Squint STRABISMUS

SquintSTRABISMUS

Muscle Primary Secondary Tertiaryaction action actionMR Adduction LR Abduction SR Elevation Intorsion AdductionIR Depression Extorsion AdductionSO Intorsion Depression AbductionIO Extorsion Elevation AbductionVergences, also called disjugate movements, aresynchronous and symmetric movements of both eyesin opposite directions e.g.:

1. Convergence. It is simultaneous inward movement of both eyes which results from contraction of the medial recti.

2. Divergence. It is simultaneous outward movement of both eyes produced by contraction of the lateral recti.Synergists, antagonists and yoke muscles1. Synergists. It refers to the muscles having the same primary action in the same eye; e.g., superior rectus and inferior oblique of the same eye act as synergistic elevators.

2. Antagonists. These are the muscles having opposite actions in the same eye. For example, medial and lateral recti,

3. Yoke muscles (contralateral synergists). It refers to the pair of muscles (one from each eye) which contract simultaneously during version movements. For example, right lateral rectus and left medial rectus act as yoke muscles for dextroversion movements.

4. Contralateral antagonists. These are a pair of muscles (one from each eye) having opposite action; for example, right LR and left LR, right MR and left MR.

Diagnostic positions of gaze: primary position (e); secondary positions (b, d, f, h); tertiary positions (a, c, g, i); cardinal positions (a, c, d, f, g, i).STRABISMUS (SQUINT)Definition

A misalignment of the visual axes of the two eyes is called squint or strabismus.Classification of strabismus

Broadly, strabismus can be classified as below:I. Apparent squint or pseudostrabismus.II. Latent squint (Heterophoria)III. Manifest squint (Heterotropia) 1. Concomitant squint 2. Incomitant squint.HETEROPHORIA Heterophoria also known as latent strabismus, is aTypes of heterophoria1. Esophoria. It is a tendency to converge. It may be: i Convergence excess type (esophoria greater for near than distance). ii Divergence weakness type (esophoria greater fordistance than near). iii Non-specific type (esophoria which does not vary significantly in degree for any distance).2. Exophoria. It is a tendency to diverge. It may be: i Convergence weakness type (exophoria greater for near than distance). ii Divergence excess type (exophoria greater on distant fixation than the near).3. Hyperphoria. It is a tendency to deviate upwards, while hypophoria is a tendency to deviate downwards.

4. Cyclophoria. It is a tendency to rotate around the anteroposterior axis. B. Physiological factors1. Age. Esophoria is more common in younger age group as compared to exophoria which is more often seen in elderly.2. Role of accommodation. Increased accommodation Is associated with esophoria and decreased accommodation with exophoria (as seen in simple myopes).3. Role of convergence..4. Dissociation factor such as prolonged constantuse of one eye may result in exophoriaSymptomsdivided into compensated and decompensated.

Compensated heterophoria. It is associated with nosubjective symptoms. maintenance of binocular vision.

Decompensated heterophoria. It is associated withmultiple symptoms which may be grouped as under:1. Symptoms of muscular fatigue. Headache and eyeache DIfficulty in changing the focus from near todistant objectsPhotophobia due to muscular fatigue2. Symptoms of failure to maintain binocular single vision are: Blurring or crowding of words while reading; Intermittent diplopia due to temporary manifest deviation under conditions of fatigue; and Intermittent squint (without diplopia) 3. Symptoms of defective postural sensations cause problems in judging distances and positionsCONCOMITANT STRABISMUSIEtiology1. Sensory obstacles. These are the factors whichRefractive errors, Prolonged use of incorrect spectacles, Anisometropia, Corneal opacities, Lenticular opacities, Diseases of macula (e.g., central chorioretinitis), Optic atrophy, and Obstruction in the pupillary area due to congenitalptosis.

2. Motor obstacles.3. CENTRAL OBSTACLESClinical features of concomitant strabismus Ocular deviation.2. Ocular movements are not limited in any direction.3. Refractive error may or may not be associated.4. Suppression and amblyopia5. A-V patternsTypes of concomitant squintThree common types of concomitant squint are :1. Convergent squint (esotropia),2. Divergent squint (exotropia), and3. Vertical squint (hypertropia).EVALUATION OF A CASE OF CONCOMITANTSTRABISMUSI. HistoryII. Examination1. Inspection. Large degree squint 2. Ocular movements. 3. Pupillary reactions. 4. Media and fundus examination. 5. Testing of vision and refractive error. It is most important, 6. Cover tests7. Estimation of angle of deviation

Hirschberg corneal reflex testTREATMENT OF CONCOMITANT STRABISMUSGoals of treatment. These are to achieve goodcosmetic correction, to improve visual acuity and tomaintain binocular single vision. Treatment modalities. These include the following:1. Spectacles with full correction of refractive error2. Occlusion therapy. 3. Preoperative orthoptic exercises. These are givenafter the correction of amblyopia to overcomesuppression.4. Squint surgery. It is required in most of the casesPARALYTIC STRABISMUSEtiologyThe lesions may be neurogenic, myogenic or at thelevel of neuromuscular junction.I. Neurogenic lesions1. Congenital. 2. Inflammatory lesions. These may be in the formof encephalitis, meningitis, neurosyphilis or3. Neoplastic lesions. These include brain tumours

INCOMITANT SQUINTIt is a type of heterotropia (manifest squint) in whichthe amount of deviation varies in different directionsof gaze. It includes following conditions:1. Paralytic squint,2. A and V pattern heterotropias,3. Restrictive squint.II. Myogenic lesions1. Congenital lesions. 2. Traumatic lesions. 3. Inflammatory lesions. Myositis 4. Myopathies.

III. Neuromuscular junction lesionmyasthenia gravis. Clinical featuresSymptoms1. Diplopia. 2. Confusion. 3. Nausea and vertigo. These result from diplopia and confusion.4. Ocular deviation. It is of sudden onset.Signs1. Primary deviation. 2. Secondary deviation. 3. Restriction of ocular movement. direction of the action of paralysed muscles4. Compensatory head posture. 5. False projection or orientationManagement1. Treatment of the cause. 2. Conservative measures. These include: wait andwatch , vitamin B-complex as neurotonic; and systemic steroids for non-specific inflammations.3. Treatment of annoying diplopia. 4. Surgical treatment. not occur in 6 months.