Amblyopia is a condition that occurs when the child’s visual system (vision) does not develop properly, resulting in abnormal sight in one or both eyes. In order to have normal vision, it is very important that both eyes develop equal vision.
When one eye develops good vision while the other does not, the eye with poor vision is called amblyopic. This condition is also called Lazy Eye.
If amblyopia is not treated early several problem can develop that can affect vision from childhood to adulthood. Vision impairment becomes permanent because as the child brain matures it will ignore the image coming for the poor seeing eye.
Signs and symptoms of Amblyopia
- Poor vision in one eye or overall poor vision
- Squinting, tilting the head or closing one eye to see
- Poor depth perception (Difficulty in judging relative distance between the object.
Refractive errors are eyesight problems due to poor focusing of light through the lens in the eye. Refractive error includes myopia (short sightedness), Hypermetropia (long sightedness) and astigmatisium. The refractive error on both eyes generally are the same or similar.
Refractive amblyopia develops when there is a difference of refraction between two eyes. If this difference is large, then brain selects the eye with better refractive error and the other eye vision subsequently drops
Strabismus Amblyopia (Squint)
A Squint is when the eyes do not look in same direction. While one eye looks straight ahead, the other eye turns in, out, up or down. As the eyes are not aligned, they focus on different things. When this happens the brain ignore the image from misaligned eye, to avoid seeing double. Subsequently the vision of misaligned eye drops resulting amblyopia.
Any disorder in a young child that prevents good vision can lead to amblyopia as the brain fails to develop the visual pathway. This is known as deprivation amblyopia. Disorders like cataract, ptosis(droopy eyelid) scarred cornea stops light getting to the back of the eyes.
Amblyopia can be diagnosed by examining the eyes and testing vision, different techniques are used to test vision, depending on the age of the child. Children with known squint are monitored carefully to see if amblyopia develops.
A comprehensive ophthalmic examination is all that is necessary to diagnose amblyopia. Components of this examination includes- acuity testing, cycloplegic refraction and retinoscopy, binocular vision, anterior segment examination, cover-uncover and alternate covertesting, dilated funduscopic examination.
The most common treatment for amblyopia is to force the brain to start using the bad/ lazy eye. The use of the good eye is restricted. This forces the affected eye to work. The most common treatment for amblyopia is patching.
This is where the good eye is covered with an eye patch, forcing the lazy eye to see. This treatment of patching is continued until either the vision is normal or until no further improvement is found. On an average patching should be done at least 2 to 6 hours a day.
Vision therapy can be used as a treatment to maintain the good work achieved by patching. This involves playing visually demanding games with a child to work the affected eye even harder.
The child should do close up activities when wearing a patch or using other amblyopia treatment. Activities like drawing, colorings, reading and school work are detailed and work the eye well.
Refractive amblyopia can be treated by correcting the optical deficit. Normal vision can be achieved simply by fully correcting the refractive error in both eyes with glasses or contact lens. Improvement in eyesight after wearing spectacles for refractive error can take 4 -6 months.
Deprivation amblyopia is treated by removing cataract. This can be followed by patching of the good eye. Squint cannot be corrected by patching or by other such treatment for amblyopia.
Patching does not correct the appearance of a squint. Treatment for strabismus amblyopia often involves squint surgery to straighten the misaligned eyes.