900 likes | 3.53k Views
Incomitant strabismus. Nadia Northway. Definition. Deviation varies with size and or direction of gaze In truth nearly all forms of strabismus are incomitant to a degree but clinically there is usually more than 5 o difference before incomitancy is noted. Aetiology.
E N D
Incomitant strabismus Nadia Northway
Definition • Deviation varies with size and or direction of gaze • In truth nearly all forms of strabismus are incomitant to a degree but clinically there is usually more than 5odifference before incomitancy is noted.
Aetiology • Vascular affects all nerves equally • Head trauma more commonly affects IVth nerve but may affect all • Aneurysm most commonly affects IIIrd nerve • Neoplasm • Unknown • Other
Systemic Diseases • Diabetes • Thyrotoxicosis • Hypertension • Aneurysm • Giant cell arteritis • Multiple Sclerosis • Myasthenia Gravis
Investigation • History and symptoms • External Examination • Cover test • Motility • Ophthalmoscopy • Fields
Symptoms • Diplopia • Abnormal head posture-chin, turn and tilt • Acuity • Associated symptoms • General health • Injury
External Examination • Strabismus • Lid position • Injury- chemosis, oedema • Proptosis • Pupils • Asymmetry
Abnormal Head Postures • Always turn in direction of action of palsied muscle e.g. LMR palsy will turn to right • Always move chin in direction of action of palsied muscle e.g. LSR palsy will elevate chin • Always tilt to lower eye
Findings on Cover Test • Small deviation in primary position may indicate very recent onset < 36 hours or mechanical problem • In palsy- will be greater when fixing with the affected eye and usually larger size of deviation
Ocular Motility • Know muscle actions • Take patients eyes into extremes of gaze • Use objective and subjective assessment- corneal reflexes and CT. Do not rely on pt reporting diplopia since suppression or poor VA may affect results. • Hess chart and diplopia chart.
Secondary actions • RAD SIN- recti adduct and superiors intort • Recti muscles pull the eye in the direction of their name in the abducted position • Obliques push the eye in the direction opposite to their name in the adducted position
Muscles Sequelae • Original palsy • Overaction of the contralateral synergist • Overaction of the ipsilateral antagonist • Inhibitional palsy • This applies to neurogenic palsy and after all stages of sequelae have occurred concomitancy is achieved
Muscle actions IO IO SR SR MR LR LR IR SO SO
Mechanical sequelae • Overaction of contralateral synergist only • Left Brown’s syndrome overaction of right superior rectus is seen
Interpretation of Hess Plot • Look for smallest field to identify affected eye • Look at center circle to determine deviation in primary position • Look for area with greatest deflection to identify affected muscles
Bielchowsky Head Tilt Test • Used to differentiate between SR and SO palsy • Muscle sequelae identical • In left SO palsy deviation will increase when head tilted to left due to unopposed action of the LIO
Third Nerve Palsy • Complete or partial • Rare to find individual muscles affected but Congenital SR palsy quite common • May also be multiple muscle involvement including pupil and ciliary body
Superior Rectus Palsy • Hypotropia of affected eye and may be slightly exo • Chin elevation • Can be longstanding -usually have enlarged fusion range and some suppression
Inferior Rectus Palsy • Hypertropia in primary position
Inferior Oblique Palsy • Hypotropia in primary position with possible slight eso.
Medial Rectus palsy • Exo deviation
Complete Third Nerve Palsy • Exotropia with hypotropia, ptosis and possible dilation of pupil and accommodation palsy
Sixth Nerve Palsy • Esotropia which is greater on distance fixation
Fourth Nerve palsy • Hypertropia with slight eso , eye also extorted, greater at near
Browns Syndrome • Small devation in primary position but hypotropia of affected eye on elevation in adduction
Blow Out Fracture • May be hypotrpia or hypertropia • Infraorbital anaesthesia • Chemosis • Vertical diplopia • Restricted eye movement in upgaze and downgaze
Dysthyroid eye disease • Wet phase when muscles swell -myogenic • Dry phase when eye movement restrictions become mechanical in characteristics • Muscles affected - IR MR SR rarely LR • Proptosis or exophthalmos • Check Fields • Lid retraction and lid lag
Differentiation of mechanical and neurogenic palsy • Neurogenic • Large deviation in pp • Ductions better than versions • Gradual failure of movement • No pain • No upshoots and downshoots • Mechanical • Small deviation in pp • Ductions and versions equal • Ceasing of movement abrupt • Pain • Reversal of diplopia • Upshoots and downshoots
Differentiation of mechanical and neurogenic palsy • Mechanical • Muscle sequelae- only overaction of contra syn • Hess chart -pointed field which look squashed • Neurogenic • Full muscle sequelae • Smoother filed on Hess
Differentiate Longstanding and Acquired Deviations • Newly acquired • Pt aware of AHP and uncomfortable • Diplopia • Sudden onset • No enlarged fusion range • Longstanding • AHP - fixed and pt usually unaware • No diplopia • Enlarged fusion ranges • Old photographs • Gradual onset of symptoms usually • Amblyopia • Suppression
Differentiate SR and SO palsy • SO • Eso deviation more typical • AHP - chin depression • V eso pattern • Greater vertical deviation at near • Bielchowsky +ve • Diplopia greatest on depression • SR • Exo deviation more typical • AHP- chin elevation • V exo pattern • Greater deviation in distance • Bielchowsky -ve • May have history of ptosis • Diplopia greatest on elevation