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Title: Breakable Bones Can Make You Blind: How Osteopetrosis Affects Vision
Authors: Amy Steinway OD, Maegan Sauer OD, Scott Richter OD, Susan P. Schuettenberg OD FAAO
Abstract: Osteopetrosis is a rare disease that can often present with ocular manifestations. This poster
will review a case study and further investigate an optometrist’s approach to treatment, management,
and inter-professional care of patients with osteopetrosis.
I.
Case History
 Patient Demographics: 20 year old Caucasian female (Ashkenazi Jewish)
 Chief Compliant: Referred for subjective decrease in VA OD.
 Ocular/Medical History: Patient was diagnosed with osteopetrosis at three months of
age; had been followed by other optometrist but referred for change in vision
 Current Medications: none
 Other pertinent information: patient had a bone marrow transplant with a course of
chemotherapy before
II. Pertinent findings
 Clinical:
 VAs: 20/200 OD, counting fingers with eccentric viewing OS
 Pupils/EOMs: 30^pd Constant Left Exotropia in all gazes, small amplitude
horizontal nystagmus with fast phase to the left that dampens on temporal
gaze, PERRL +APD OS, comitant with no muscle restrictions OU
 CVF: restricted temporally OD/OS
 Tonometry: 22/24 with Goldmann; 20/20 with handheld Perkin’s tonometer
 Gonioscopy: open to scleral spur with poorly defined trabecular meshwork 360
OU
 Pachymetry: 521/591
 Physical:
 Dilated Fundus Exam: c/d ratio of 0.7/0.6 OD/OS with pallor 360, well-defined
nerves but decreased vascular count; normal macula, vitreous, retina
 Visual Field Exam with HVF 24-2 and Goldmann: bitemporal field defects
encroaching into macular area OS
III. Differential diagnosis
 Primary: Bilateral Optic Atrophy secondary to Osteopetrosis, Ocular Hypertension
 Others: pituitary adenoma, other compressive etiology, dominant optic atrophy, openangle glaucoma
IV. Diagnosis and Discussion
 General

 Osteopetrosis is a rare disease that causes bones to become dense, yet very
fragile. It is caused by a genetic defect where defective osteoclasts cause
increased skeletal mass1. It is most often diagnosed with radiographic imaging
such as x-rays, where bones have a chalky white appearance2. It can affect many
of the cranial nerves due to the changes in the foramina they travel through3.
The condition can therefore present with ophthalmic complications.
 There are two main types of osteopetrosis: the autosomal dominant form
occurs in 1/20,000 while the autosomal recessive form occurs in about
1/250,000 people4. The autosomal dominant form involves a milder
presentation and is more likely of late onset. The autosomal recessive type is
diagnosed early on with changes in bone structure, hematologic sequelae, and
neurological deficiencies4. The risk of developing vision loss is 75% within one
year of birth in the recessive form1.
 Vision loss is one possible outcome of osteopetrosis due to direct compression
of the optic nerves by an overgrowth of orbital bones. Optic atrophy can
present secondary to the narrowing of the optic nerve canal and other changes
in the base of the skull or due to elevated intracranial pressure from decreased
venous outflow5. Other common ophthalmic findings include nystagmus,
proptosis, ptosis, strabismus, papilledema and chorioretinal degeneration.
 Additional testing such as VEP and ERG can be used to determine optic nerve
function and retinal involvement. If a patient has an associated retinal
degeneration the ERG would be affected by lower amplitudes and there is no
treatment option available. A flash VEP might reveal a delay which can precede
the pallor and other indications of compression7.
Case Study
 This patient had been diagnosed with autosomal recessive osteopetrosis at
three months of age. She had undergone a successful bone marrow transplant,
but decreased vision remains. Due to the bilateral hemianopic visual field at
initial presentation, this patient was referred for an MRI of the brain with and
without contrast to rule out a pituitary adenoma or other compressive etiology.
After several up visits, ocular hypertension was diagnosed due to above average
pressure readings that were consistently elevated.
V. Treatment and Management
 General
 Optic nerve decompression is a surgical intervention performed to prevent
further gradual vision loss by altering the size of the optic canal6. Optic nerve
sheath fenestration is another controversial option to stop vision loss.
 Bone marrow transplants are recommended to exchange damaged osteoclasts
for properly working ones and has a success rate of 50%1.
 Case Study
 Managing the patient’s symptoms of decreasing vision is crucial. Due to the
binocular presentation, visual acuities were attempted with a face turn to the
left and with base in prism OD with no improvement. The patient uses a low
vision device (Designs for Vision Type II 6x microscope doublet- near vision is
0.5M at 4cm OD/ 1.6M at 15cm OS) to assist her with near tasks. She enlarges
the print on her cell phone when necessary and chooses not to wear distance
vison correction which subjectively improved her vision mildly.
 Due to the optic nerves being compromised and the difficulty of following with
an HRT and OCT, treatment with ocular anti-hypertensives was recommended.
Therefore, a monocular trial of Xalatan was started OD. The prostaglandin
analog was discontinued one month later due to inefficiency and the patient
was prescribed Alphagan 0.15% BID in a monocular trial. The pressure was
lowered sufficiently, so the drop was given BID for both eyes. Two years later,
there was a drift with increasing intraocular pressure so the dose was increased
to TID. After relatively controlled IOPs, the patient became pregnant and
wanted to discontinue treatment until nursing was completed. IOPs off of the
medication returned to her initial IOP range without treatment. She continues
to return for quarterly visits to check her IOPs without medication.
 Carbonic anhydrase inhibitors were contraindicated due to the carbonic
anhydrase II deficiency of autosomal recessive osteopetrosis.
 During the course of management, the patient became pregnant twice and
decided to discontinue the medications treating the ocular hypertension due to
the potential risk to the fetus.
VI. Conclusion
 For patients diagnosed with osteopetrosis, an important aspect of care is comanagement. Optometrists and ophthalmologists are necessary to monitor vision and
manage ocular symptoms. Communicating any changes of findings in visual field testing
or optic nerve presentation with other professionals on the medical team is important
for the continuity of care. Working closely with the orthopedist or hematologist is
necessary to provide the ultimate patient care to manage the patient’s symptoms and
to check for stability.
 The optometrist has a critical role in the treatment of patients with osteopetrosis. Being
able to manage the visual demands while monitoring for changes in neurological
presentation is an asset to the team of doctors providing care.
 Early diagnosis as an infant could allow for earlier intervention and possibly save vision.
Current research is being done to develop an in utero diagnostic test, and new surgical
treatment modalities are being explored.
Sources
1. Siatkowski, R.M., et al. “Blindness From Bad Bones.” Survey of Ophthalmology.1999; Vol 43 (6):
487-490.
2. http://www.niams.nih.gov/health_info/bone/additional_bone_topics/osteopetrosis.pdf.
“Osteopetrosis Overview.” NIH Osteoporosis and Related Bone Diseases National Resource
Center. January 2012.
3. Essabar, L. et al. “Malignant infantile osteopetrosis: case report with review of literature.” Pan
African Medical Journal. 2014; 17:63.
4. Stark, Z. and R. Savarirayan. “Review: Osteopetrosis.” Orphanet Journal of Rare Diseases. 200;
4:5.
5. Gerritsen, E. J. A, et al. “Autosomal Recessive Osteopetrosis: Variability of Findings at Diagnosis
and During the Natural Course.” Pediatrics. 1994; Vol. 93 (2): 247-253.
6. Hwang J.M. et al. “Complete visual recovery in Osteopetrosis by early optic nerve
decompression.” Pediatric Neurosurgery. 2000; 33:328-332.
7. Thompson D.A, et al. “Early VEP and ERG evidence of visual dysfunction in autosomal recessive
osteopetrosis.” Neuropediatrics. 1998; 29 (3): 137-144.