Strabismus - Symptoms, Causes & Treatment
Strabismus is a vision disorder characterized by the inability of the eyes to align themselves and work in conjunction. In other words, people with strabismus usually have one eye that looks at the objects that they are focusing on, while the other one is misaligned inward, outward, upward, or downward. The symptoms of strabismus can be continual or transient (coming and going), but the disorder is usually unilateral (affecting one eye), and is only rarely bilateral (affecting both eyes - alternating strabismus).
Because strabismus usually develops early in life, the brain attempts to compensate and eliminate the possibility of double vision by ignoring visual input originating from the eye that has trouble aligning itself. This usually results in a condition called "lazy eye," medically known as amblyopia. Although strabismus is the most common cause of amblyopia, it is important to note that despite being confused for one another, the two are separate conditions.
Symptoms of Strabismus
The main symptoms of strabismus are easily recognized, as the disorder causes a noticeable misalignment of one or both eyes. The severity of strabismus is classified into two categories – large angle (in which the angle of misalignment is more pronounced) and small angle (in which the angle of misalignment is less noticeable).
In cases of large angle strabismus the brain usually does not try to realign the eyes, and instead chooses to completely ignore visual input from the affected eye. Thus, people with large angles strabismus usually do not experience symptoms like headaches or eyestrain.
Surprisingly, although small angle strabismus is less severe in terms of misalignment issues, it causes more troublesome symptoms, particularly if it occurs intermittently or switches from eye to eye. Small angle strabismus usually leads to symptoms like eyestrain, headaches, difficulty reading, and jumpy or jittery vision. Cases of constant small angle strabismus that are unilateral usually lead to amblyopia (lazy eye) in the affected eye. It should be noted that both forms of the condition can lead to significant social, mental, and emotional challenges.
If you notice that your infant has crossed eyes, do not fret prematurely as this may simply be a sign of incomplete visual development; a symptom that usually disappears as the infants eyes develop. Unfortunately, such temporary misalignment problems are rare in comparison to most forms of strabismus, which do not disappear as a child ages.
Causes of Strabismus
Strabismus is caused by the inability of the extraocular muscles (six external muscles that control the eyes movements) to coordinate and function in conjunction with each other. In people with normal vision, the positioning of the eyes is easily controlled by these muscles. Strabismus occurs when anatomical or neurological issues decrease these muscles' ability to function properly. The muscular dysfunction can originate due to neurological conditions that affect the brain's vision center, nerve issues, or problems within the extraocular muscles themselves. In addition, studies have shown that some people are more genetically predisposed to developing strabismus, particularly if one of their parents had the condition.
There is also a type of strabismus that is acquired early in life when a child that is farsighted attempts to focus on objects that are nearby, causing the eyes to cross due to excessive strain while focusing. Although this type of strabismus (known as accommodative esotropia) typically becomes evident during the first two years of a child's life, it is possible for symptoms to manifest at any time during childhood.
Strabismus Treatment and Prognosis
Unfortunately, most cases of strabismus can only be effectively treated using surgery. Success rates for strabismus surgery depend on a variety of factors, including the severity of the condition and the direction in which the misalignment occurs. In many cases, multiple surgeries may be required before treatment is successful. While strabismus surgeries are usually used to correct the condition during childhood, people with adult strabismus may also see success with surgical treatment, although some degree of amblyopia (lazy eye) will likely remain. Thus, early diagnosis and treatment is imperative in successfully treating strabismus.
Fortunately, children with accommodative esotropia (the kind caused by farsightedness) are usually able to have their condition treated successfully with corrective lenses. Routine eye exams during early childhood are the best way to diagnose strabismus and improve the success rates of treatment options. If the condition is left untreated, it is not uncommon for patients to develop amblyopia, double vision, or other visual problems that could significantly impair their ability to perform in the classroom and enjoy activities like reading.