Adult Strabismus

Strabismus is a misalignment of the eyes, making it impossible for them work together as a team.

If you have strabismus, one eye looks directly at the object you are viewing, while the other eye is misaligned inward (esotropia, “crossed eyes” or “cross-eyed”), outward (exotropia or “wall-eyed”), upward (hypertropia) or downward (hypotropia).

Strabismus can be constant or intermittent. The misalignment also might always affect the same eye (unilateral strabismus), or the two eyes may take turns being misaligned (alternating strabismus).

Adult strabismus refers to ocular misalignment in patients over 18 years of age. The misalignment may start during childhood or be acquired in adulthood. Common causes include residual or recurrent childhood strabismus, cranial nerve palsies, thyroid eye disease, adult onset distance esotropia, intermittent exotropia, ocular surgery and trauma. If strabismus develops after visual maturation (about 10 years of age), affected individuals may experience double vision (diplopia), visual confusion and problems with depth perception. Although the evaluation of an adult with strabismus may be more complex than that of a child, treatment may be highly effective. Non-surgical treatment options include glasses with prisms, occlusion, and botulinum toxin (Botox™) injections.

Strabismus signs and symptoms

The primary sign of strabismus is a visible misalignment of the eyes, with one eye turning in, out, up, down or at an oblique angle.

Corneal light reflex (Hirschberg) test: A screening test for strabismus that evaluates eye alignment based on the location of reflections of light shined at the eyes.

When the misalignment of the eyes is large and obvious, the strabismus is called “large-angle,” referring to the angle of deviation between the line of sight of the straight eye and that of the misaligned eye. Less obvious eye turns are called small-angle strabismus.

Typically, constant large-angle strabismus does not cause symptoms such as eye strain and headaches because there is virtually no attempt by the brain to straighten the eyes. Because of this, large-angle strabismus usually causes severe amblyopia in the turned eye if left untreated.

Less noticeable cases of small-angle strabismus are more likely to cause disruptive visual symptoms, especially if the strabismus is intermittent or alternating. In addition to headaches and eye strain, symptoms may include an inability to read comfortably, fatigue when reading and unstable or “jittery” vision. If small-angle strabismus is constant and unilateral, it can lead to significant amblyopia in the misaligned eye.

Both large-angle and small-angle strabismus can be psychologically damaging and affect the self-esteem of children and adults with the condition, as it interferes with normal eye contact with others, often causing embarrassment and awkwardness.

Strabismus surgery

In many cases, surgery may be considered to align the eyes, alleviate double vision and improve psychosocial well-being. Adult patients have the option of having local anaesthesia with intravenous sedation or general anaesthesia. They frequently also have the opportunity of selecting an adjustable suture technique, which allows fine-tuning of the ocular alignment shortly after surgery. Your physician will discuss the options that are best suited for you at the time of your visit.

The success of strabismus surgery depends on many factors, including the direction and magnitude of the eye turn. In some cases, more than one surgery may be required. The strabismus surgeon can give you more information about this during a pre-surgical consultation.

Strabismus surgery can effectively align the eyes of adults with long-standing strabismus. In many cases of adult strabismus, however, a significant degree of amblyopia may remain even after the affected eye is properly aligned. This is why early treatment of strabismus is so important.

The earlier strabismus is treated surgically, the more likely it is that the affected eye will develop normal visual acuity and the two eyes will function together properly as a team.

Non-surgical strabismus treatment

In some cases of intermittent and small-angle strabismus, it may be possible to improve eye alignment non-surgically with vision therapy.

Questions to ask

When consulting with your eye doctor or strabismus surgeon prior to treatment, here are a few important questions to ask:

• If surgery is recommended, inquire whether one surgery will suffice or if additional procedures are likely to be necessary.

• Ask the eye surgeon about the success rates for the type of strabismus and the surgery he or she is recommending.

• Ask what criteria are used to determine if the treatment is a success. In other words, is “success” defined as reducing the eye turn so the eyes are better aligned and look more natural in appearance, or is success defined as eyes that are perfectly aligned with normal visual acuity, eye teaming and depth perception.

• For optometrists or orthoptists, ask about the success rate, likely duration and costs of vision therapy (or orthoptics).

• Ask if any of the costs of surgical or non-surgical treatments for strabismus are covered by health insurance or vision insurance.

Remember, children do not “outgrow” strabismus. For best visual outcomes and to prevent developmental delays and other problems, seek treatment for strabismus as soon as possible.