Strabismus, commonly referred to as crossed eye, is a condition in which the affected individuals fail to aim at a single object at the same time. Lack of coordination between the eye muscles causes such a condition to develop.
Presentation
Development of crossed eyes and inappropriate alignment of eyes in the same direction are the classical symptoms of strabismus. In addition to these, the eye disorder can also cause double vision, loss of vision, loss of perception of depth and difficulty in moving both the eyes together [6].
Workup
At the preliminary level, a detailed physical examination of the eye will be carried out. This will be followed by various eye tests which would provide information about the extent of misalignment of the eyes. These tests include retinal exam, Hirschberg test, visual acuity, corneal light reflex and standard ophthalmic examination. In addition, neurological examination would also be performed to assess the neurological functioning [7].
Treatment
Strabismus can be treated in several ways which include the following:
- Eye glasses or patch: Children with strabismus are prescribed eye glasses if required. Also, it is necessary to treat amblyopia at first and therefore a patch is recommended which covers the healthy eye and forces the child to see with the weak eye.
- Eye muscle surgery: When other treatment methods fail, eye surgery is usually the last resort. Through this surgery, the muscles of the eye will be made stronger or weaker depending on the condition. However, eye surgery would still require the child to wear glasses. It is also recommended that sooner the surgery is done better will be the outcome [8].
- Eye exercises are recommended for both children and adults with strabismus. This helps the eye muscles to strengthen and keep the eyes straight.
- Botulinum toxin therapy was approved by the FDA way back in the year 1989 for treatment of strabismus in children over 12 years and adults. Children affected by infantile estropia benefit from this method. In this procedure, the toxin is injected in the stronger muscles in order to temporarily paralyze it [9] [10].
Prognosis
The prognosis of the condition post treatment is usually favorable. However, children and adults would continue to have vision problems. This may cause reading problems in children and adults would face difficulty while driving. Delay in treatment may lead to permanent vision loss in the weak eye. Follow up treatment and constant monitoring is a must as chances of recurrence of strabismus is high.
Etiology
Strabismus is a common phenomenon both in children and adults. Failure of the eye muscles to work in coordination causes both the eyes to look in two different directions. Certain underlying disease conditions which can also lead to strabismus in children include cerebral palsy, Apert syndrome, retinoblastoma, congenital rubella, Noonan syndrome, Prader-Willi syndrome, traumatic brain injury, incontinentia iigmenti syndrome, trisomy 18 and development of hemangioma near the eye during infancy.
Various diseases associated with strabismus in adults consist of diabetes, botulism, stroke, eye injury, vision loss due to eye injury or disease, Guillain-Barré syndrome and shellfish poisoning. In addition to the above mentioned factors, heredity is also known to be a strong risk factor for development of strabismus [2].
Epidemiology
It has been estimated that 4% of individuals in United States develop strabismus. Of the several forms of strabismus, estropia usually develops in the first decade of life [3]. It has also been reported that about 1/3rd of children with strabismus are at an increased risk of developing amblyopia.
Pathophysiology
Under normal conditions, the normal movement and alignment of human eye is governed by 6 muscles that work as a team. These ocular muscles help the eye to focus on the same object at same time. However, in instances when the muscles do not work appropriately it causes both the eye to look differently at two different objects.
As a result of this phenomenon, the brain receives information about 2 different objects. In children, the brain tends to ignore the information sent from the weak eye. In such situations, if strabismus is not promptly treated, then the brain will forever ignore information from the weak eye and as a result that eye will have poor vision. Such a condition is termed as amblyopia [4] [5].
Prevention
So far there are no known methods of preventing strabismus. Its associated complications can however be prevented with early initiation of treatment.
Summary
When the eyes align inappropriately with each other, they are unable to focus together on the same point at the same time. Strabismus gravely affects the binocular vision and in turn affects the depth perception as well. A prompt treatment regime is required to correct the condition so that maximum vision acuity can be retained. Strabismus can be classified into 4 different types, depending on directional prefixes. These include estropia, exotropia, hypotropia and hypertropia [1].
Patient Information
Definition
Strabismus is an eye disorder characterized by inappropriate alignment of the eyes which does not allow both the eyes to focus at the same object at same time. An estimated 4% US population develops this eye disorder. Early initiation of treatment can help in preventing onset of complications.
Cause
A total of 6 eye muscles work in coordination to provide appropriate alignment to the eyes. When the muscles do not work as a team, then strabismus develops. In addition, certain underlying disease conditions such as diabetes, eye injury, stroke, eye disease, restinoblastoma, Noonan syndrome, Apert syndrome, congenital rubella, trisomy 18, cerebral palsy and Prader-Willi syndrome can also predispose children and adults to develop such a condition.
Symptoms
Crossed eyes and inappropriate eye alignment are the major symptoms experienced. In addition, individuals also experience poor vision, loss of vision, loss of depth perception and inability to move both eyes together.
Diagnosis
Diagnosis of strabismus begins with preliminary physical examination of the eyes. In addition, neurological examination is also carried out to assess the neurological functioning. Following this various eyes tests such as corneal light reflex, retinal exam, cover/uncover test, visual acuity and standard ophthalmic test are also performed.
Treatment
Treatment of strabismus includes prescribing eye glasses and patches to the children. In case, when these do not work then eye surgery is recommended. In addition to these methods, botulinum toxin injection is also employed for treating strabismus.
References
- Harley RD. Pediatric Ophthalmology, WB Saunders Company, Philadelphia 1983. p.143.
- Aurell E, Norrsell K. A longitudinal study of children with a family history of strabismus: factors determining the incidence of strabismus. Br J Ophthalmol 1990; 74:589.
- Greenberg AE, Mohney BG, Diehl NN, Burke JP. Incidence and types of childhood esotropia: a population-based study. Ophthalmology 2007; 114:170.
- Archer SM, Sondhi N, Helveston EM. Strabismus in infancy. Ophthalmology 1989; 96:133.
- Mohney BG. Common forms of childhood esotropia. Ophthalmology. Apr 2001;108(4):805-9.
- The eyes. In: Pediatric diagnosis: Interpretation of symptoms and signs in children and adolescents, 6th, Green M (Ed), WB Saunders Company, Philadelphia 1998. p.15.
- Committee on Practice and Ambulatory Medicine, Section on Ophthalmology. American Association of Certified Orthoptists, American Association for Pediatric Ophthalmology and Strabismus, American Academy of Ophthalmology. Eye examination in infants, children, and young adults by pediatricians. Pediatrics 2003; 111:902.
- Ho TH, Lin MC, Sheu SJ. Surgical treatment of acquired esotropia in patients with high myopia. J Chin Med Assoc. Aug 2012;75(8):416-9.
- Birch E, Stager D, Wright K, Beck R. The natural history of infantile esotropia during the first six months of life. Pediatric Eye Disease Investigator Group. J AAPOS 1998; 2:325.
- Fukai S, Arai N, Hayakawa T, Kimura H. Studies on the botulinum therapy for esotropia improvement of retinal correspondence. Nippon Ganka Gakkai Zasshi. Jun 1993;97(6):757-62.