Common complaints encountered with visual loss include so-called negative phenomena such as blurry vision or gray vision. Patients with higher cortical disorders often have nonspecific complaints such as "I'm having trouble seeing" or "difficulty focusing." Patients with lesions of the afferent visual pathway may also complain of positive phenomena, such as flashing or colored lights (phosphenes or photopsias), jagged lines, or formed visual hallucinations (illusions of something that is not there). The level of visual image complexity does specify localization (see later).
The temporal profile of the visual loss suggests possible diagnoses, and its monocularity or binocularity helps in localization. As a general rule, acute or subacute visual deficits result from ischemic or inflammatory conditions or may be caused by a vitreous hemorrhage or retinal detachment. Chronic or progressive visual loss, in turn, may result from a compressive, infiltrative, or degenerative process. Cataracts, refractive error, open-angle glaucoma, and retinal disorders such as age-related macular degeneration or diabetic retinopathy also need to be considered when visual symptoms are insidious.
If a patient complains of monocular visual loss, a process
in one eye or in the optic nerve should be considered. Painful monocular visual loss is characteristic of an inflammatory or demyelinating optic neuropathy. With binocular visual loss, a lesion of both eyes or optic nerves, or of the chiasm, tract, radiations, or occipital lobe should be investigated. Associated neurological deficits, such as motor or sensory abnormalities, also assist in localization and often indicate a hemispheric abnormality. Medical conditions should always be investigated in the review of systems. Hypertension and diabetes, for instance, predispose the patient to vascular disease, and a history of coronary artery disease should alert the examiner to the possibility of carotid artery insufficiency as well. Visual loss accompanied by endocrine symptoms, such as those consistent with hypopituitarism (e.g., amenorrhea, decreased libido, impotence) or pituitary hypersecretion (e.g., galactorrhea, acromegaly), suggests a chiasmal disorder.
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