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Abstract
Diplopia can be a challenge to handle in the eye examination room. Due to the many
causes of diplopia, some of which being dangerous to the patient’s overall health, it is
important to take a thorough case history and pay close attention to certain entrance exam
tests. Simple tests, such as cover test and pupil and extraocular muscle evaluation, we as
optometrists may perform quickly or even have technicians performing for us. However, in a
case of diplopia those tests become very important and may deserve a second look.
I. Case History
a. Patient demographics – 86 year old white male
b. Chief complaint – brought down to the eye clinic from the admitted hospital
floor with complaint of left eye turned out giving him double vision that started 5
days ago
c. Ocular History – Age related cataracts, Dry eye syndrome, Hyperopia, and
Presbyopia
d. Medical History – History of hospitalization two days before eye exam for severe
vomiting, hypertension, hypercholesterolemia, GERD, Chronic kidney disease,
pulmonary fibrosis, anemia, osteoarthritis, BPH, and PTSD
e. Medications – Topiramate, Ranitidine, Lorazepam, Aspirin, Tramadol,
Simvastatin, Sertraline, Metoprolol, Enalapril, Nitroglycerin, Prednisone, Insulin,
Furosemide, Albuterol
f. Other Salient information – Patient has also had trouble swallowing in the last
week
II. Pertinent findings
a. Clinical and Physical
i. Best visual acuity sc 20/20 OD and 20/20 OS
ii. Pupils were equal round and responsive to light, No APD
iii. EOMs – right eye unable to cross the midline and left eye sits down and
out unable to cross midline and with restricted up gaze
iv. Left upper lid ptosis
1. Ice pack test did not show much improvement
v. IOP – 12/12 applanation tonometry
vi. Anterior segment positive for meibomianitis and dry eye. All other
findings were unremarkable
vii. Posterior segment all unremarkable, no optic nerve edema or pallor
b. Laboratory studies
i. ESR, C-reactive protein, TSH, Acetylcholine receptor binding antibody
1. All testing came back normal except for the Ach Receptor binding
antibody which was 11.70 nmol/L
c. Radiology studies
i. MRI ordered by PCP upon admittance to the hospital. Showed no signs of
aneurism or mass
III. Differential diagnosis
a. Primary/leading – Multiple extraocular muscle palsies secondary to myasthenia
gravis
b. Others –
i. Thyroid eye disease
ii. Chronic progressive external ophthalmoplegia
iii. Side effect of systemic hypertension
iv. Miller-Fisher variant of Guillain-Barre syndrome
1. Accounts for small percentage of Guillain-Bare patients and
usually affects the eye muscles first.
IV. Diagnosis and discussion
a. Condition of Myasthenia Gravis
Myasthenia gravis is an autoimmune disorder that targets the
acetylcholine receptors on voluntary muscle cells, weakening the muscles ability
to contract. Impairment of breathing, swallowing, eye and facial movements are
symptoms of this condition. Its prevalence in the United States is estimated at 14
to 20 per 100,000 people, with approximately 36,000 to 60,000 total cases
diagnosed. The most common age of diagnosis is under 40 in women and over
60 in men.
Diagonsing these patients can be as simple as a blood test for
acetylcholine receptor binding antibody. However, these auto-antibodies are not
present in about half of patient’s with only ocular manifestations of the disease.
In those cases it may be indicated to test for an antibody called AntiMuSK which
targets tyrosine kinase receptors on the muscle cells. A Tensilon test can also be
done to establish a diagnosis. The drug is injection intravenously and allows the
acetylcholine more time in the neuromuscular junction in order to properly
stimulate the muscles. Injecting Tensilon can have serious side effects so it is not
a procedure done routinely in an optometrist’s office.
b. Unique features
i. Multiple muscle palsies
ii. Eyelid ptosis – often improved after ice pack test
iii. In this patient’s case difficulty swallowing
V. Treatment and Management
a. Once diagnosed with Myasthenia gravis our patient was put on pyridostigmine
to improve his muscle function. Upon follow up examination 10 days later the
ptosis was resolved, the EOM movement was much improved, and the patient
no longer had symptoms of diplopia. The patient is still in the hospital under
close observation due to having a heart attack two day prior to follow up eye
examination.
VI. Conclusion and Clinical Pearls
As optometrists we are the primary health care providers for the eyes. We diagnose
and manage many conditions directly related to the visual system that can improve
patients’ visual function. Things such as prescribing glasses for refractive error and
managing ocular health conditions like glaucoma can significantly improve a
patient’s quality of life. Other ways that we can improve a patient’s quality of life is
identifying systemic disease through ocular symptoms. In the case of this patient,
the ocular symptom of diplopia led us to discover the underlying systemic disorder
of myasthenia gravis. For a patient with many health concerns prior to entering the
examination room, it makes a difference to be able to solve some of his problems
instead of just adding to the symptoms he has to live with. One issue completely
unrelated to his vision, his difficulty swallowing, was able to be addressed due to the
diagnosis we were able to uncover with his eye examination and specific blood
testing.
Another key point we as optometrists should take away from this case is the
necessary testing needed to find the problem was limited. Ordering an MRI was
important in the beginning due to the initial presentation of the patient’s left eye.
However after the reassurance the scan was normal, we narrowed down the further
testing based on the symptoms of multiple muscle palsies and eyelid involvement.
Another symptom of importance was his disphagia. With these symptoms the
differential diagnosis of myasthenia gravis was brought to the top of the list. There
are many tests that can be ordered to diagnose this condition, but simple ones such
as the ice pack test and blood work for the acetylcholine receptor binding antibody
are ones that do not take much time and are non-invasive for the patient.
Treatment for this patient was coordinated with his primary care physician while he
was still in the hospital. Due to the fact that this patient has a heart condition and
very recent heart attack he will be kept under close surveillance by the hospital and
we will also continue to follow his progress in the eye clinic as needed.
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Franklin, Gary M, Kissel, Jerry T, Treatment of myasthenia gravis: A call to arms Neurology July 12, 2000
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Werner Hoch1, John McConville2, Sigrun Helms1, John Newsom-Davis2, Arthur Melms3 & Angela Vincent2
Auto-antibodies to the receptor tyrosine kinase MuSK in patients with myasthenia gravis without
acetylcholine receptor antibodies Nature Medicine 7, 365 - 368 (2001)
Ehlers, Justis P., and Chirag P. Shah. The Wills Eye Manual: Office and Emergency Room Diagnosis and
Treatment of Eye Disease. Philadelphia: Lippincott Williams & Wilkins, 2008. Print.