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NeuroRehabilitation 27 (2010) 255–259
DOI 10.3233/NRE-2010-0606
IOS Press
A new prism use for treatment of
cyclo-deviation in trochlear nerve injury
Thomas Politzer∗ , Mark Cilo and Alan Weintraub
Craig Hospital, Englewood, CO, USA
Abstract. Visual problems are common in patients with severe TBI [1]. Diplopia is among the most frustrating of visual
disturbances for patients, due to its functional consequences. This is further compounded by often slow, and at times, incomplete
or partial recovery over six months or longer. Ocular cranial nerve injuries (particularly trochlear nerve) occur in 0.2%–1.4%
of severe TBI patients [2]. This paper presents a new prism treatment application for treating rotational diplopia arising from
Trochlear nerve injury.
1. Background
Diplopia is a serious and often intolerable visual condition that occurs following an acquired, decompensated, and/or non-suppressed strabismus [2]. Not only is
the diplopia itself a problem, but it frequently has a negative effect on rehabilitation therapy in other domains
(i.e. speech and language, cognition, perception, mobility, and activities of daily living or ADL). For these
reasons, it is important to diagnose and treat diplopia
as soon as possible.
Of particular difficulty and frustration is the treatment of a rotational [torsional] deviation. Most commonly the rotational deviation is outward (excyclotorsion) and is caused from damage to the Trochlear
Nerve (CNIV). The Trochlear Nerve innervates the superior oblique muscle whose action is to lower the gaze
of the eye when it is adducted and to in-cyclo rotate the
eye in all positions except for adduction.
Trochlear nerve palsy has been mentioned in ophthalmology texts dating back to the mid nineteenth
century. Historically, it received little attention until
Bielschowsky, in 1935, correctly reported that trochlear
nerve palsy was the most common cause of vertical
diplopia and introduced his classic head-tilt test [3].
∗ Addresss
for correspondence: Dr. T. Politzer, Craig Hospital,
3425 S Clarkson St., Englewood, CO 80113, USA. E-mail: tpolitzer
@msn.com.
Many treatments have been used over the years to
correct, or reduce diplopia from an acquired strabismus.
These have included lenses, prisms, patching, surgery
and medication. Most of these approaches have been
used for over 50 years. Unfortunately, the non commitant [variable depending on direction of gaze] and torsional deviation resulting from Trochlear Nerve injury
make it particularly refractive to successful treatment.
2. Signs and symptoms
Patients with an acquired Trochlear Nerve injury will
typically complain of a variable vertical, angular and
tilted diplopia. This is especially prominent in down
gaze. The patient frequently exhibits a head tilt away
from the affected side. Visual acuity should not be
affected and there is rarely pain. However, obtaining reliable complaints from TBI patients is difficult,
due to their confusion or aphasia or other neurological
deficits; thus the subjective experience of their diplopia
is difficult to elicit.
3. Anatomy and pathophysiology
The Trochlear Nerve nucleus is located in the dorsal
aspect of the midbrain. It is the only Cranial Nerve to
exit the brainstem dorsally. The nerve travels a long
ISSN 1053-8135/10/$27.50  2010 – IOS Press and the authors. All rights reserved
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T. Politzer et al. / A new prism use for treatment of cyclo-deviation in trochlear nerve injury
course. From the nucleus, fibers traverse the subarachnoid space, the cavernous sinus, the superior orbital fissure to the orbit and then innervate the superior oblique
muscle [4].
The Trochlear Nerve is particularly vulnerable to
trauma as it exits the brain stem. Closed head injury is
the most common cause of Trochlear Nerve palsy [4]
Khawam and co-workers reviewed 3000 cases of strabismus, in which there were 40 cases of acquired superior oblique palsy. Sixty-eight per cent of the acquired
superior oblique palsies were caused by closed-head
trauma. Uncertain etiology was noted in 20 per cent,
and the remainders were from stroke, diabetes, brain
tumor, ethmoiditis, and mastoiditis [6] Von Noorden
reviewed 270 cases of superior oblique paralysis and
found that 40 percent were congenital, 34 percent were
traumatic, 23 percent were idiopathic and 3 percent
were due to other causes such as vascular disease, tumors or myasthenia gravis. Frequently no definitive
cause was identified [5].
4. Evaluation
With the presentation of new onset diplopia caused
by a Trochlear Nerve palsy, it should be determined if
the palsy is acute, or from a latent disorder that has decompensated. Newly acquired palsy requires detailed
evaluation including neurologic examination and neuro
imaging.
The Park three-step test is used in evaluation of vertical diplopia caused by a paretic cyclovertical muscle [7] Each step reduces by half the number of possible
affected muscles until only 1 remains.
The Bielschowsky head-tilt test stimulates intorsion
of the globe on the side to which the head is tilted and
extorsion of globe on the side away from which the
head is tilted. The presence of an excyclotorsion can
be determined by using a single or double Maddox rod
test.
5. Historical treatment
Patching an eye that deviates and causes diplopia
has been used for over a hundred years. Full patching
will relieve the diplopia, but causes a 25% to 30%
reduction of peripheral vision to the patched side and
eliminates binocular stereoscopic vision. The “Spot
Patch” [Politzer] is a method of partial patching without
these limitations [8].
Prisms have been used with good success for patients
with diplopia without torsional component. Non commitance of deviation will, however, reduce the effectiveness of prism therapy.
Botulinum toxin has been studied in treatment of
Trochlear Nerve palsy. Use of this agent as primary
therapy has not been satisfactory [3].
In the 1970s, Knapp developed a surgical approach
for superior oblique palsy [9] Plager described a tailored treatment plan that evolved from Knapp’s recommendations, with some additions based on more recent
operative algorithms [10] The modified Harada-Ito procedure is useful for patients with large excyclotorsional
deviation [3].
6. Prognosis
Prognosis of trochlear nerve palsy varies depending
on etiology. According to records collected at the Mayo
Clinic over the past 40 years the following has been
found. Recovery is most likely in patients whose superior oblique palsy is secondary to microvascular disease. Idiopathic cases have greater than 50% likelihood
of spontaneous recovery. Most cases resolve within
weeks to months, with the vast majority completely recovering by 6 months. Some cases may resolve slowly
over the course of a year. Patients with TBI were less
likely to recovery; yet, nearly 50% of these patients
showed some degree of improvement [9]. Cases due to
aneurysm or neoplasm were least likely to have functional recovery. Unfortunately, partial recovery may
only alter or diminish, but not eliminate all aspects of
the diplopia [10].
7. The cyclo prism
While surgery may or may not ultimately be the
method indicated for treatment of diplopia from a
Trochlear Nerve Palsy there are several issues to consider. Most importantly is how to help the patient during the time period when the patient is having diplopia. It will be more bothersome when superimposed on
other neurologic deficits. It can affect recovery and
interfere in other areas including functional cognition,
mobility and activities of daily living.
When there is a rotational deviation, the use of prisms
has been ineffective up to now. Prism bends light in a
linear fashion, but what is needed is a rotational bend.
It has been discovered that tilting a prism 10 to 15
T. Politzer et al. / A new prism use for treatment of cyclo-deviation in trochlear nerve injury
257
Fig. 1. Left Retro Tilt.
degrees around the axis passing from its apex to the
base gives a two dimensional displacement of approximately 8 degrees. For example: a 2 diopter base out
prism tilted so the bottom is moved out relative to the
top [retroscopic tilt] gives the perception of the viewed
object in an “in-cyclo” rotated manner [to compensate
for an ex-cyclo deviation]. A base in prism tilted so the
top is moved out relative to the bottom [pantoscopic
tilt] also gives the perception of the viewed object in an
“in-cyclo” rotated manner. A base down prism angled
so the outer lateral side of the prism is moved away
from the patient this will give the perception of incyclorotation. From a clinical and visual perspective, this
two-dimension displacement closely simulates a rotational displacement and has been found to be effective
in compensating for a cyclo-deviation.
Once the cyclo deviating eye is determined [or both
as with bilateral Trochlear Nerve palsy] then measurements to determine the amount of prism to neutralize
are done with a trial frame. Combinations of prism are
used until the least amount of prism that gives a range of
single vision is determined. The appropriate amount of
tilt can be obtained by “X’ing” or twisting the eyeglass
frame the required amount as noted in these photos
(Figs 1 and 2).
8. Case reports
T.K. was a 57 year old male when he suffered acute
bilateral cerebellar and right occipital ischemic strokes.
He complained of intermittent double and “tilted” vi-
sion. Additional symptoms included dizziness and he
was unable to perform his in hospital vestibular therapy
because of his vision.
Uncorrected distance visual acuity was 10/15 right
eye and 10/20 left eye. Cover test showed a very small
angle left hyper phoria. Maddox rod testing showed a
gaze dependent variable left excyclo deviation. Ocular
fixations were intact without nystagmus. Ductions and
versions were full. Pursuits were noteworthy for a
+2 ataxia. Saccades were intact. Convergence was 4
inches. Pupil reflexes were intact direct, consensual
and to accommodation with no afferent defect. Visual
field testing was full. External and fundus exams were
unremarkable. Binocular testing showed elimination
of the “tilted” vision with 2 base out retro tilt prism
left eye. With prism in place vestibular exercises were
done easily and without complaint.
T.K. was diagnosed with a mild Fourth Nerve palsy
left eye. He was prescribed 2 base-out prism retro tilt
left eye to be worn during therapy and while ambulating. Follow-up was scheduled for two weeks.
T.K. was re-examined 10 days later. The therapist
reported he had discontinued wearing the prism. T.K.
reported they helped significantly at first and then he
did not feel he needed them after about a week. He
no longer had any complaints of “tilted” vision, or
dizziness. Testing showed resolution of the excyclo
deviation.
A.B. was a 23 year old male when first examined.
He had sustained a TBI with diffuse axonal injury one
month prior from falling down some stairs. His chief
visual complaint was of constant double and tilted vision.
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T. Politzer et al. / A new prism use for treatment of cyclo-deviation in trochlear nerve injury
Fig. 2. Left Panto Tilt.
Examination was completely normal except for a non
commitant left hyper excyclo deviation consistent with
left Trochlear nerve palsy. Prism was trialed and he
was able to achieve a moderate range of single straight
vision with 3 base up prism right eye and 4 base down
lateral tilt left eye. This was placed on a temporary
eye glass frame with Fresnell prisms. Therapy was
prescribed to enhance the range of single vision.
In most acute care rehabilitation hospitals, the occupational therapist is charged with addressing vision.
In hospitals with a vision clinic therapy is typically
done by the patients’ primary occupational therapist.
While OT’s are taught the basics of vision in school,
the OT’s in our clinics have received additional post
graduate training in vision rehabilitation. Resources
are available through different organizations and individuals (Appendix 1).
At subsequent follow-up visits the amount of prism
was reduced and therapy continued. At discharge he
had single vision 80% of the time to all but far lower
right gaze. He was dispensed a retainer prism and has
not regressed.
scopic vision, and places the cornea at risk in TBI patients. A novel prism application has now been defined
that can help the patient achieve greater relief from
diplopia from Trochlear nerve involvement. Even for
patients who might spontaneously improve with time,
it is an effective tool to manage symptoms during their
recovery. For TBI patients engaged in a comprehensive, in-patient rehabilitation program, a reduction in
their diplopia will have significant positive impact on
all other aspects of their treatment, thus facilitating
functional progress and overall improvement in vision
and quality of life.
Appendix 1
Resources for post graduate education in vision rehabilitation
1. Neuro-Optometric Rehabilitation Association
(a) www.nora.cc
2. College of Optometrists in Vision Development
(a) www.covd.org
9. Conclusion
Diplopia resulting from a Trochlear Nerve is a difficult strabismus to treat. Previously, patching the eye
was the most common approach to eliminate diplopia due to the refractory nature of the condition to vision therapy and surgery. As noted, however, patching
reduces peripheral vision, eliminates binocular stereo-
3. visABILITIES, Mary Warren, M.S., OTR/L.
(a) www.visabilities.com
4. NeuroVision ED – Clinical Evaluation and Management of Vision and Perceptual Impairments
Following Acquired Brain Injury
(a) www.neurovisioned.com
T. Politzer et al. / A new prism use for treatment of cyclo-deviation in trochlear nerve injury
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