Definition
Misalignment of visual axes of the two eyes in the vertical direction in any of the nine cardinal positions of gaze, latent or manifest, constant or intermittent is called vertical strabismus.
Vertical strabismus is more symptomatic than horizontal strabismus. Usually the vertical recti or the oblique muscles are involved. Diagnosis, analysis and treatment is often more complex than horizontal strabismus.
Symptoms
Common symptoms of vertical strabismus are vertical diplopia, vertical deviation of the eyes and abnormal head posture – head tilt and chin up or down.
Signs
Common signs include ocular deviation in the vertical direction in any of the nine cardinal positions of gaze with either eye fixing on Hirschberg test and prism cover tests.
Ocular motility tests can show limitation of movements in the vertical direction. The tests used in these cases include Diplopia charting (note the presence of vertical diplopia and the position of maximum separation of images), Hess charting, double Maddox rod test, binocular field of fixation, Parks 3 step diagnostic test, Forced duction test, Force generation test, etc.
TYPES OF VERTICAL STRABISMUS
1. Comitant vertical strabismus
Dissociated Vertical Deviation
2. Incomitant Vertical squint
2.1 Neurogenic palsy
a. Supra nuclear (gaze) palsy, b. Nuclear, c. Infra nuclear palsy (3rd and 4th cranial nerve palsy).
2.2 Myogenic dystrophies and myasthenia
2.3 Restrictive squints
a. Vertical deviations in Duanes retraction syndrome,
b. Browns syndrome,
c. Congenital muscle fibrosis,
d. Dysthyroid orbitomyopathy,
e. Post traumatic orbital wall fractures,
f. Tumors, pseudotumors and cysts in the orbit.
2.4 Deviations with primary overaction of the inferior oblique
3. Other conditions
Monocular elevation deficiency, monocular depressor deficiency, heavy eye syndrome, post surgery- retinal detachment, squint, conjunctival, orbital surgeries-scarring (restrictive) or paralysis.
4. Cyclovertical motility abnormalities with horizontal deviations: alphabet pattern squints.
1. Comitant vertical strabismus
Dissociated Vertical Deviation (DVD)
Dissociated vertical deviation is characterized by spontaneous upward deviation of an eye frequently associated with abduction and excycloductionof the deviating eye and latent nystagmus. It becomes more obvious on fatigue, day dreaming or covering one eye. On recovery the eye slowly drifts back into position. As the eye comes down there is no downward movement of the other eye. It usually presents from 2 to 5 years of age. It has a common association with infantile esotropia and sometimes with infantile exotropia, sensory heterotropias, Duanes retraction syndrome, etc.It is usually bilateral but asymmetrical. In deeply amblyopic eyes or in sensory heterotropias it is unilateral.
Important differential diagnosis
Dissociated vertical deviation must be differentiated from Inferior oblique over action since both conditions can cause hypertropia.
The features of inferior oblique over action are: Hypertropia maximum in adduction and never in abduction, on the cover-uncover test the refixation movement of the deviating eye is quick, ipsilateral superior oblique usually underacts, V-pattern is present, no incycloduction on refixation, may be associated with latent nystagmus, Bielschowsky’s phenomenon is absent and on the red filter test red image is higher or lower on alternation.
The features of Dissociated vertical deviation are: Hypertropia is same in adduction, abduction or primary position, on the cover uncover test the refixation movement of the deviating eye is a slow drift downwards, Superior oblique may overact, v-pattern may be present, Pseudo paresis of the contralateral superior rectus is absent, Incycloduction on refixation is present, latent nystagmus often present, Bielschowskys phenomenon is present, on the red filter test-red image is always lower as the eye behind the red filter is always higher.
Probable etiology– imbalance of binocular stimulation.
Diagnostic tests
1. Spielmanns translucent occluder testdemonstrates the slow up drift with or without
excyclotorsion and abduction on cover and the characteristic slow downward recovery movement on removing the occluder.
2. Bielschowsky’s or Bagolini’s graded density filter bar can be used to demonstrate that as the density is increased the eye drifts up and as the density is decreased the eye comes down.
3. Red filter test dissociates the two eyes. The eye behind the filter drifts up and the patient appreciates diplopia with the red image being lower. If the red filter is transferred to the other eye that eye deviates up in bilateral DVD and the red image is again at a lower level.
4. If we perform the cover test with the fixating eye in surso-adduction the eye behind the cover still drifts up.
Treatment
1. Recession of Superior rectus muscle (7-9 mm) –good for bilateral cases.
2. Retro equatorial myopexy of the Superior rectus combined with Superior rectus recession.
3. Total anterior positioning of the Inferior oblique muscle if the DVD is associated with inferior oblique over action.
2. INCOMITANT VERTICAL SQUINT
2.1 Neurogenic palsy
a. Supra nuclear (gaze) palsy usually causes lack of conjugate gaze movements like paralysis of up gaze(Parinaus syndrome) but no loss of parallelism of the visual axes. Supra nuclear lesions can also cause unilateral paralysis of elevation characterised by absence of active elevation of one eye, both voluntary and automatic, except for Bell’s sign which is intact. No deviation is seen in primary position. Differential diagnosis is from double elevator paralysis which exhibits hypotropiain primary position and absence of Bell’s sign.
b. Nuclear and c. Infranuclear palsy.
Third cranial nerve palsy
Third cranial nerve palsy is a common cause for hypotropia. The third cranial nerve supplies the levator palpabrae superioris & superior rectus (superior division) and the medial rectus, inferior rectus, inferior oblique, sphincter pupillae and the ciliary body( inferior division).
In a total third nerve palsy there is ptosis, limitation of elevation (both in adduction and abduction), adduction and depression, iridoplegia and cycloplegia.
Partial 3rd nerve lesions manifest with affection of the corresponding muscles.
In isolated 3rd cranial nerve palsy,the eye is deviated down and out because of unopposed action of the lateral rectus and the superior oblique muscles.
Third nerve palsy can be congenital or acquired. In congenital 3rd nerve palsy the intrinsic muscles are seldom affected and usually lateral rectus contracture is absent. In acquired 3rd nerve palsy there is a greater tendency for lateral rectusand superior oblique contracture. Hence there is a larger exotropia and a small hypotropia in acquired 3rd nerve palsy compared to congenital 3rd nerve palsy.
4th cranial nerve palsy (Superior oblique Muscle palsy)
Superior oblique muscle palsy is a common cause for hypertropia. Trochlear nerve supplies the superior oblique muscle. It is a crossed cranial nerve. The 4th nerve nucleus innervates the contralateral superior oblique muscle hence nuclear lesions of the 4th nerve nucleus produces contralateral superior oblique weakness. Lesions of the nerve produce ipsilateral superior oblique weakness. Fourth nerve palsy can be congenital or acquired, unilateral or bilateral.
The clinical features in Left 4th nerve palsy are left hypertropia in primary position. Increase in left hypertropia on right gaze due to left inferior oblique overaction , limitation of left depression on adduction, normal left abduction, left elevation and depression in abduction.
Diplopia is vertical, torsional and worse on looking down (Patient has difficulty coming down the stairs). Abnormal head posture consists of tilt and turns to the opposite side and chin depression.
Bilateral involvement should always be suspected until proved otherwise. It is characterized by right hypertropia in left gaze and left hypertropia in right gaze, greater than 10 degrees cyclodeviation on double Maddox rod test, V-pattern esotropia and bilaterally positive Bielschowsky test.
Management
Management is based on Knapp’s classification.
The directions in which maximum gaze involvement occurs can differ in different cases and determines the choice of surgery.
Example: In Right superior oblique palsy the gaze position of maximum involvement and the choice of surgery are as follows:
1.Levoelevation - Right inferior oblique recession
2.Levodepression - Right superior oblique tucking, left inferior rectus recession or modified Harada Ito procedure.
3. All levoversion positions- RIO recession or RIO recession with RSO tuck.
4. All down gaze positions and levo positions –as in class 3 + Left inferior rectus recession or Right superior rectus recession (if FDT shows tight superior rectus)
5. All down gaze positions –Right superior oblique tuck and left inferior rectus recession.
6.Bilateral palsy with V pattern- bilateral surgery as above.
7. All down gazes, primary position and levoversion- explore trochlea.
2.2 Myogenic dystrophies and myasthenia
Chronic progressive external ophthalmoplegia of unknown etiology, CPEO+/ Kearns seare syndrome– bilateral symmetric and progressive limitation of all ocular movements including in the vertical direction and no diplopia.
Myasthenia: The clinical features are variable ptosis, irregular paresis of extrinsic ocular muscles, diurnal variation, improving with rest and increasing with exercise. May be associated with difficulties in speech, swallowing, breathing or fatigue of the limbs. Investigations include Tensilon test and electromyography. Treatment is medical.
2.3 Restrictive squints
a. Vertical deviation in Duanes retraction syndrome, b.Browns syndrome, c.Congenital
muscle fibrosis, d.Dysthyroid orbitomyopathy myositis e.Post traumatic orbital wall fractures, f.Tumors,pseudotumors,cysts in the orbit.
“a- Vertical deviation in Duane syndrome and b, Brown syndrome is given in details in previous articles on aamerniazi.blogspot.com”.
c. Congenital fibrosis of the extraocular muscles
It is a rare nonprogressive usually autosomal dominant familial disorder presenting with bilateral ptosis (chin elevation), fixed hypotropia with severe upgaze restriction above the horizontal plane.Perverted convergence on attempted upgaze and divergence on down gaze may be present. These features are due to fibrosis of extraocular muscles and the tenons capsule with adhesions between muscles, tenons and the globe. It may be associated with Marcus-Gunn jaw winkling phenomen, ventricular septal defect, and facial palsy.
Management
Supramaximal recession of inferior recti ( 6 to 8mm) with Crutch glasses.
DYSTHYROID OPHTHALMOPATHY
Unilateral or asymmetric bilateral involvement of extraocular muscles causing restrictive limitation of ocular movements is a feature of dysthyroid ophthalmopathy. Inferior rectus is most commonly involved and hence there is limitation of elevation. Associated lid lag, lid retraction and exophthalmos help in the diagnosis. CT scan shows fusiform enlargement of the proximal part of the extra ocular muscles. There is also risk of exposure keratitis and compressive optic neuropathy.
Management strategies include correction of thyroid imbalance and systemic steroids or immunosupression to control orbital inflammation. Squint surgery is considered after all inflammatory processes are controlled and the deviation is static for at least 6 months.
“Maximal recession of the affected Inferior rectus, medial rectus or superior rectus will be helpful.”
Blow out fracture of the orbital floor and entrapment of the Inferior rectus muscle:
Injuries of the orbit caused by objects bigger than the orbital aperture can cause fracture along the thin bone covering the infra orbital canal with incarceration of the inferior rectus or the inferior oblique muscle.There is limitation of movements and diplopia both in up gaze and down gaze. Associated infraorbital anesthesia, enophthalmos,CT scan findings,Hess chart will help in the diagnosis.
If diplopia persists in the primary position inferior rectus recession and then superior rectus resection may be helpful.
2.4 Deviations with Inferior oblique muscle over action
This can be primary or secondary to superior oblique weakness. Inferior oblique over action is commonly seen with infantile esotropia and can be unilateral or bilateral. The eye deviates up on adduction. The hypertropia must be differentiated from Dissociated vertical deviation. It can be treated by weakening the inferior oblique either by recession or myectomy. It also corrects the V-pattern strabismus seen in Inferior oblique over action.
3. Other conditions
Monocular elevation deficiency
1.Supranuclear paresis of Monocular elevation: Acquired monocular limitation of elevation. No vertical squint in primary position and down gaze. No ptosis. Normal bells
phenomenon and Dolls eye movement.
2.Congenital monocular elevation deficiency(MED): Congenital unilateral limitation of
elevation with ptosis and hypotropia in primary position. In contrast to brown syndrome the limitation of elevation is seen in all three up gaze positions i.e.in adduction,direct elevation and in abduction. It may be associated with Marcus gunn jaw winking phenomenon.
Management
Milder cases can be managed with base up prismsin front of the affected eye. If fusion is compromised in primary position or patient has abnormal head posture, surgeryis indicated. FDT is performed to look for a tight inferior rectus and if positive, recession of the inferior rectus is indicated.
Monocular depressor deficiency (MDD.)
It is a rare condition similar to MED but limitation of all downward movements in one eye. It may be due to paralysis of both the superior oblique and the inferior rectus resulting in defective depression of the affected eye.
Heavy eye syndrome: This condition is seen in high myopia. The affected eye is hypotropic.
4. Cyclovertical motility abnormalities with horizontal deviations- alphabet pattern squints.
The angle of deviation an horizontal squint can increase or decrease on up gaze or down gaze and the movements resemble alphabets resulting in A,V,Y X patterns.
Alternating Skew deviation:
(Please visit aamerniazi.blogspot.com to see previous article “Prismatic correction to restore binocularity in adults Diplopia”)
It is an acquired supranuclear divergence. It may be comitant or incomitant. One eye is deviated downward and medially and the other one upward and laterally. It should not be mistaken for superior oblique palsy and the patient has to be investigated for brain stem or cerebellar lesions.
