Exotropia is a common form of strabismus, defined by the misalignment of the eyes where one or both eyes turn outward. Proper alignment is required for the brain to fuse two separate images into a single, three-dimensional view. When exotropia occurs, this outward turning disrupts the process, leading to loss of depth perception and, in some cases, double vision. Correcting the alignment restores proper binocular function and prevents the brain from suppressing the image from the misaligned eye.
Assessing the Misalignment
Before any correction begins, a medical professional must conduct a comprehensive eye examination to determine the severity and nature of the deviation. This evaluation is necessary because the chosen treatment path depends entirely on the characteristics of the exotropia. Exotropia can be categorized as either constant, where the eye is always turned outward, or intermittent, where the eye only deviates occasionally, often when a person is tired or looking into the distance.
The assessment typically involves specialized measurements to quantify the angle of the misalignment. The cover test and prism cover test are standard diagnostic tools used to accurately measure the extent of the outward turn. These tests use prisms to determine the amount of light redirection required to bring the eyes into alignment, providing a precise measurement known as prism diopters. In children, it is important to identify the condition early, as exotropia often begins as an occasional deviation, known as exophoria, and can progress into a constant misalignment over time.
Vision Therapy and Optical Correction
For many patients, particularly those with intermittent exotropia or a specific type called convergence insufficiency, non-surgical approaches can be highly effective in managing or correcting the problem. Vision therapy focuses on a structured program of orthoptic exercises designed to train the eyes to work together more effectively. These exercises specifically aim to improve convergence, which is the ability of the eyes to turn inward to maintain focus on near objects.
Common orthoptic exercises include techniques like “pencil push-ups,” where the patient focuses on an object as it is slowly moved toward the nose, forcing the eyes to converge and maintain a single image. This type of office-based vergence and accommodative therapy, often reinforced with home exercises, has been shown to benefit both unoperated patients and those who have had previous surgery. The goal is to strengthen the muscle control necessary to prevent the eye from drifting outward.
Optical solutions are another non-invasive method, often used with vision therapy. Corrective lenses address underlying refractive errors, such as nearsightedness or farsightedness, which can contribute to the misalignment. Prism glasses alleviate double vision by bending light, shifting the image so the brain perceives the eyes as aligned. While prisms resolve the symptom of double vision, they do not correct the physical outward turn. Patching or occlusion of the stronger eye is sometimes used to force the misaligned eye to strengthen its visual acuity, especially when amblyopia is present.
Surgical Procedures for Eye Realignment
When non-surgical treatments fail to control the exotropia, or if the misalignment is constant and severe, surgical intervention is generally considered the definitive treatment. The procedure is performed by an ophthalmologist and involves adjusting the tension of the extraocular muscles that control eye movement. The goal of this surgery is not to cut the eye itself but to reposition or shorten the muscles on the outside of the eyeball to allow for proper alignment.
The two primary surgical techniques are muscle recession and muscle resection. Recession involves detaching a muscle, such as the lateral rectus muscle responsible for pulling the eye outward, and reattaching it further back on the eyeball to weaken its pull. Conversely, resection involves shortening a muscle, such as the medial rectus muscle that pulls the eye inward, and reattaching it at its original insertion point to strengthen its pull. The decision regarding which eye to operate on and the combination of techniques used is based on the specific type and magnitude of the deviation.
In adult patients, and sometimes in older children, surgeons may use adjustable sutures to secure the repositioned muscles. A temporary knot is placed, allowing the surgeon to fine-tune the eye’s alignment in the immediate post-operative period, typically within the first 24 hours. This adjustment is performed while the patient is awake using a topical anesthetic, which allows for a more precise final positioning and increases the overall success rate. Achieving a slight initial overcorrection, where the eye temporarily turns inward, is often intentional, as the eye commonly drifts back toward an outward position over time. Due to the recurrence of the deviation, a percentage of patients may require a second surgery.
Post-Treatment Care and Follow-Up
The immediate recovery following exotropia surgery is generally brief, with most patients returning to normal activities within a few days to a week. It is common to experience symptoms such as redness, mild discomfort, and a scratchy sensation due to the dissolving stitches on the surface of the eye. Eye drops, typically a combination of an antibiotic and an anti-inflammatory medication, are prescribed for several weeks to prevent infection and reduce swelling.
Patients must avoid swimming for up to a month and refrain from rubbing the eyes to prevent complications. While the eye’s final alignment may take several months to stabilize, follow-up appointments are scheduled early, often within two to three weeks, to monitor healing and measure the initial alignment. Ongoing monitoring is necessary for children due to the risk that the eye may gradually drift back outward over the years. Continued vision therapy is often recommended after surgery to solidify the new alignment and ensure the patient utilizes binocular vision skills.