12/09/2020
Our vision is a complex interplay of our eyes and brain working in perfect harmony. When this coordination falters, the results can be disorienting and impact our daily lives significantly. One such condition that affects this delicate balance is strabismus, commonly referred to as 'crossed eyes'. This is a condition where the eyes do not align properly, with one eye looking straight ahead while the other turns inward, outward, upward, or downward. This misalignment isn't just a cosmetic concern; it can lead to a range of visual disturbances and, if left untreated, more serious long-term consequences. Understanding strabismus is the first step towards effective management and treatment, ensuring clearer vision and improved quality of life.
What Exactly is Strabismus?
Strabismus is a condition characterized by the lack of proper alignment between the eyes. Normally, the six muscles that control eye movement work in unison, ensuring both eyes focus on the same point simultaneously. In individuals with strabismus, this coordinated effort is disrupted. This can be due to an imbalance in the eye muscles, faulty nerve signals that control these muscles, or issues with the brain's ability to coordinate eye movements. The misalignment can be present from birth (infantile strabismus), develop in childhood, or manifest in adulthood due to various factors like neurological conditions, trauma, or eye muscle disorders. The visual input from each eye should converge on a single point, allowing the brain to fuse these images into a single, three-dimensional perception. When eyes are misaligned, the brain receives two different images, which can lead to various visual disturbances.
The Many Faces of Strabismus: Types and Causes
Strabismus is not a one-size-fits-all condition; it manifests in several forms, each with its own characteristics and underlying causes:
Common Types of Strabismus:
- Esotropia: Inward turning of one or both eyes. This can be accommodative (related to focusing effort, often seen in farsighted individuals) or infantile (present in babies before six months old).
- Exotropia: Outward turning of one or both eyes. This can be intermittent, meaning it occurs occasionally, or constant.
- Hypertropia: Upward turning of one eye.
- Hypotropia: Downward turning of one eye.
The underlying causes of strabismus are varied. Genetics plays a significant role, with a family history of the condition increasing the risk. Trauma or injury to the eye or head can disrupt the delicate balance of the eye muscles and nerves. Neurological conditions such as cerebral palsy, stroke, or brain tumours can affect the nerve signals controlling eye movements. Certain health problems, like diabetes or thyroid eye disease (Graves' disease), can also contribute to strabismus. In some cases, damage to eye muscles during previous eye surgery can lead to misalignment.
Recognising the Signs: Symptoms of Strabismus
The most apparent symptom of strabismus is the visible misalignment of the eyes. However, other visual disturbances can also occur:
| Symptom | Description |
|---|---|
| Diplopia | Double vision, where the individual sees two of one image. This is more common in adults whose brains have already learned to process input from both eyes. |
| Asthenopia | Eye strain and fatigue, particularly after prolonged visual tasks like reading or computer work. |
| Headaches | Pain in the head, often associated with the effort of trying to focus or maintain visual clarity. |
| Difficulty with Depth Perception | Trouble judging distances, which can affect activities like driving or catching a ball. |
| Squinting or Tilting the Head | Individuals may unconsciously tilt or turn their head to find an angle where they can see a single, clear image. |
In young children, the brain may adapt by suppressing the image from the misaligned eye to avoid double vision. This can lead to amblyopia, or 'lazy eye', where the visual acuity of the suppressed eye deteriorates over time, potentially causing permanent vision loss if not addressed early.
Diagnosis: Uncovering the Cause
A thorough diagnosis is crucial for effective treatment. This typically involves a comprehensive eye examination conducted by an ophthalmologist or optometrist. The examination may include:
- Visual Acuity Test: To measure how clearly you can see at various distances.
- Cover Test: A simple yet effective test to assess eye alignment by covering and uncovering each eye.
- Refraction: To determine if glasses or contact lenses are needed to correct refractive errors like farsightedness or nearsightedness, which can sometimes contribute to strabismus.
- Eye Muscle Movement Tests: To evaluate the strength and coordination of the muscles controlling eye movement.
In some cases, especially if a neurological cause is suspected, imaging tests such as an MRI or CT scan of the brain and orbits may be recommended to identify any underlying issues.
Treatment Strategies: Restoring Alignment and Vision
The treatment approach for strabismus is tailored to the individual's specific type, severity, and cause. The goal is to improve eye alignment, restore binocular vision (the ability of both eyes to work together), and prevent amblyopia. Several treatment options are available:
1. Corrective Lenses:
For cases related to refractive errors, such as farsightedness causing accommodative esotropia, prescription eyeglasses or contact lenses can significantly improve eye alignment by reducing the focusing effort required. Prism lenses, which are specially ground lenses that bend light rays, can also be incorporated into eyeglasses to help redirect images and reduce double vision in milder cases.
2. Eye Patching:
If amblyopia is present, an eye patch is often prescribed to be worn over the stronger, "good" eye. This forces the brain to use the weaker, misaligned eye, thereby strengthening its vision and improving coordination. The patch is typically worn for a prescribed number of hours each day.
3. Vision Therapy:
Also known as orthoptics, vision therapy is a structured program of eye exercises and visual activities designed to improve eye coordination, focusing skills, and binocular vision. These exercises can be very effective, particularly for certain types of strabismus like convergence insufficiency, where the eyes struggle to turn inward for close work.
4. Botulinum Toxin (Botox) Injections:
In some adult cases, particularly those with recent onset due to neurological issues, Botox injections can be used. The toxin is injected into specific eye muscles to temporarily weaken them, allowing the opposing muscles to pull the eye into better alignment. The effects can last for a few months, and in some instances, may lead to a permanent improvement in alignment.
5. Eye Muscle Surgery:
Surgery is often considered the most definitive treatment for strabismus, especially when non-surgical methods haven't achieved satisfactory results or for more significant misalignments. The procedure involves adjusting the length or position of the eye muscles to achieve proper alignment. The surgeon may loosen tight muscles, tighten weak muscles, or reposition them. While a single surgery can be effective, some individuals may require more than one procedure to achieve optimal results. Surgery is typically performed as an outpatient procedure under local or general anaesthesia.
Living with Strabismus: Coping and Prevention
Living with strabismus can present challenges, but effective coping strategies can significantly improve daily life. Taking regular breaks during visually demanding tasks, ensuring adequate lighting, and maintaining good posture can help reduce eye strain. Support groups can offer valuable emotional support and practical advice from others who have similar experiences. While not all cases of strabismus are preventable, maintaining good overall eye health through regular eye examinations, protecting eyes from injury, and adopting a healthy lifestyle can contribute to better eye muscle function.
Frequently Asked Questions
- Q1: What are the main symptoms of strabismus?
- The most obvious symptom is eyes that appear to be misaligned. Other common symptoms include double vision, blurred vision, headaches, eye strain, and difficulty with depth perception.
- Q2: Can strabismus be treated in adults?
- Yes, strabismus can be effectively treated in adults. While early intervention is often ideal, various treatment options can improve alignment and vision at any age.
- Q3: Is eye muscle surgery painful?
- Eye muscle surgery is performed under anaesthesia, so you will not feel pain during the procedure. Post-operative discomfort is usually mild and manageable with prescribed pain relief.
- Q4: How long does it take to recover from strabismus surgery?
- Most people can return to their normal daily activities within a few days to a week after strabismus surgery. However, complete visual recovery and adaptation can take longer.
- Q5: Can I prevent strabismus?
- While genetic and certain neurological factors can predispose individuals to strabismus, regular eye check-ups are crucial for early detection and management. Maintaining overall eye health is also beneficial.
In conclusion, strabismus is a common yet treatable condition that affects eye alignment. By understanding its causes, recognising its symptoms, and seeking timely and appropriate medical attention, individuals can effectively manage this condition and regain clear, comfortable vision. Whether through glasses, vision therapy, or surgery, there are pathways to improved eye coordination and a better quality of life.
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