The presenting visual symptoms of optic chiasmal disease

Approach to Vision Loss

OBJECTIVE

Diagnosing and differentiating among the many possible localizations and causes of vision loss is an essential skill for neurologists. This article outlines the examination of the eye and visual pathways and the differential diagnosis of pathophysiologic processes that can affect visual function.

LATEST DEVELOPMENTS

The eyes, optic nerves, and intracranial pathways of vision account for more than one-third of the volume of the human brain, and patients with vision loss are commonly seen by both eye care specialists and neurologists. A basic examination of the eye and visual pathways allows the neurologist to localize the abnormality causing the vision impairment and generate a differential diagnosis of the potential pathophysiologic processes that can cause a vision problem at that particular location. Neurologists should be aware of the many ocular causes of vision loss and recognize when a visual problem is not the result of an optic neuropathy or brain parenchymal lesion. The standard bedside examination of the visual system can be augmented using specialized ancillary testing of visual pathway structure and function, which is most often the purview of eye care specialists, although portable instruments such as small visual field machines and nonmydriatic ocular fundus imaging can be easily used in hospitals and neurology clinics.

ESSENTIAL POINTS

The approach to vision loss should include a history and examination geared toward localization, followed by a differential diagnosis based on the likely location of the pathophysiologic process. Coordinated care between neurologists and eye care specialists is essential for patients with optic neuropathy or other lesions of the intracranial pathways.

Neuro-ophthalmic evaluation and management of pituitary disease

Neuro-ophthalmic evaluation is a crucial component of the diagnostic and prognostic assessment of pituitary disease and compressive chiasmopathy, and can inform the timing of vision-restoring tumour resection surgery. The most common disease affecting the pituitary with neuro-ophthalmic implications are pituitary adenomas. Neuro-ophthalmic manifestations include decreased vision, abnormal colour vision and impaired visual field or diplopia. The recognition of these syndromes is critical to achieve early diagnosis and treatment and to improve prognosis. The pattern of vision loss in chiasmal compression is determined by the anatomical relationship between the pituitary lesion and optic chiasm, and potential visual field defects include bitemporal deficits, junctional scotomas, monocular cecocentral defects, and incongruous homonymous hemianopias. Rarer neuro-ophthalmic manifestations of pituitary disease include ophthalmoplegia, nystagmus, and obstructive hydrocephalus. There is growing evidence that demonstrates the strong diagnostic utility of optical coherence tomography (OCT) parameters in detecting the presence of compressive chiasmopathy, as well as the prognostic ability to predict the rate and degree of visual recovery following decompression surgery. Long-term neuro-ophthalmic monitoring is critical for detecting delayed vision loss following resection surgery, which may represent tumour recurrence or secondary complications.