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الكلية كلية الطب
القسم الجراحة
المرحلة 5
أستاذ المادة اسعد جعفر عبد السادة الطائي
4/19/2011 9:25:25 PM
Strabismus (Squint)
Clinical evaluation:
History:
Age of onset, duration, previous photographs may prove helpful. Symptoms, variability (intermittent or constant, alternating or unilateral), general health, birth history, family history & previous ocular history.
Examination:
? Inspection especially any abnormal head posture (which may be either face turn, head tilt, or chin elevation, in horizontal, cyclovertical, & lid elevation defects respectively), nystagmus, or any associated gross ocular or facial abnormalities.
? Visual acuity (VA): for each eye with & without correction to detect amblyopia.
? Anterior segment examination preferably by using the S/L to detect medial opacities.
? Ophthalmoscopy: to detect serious fundus abnormalities that may have caused the squint.
? Cover test: to detect alternation.
? Ocular movement examination: to detect comitance.
? Refraction under cycloplegia: should be done to all children & young adults especially in cases of accommodative squint.
Concomitant squint:
Esotropia: most common.
Early onset (congenital, essential, infantile):
Up to 4 months of age infrequent episodes of convergence are normal. After 4 months misalignment is abnormal. Early onset esotropia is an idiopathic condition developing within the first 6 months of life in an otherwise normal infant with no significant refractive error. The angle is usually large, fixation is alternating in primary position & crossed in side gaze (this may be misdiagnosed as bilateral abducens palsy). To differentiate we may use doll s head manoeuvre, or uniocular patching for a few hours. Horizontal nystagmus, latent or manifest may be present.
Treatment: Ideally, surgery before age 12 months, after correction of amblyopia or refractive error if present.
Accommodative esotropia:
Near vision involves both accommodation & convergence. Both are quantitatively related to the proximity of the target, & have a fairly constant relationship to each other called AC/A ratio. Types:
(1) Refractive : AC/A ratio is normal, hypermetropia is +2 to +7 D. The difference between far & near deviation is usually small.
(2) Non refractive: AC/A ratio is high. This occurs independently on refractive error, although hypermetropia frequently coexists.
Medical treatment: Refractive error should be corrected, & it is the full cycloplegic correction before 6 years, & the maximum amount of plus lenses of the non cycloplegic correction that the patient can tolerate if he is more than 8 years of age.
If the child still converges for near prescribe a bifocal for him. You may be able to reduce them gradually till the teenage. If this failed, sugery is the answer, but only after amblyopia correction.
Exotropia: less common than esotropia
Constant (early onset) exotropia:
Presentation is often at birth. Refraction is normal & the angle of deviation is large. Neurological anomalies are frequently present, in contrast with early onset esotropia.
Treatment is surgical.
Intermittent exotropia:
The most common of exotropias. Presentation is often around 2 years with exophoria, which breaks down to exotropia under conditions of visual inattention, bright light (resulting in reflex closure of the affected eye), fatigue or ill health. Signs: The eyes are straight with BSV at times, & manifest with suppression at other times. The control of the squint varies with the distance of fixation & other factors such as concentration.
Treatment: Spectacle correction in myopic patients may, in some cases, control the deviation. Over minus prescription may even be useful. Orthoptic treatment: Part time occlusion of the deviating eye may improve control in some patients, & orthoptic exercises may be helpful for near exotropia. Surgery: Patients with good & stable control are often just observed. Surgery is indicated if control is poor, or is progressively deteriorating.
Sensory exotropia:
Secondary (sensory) exotropia is the result of monocular or binocular visual impairment by acquired lesions, such as cataract or other opacities of the media. Exodeviations tend to occur in older children or adults. Esodeviation tends to occur in infancy, but this is not invariable. Treatment consists of correction of visual deficit, if possible, followed by surgery if needed.
Inconcomitant strabismus:
Characterized by normal sensory & central components of the binocular reflex, the lesion lying somewhere along the efferent motor pathway, i.e. between the motor nucleus in the brainstem & the extra-ocular muscle. Such lesions are generally neurogenic, affecting the III, IV or VI cranial nerves.
Paralytic strabismus:
The most common of the inconcomitant strabismus. The main symptom of the acquired type in adults is diplopia & the main sign is abnormal head posture. In addition to the variable angle, other neurological findings may be found. Primary deviation is when the normal eye fixates, & secondary deviation is when the eye with the paralysed muscle fixates. Secondary deviation is usually larger than the primary, according to Hering s law. Management: wait for 6–9 months for the nerve to regenerate & regain function, if after that there is still deviation in primary position or down gaze, the answer is surgery.
Restrictive strabismus:
The least common, as an example dysthyroid ophthalmopathy.
Here is a list of tests & instruments used for inconcomitant squint examination, in addition to those mentioned in the clinical evaluation:
? Forced duction test.
? Hess screen & Lees screen.
? Nine square chart.
? Bielschowsky head tilt test.
? Mnemonic of Maddox.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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