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A 62-year-old woman with a history of chronic angle-closure glaucoma and bilateral peripheral iridotomies sought a second opinion for worsening visual acuity in the left eye for 2 months. She had been treated for glaucoma for approximately 1 year. Review of systems was negative for previous episodes of eye pain, redness, or emesis. Her medical history included hyperlipidemia, obesity, and prior cataract surgery in both eyes. On examination, best-corrected visual acuity was 20/20 OD and 20/80 OS. The patient’s pupils were equal, round, and reactive to light without a relative afferent pupillary defect. Intraocular pressure was 11 mm Hg bilaterally without medication. Slitlamp findings were notable for patent peripheral iridotomies, open angles on gonioscopy, and an asymmetrically enlarged cup-disc ratio with mild pallor of the left optic nerve. Color vision was decreased in the left eye. Visual field (VF) testing as well as ganglion cell layer (GCL) segmentation by optical coherence tomography (OCT) were obtained for both eyes (Figure 1).
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Nonglaucomatous optic neuropathy secondary to a pituitary adenoma
D. Order brain magnetic resonance imaging
Optic chiasm compression from a pituitary adenoma classically produces bitemporal vision loss. Most adenomas are nonfunctional or prolactinomas.1,2 Adenomas causing 3 mm or more of chiasm displacement are associated with VF defects and initially compress inferior nerve fibers leading to superior VF defects.3 Diagnosis is confirmed after tumor resection and pathologic analysis. In a 2019 study, most patients undergoing resection presented with vision loss (61.7%), followed by headache (40.0%) or endocrine dysfunction (21.8%).1
Optic neuropathies are associated with loss of retinal ganglion cells and retinal nerve fiber layer (RNFL) axons. Nasal retinal nerve fibers decussate at the optic chiasm, supplying the temporal visual hemifield. The papillomacular bundle describes the central macular retinal nerve fibers, which lie just temporal to the optic nerve; these fibers are typically not affected in glaucoma. Topographically, papillomacular bundle injury would demonstrate nasal thinning on macular GCL OCT segmentation and temporal thinning on circumpapillary RNFL OCT scans.4 The distribution of nasal retinal nerve fibers also explains the bow tie optic nerve pallor associated with compressive chiasmal lesions.4,5 Other findings may include relative afferent pupillary defect, dyschromatopsia, and bitemporal hemianopsia. However, most patients do not present with complete bitemporal hemianopsia, and, therefore, chiasmal lesions must be suspected in cases of incomplete temporal field defects or those crossing the vertical midline due to extrachiasmal extension.3 In a 2018 study, OCT GCL and RNFL analyses were able to detect chiasmal lesions significantly earlier than by clinical examination or VF testing.6 Greater preoperative RNFL/GCL thicknesses are associated with better visual recovery after tumor resection.4 Tumor recurrence is monitored at least yearly with neuroimaging and VF testing.2
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Corresponding Author: Swarup S. Swaminathan, MD, Bascom Palmer Eye Institute, 900 NW 17th St, Miami, FL 33136 (firstname.lastname@example.org).
Published Online: September 10, 2020. doi:10.1001/jamaophthalmol.2020.1746
Conflict of Interest Disclosures: None reported.
Funding/Support: Bascom Palmer Eye Institute receives support from a National Institutes of Health Center Core Grant (P30EY014801) and a Research to Prevent Blindness Unrestricted Grant.
Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: We thank the patient for granting permission to publish this information.
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