Dr Ben Wild
Overview |
Our vision comes from light waves stimulating retinal photoreceptors and these photoreceptors transferring their signals through a multitude of other cells to the ganglion nerve cells. These ganglion cells bunch together and form the optic nerve. The optic nerve then sends the signal to the occipital lobe in the brain where vision is interpreted and recognized.
Amblyopia refers to a condition where the vision is sub-optimal despite a healthy eye. It is now known to be caused by the improper development of the visual system within the brain. The other term for this is a “lazy eye”. Amblyopia is usually unilateral (affects one eye) but sometimes bilateral (both eyes).
Signs and Symptoms |
Signs
There are no signs of amblyopia other than slower brain transmission of visual information only noticed in highly specialized visual evoked potential testing.
Symptoms
Decreased vision. More difficulty recognizing letters in a row than the same letters one by one.
Causes and Risk Factors |
Causes
Visual deprivation (congenital cataract, corneal scar, retinal dystrophy, droopy eyelid, etc., blocking vision so the brain never develops the vision in that eye), strabismic (one eye is turned and to avoid double vision the brain does not develop the vision in that eye), anisometropic (one eye has a prescription so different from the other that the brain only develops the vision from one eye), ametropic (the prescription is so high in both eyes that the visual system did not develop properly).
Risk Factors
High prescription is one or both eyes, congenital cataracts, droopy eyelid, corneal scars, retinal dystrophy, congenital malformations, strabismus (eye turn).
Prevention and Treatment |
Prevention
1st eye exam around 1 year old followed by another at 3-4 years old to ensure proper development of the eyes and visual system.
Treatments
· Occlusion of the good eye to force the patient to use their poor eye and force the brain to develop the visual pathways (only effective until teenage years).
· Penalization of the good eye by making it blurry with the use of filters on glasses or atropine eyedrops.
· Vision therapy involving games that can only be played if the player is using both eyes.
Prognosis |
Amblyopia is manageable at early ages. In most instances, glasses alone can improve vision in the weaker eye, or in both eyes, significantly within a few months. In some cases, occlusion or penalization of the good eye is required between 2 hours a day and all day. Vision therapy with games requiring the use of both eyes has shown immense promise in being the best solution and seems to be able to improve vision in the worse eye even in adulthood.