Patients often present with visual symptoms, and are understandably concerned that they may be going blind. There are many local and systemic causes, and some are very serious. You need to assess your patient carefully, reassure where possible and refer promptly if the condition may be serious.
History
As with any neurological condition, it is critically important to take a comprehensive history:
- Can the patient describe their symptoms?
- Was the onset acute or gradual? Are symptoms permanent, transient or recurrent?
- Is one or are both visual fields affected?
- Is the image blurred, dim, distorted, double?
- Do the symptoms and signs resonate with any of the conditions described below?
Diplopia is a relatively common and important symptom. It can be a manifestation of an underlying neurological (e.g. multiple sclerosis) or neuromuscular (e.g. myasthenia gravis) disorder.
Examination
Examine your patient as in Chapter 53. You must also assess the visual fields using a finger or hat pin (confrontation).
A full neurological or cardiovascular examination may be needed – or both, for instance if you suspect a stroke may be causing the visual symptoms.
Summary of Conditions Presenting with Visual Symptoms in Primary Care
We all see floaters, especially on looking at a bright, even background such as a blue sky. Although some are embryonic deposits, they increase with age as degenerative changes involve the vitreous and retina.
Patients frequently present with a typical history of classical migraine with a visual aura (usually their first attack). Some patients have an aura with little or no headache. Migraine without visual symptoms is much more common, and some 75% of patients have this common form of recurrent headache. Many visual symptoms are associated with migraine. A scintillating scotoma (fortification spectra) is the classic visual aura of migraine. Typically, it begins as a spot near to the centre of the field of vision. It then evolves into a shimmering and enlarging zigzag peripheral arc (usually bilateral) before resolving.
Patients presenting with cataract are usually older and may have been referred by an optician. Cataracts are more common in diabetes. Cataract surgery is now one of the most common operations in the elderly.
Primary/chronic open angle glaucoma (POAG) has an insidious onset and can present late with tunnel vision.
Loss of peripheral vision may present with a tendency to trip over, miss the kerb or steps or bump into things.
Visual loss is caused by irreversible damage to the optic disc and retina. Raised pressure without visual loss is called ocular hypertension.
Posterior vitreous detachment affects some 75% of over-65-year-olds. As the jelly-like vitreous ages, it liquefies centrally and this pulls the vitreous cortex from the retina. Patients may describe floaters and 
flashes (photopsia from stimulation of retinal receptors by the pull of the vitreous cortex).
Patients with retinal tears and detachments often report 
a marked increase in the number of floaters (dots if there is haemorrhage) or 
flashes seen. If there is full detachment, the patient may have a 
curtain or shadow coming across the field of vision. If the macula is involved, visual loss is profound.
The circulation to the retina can be compromised (e.g. from a carotid artery embolus). Ischaemia is transient in amaurosis fugax which has an annual incidence of 1 in 10,000. The patient may give a history of a brief (seconds or minutes) painless unilateral loss of vision, typically a shade or curtain coming across the eye. Sudden (over seconds) permanent visual loss in one eye is a feature of central and branch retinal artery occlusion (CRAO and BRAO, respectively). Acuity is typically reduced to counting fingers.
A stroke (cerebrovascular accident [CVA]) involving the optic radiation may be associated with the abrupt onset of typically binocular visual loss (which is temporary in a transient ischaemic attack [TIA]). As in retinal detachment, the patient may describe a curtain coming across part of the visual field, but both eyes are usually affected, not one. The pattern of field loss is determined by the site of the vascular insult. The patient may have other systemic features.
Focus on Age-Related Macular Degeneration
One consequence of the growing elderly population is the relentless rise in age-related macular degeneration (ARMD). Some 30% of over-75-year-olds are affected and ARMD is the most common cause of blindness in the UK. There is an association with smoking.
There are two forms:
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