Contrary to what most people believe, Amblyopia is not an organic problem in the eye, rather, it is a developmental problem in the brain. Amblyopia ex anopsia results if a defect in the nerve pathway from one eye to the brain does not develop during childhood. This defect causes the images produced by the two eyes to be substantially different from the other. And because the brain is not able to fuse the two different images, the brain suppresses the blurrier image. This suppression can lead to amblyopia, rendering the weaker eye or “lazy eye” to further visual deterioration.
Definition Of Amblyopia
Amblyopia comes from the Greek word “amblys” meaning blunt, dull, faint, or dim and “-opia” from the Greek “ops” meaning eye, referring to vision. So to literally define Amblyopia , it means “dim vision”. The term “amblyopia” is oftentimes erroneously interchanged with “lazy eye”.
What Is Amblyopia?
Amblyopia is the partial or complete loss of vision in one eye caused by conditions that affect the normal development of vision. Normally, during our first few months of life, our brain develops binocularity, or the ability to fuse the 2 images being taken in into one image. Children with amblyopia never developed binocularity, so the brain compensated by turning off or ignoring the other eye.
There are two categories for the amblyopia; amblyopia and the toxic amblyopia. The former occuring more often in young children whose eyes are not properly lined up; resulting to condition called strabismus. In toxic amblyopia, certain toxic agents, such as cyanide in tobacco, cause a reaction in the optic nerve and results in visual loss. Common symptoms of Amblyopia include:
>Strabismus – in which the two eyes are looking in two different directions at the same time
>Exotropia – in which the eyes are crossed inward or turned outward
>Anisometropia (Refractive Amblyopia) – in which there is a major difference in refractive error between the two eyes from nearsightedness, farsightedness, or astigmatism.
>Ptosis – drooping of one eyelid
>Corneal disease – light is prevented from entering the eye
>Congenital cataract – a clouding that develops in the crystalline lens of the eye (Cataracts that occur in infants are typically bilateral cataracts)
>Injury to the eye
Amblyopia In Children
Some children with cerebral palsy, Noonan’s or Down syndrome, hydrocephalus, brain injury or brain tumors, retinoblastoma and other conditions can also be affected with strabsimus. However, 4 in 100 children or 2 to 3% of children in the US are born with “congenital strabsimus” with unknown causes, which can develop within the first 6 months from birth.
Diagnosing Amblyopia in children can be difficult, therefore it is important to look out for the presence of the following symptoms so early treatment can be sought:
Rubbing of eyes often
Squinting or turning head often while trying to focus on an object
Verbalizes that things are blurry or hard to see
Disinterest in reading or viewing faraway objects
A family history of vision problems
Problem in perception of depth
Wandering or crossed eyes
Treatment of Amblyopia
Treatment of Amblyopia involves glasses, drops, vision therapy and eye patches or patching.
Wearing an eye patch over and the use of atropine eye drops to blur the vision temporarily on the stronger eye helps train the weaker eye and forces the weaker eye to work.
In severe refractive errors, it should be corrected by glasses, contact lenses or, if appropriate, Lasik (laser-assisted in situ keratomileusis). Treatment of strabismus may involve surgical correction of the eye muscle imbalance.
Another treatment program for amblyopia which can be considered as physical therapy for the eyes is vision therapy. Not relegated to eye exercises alone or through the use of pictures, visual therapy is practiced by using various specialty medical devices and equipments such as therapeutic and prescription lenses, optical fillers, prisms, computer software, eye balancing equipment, and eye patches.
Amblyopia In Adults
It was initially thought that after the age of 12, amblyopia would be permanent. However, recent research indicates that even a 20-year old adult can show improvement using similar treatments given to a child.
A study conducted by Dr. Thompson and Dr. Robert Hess on a non-invasive, painless technique called repetitive transcranial magnetic stimulation (rTMS) shows promise for treating Amblyopia in adults. rTMS involves application of rapidly changing magnetic fields to the head with a hand-held coil. These fields, in turn, induce weak electric currents within the brain which excite neurons in targeted areas. This simple and safe technique has been used in the past to treat conditions like Parkinson’s disease, migraines, clinical depression and the aftereffects of stroke, but this study marks its first known application to amblyopia. The study demonstrates that 15-minute treatments with rTMS temporarily improved vision in the amblyopic eyes of volunteer subjects for up to 30 minutes.
Refractive Amblyopia is when one eye is either more nearsighted or farsighted than the other. This usually develops early in life. Since one eye has blurry vision the brain stops using that eye instead of working harder to try to fuse the blurry and clear image together. The result is that the long term suppression of the blurry eye causes the vision to stop developing.
This is the second type of amblyopia. In this defect, an eye is either pointing up, down, in, or out. This misalignment with the eyes causes the brain to take in two different images. Again, instead of working harder to fuse, the brain shuts off the eye that is misaligned to avoid double vision.
Anisometropic amblyopia occurs when unequal focus between the two eyes causes chronic blur on one retina and can occur with relatively small amounts of asymmetric hyperopia or astigmatism.
Unlike strabismic amblyopia, the eyes appear normal to an observer. An insidious disease, this type is most commonly caught through vision screening.
There has been much debate over the use of patches vs corrective surgery in amblyopic patients.
Lasik surgery can correct the muscle disorder that causes the strabismus in the first place and make the eye appear more “normal” or straighter by cutting it and repositioning the eyes but a lot of doctors think that surgery may not fix the underlying visual problems. Many doctors say that eye surgery does not restore the normal binocular vision, which is a process controlled by the brain. So in order for the problem to be truly fixed, the brain must learn to use both eyes more properly.