Eye disorders that affect vision can be divided into 2 groups:
Refractive errors. These eye disorders cause blurred vision. They occur because the shape of the eye does not refract the light that enters the eye properly.
Nonrefractive errors. These eye disorders are caused by eye diseases. They are not caused by refractive errors.
Refractive errors are seen in almost 20% of children. The following are the most common refractive errors, all of which affect vision:
Nearsightedness (myopia). Being nearsighted means that a child can see clearly close up, but has problems seeing things far away. It is often not present at birth, but begins to develop as the child gets older. It is often seen in children around age 9 or 10. For example, a child may not be able to read the blackboard from the back of the room, but can see to write and read without a problem. Other symptoms may include headaches, or nausea after reading. A child may hold books close to their face, or write with their head very close to the table.
Farsightedness (hyperopia). A child who is farsighted may or may not see things close to them, but they have no problem seeing things far away. Squinting, eye rubbing, lack of interest in school, and trouble reading may be seen in children with hyperopia.
Astigmatism. This condition makes objects that are close up and at a distance look blurry. It is caused by an abnormal curvature of the cornea. This can start in childhood or in adulthood. Astigmatism can be easily corrected if it is causing problems. Some symptoms may include headache, eye strain, trouble reading, and extreme tiredness (fatigue). Depending on the severity, eyeglasses or contact lenses may be needed.
Lazy eye (amblyopia). Amblyopia is a common type of visual condition. It can happen even when there is no problem with the structure of the eye. The decrease in vision occurs when one or both eyes send a blurry image to the brain. Then the brain learns to see only blurry with that eye. Early treatment can lead to better treatment success.
Crossed eyes (strabismus). Strabismus is one of the most common eye problems in children. It is when the eyes don’t line up, or they are crossed. The eyes (one or both) may turn inward, outward, turn up, or turn down. At times, more than one of these conditions are present. It is also called crossed eyes or wandering eye. Children younger than 6 months old may have a common form of strabismus that comes and goes. This type of strabismus may be normal. Most strabismus is caused by abnormality of neuromuscular (including brain) control of eye movement. Strabismus caused by poor eye muscle strength is less common. Symptoms may include squinting, not being able to judge distance to pick up things, closing one eye to see better, dizziness, or the eyes moving inward or outward. Early diagnosis of the underlying problem is key to prevent vision loss. Treatment may include patching the stronger eye to strengthen the weaker eye, eyeglasses, eye drops, surgery to straighten the eyes, or eye exercises.
The following are some causes of nonrefractive errors:
Glaucoma occurs when the normal fluid pressure inside the eyes (intraocular pressure, or IOP) slowly rises. This happens because the fluid aqueous humor—which normally flows in and out of the eye—can’t drain correctly. Instead, the fluid collects and causes pressure damage to the optic nerve. This nerve connects the eye to the brain. This condition also causes vision loss Glaucoma is classified according to the age when it starts. Glaucoma that begins before age 3 is called infantile or congenital (present at birth) glaucoma. Glaucoma that happens in a child is called childhood glaucoma.
Symptoms may include excessive tearing, light sensitivity (photophobia), closing one or both eyes in the light, a cloudy and enlarged cornea, one eye being larger than the other, and vision loss. Treatment often includes surgery. Without treatment, blindness may happen.
A cataract is a clouding or not clear (opaque) area in the lens of the eye. This area is normally clear (transparent). As this clouding happens, it prevents light rays from passing through the lens and focusing on the retina. The retina is the light-sensitive tissue in the back of the eye. This clouding is caused when some of the protein which makes up the lens clumps together and interferes with vision. Cataracts can affect either one eye (unilateral) or both eyes (bilateral). Cataracts in children are not common. A child may be born with cataracts (congenital). Or the condition may develop later in life (acquired). Possible causes of cataracts include the following:
Other childhood diseases, such as rheumatoid arthritis
Complications from other eye diseases, such as glaucoma
Most congenital cataracts (those present at birth) occur in children who also have other eye problems or other health problems. In about 25% of children born with congenital cataracts, the condition is due to a genetic cause, such as a metabolic disorder (caused by an inherited enzyme deficiency) or a chromosome abnormality (such as Down syndrome).
Symptoms of a cataract may include the following:
White pupil on flashlight exam
Eyes don’t line up
Involuntary rhythmic movements of the eyes back and forth, up and down, around, or mixed (nystagmus)
Cloudy or blurry vision
Lights seem too bright or present a glare or a surrounding halo
Treatment often includes cataracts surgery.
Retinoblastoma is a rare cancer of the retina. The retina is the innermost layer of the eye. It is located at the back of the eye. It receives light and images needed for vision. About 250 children in the U.S. are diagnosed with this type of cancer each year. It mostly happens in children the age younger than 5. Most cases happen between infancy and age 2. Both boys and girls are affected equally. Retinoblastoma can happen in either eye. But in about 25% to 30% of the cases, the tumor is in both eyes.
Symptoms of retinoblastoma may include:
Leukocoria. A white light reflex that happens at certain angles when light is shown into the pupil.
Crossed eyes (strabismus). This is when the eyes don’t line up. One or both eyes don’t seem to be looking in the same direction. It is also called wandering eye.
Pain, swelling, or redness around the eyes.
Treatment for retinoblastoma may include 1 or more of the following:
Surgery (removal of the eyeball which may be followed up with an artificial eye implant)
Heat treatment (uses extreme heat directed toward cancer cells)
Laser therapy (uses light to destroy the blood vessels that nourish the tumor)
Cryotherapy (uses a freezing process to destroy the tumor)
Additional follow-up treatments may include 1 or more of the following:
Fitting and training for a prosthesis (artificial eye)
Blind or decreased vision adaptation training
Supportive care (for the side effects of treatment)
Antibiotics (to prevent or treat infection)