Introduction
Duane syndrome is a congenital eye misalignment. There is difficulty in moving the eyes from side to side. There is difficulty in one or both eyes looking inwards towards the nose or outward towards the ear. There is also trouble in looking upward or downwards. The eyelids tend to move when the eyes move. In about 80 to 90 percent of cases, Duane syndrome is found to be unilateral, meaning only one eye is affected. The left eye is the most commonly affected. Horizontal eye movement limitations mainly characterize it. The eye-opening also narrows. This is also known as Duane retraction syndrome (DRS) and is non-progressive. Although rare, it must be excluded in patients with abnormal ocular motility and strabismus. To overcome this condition, a multidisciplinary team approach is needed to ensure improved patient condition.
What Is Duane Syndrome?
Duane syndrome is a condition of the eye that is congenital. It is a non-progressive limited horizontal eye movement, which is accompanied by globe retraction, which narrows the palpebral fissure. There is also a lateral movement anomaly. At birth, the affected infant has a restricted ability to move the eyes, although the limitation of movements does not get recognized early until infancy. Most affected individuals have isolated Duane syndrome, which means they are unaffected by any other congenital disease. This syndrome was previously known as Stilling-Turk-Duane syndrome, characterized by the absence or partial development of an abducent nucleus or nerve. Evaluating and managing this condition can be challenging, and a reasonable approach is necessary.
What Is the Cause of Duane Syndrome?
Although, firstly, this condition was described in the literature in 1887, the etiology remains elusive; with the advent of imaging technologies like magnetic resonance imaging (MRI), the underlying pathology for Duane retraction syndrome (DRS) could be better understood. It mainly results in the miswiring of the eye nerves. In this syndrome, the sixth cranial nerve, which controls the lateral rectus eye muscle, does not function properly; the muscle pulls the eye out towards the ear. As the nerve does not develop properly, even if the muscle does not develop properly, it could become weak or tight. There could also be miswiring of the third cranial nerve, which controls the medial rectus muscle; it is the muscle that pulls the eyes towards the nose. Thereby leading to the problem for people looking right or left.
How Prevalent Is Duane Syndrome?
Mostly, the condition is seen spontaneously, even when no one in the family has it, and mostly, only one eye gets affected. In about ten percent of the cases, it could be familial. It has been seen to occur in both autosomal dominant and autosomal recessive forms, presenting with genetic mutations. The left eye is most commonly affected in comparison to the right eye. The female gender is more affected than the males.
What Are the Features of Duane Syndrome?
The clinical features of Duane syndrome include:
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Abduction Limitation: There is subnormal innervation of the lateral rectus. It is most likely due to an abnormal adduction deficit.
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Abnormal Head Posture (AHR): Commonly seen in the unilateral cases. The head turns towards the affected eye.
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Globe Retraction: There is a narrowing of the palpebral fissure on adduction.
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Upshoots and Downshoots: These may be mechanical or innervational. The mechanical shoots, a sudden abrupt movement following a small vertical movement in adduction, are seen. In innervational shoots, gradual elevation or depression of the eye as it adducts is noted.
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Alphabet Patterns: The V pattern is the most common, and the A pattern is the least commonly found.
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Strabismus: The misalignment of the eyes. The eyes point in different directions.
Is Duane Syndrome Hereditary?
It is a condition that is very much hereditary; it is present since birth but may not always be seen during infancy. Most often people with a head tilt or turn or eye movement problem can be found in old photographs taken in early childhood, for people later found to have been suffering from this syndrome. Most of the time, it might not be hereditary; in about 90 percent of cases, it might not be. Only in ten percent of cases will people have an affected member in the family; in such cases, both eyes tend to have Duane syndrome.
Are There Different Types of Duane Syndrome?
Generally, Duane syndrome is of three types:
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Type I: There is difficulty in moving the eye outward towards the ear. It is the most common type of Duane syndrome. In this, the head is tilted toward the eyes with the problem of moving and will look like there are crossed eyes when looking straight forward.
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Type II: Difficulty for the eyes to move inwards towards the nose.
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Type III: Difficulty for the eyes to move inward and outward.
Duane syndrome may sometimes be accompanied by other eye symptoms like back-and-forth eyeball movement, cataracts, blurry vision, lazy vision, optic nerve problems, abnormally small eyes, and crocodile tears.
How Does Duane Syndrome Get Diagnosed?
The evaluation for this condition is very similar to strabismus, which includes the vision assessment, inspection, motor evaluation, and assessment of binocularity, along with other supplemental tests. Mostly, the diagnosis is made based on the clinical findings of the ophthalmologist. Genetic etiology is lacking in about 98 percent of those who show no family history and present with isolated Duane syndrome. A complete family history and medical history is a must. The degree of eye misalignment is measured, and the range of eye movement is tested. It is also determined if an abnormal head turn is an attempt to see better.
What Are the Treatment Options for Duane Syndrome?
The course of treatment is determined by the age, type, related disorders, specific symptoms, and family preferences. The non-surgical treatment includes contact lens spectacles and prism glasses to improve compensatory head position. The efficacy of botulinum toxins has also been investigated. The surgical option is not required for most patients, but the surgery can improve eye movement. Some people might need multiple surgeries, and the full effect of surgery may be seen in a few weeks and months. Surgeries are only indicated if there is a significant deviation of ocular deviation in the primary position, marked abnormal head position, or disfiguring retraction of the eye globe and upshoots and downshoots.
Conclusion:
Although an ophthalmologist does the initial evaluation, an interdisciplinary approach is needed to rule out uncommon systemic complications. Also, enhanced technologies and genetic studies need to be undertaken to improve the life quality of the patients and their families.
