Understanding Adult Onset Strabismus
Adult onset strabismus, or acquired strabismus, is a condition where the eyes lose their proper alignment and do not work together as a team. Unlike congenital strabismus, which is present from birth or early childhood, adult-onset cases occur later in life. A variety of factors can contribute to its development, and for many, it can cause distressing symptoms such as double vision (diplopia), eye strain, headaches, and impaired depth perception. Timely diagnosis and treatment can significantly improve quality of life.
Causes and Contributing Factors
The causes of adult onset strabismus are diverse and often different from those in children. Understanding the root cause is crucial for determining the most effective treatment plan. Some common causes include:
- Neurological Conditions: Diseases or events affecting the brain's control over eye muscles are a primary cause. These include stroke, brain tumors, traumatic brain injury, and cranial nerve palsies. For example, a sixth nerve palsy is a frequent cause of horizontal eye misalignment.
- Systemic Diseases: Certain medical conditions can trigger strabismus in adulthood. Examples include Graves' disease (thyroid eye disease), diabetes, and myasthenia gravis.
- Age-Related Changes: As part of the natural aging process, changes in the eye muscles and surrounding soft tissues can sometimes cause the eyes to become misaligned. This is particularly noted with an increased incidence after the sixth decade of life.
- Ocular Surgery or Trauma: Damage to the eye muscles during previous surgeries, such as cataract or retinal surgery, or physical trauma to the eye area can lead to strabismus.
- Sensory Fusion Loss: In rare cases, severe vision loss in one eye due to conditions like cataracts or retinal detachment can cause the eyes to drift out of alignment.
Types of Adult Onset Strabismus
Just as with childhood strabismus, adult-onset cases are categorized by the direction of the eye misalignment. A study on a U.S. population found paralytic strabismus to be the most common subtype, highlighting the importance of thorough neurological evaluations.
| Type of Strabismus | Direction of Misalignment | Common Associated Cause(s) |
|---|---|---|
| Esotropia | Inward turning (crossed eyes) | Convergence insufficiency, nerve palsies, neurological issues |
| Exotropia | Outward turning (wall eyes) | Neurological issues, pre-existing childhood strabismus |
| Hypertropia | Upward deviation | Thyroid eye disease, nerve palsies |
| Hypotropia | Downward deviation | Thyroid eye disease, nerve palsies |
| Paralytic | Misalignment due to nerve palsy | Stroke, head injury, diabetes |
Diagnosing Adult Onset Strabismus
A comprehensive eye examination by an ophthalmologist, particularly one who specializes in strabismus, is necessary for proper diagnosis. The evaluation process helps identify the cause and guides treatment. The diagnosis will typically include:
- Patient History: Discussing symptoms, medical history, and onset of misalignment.
- Visual Acuity Test: Assessing sharpness of vision.
- Refraction Test: Checking for refractive errors like nearsightedness or farsightedness.
- Cover Test: A key diagnostic tool where the doctor covers one eye and observes the movement of the other.
- Eye Movement Assessment: Evaluating how the eyes track objects together.
- Additional Tests: In cases where a neurological or systemic cause is suspected, an ophthalmologist may order blood tests or imaging studies, such as a CT or MRI scan.
Treatment Options for Adults
Adults with strabismus have several treatment options. Unlike in children, where vision development is still in progress, the goal in adults is typically to alleviate symptoms, improve cosmetic appearance, and restore binocular vision and depth perception, where possible. Treatment depends on the underlying cause and severity:
- Prism Eyeglasses: Special lenses that bend light (refract) can be incorporated into glasses to realign the images seen by each eye, effectively treating mild cases of double vision.
- Eye Muscle Exercises (Vision Therapy): These exercises can help strengthen eye coordination, especially for conditions like convergence insufficiency, where the eyes have difficulty turning inward for close tasks.
- Botulinum Toxin Injections (Botox®): Injections of botulinum toxin into specific eye muscles can temporarily weaken or paralyze them, allowing the eyes to realign. This can be effective for certain types of paralytic strabismus and may result in permanent improvement.
- Strabismus Surgery: This is often the most effective and permanent solution for larger or more complex misalignments. The surgery involves adjusting the length or position of the eye muscles to improve alignment. It is typically an outpatient procedure and can be performed under local or general anesthesia. Modern techniques, like adjustable sutures, allow for fine-tuning of the alignment shortly after the procedure.
Don't Wait to Seek Treatment
Many adults mistakenly believe that treatment for strabismus is only possible in childhood or that it is solely a cosmetic procedure. This is a myth. Correcting strabismus in adults can have profound positive effects, including the resolution of debilitating double vision, reduced eye strain, and significant improvements in social confidence and even employment opportunities. It's crucial to consult with a qualified ophthalmologist who specializes in strabismus to discuss the best course of action.
For more information on the various types of strabismus and treatment options, the American Academy of Ophthalmology offers a comprehensive guide on the condition and its management.
Conclusion: A Widespread but Treatable Condition
Adult onset strabismus is a surprisingly common condition that can arise from a variety of causes related to aging, disease, or injury. Affecting a significant portion of the population, particularly in later life, it is far from an unmanageable issue. Fortunately, with advances in ophthalmology, effective treatments—from specialized glasses to surgical correction—are available at any age to restore alignment, alleviate symptoms, and dramatically enhance a patient's overall quality of life. The key is seeking expert evaluation to determine the underlying cause and the most appropriate therapeutic approach.
