Strabismus: A Comprehensive Overview

Strabismus, commonly referred to as “crossed eyes” or “wandering eyes,” is a visual condition characterised by the misalignment of one or both eyes. This condition can have significant implications for visual acuity and quality of life. Below is a detailed discussion on strabismus, diagnosis, affected populations, treatments, and potential complications, intended to provide medical professionals with a comprehensive understanding of this condition.

What is Strabismus?

Strabismus is a condition where the eyes are not symmetrically aligned with each other when looking at an object. The misalignment can be constant or intermittent, and it may affect one or both eyes. Depending on the direction of the eye misalignment, strabismus is categorised into various types, including:

  • Esotropia: The inward turning of the eye.
  • Exotropia: The outward turning of the eye.
  • Hypertropia: The upward turning of the eye.
  • Hypotropia: The downward turning of the eye.

Strabismus can occur due to imbalances in the muscles controlling eye movement, neurological issues, or refractive errors. The condition can manifest in infancy (congenital) or develop later in life (acquired), often impacting depth perception and binocular vision.

How is it Diagnosed

Diagnosis of strabismus involves a comprehensive eye examination by an ophthalmologist or optometrist. The evaluation generally includes:

  • Visual acuity testing: This helps in determining the degree of vision impairment.
  • Cover-uncover test: A common test used to assess ocular alignment. The patient’s eyes are alternately covered while observing any movements of the uncovered eye.
  • Corneal light reflex test: A light is shone into the eyes to check for symmetry in the reflection. A misalignment indicates the presence of strabismus.
  • Refraction test: This helps determine if refractive errors (e.g., hyperopia, myopia) are contributing to the condition.
  • Ocular motility testing: This evaluates the coordination of eye movements and helps determine any limitations in muscle function.
  • In some cases, additional diagnostic tools, such as imaging studies (e.g., MRI or CT scans), may be necessary to rule out neurological or structural causes.

Who is Primarily Affected?

Strabismus can affect people of all ages, but certain populations are at higher risk:

  • Infants and young children: Congenital strabismus typically manifests in early childhood. It is estimated that 2-4% of children are affected by some form of strabismus before reaching the age of five.
  • Adults: While strabismus is more common in children, it can also occur in adults due to trauma, stroke, or neurological conditions.
  • People with certain medical conditions: Individuals with cerebral palsy, Down syndrome, or other neurological disorders have an increased risk of developing strabismus.
  • Family history: Genetic predisposition plays a significant role, with a higher likelihood of strabismus occurring in individuals with a family history of the condition.

How is it Treated

Treatment for strabismus is crucial to prevent long-term complications such as amblyopia (lazy eye) and loss of binocular vision. The main treatment modalities include:

  • Corrective glasses: Refractive errors contributing to the misalignment can be managed with glasses, especially in children. Hyperopia (farsightedness) is a common refractive cause of esotropia.
  • Prism lenses: These can help correct mild forms of strabismus by bending light and reducing the effort required to align the eyes.
  • Vision therapy: Orthoptic exercises, designed to improve coordination between the eyes, may be effective in cases of intermittent or mild strabismus.
  • Botulinum toxin (Botox) injections: In certain cases, Botox can be injected into the extraocular muscles to temporarily paralyze overactive muscles, allowing the opposing muscle to regain alignment.
  • Surgical intervention: Strabismus surgery involves repositioning or tightening the extraocular muscles to improve eye alignment. This is often required in more severe cases or when other treatment options are ineffective. Surgical success rates are high, particularly when performed early in life.

The choice of treatment depends on factors such as the type, severity, and underlying cause of the strabismus, as well as the age and overall health of the patient.

What are the Complications?

If left untreated, strabismus can lead to several complications that may significantly impact visual function and quality of life. These include:

  • Amblyopia (lazy eye): A major concern in paediatric strabismus, amblyopia occurs when the brain favours one eye over the misaligned eye, leading to reduced vision in the affected eye.
  • Loss of binocular vision: Strabismus can disrupt binocular vision, which is necessary for depth perception and three-dimensional viewing. This can affect day-to-day activities such as driving, reading, or playing sports.
  • Psychosocial impact: In children and adults alike, visible eye misalignment can lead to social and psychological challenges, including reduced self-esteem, social withdrawal, and emotional distress.
  • Double vision (diplopia): In cases of acquired strabismus, particularly in adults, patients may experience diplopia due to the brain’s inability to merge the images from each eye.
  • Recurrent strabismus: Even after successful treatment, strabismus may recur, requiring ongoing monitoring and, in some cases, repeat interventions.

Conclusion

Strabismus is a condition with significant clinical implications, particularly if left untreated. Early diagnosis and intervention, especially in children, are crucial to prevent complications such as amblyopia and impaired binocular vision. Treatment options are varied and should be tailored to the individual patient, depending on the type and severity of the misalignment. For medical professionals, a multidisciplinary approach involving ophthalmologists, neurologists, and paediatricians may be necessary to ensure optimal outcomes.

References
  • Donahue SP, Baker JD. Procedures for the evaluation of strabismus in children. Pediatrics. 2016;137(5)
  • S.E. Olitsky, D.K. Coats, Complications of Strabismus Surgery, Middle East Afr J Ophthalmol. 22 (2015) 271–278. https://doi.org/10.4103/0974-9233.159692.
  • Kanukollu VM, Sood G. Strabismus. [Updated 2023 Nov 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560782/Management of Strabismus: An Atlas of Strabismus Surgery, 5th ed. Springer; 2010.

Written by Dr Cyra Asher (SHO) & Reviewed by Ms Anupama Pherwani (Consultant Ophthalmologist)

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