1. İ.Ü. Cerrahpaşa Tıp Fakültesi, Göz Hastalıkları Anabilim Dalı
Strabismus
Prof.Dr. Emel Başar
İ.Ü. Cerrahpaşa Tıp Fakültesi,
Göz Hastalıkları Anabilim Dalı

2. SYNONYMS
Squint
Cross-eyed
Wall-eyed

3. DESCRIPTION
Misalignment of the eyes, such that both eyes are not simultaneously directed at the same object
Esotropia is a common type of strabismus characterized by inward deviation of one eye relative to the other
Infantile esotropia is inward deviation of the eyes noted before the patient reaches age 6 months
Exotropia is a common type of strabismus characterized by outward deviation of one eye
relative to the other

4. CONCOMITANT STRABISMUS

5. EPIDEMIOLOGY Incidence and prevalence PREVALENCE
One of the most prevalent ocular problems among children, affecting 50 in every 1000 US citizens, or some 12 million people in a population of 245 million
Estimated prevalence of strabismus in the general population is 20-60/1000
Of this, infantile esotropia is believed to affect about 1 % of full-term, healthy newborns and a much higher percentage of newborns with perinatal complications due to prematurity or hypoxic/ischemic encephalopathy

6. EPIDEMIOLOGY Demographics AGE
Usually presents in patients aged 2-3 years
By definition, infantile esotropia is seen in infants before age 6 months
GENDER
No gender predilection exists.
RACE
No racial predilection exists.
GENETICS
It is strongly believed that a genetic component exists, but a solid basis for linkages among family members is still to be established
Around 20-30% of children born to a strabismic parent will eventually develop strabismus

7. CAUSES OF STRABISMUS Common causes
Exact cause of infantile esotropia remains unknown
Results from paralysis of one or more ocular muscles; may be caused by a specific oculomotor nerve lesion (Paralytic Strabismus)
Disuse of an eye, as in cases of severe refractive error or impaired vision due to disease, may also result in strabismus
Ambiyopia or lazy eye (reduced visual acuity caused by an abnormal visual experience early in life) may occur in strabismus, usually due to cortical suppression of the image in the deviating eye to avoid confusion and diplopia

8. CAUSES OF STRABISMUS Rare causes
Patients with craniofaciai syndromes, ocular albinism, midline defects, and cerebral palsy may present with congenital exotropia.

9. CAUSES OF STRABISMUS Serious causes
A specific oculomotor nerve lesion may cause paralysis of one or more ocular muscles
In children, such a nerve lesion may be caused by cerebral palsy, Down syndrome,hydrocephalus, or brain tumors
In adults, nerve lesion may be caused by stroke, diabetes, cardiovascular disease, tumors, or trauma
If there is a cranial nerve lesion the strabismus it is paralytic

10. CAUSES OF STRABISMUS Contributory or predisposing factors
Infantile esotropia: perinatal complications (e.g. prematurity, birth injury, low birthweight).

11. CARDINAL FEATURES General
Deviation may be constant, or it may come and go
May be present at birth, become apparent at a later age, or occur following an illness or accident
Horizontal deviations can be divided into two broad categories - esotropias and exotropias. Esotropia designates a convergent horizontal strabismus (one eye turns in) and exotropia designates a divergent horizontal strabismus (one eye turns out)
If angle of deviation remains same for all gaze directions this a CONCOMITANT STRABISMUS

12. CARDINAL FEATURES General
Misalignment of the visual axes of the two eyes may interfere with patient's ability to fuse and to develop normal binocular vision, this may cause suppression in one eye (amblyopia or lazy eye) in children and diplopia (double vision) in teenagers and adults
Abnormal vertical head postures, e.g. head turning, may develop to place the eyes in position of minimal deviation to restore single binocular vision

13. CARDINAL FEATURES Esotropia
Accommodative esotropia (refractive accommodative esotropia) - an esodeviation due to normal accommodation in uncorrected hyperopia (far-sightedness)
Uncorrected hyperope must exert accommodation to clear a blurred retinal image. Process of accommodation will stimulate convergence and strain fusional divergence. When fusional divergence is overcome, the eyes cross

14. CARDINAL FEATURES Esotropia
Patient with uncorrected hyperopia can see either a single blurred image or a double image in which one image is clear and one is blurred
Over time, the blurred image can be suppressed, fixation can alternate, or, more commonly, amblyopia (lazy eye) can occur

15. CARDINAL FEATURES Infantile esotropia
Inward deviation of the eyes noted before the patient reaches age 6 months
Infantile esotropia is not believed to be connatal, but develops in the first few weeks or months after birth
Children who undergo surgical alignment at age 6 months have a higher prevalence of coarse stereopsis than those who are corrected surgically at age 7-15 months

16. CARDINAL FEATURES Infantile esotropia
Amblyopia is relatively common in patients with infantile esotropia Amblyopia should be suspected strongly in patients with esotropia and asymmetric inferior oblique activity, specifically in the eye with more inferior oblique overaction
Virtually all patients with infantile esotropia fail to develop normal binocular vision and stereopsis

18. CARDINAL FEATURES Exotropia
As many as 60% of patients who have exotropia may develop oblique muscle dysfunction, dissociated vertical deviation, and amblyopia
Nystagmus is rare

20. CARDINAL FEATURES Adult strabismus
When strabismus occurs in an adult for the first time, it leads to double vision, or diplopia
Secondary to the inability of a person to use both eyes together (binocular vision) or other unknown causes
Most often, the poor-seeing eyes drift outward

21. DIFFERENTIAL DIAGNOSIS
Oculomotor nerve palsy
Extraocuiar muscle paralysis resulting from destructive lesions in one or all of the cranial nerves results in failure of one or both eyes to rotate in concert with the other eye.

22. DIFFERENTIAL DIAGNOSIS
Oculomotor nerve palsy
FEATURES
Diplopia from misalignment of visual axes
With unilateral third cranial nerve palsy, the involved eye usually is deviated down and out (infraducted, abducted), and ptosis may be present, which may be severe enough to cover the pupil
Pupillary dilatation can cause symptomatic glare in bright light (if ptotic lid does not cover the pupil)
Paralysis of accommodation causes blurred vision for near objects
Glare sensation and photoaversion in bright light

24. DIFFERENTIAL DIAGNOSIS
Abducens nerve palsy
Cranial (abducens) nerve VI defect. Ipsilateral lateral rectus, which is solely innervated by the involved peripheral sixth cranial nerve, is affected.

25. DIFFERENTIAL DIAGNOSIS
Abducens nerve palsy
FEATURES
Horizontal diplopia and an esotropia in primary gaze
Deviation greater when the patient fixates with the paretic eye
Head-turn to maintain binocularity and binocular fusion, and to minimize diplopia

27. DIFFERENTIAL DIAGNOSIS
Duane syndrome
Congenital ocular motiiity disorder characterized by limited abduction and/or limited adduction.

28. DIFFERENTIAL DIAGNOSIS
Duane syndrome
FEATURES
Upward or downward deviation may occur with attempted adduction due to a leash effect
Face-turn with strabismus in primary position
Upshoot or downshoot during adduction
Vertical deviation in primary position
Retraction during adduction
Enophthalmos

30. MANAGEMENT ISSUES Goals Preserve vision Straighten the eyes
Restore binocular (two-eyed) vision
Prevent amblyopia
Prevent diplopia in adults
Obtain normal visual acuity in each eye
Obtain and/or improve fusion

31. MANAGEMENT ISSUES Goals
Obtain favorable functional appearance of alignment of eyes
The best optical correction that allows a clear retinal image to be formed in each eye is generally the starting point for all treatments

32. SUMMARY OF THERAPEUTIC OPTIONS
Choices
First choice is corrective lenses and prisms. The eye caregiver will determine whether or not a trial of spectacles can treat the strabismus
Second choice is patching. In cases of amblyopia, early treatment with patching the normal eye is the mainstay of treatment, often associated with use of spectacles
Third choice is surgery. The eye caregiver may determine that surgery is needed to correct the strabismus

33. SUMMARY OF THERAPEUTIC OPTIONS
Choices
Fourth choice is botulinum toxin. Chemodenervation using botulinum toxin as an alternative to conventional incisional surgery is used in selected strabismic patients (those with small-to-moderate degrees of horizontal ocular misalignment, postoperative residual strabismus, acute paralytic strabismus)
Fifth choice is anticholinesterase miotics. These can serve as temporary alternatives to corrective glasses and bifocal lenses for children with accommodative esotropia