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Strabismus

What it is, what causes it, how it is diagnosed, and what modern treatment options are available.
Content
Strabismus
What is strabismus?
Causes of Strabismus
Symptoms of Strabismus
Diagnosis of Strabismus
Strabismus Treatment
Prevention of Strabismus
Frequently Asked Questions – Strabismus

What is strabismus?

Strabismus is a condition in which the eyes are not properly aligned and the visual axes are not directed at the same point. This may manifest as a constant or intermittent deviation inward, outward, upward, or downward. Any suspicion that the eyes are misaligned, even temporarily, requires prompt evaluation by a specialized ophthalmologist, as early diagnosis is critical for preserving normal visual development.

Causes of Strabismus

Strabismus can result from abnormalities affecting the extraocular muscles or the nerves that control eye movements. It is often associated with congenital abnormalities, a family history, or refractive differences between the two eyes, such as hyperopia, myopia, or astigmatism.
Other causes include paralytic strabismus, strabismus associated with thyroid disease, myasthenia gravis, or other neurological conditions. Nystagmus and oculomotor nerve palsies may also be associated with abnormal ocular alignment, although these do not represent classic forms of strabismus.

Symptoms and Diagnosis

Symptoms of Strabismus

Strabismus manifests as visible misalignment of the eyes, which may be constant or occur only when the patient is tired. Adults often report diplopia (double vision), while children may experience blurred vision or reduced visual acuity in the deviating eye.
The condition can cause headaches, discomfort, and fatigue during visual tasks, as well as difficulty using both eyes simultaneously. In untreated childhood cases, amblyopia may develop, resulting in permanently reduced vision in the affected eye.

Diagnosis of Strabismus

Strabismus is diagnosed through a comprehensive eye examination by an ophthalmologist specializing in strabismus.
The direction of the deviation (esotropia, exotropia, hypertropia, hypotropia, cyclotropia), its pattern (constant or intermittent), and whether it is manifest or latent are evaluated.
It is also assessed whether the angle of deviation is the same in all gaze positions (concomitant or non-concomitant strabismus), as well as whether the strabismus is unilateral or alternating.
Finally, binocular vision, the presence of diplopia, and any associated ocular or neurological conditions are evaluated.

What are the types of strabismus?

Approximately 5% of the population has some form of strabismus. Strabismus is divided into many subcategories, and its terminology often describes the characteristics of the deviation.
This is how, for example, the direction of the deviation is described—such as esotropia, exotropia, hypertropia (upward), and hypotropia (downward), as well as esotropic and exotropic cyclotropic strabismus—the presence or absence of strabismus (manifest or latent, tropia or phoria), whether the strabismus is continuous or intermittent (constant or intermittent strabismus), the constant angle of deviation in various gaze positions (concomitant, non-concomitant), and depending on whether only one eye or both eyes deviate, we classify strabismus as heterophoric or alternating.
Other important categories include paralytic strabismus, restrictive strabismus, strabismic syndromes, and strabismus associated with systemic diseases (e.g., thyroid eye disease or myasthenia gravis).
The examples above are intended to illustrate the complexity of strabismus, its many underlying causes, and, most importantly, the need for an individualized approach to the diagnosis and treatment of each patient.

Strabismus Treatment

The treatment of strabismus is personalized and depends on the type of strabismus, the patient’s age, and the presence or absence of amblyopia. It combines conservative and surgical approaches, aiming not only to achieve proper ocular alignment but also to restore binocular vision whenever possible.

1. Conservative Approaches

Before considering surgical options, all conservative measures that can improve or eliminate strabismus are implemented. These include:
  • Refractive correction with glasses or contact lenses, particularly in cases of strabismus associated with hyperopia (accommodative esotropia), where proper refractive correction alone can completely eliminate the deviation.
  • Prismatic lenses incorporated into eyeglasses, which optically shift the image and can relieve diplopia in patients with small, stable angles of deviation. They are often useful as a temporary measure before surgery or as a permanent solution in selected cases.
  • Patching of the better-seeing eye when amblyopia is present. Amblyopia should be treated first, as it influences both surgical planning and the final outcome.
  • Botulinum toxin (Botox) injected into selected extraocular muscles, producing temporary muscle relaxation. It may provide temporary ocular alignment (e.g., in sixth cranial nerve palsy) or be used to assess a patient’s tolerance to postoperative diplopia (Murray et al., Br J Ophthalmol, 2007).
  • In selected cases of accommodative strabismus associated with hyperopia, refractive surgery using an excimer laser or pharmacological treatment with eye drops may reduce or eliminate the need for glasses.

2. Surgical correction — the primary treatment option

When conservative approaches are insufficient, surgical correction is the primary treatment for strabismus—particularly in adults with known long-standing strabismus, in infants with congenital strabismus, and in all cases where the angle of deviation cannot be corrected with glasses or prisms.
The procedure is performed on the extraocular muscles (outside the eyeball) using microsurgical techniques under an operating microscope, with absorbable sutures in most cases.

Reconstructive, not cosmetic

A belief has spread among some in the medical community that surgical treatment of strabismus in adults is merely a cosmetic procedure, with no functional benefit. This position is incorrect and has been officially refuted by both the American Academy of Ophthalmology (AAO) and the European strabismus societies (ESA, EPOS).
Strabismus surgery in adults is classified as reconstructive rather than cosmetic, and its benefits are documented on three levels:


(1) widening of the visual field (usually by 20–30 degrees) and improvement in depth perception, even when full stereoscopic vision is not restored;
(2) elimination of the compensatory abnormal head posture, which many patients adopt to avoid double vision;
(3) measurable improvement in quality of life, as demonstrated by the internationally validated Adult Strabismus-20 (AS-20) questionnaire in numerous published studies.
The professional, social, and psychological impact of correction is also significant, but it is not the sole reason for surgery.

3. Anesthesia in adults — the option of local anesthesia

A particularly important consideration for adult patients considering the procedure is the option of performing the surgery under local anesthesia—a technique that we routinely use for the majority of adults undergoing surgery at Athens Vision.
  • Avoidance of the risks and burden of general anesthesia—particularly important in elderly patients and those with cardiovascular, respiratory, or other systemic comorbidities.
  • Faster recovery and same-day discharge (day surgery), without postoperative nausea or lethargy associated with general anesthesia.
  • The ability to perform intraoperative reassessment of ocular alignment, with the patient in a sitting position if necessary, improving the accuracy of the final result.
  • Compatibility with the adjustable suture technique (see next section), which allows fine adjustment of the result postoperatively.
For children and infants, general anesthesia remains the only option.

4. Adjustable sutures

In cooperative adult patients, we use the adjustable suture technique: the sutures placed in the muscles during surgery are not tied permanently but are left adjustable. Thus, on the same day or the following day—with the patient sitting upright and awake under local anesthesia—we can precisely align the position of the ocular axes by adjusting the sutures by a few millimeters. The procedure is brief and virtually painless.

5. Postoperative diplopia — the actual picture based on the international literature

An important concern for adult candidates for strabismus surgery is the risk of postoperative diplopia (double vision), especially in patients with chronic strabismus dating back to childhood, who have developed sensory adaptation to the abnormal alignment. This concern is reasonable and requires an objective answer based on the published literature.

Data from classic studies

The most comprehensive study on the subject is that of Burton J. Kushner (University of Wisconsin, USA), published in the Archives of Ophthalmology in 2002 (“Intractable Diplopia After Strabismus Surgery in Adults”), which evaluated 424 adult patients who underwent strabismus surgery.
The findings are clear and reassuring: transient postoperative diplopia (which resolves spontaneously within six weeks) occurred in 9% of patients, while persistent diplopia lasting longer than six weeks occurred in only 0.8% (approximately 1 in 125 patients).

Efficacy and likelihood of a second surgery

The majority of patients require only one surgery. Approximately 20% of patients, despite an initially successful outcome, may benefit from a second procedure—either because the strabismus was not fully corrected or because it recurred over time. The adjustable suture technique significantly reduces this rate. In patients with thyroid eye disease, the outcome is less predictable and is closely related to the clinical course of the disease.

Possible complications

The procedure is performed on the extraocular muscles, outside the eyeball, and therefore serious intraocular complications are extremely rare (endophthalmitis, retinal detachment related to the procedure: less than 1 in 3,500 procedures). The use of an operating microscope and microsurgical sutures further minimizes these risks. The most common temporary postoperative symptoms are tearing, mild redness, temporary eyelid drooping, and occasionally temporary double vision (see Section 5). Statistically, the most common “complication” is incomplete correction, which may require a second surgery.

Efficacy and likelihood of a second surgery

The majority of patients require only one surgery. Approximately 20% of patients, despite an initially successful outcome, may benefit from a second procedure—either because the strabismus was not fully corrected or because it recurred over time. The adjustable suture technique significantly reduces this rate. In patients with thyroid eye disease, the outcome is less predictable and is closely related to the clinical course of the disease.

Possible complications

The procedure is performed on the extraocular muscles, outside the eyeball, and therefore serious intraocular complications are extremely rare (endophthalmitis, retinal detachment related to the procedure: less than 1 in 3,500 procedures). The use of an operating microscope and microsurgical sutures further minimizes these risks. The most common temporary postoperative symptoms are tearing, mild redness, temporary eyelid drooping, and occasionally temporary double vision (see Section 5). Statistically, the most common “complication” is incomplete correction, which may require a second surgery.

Can strabismus be prevented?

The prevention of strabismus relies primarily on early diagnosis and regular follow-up. Systematic eye exams for children—especially in families with a history of strabismus—are crucial for preventing neglected cases and amblyopia. In adults, early evaluation by a specialist helps in selecting the appropriate treatment before symptoms such as double vision or functional visual impairment develop.

Frequently Asked Questions

The procedure is performed as a day-case procedure: adult patients are discharged on the same day. Postoperative redness and tearing usually subside within one to three weeks. Most patients can return to their normal daily activities (office work or school for children) within one to seven days. Swimming (in pools or the sea) and strenuous physical activity should be avoided for two weeks, while contact sports should be avoided for four weeks. Driving is permitted as soon as any temporary diplopia (double vision) has resolved and the patient feels comfortable.

In the vast majority of cases, the result is stable. However, in approximately 20% of cases (as mentioned above), the strabismus may, over time, either remain partially undercorrected or recur, particularly in patients who have undergone multiple surgeries since childhood or in cases of strabismus associated with systemic diseases (e.g., thyroid eye disease, myasthenia gravis). In these cases, a second surgery may achieve the desired result. The adjustable suture technique significantly reduces the likelihood of needing additional surgery.

In some cases, particularly when the initial angle of deviation was large or the strabismus was chronic, a small residual angle of deviation may remain after surgery. If this is minor and the patient is asymptomatic and functions comfortably, no further intervention is required. If it causes symptoms (e.g., mild diplopia (double vision) or fatigue during prolonged reading), treatment is often non-surgical, involving prism correction incorporated into the patient’s glasses. A second surgical procedure is recommended only when there are clear functional or cosmetic indications.

Given that strabismus surgery in adults is internationally classified as reconstructive surgery—as discussed above, with documented functional benefits rather than purely cosmetic ones—it is generally covered by EOPYY and most private insurance companies. The exact coverage depends on the patient’s insurance policy. At our center, we provide all the documentation required for pre-authorization and reimbursement, based on the international guidelines of the AAO and ESA regarding the reconstructive nature of the procedure.

At Athens Vision, we offer specialized strabismus evaluations for adults and children. The preoperative evaluation includes measuring the angle of deviation in all positions of gaze, assessing binocular vision and stereoscopic function, a prism adaptation test (PAT), when indicated, and a thorough discussion of both conservative and surgical treatment options based on the patient’s individual clinical findings. The decision to proceed with surgery is made after a comprehensive consultation and mutual agreement between the patient and the surgeon.

A doctor who specializes in this condition

Anastasios Charonis

Ph.D. from the University of Freiburg, Board Certified by the American and European Boards of Ophthalmology
Specialties: Corneal Surgery – Transplants, Cataracts, Refractive Surgery, Pediatric Ophthalmology, Strabismus
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