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

SYNONYMS Squint Cross-eyed Wall-eyed

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

CONCOMITANT STRABISMUS

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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.

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

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

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

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

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

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

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