two eyes. A study shows that about 6% of those between the ages of 6 and 18 are affected with this condition. Those who have a large degree of defect of anisometropia would need spectacles to correct the condition.
- However, studies have shown that spectacle correction sometimes causes the person to experience slight differences in image magnification in between the two eyes. It is not also seen to show developments in the binocular vision of the patient especially if the patient has had the condition for a longer period of time. It is like the brain is ignoring the visual images from the weak eye even if it is already capable of seeing things normally. The brain selectively manages the images from the strong eye. The corrective spectacles are indeed helpful; it is just that they are not like the ordinary eyeglasses wherein one would be able to see things clearly upon wearing them. Correcting a condition like anisometropic amblyopia with the spectacles would take time. The patient has to let the brain learn to process the images seen by the weak eye again.
- Early cure of anisometropic amblyopia would give good prognosis of the condition. However, this is sometimes difficult because most conditions are diagnosed when children are older. In cases of late diagnosis, the first step of the treatment is to give the weaker eye a clear image with the help of optical correction such as contact lenses or prescription glasses.
- Optical correction has to be worn at all times so as visual development is not interrupted and to ensure successful remedy of anisometropic amblyopia. This is why treatment should be continued until the child’s vision becomes normal or until they reach the age of eight till ten. After they reach the critical age, the vision system of the brain is already complete and do not develop anymore. If amblyopia children are not treated by this age, the child will have the condition for life and it will be impossible to fix.