Answers on Ocular Motility
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    1.    a.T    b.T    c.T    d.T    e.F
     

      • This patient has intermittent exotropia of the divergence excess type because there is a difference of greater than 10 prism dioptre between near and distance and the patching did not eliminate this difference.
      • Binocular single vision is often suppressed on distant fixation when the exotropia is manifested, but it is usually normal with near fixation
            • Patching is useful to suspend the tonic fusional convergence and to

              • reveal the full latent deviation at near.
            • Spontaneous resolution is uncommon for intermittent exotropia.
          2.    a.T    b.T    c.T    d.F    e.T
             
            In intermittent exotropia:
             
            • tinted glasses are useful if bright light constitutes a major dissociative factor and allow the patient better control the deviation
            • concave glasses are useful in stimulating accommodation and convergence
            • orthoptic exercise is useful but is rarely successful if the deviation is more than 15 prism dioptre
            • base-in prism is used preoperative to control
            • the deviation and is usually in combination with exercise
            • miotic decreases accommodation and therefore make the exotropia worse

           
           
           

          3.     a.F    b.F    c.F    d.T    e.T
           

            Post-operative esotropia:
             
            • a small degree of consecutive esotropia is desirable and usually decreases as the effect of the surgery is lessen.
            • postoperative diplopia is common and usually resolves within 2 weeks.

              • patching is not needed as the patient is now 8 year-old and amblyopia is unlikely to develop.

           
           
           

          4.    a.T    b.F    c.F    d.T    e.F
           

            • The history and the orthoptic findings suggest that the patient has consecutive exotropia with dissociated vertical deviation and latent nystagmus. The underlying condition prior to surgery is likely to be infantile esotropia.
            • The majority of infantile esotropia  has a deviation of greater than 30 prism dioptres.
            • The binocular single vision is usually subnormal even with early surgery.
            • Asymmetrical optokinetic nystagmus is common.
              A small exotropia is cosmetically acceptable and does not require surgery.

           
           
           

          5.    a.F    b.T    c.F    d.T    e.T
           

            • The diagnosis is dissociated vertical deviation. It is seen in

              • 60 to 90% of infantile esotropia.
            • Bielchowsky phenomenon refers to elevation of the eye when the light entering that eye is reduced.
            • The majority of the cases are bilateral but may be asymmetrical.
            • In inferior oblique muscle overaction, the eye does not elevate when it is covered but shows elevation on adduction.

           
           
           

          6.    a.F    b.T    c.T    d.F    e.F
           

            • The patient has latent nystagmus. Manifest latent nystagmus is present when the nystagmus remains when both eyes are uncovered.
            • The fast phase is toward the side of the uncovered eye and increases on abduction.
            • Unlike congenital nystagmus, the wave form has a decreasing velocity slow phase.
              The cause is unknown but is not associated with cerebellar dysfunction.

           
           
           

          7.    a.F    b.T    c.F    d.F    e.F
           

            • Duane's retraction syndrome is more common in female than male and more likely to affect the left than right eye.
            • The type of Duane's retraction syndrome is type II
            • Narrowing of the lid is caused by globe retraction.
            • Amblyopia is uncommon and found in only 10% of the patient.

           
           
           

          8.    a.T    b.T    c.F    d.T    e.T

          Associated signs are:
        • cataract
        • heterochromia iridies
        • microphthalmos
        • crocodile tears
        • Marcus Gunn Jaw winking
        • Goldenhar's syndrome
        • Klippel-Feil's syndrome

          •  

          9.    a.F    b.F    c.T    d.T    e.T
           

            • The strabismus is incomitant.
            • Surgery is indicated to reduce or eliminate the abnormal head posture, or place the field of binocular single vision more central and enlarge the field.
            • However, the ocular movement does not improve with surgery.
            • Resection can worsen the globe retraction and narrowing of the lid fissure.
            • Faden procedure is useful in reducing the upshoot.

           
           
           

          10.    a.T    b.T    c.T    d.F    e.T
           

            In fourth nerve palsy:
            • The affected side is hyperdeviated and therefore the image is seen as lower and in addition the eye is extorted and therefore the image will also appear intorted giving the diagram as shown with the point of the V pointing towards the abnormal side
            • deviation of the eye in fourth nerve palsy depends on which eye is the fixating eye. If the fixating eye is the right eye, then the left eye will become hypodeviated and vice versa
            • in the three step test, the right eye is hyperdeviated in the primary position, on left gaze and right head tilt

           

          11.    a.T    b.F    c.F    d.T    e.F
           

            Feature of congenital fourth nerve palsy include:
             
            • absence of cyclotorsion
            • higher vertical fusional amplitude


            Abnormal head posture occurs in any long-standing fourth nerve palsy as a compensatory device and is not specific to congenital palsy.
             
             
             
             

          12.    a.T    b.T    c.T    d.F    e.T
           
            Features in favour of bilateral fourth nerve palsy include:
             
            • slight hyperdeviation in primary position
            • reversal of hyperdeviation and diplopia on lateral versions
            • large V pattern
            • chin depression being the main abnormal head posture with little or no head tilt
            • extorsion of more than 10 degrees
            • positive Bielchowsky head tilt test with head tilt to either shoulder
          13.   a.T    b.F    c.T   d.F    e.F
           
            Surgical treatment may involve:
             
            • right inferior oblique recession or left inferior rectus recession to control the vertical deviation
            • right Harada-Ito's procedure to control the cyclotorsion
           
           
           

          14.    a.T    b.F   c.T    d.T    e.F
           

            Sixth nerve palsy:
            • this patient has a right sixth nerve palsy
            • the esotropia is worse for distant than near
            • face turn to the affected side and therefore the right
            • duction is better than version and therefore the ocular movement is better when the unaffected side is closed
            • V pattern is common on upgaze
             
          15.    a.F   b.T    c.T    d.T    e.F
             
            Muscle sequelae are:
             
            • overaction of the left medial rectus
            • contraction of the right medial rectus
            • secondary inhibitional palsy of the left lateral rectus
           
           
           

          16.       a.F    b.T    c.F    d.T    e.T
           

            Additional signs and location:
             
            • both sixth nerve palsy and swollen discs can result from raised intracranial pressure and are of not localizing value
            • presence of Horner's syndrome point to a lesion in the cavernous sinus
            • presence of fourth nerve palsy can result from a lesion in the cavernous sinus
            • Folville's syndrome result from a lesion in the dorsal pons with ipsilateral abduction weakness, ipsilateral facial weakness and analgesia, ipsilateral peripheral deafness, loss of taste from the anterior two-third of the tongue and ipsilateral Horner's syndrome.
            • Millard-Gubler's syndrome result from a lesion in the ventral pons. The signs in additional to those seen in Folville's syndrome has an additional contralateral hemiplegia.
           
           
           

          17.    a.T    b.T    c.T    d.T    e.T
           

            Treatment of right sixth nerve palsy:
             
            • the use of botulinum toxin into the right medial rectus will reduce the contracture of the right medial rectus
            • use of base out Fresnel prism over the paralysed can help to fuse the double images
            • in patient without inhibitional palsy of the left lateral rectus, the following operation may be used:
                • a. recession of the left medial rectus combined with resection of the paresed lateral rectus
                b. Faden operation on the left medial rectus
            • in patient with fully developed muscle sequelae, the choice of surgery is recession of the right medial rectus combined with resection of the right lateral rectus.

           
           

          18.    a. T    b.F    c.F    d.T    e.T

             
            Microtropia:
             
            • a common form of anomalous binocular single vision
            • the strabismus is 10 prism dioptres or less
            • the squinting eye has reduced vision
            • anisometropia is found in most cases
            • stereopsis is reduced but rarely absent
            • foveal suppression scotoma is present in the affected eye and can be tested by placing a base out 4 dioptre prism over the affected eye; there is absent of eye movement.

           

          19.    a.F    b.T    c.F    d.T    e.F
           

            Spasmus nutans:
             
            • consists of nystagmus, involuntary head movement and abnormal head posture
            • usually begins between 3 to 18 months of age
            • nystagmus is jerky but of small amplitude and high frequency
            • involuntary head movement can be either head nodding or shaking or both
            • most resolves by 3 years of age
            • rarely associated with neurologic dysfunction but in some cases may be associated with glioma of the chiasm
           

          20.    a.T    b.T    c.T    d.T    e.F
           

            Accommodative esotropia:
             
            • usually occurs around 2 years of age
            • patients with accommodative esotropia usually suppress the deviating eye and therefore diplopia is uncommon; however due to the suppression amblyopia is common unless the patient has alternating esotropia
            • there is usually hypermetropia of greater than +3.00D or a high AC/A ratio

             

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