Look for commonly missed etiologies to explain visual loss with normal fundus

CHICAGO — When confronted with unexplained visual loss in patients with a normal fundus, neuro-ophthalmologists should first seek to identify the anatomic location of the pathology and then, if no pathology is found, seek to prove that the visual loss is nonorganic, according to a presenter here.

Karl C. Golnik, MD, said pathologies can reside in different areas of eye, including the aqueous media, retina and choroid, or in the optic nerve. He spoke during the Neuro-Ophthalmology Subspecialty Day preceding the American Academy of Ophthalmology annual meeting.

The most commonly missed refractive etiologies include irregular astigmatism, oil-droplet cataract and occult corneal disease, Dr. Golnik said. Of the available evaluation tools, he described color vision as neuro-ophthalmology’s “secret weapon.” Another tool, direct ophthalmoscopy, is a “dying art these days, but probably the best way,” to evaluate patients, Dr. Golnik said.

Among retinal pathologies, the most commonly missed etiologies for unexplained visual loss include old ischemic insult, cone dystrophy and paraneoplastic retinopathies.

Often-overlooked pathologies of the optic nerve include retrobulbar optic neuropathy, small homonymous hemianopic scotomas and a visual variant of Alzheimer’s disease, he said.

If all possibilities have been explored and no pathology is identified, the visual loss is likely nonorganic, a broad term encompassing Munchausen’s syndrome, conversion disorder or hypochondriasis, Dr. Golnik said. Nonorganic visual loss typically manifests as unilateral loss of acuity or generalized constriction of the visual field, he said.