Amblyopia Amblyopia is the loss or lack of the full development of
vision in one eye. The condition is common, affecting as many as three out of
every 100 children. It is usually due to conditions such as crossed-eyes (strabismus) or a large difference in the refractive error
between the two eyes.
It is important that amblyopia be treated as soon as possible. If it is left
untreated, it can cause irreversible vision loss. The best time to correct
amblyopia is during infancy or early childhood. After the first nine years of
life, the visual system is usually fully developed and cannot be changed.
To correct amblyopia, a child must use the weak eye. In young children, patching the good eye for weeks or months may
help the amblyopic eye improve. Although children may not like to have their eye
patched, it is important that you faithfully follow the patching instructions and attend scheduled ophthalmology
examinations. Children who cannot tolerate a patch can sometimes be
treated with an eyedrop therapy called “penalization.” Prescribing
glasses or performing strabismus surgery may also become part of the treatment plan
for children with amblyopia. Your pediatric ophthalmologist will decide which treatment will be best for your child.
Strabismus is a vision condition in which the eyes are not properly aligned
with each other. The misalignment can be present full time or occur
intermittently when tired or focusing at near or distant targets. The eyes can
be misaligned in any direction. If the eyes turn in or cross, it is called
esotropia. If the eyes drift apart or out, it is called exotropia. If one eye
drifts up, it is called hypertropia. Strabismus occurs in about four of every
100 children in the United States.
Since strabismus can sometimes occur when one eye has a serious anatomic
problem, such as a cataract or a retinal disorder, all children with strabismus
should have a complete eye exam. Strabismus also can be caused by high or uneven
refractive error, so eyeglasses may be used in the treatment of a child with
strabismus. Strabismus surgery can be used to correct the unbalanced eye muscles
and straighten the eyes.
It is important to remember that amblyopia can be caused by strabismus and therefore children with strabismus must often do patching therapy.
Esotropia is a type of strabismus. The misalignment or deviation of the eyes
is inward toward the nose. The common term used to describe children with
esotropia is “cross-eyed." Children with esotropia can often be divided
into two groups:
Accommodative esotropia is usually first seen when the child is
between 2 and 4 years of age. The crossing eye may be seen intermittently when
the child is tired or focusing on a toy at near. If untreated, it may increase
in frequency and the eye may later remain crossed full time. On examination,
these children are found to be highly far-sighted. Prescribing glasses to
correct the far-sightedness usually straightens the eyes out. Children who
don’t straighten out with glasses may also require strabismus surgery. The longer a child
with accommodative esotropia remains untreated, the more likely amblyopia will also develop. Some children with accommodative esotropia need to undergo patching therapy as well as wear glasses.
Congenital esotropia is usually first seen at birth or in early
infancy. The eyes usually cross a large amount. Amblyopia may or may not be
present. Glasses are usually not helpful, but a short trial of glasses may be
used in some infants. A schedule of patching is begun, and if the eyes remain
crossed, early strabismus surgery is required to realign the eyes. Follow-up
is needed after surgery and throughout early childhood. The eyes of children
with congenital esotropia that have undergone successful strabismus surgery
may drift again in later childhood. Sometimes these children require
additional strabismus surgery at a later age.
Exotropia is a type of strabismus. The misalignment or deviation of the eyes is outward or away from the nose. Parents often describe the eye as “drifting out." Children with exotropia can be divided into three groups:
Congenital exotropia is usually first seen at birth or in early
infancy. The eyes are significantly deviated outward and almost never
straight. Amblyopia may or may not be present. A schedule of patching is
established to develop equal vision in each eye. When this is accomplished,
strabismus surgery is usually the next step needed to align the
eyes.
Intermittent exotropia
is
a situation where an eye drifts out intermittently during the day, usually
when a child is sick, tired or looking at a distant target. In bright
sunlight, the child may be seen squinting one eye shut. Parents may
first notice the eye drifting between age 2 and 4 years, but it may show up
earlier or later in some children. If untreated, an intermittent exotropia can
increase in frequency, and the eye can be seen in a drifted, outward position
for longer periods of time. Initial treatment consists of glasses, if needed,
and a schedule of patching. Patching can improve a child’s ability to control
an intermittent exotropia to a point where a parent may no longer see the eye
drift. If patching does not restore muscle control, strabismus surgery may be needed.
Full time exotropia is an exotropia that is seen all of the time.
This is usually seen in a child with an intermittent exotropia who has “broken
down” or deteriorated to a point where the eye is constantly drifted and
misaligned. At this point strabismus surgery is usually recommended in an
attempt to restore ocular (eye) alignment.
Refractive error is the term used to describe an eye that is optically out of focus. Glasses are used to correct refractive errors in children and provide them with clear sharp vision at both distance and near. There are three common types of refractive errors:
Nearsightedness (myopia) is a vision condition in which only close objects are clear. Objects seen in the distance are blurred.
Astigmatism is a vision condition in which the front surface of the cornea is slightly irregular in shape, resulting in blurred vision at all distances.
Farsightedness (hyperopia) is a vision condition in which the image is not properly focused on the retina. It is not as straightforward as its name implies. Children with a small amount of hyperopia can use an internal focusing system called accommodation to focus images and see clearly at all distances without glasses. If a child has a large amount of hyperopia, or if one eye is significantly more hyperopic (farsighted) than the other, the child will not be able to focus properly and significant problems such as esotropia and amblyopia can develop.
All significant refractive errors can be corrected with glasses. The pediatric ophthalmologist can measure refractive errors during the eye exam by a technique called retinoscopy. This technique does not depend on verbal responses from the child and can be performed in infants. Eyedrops are placed in the eyes prior to the measurement. The eyedrops dilate the pupils and relax accommodation or focus. This allows for a more accurate measurement for glasses.
Retinopathy of Prematurity, or ROP, is a disease of the retinal blood vessels which affects premature infants with low birth weights. The smaller the birth weight, the higher the risk of developing ROP. The disease develops in the infant’s eyes about 4 to 6 weeks after birth. Fortunately, in the majority of infants, the disease will resolve spontaneously and normal vision will develop.
In a small number of infants, however, the disease will progress to a point where the retinas can detach resulting in blindness. It is crucial that all high-risk infants have a retinal exam by age 6 weeks, and a follow up exam every two weeks until the retinal vasculature (need to explain)is fully mature and the disease has resolved. Then, if ROP is progressing toward retinal detachment and blindness, it can be identified. A laser treatment can be given to infants with significant ROP, which can save vision and prevent blindness in most cases.
The nasolacrimal system is the name given to the tear ducts that drain excess
tears from the eyes into the nose. Obstruction of the nasolacrimal system occurs
in one to six percent of infants. Symptoms include tearing (watering) of the
eyes, or discharge and mattering collecting on the eyelids and eyelashes. In
severe cases, the eyelids may become red and swollen. Infections are treated
with antibiotic drops that can clear up the discharge, but since obstruction is
present, the symptoms often recur when the drops are stopped.
Infants with symptoms of obstruction are treated with eyedrops and massage to
the inner corner of the eyelid in an attempt to relieve obstruction. Many
infants with nasolacrimal duct obstruction will resolve spontaneously and
symptoms will disappear. Infants with persistent symptoms past six months of age
can be treated with a procedure called lacrimal probing. A very fine instrument
called a probe is passed through the nasolacrimal system and can relieve the
obstruction. Most pediatric ophthalmologists can perform this procedure in
infants between six and 13 months of age right in their office. Older children
will require that the procedure be performed in the operating room under general
anesthesia.
Cataracts can occur in infants and children. The lens of the eye is normally
a clear structure, but if cloudiness or opacities form in the lens, it is called
a cataract. A cataract can sometimes be seen as a white opacity in the usually
dark pupil, however some cataracts cannot be detected without a complete medical
eye exam.
Congenital cataracts are cataracts present at birth. Developmental cataracts
appear later in a child’s life and may progress. Congenital and developmental
cataracts may affect multiple family members over several generations. They may
be associated with infections during pregnancy, metabolic abnormalities, or
genetic diseases.
Cataracts in children can prevent vision from developing normally. If not
treated quickly, cataracts can cause permanent visual loss which will not
improve even after the cataract is removed.
Visually significant cataracts in infants and children are treated by
surgical removal of the cloudy lens. After surgery, small infants will require
glasses or contact lenses to provide a focused image to the eye and allow vision
to develop. Older children who have cataract surgery can have an intraocular
lens implant placed in the eye at the time of surgery, which eliminates the need
for thick glasses or contact lenses following the procedure. Patching may also
be needed after cataract surgery to maximize visual development in some
children.
Adults may occasionally experience symptoms or problems related to
strabismus. In most cases the strabismus had its onset in childhood. Some
patients will experience intermittent diplopia (double vision) or note a
worsening misalignment of their eyes. Potential treatment options might include
prism incorporated into their glasses or strabismus surgery. It is important to
remember that amblyopia associated with strabismus that was untreated or did not
respond to treatment in childhood, cannot be improved in adulthood.
Some adults may develop a new onset strabismus, usually associated with
double vision. The double vision may improve or worsen when looking in different
directions. This special form of strabismus may be the result of a head injury,
tumor, stroke, diabetes, or thyroid disease. It is important to find and treat
the cause of this type of strabismus. This may involve evaluation and testing by
other medical specialists. Eye treatment sometimes involves the use of prism in
glasses or temporarily covering one eye to eliminate double vision. If no
improvement is seen after a period of observation, strabismus surgery may be
required.
When the eyes are aligned and working properly, the images seen by each eye are merged or fused in the brain forming a single “binocular” image. When viewing objects through properly aligned eyes, the images have a three dimensional or stereoscopic quality that is not appreciated when viewing through one eye alone.
If the eyes are misaligned, the images cannot be fused and double vision (diplopia) will result. Adults who develop new onset strabismus
will be
particularly bothered by double vision. Adults with old strabismus may
occasionally note double vision, which may change or worsen as they age. Because pediatric ophthalmologists have considerable experience with eye muscle
related conditions, they are often involved in the evaluation and treatment of
adults with strabismus and diplopia.
Diplopia in children is more rare. This is because infants and young children
can rapidly adapt to a misalignment of the eyes, by learning to suppress (or
shut off) the second image. Once suppression develops, amblyopia and visual loss
often follows. Prompt evaluation and treatment of strabismus in children, allows
each child to develop their maximum individual binocular visual
potential.
