Exotropia is a type of strabismus, or eye misalignment, where one or both eyes turn outward, away from the nose. This outward turning, sometimes called a divergent squint, can be constant or intermittent, occurring only when the person is tired or looking at a distance. When non-surgical treatments like vision therapy, patching, or prism glasses fail to achieve stable alignment, surgery becomes a common and effective treatment option. The goal of this procedure is to reposition the eye muscles to restore proper alignment, which can help improve binocular vision and depth perception.
Determining the Need for Surgical Intervention
The decision to proceed with surgery is based on a thorough evaluation of several factors that indicate the deviation is negatively impacting the patient’s visual system. A major consideration is the size of the deviation, often measured in prism diopters, as larger angles of misalignment are more likely to require surgical correction. The frequency of the deviation is also important, particularly when intermittent exotropia progresses to a constant misalignment.
The ophthalmologist will assess whether the patient is losing their ability to use both eyes together, known as binocular vision, or is experiencing symptoms like double vision, frequent squinting, or eyestrain. If the eye turns out significantly when focusing on near objects, or if the deviation causes headaches due to the patient constantly trying to control the misalignment, surgery may be recommended. For children, the procedure is often performed before school age to give the eyes the best chance to develop binocular function.
Mechanics of the Eye Muscle Adjustment
Exotropia surgery directly addresses the imbalance in the six extraocular muscles that control eye movement. The procedure is performed by making a small incision in the conjunctiva, the tissue covering the white of the eye, to access these muscles. The surgery aims to balance the forces exerted by the muscles responsible for turning the eye outward (lateral rectus) and those responsible for turning it inward (medial rectus).
Two main techniques are used to adjust the muscle tension: recession and resection. Recession is a weakening procedure where the muscle’s attachment point is moved farther back on the eye’s surface. For exotropia, the lateral rectus muscle, which pulls the eye outward, is often recessed to reduce its pulling force. This action effectively increases the muscle’s slack, resulting in less tension and a weaker pull.
Resection is a strengthening procedure that involves surgically shortening the muscle before reattaching it to its original location. For exotropia, the medial rectus muscle, which pulls the eye inward, may be resected to increase its tension and pulling force. The specific combination of recession and resection, often unilateral (on one eye) or bilateral (on both eyes), is determined by the surgeon based on the size of the deviation. The entire procedure is typically performed on an outpatient basis, usually under general anesthesia.
Preoperative Planning and Recovery Instructions
Patients are typically instructed to stop eating or drinking anything after midnight on the night before the procedure, following standard fasting guidelines for general anesthesia. It is also common practice to discontinue certain medications, such as aspirin or other blood thinners, for up to two weeks before surgery, as these can increase the risk of bleeding.
Following the surgery, patients should expect some immediate discomfort, which is often described as a mild, scratchy pain, especially when moving the eyes. The eye will appear red due to blood vessels in the conjunctiva being temporarily disrupted, and some swelling and bruising of the eyelid are also common. Prescribed antibiotic and anti-inflammatory eye drops are a standard part of post-operative care, used to prevent infection and manage inflammation.
Physical activity restrictions are put in place to ensure proper healing and prevent complications. Patients are advised to avoid swimming for two to four weeks to prevent infection and should limit strenuous activities like heavy lifting or intense aerobic exercise for about two weeks. Most people can return to work or school within a few days, but the final eye position may take several weeks or even months to stabilize.
Long-Term Results and Monitoring
Exotropia surgery generally has a favorable long-term prognosis, but the success rate can vary depending on the patient’s specific condition. Success is often defined as achieving eye alignment within a small, acceptable range, typically between 5 prism diopters of esodeviation (inward turn) and 10 prism diopters of exodeviation (outward turn). Studies suggest that long-term success rates can range from approximately 70% to over 80% at the two-year mark.
The possibility of recurrence, where the eye begins to turn outward again, remains a concern, and this often requires ongoing monitoring. Younger age at onset and a larger angle of deviation before surgery are sometimes associated with a higher risk of recurrence. To achieve a stable result, surgeons sometimes aim for a slight overcorrection immediately after surgery, meaning the eye is temporarily turned slightly inward (esodeviation). Regular follow-up appointments are necessary to monitor the stability of the alignment and ensure the continued development of binocular vision, which is particularly important for children.