LAUSR

Sudden loss of vision, which causes consternation for both the patient and clinician, is a clinical problem that is encountered fairly regularly in most primary healthcare settings. Sudden visual loss or obscuration which is transient may simply be a symptom of a dry eye or a migraine, but it may also be the onset of irreversible visual loss or a stroke. Most cases of sudden loss of vision are serious, require referral and have an associated underlying systemic disease. Visual loss is usually unilateral, but may be bilateral. This clinical problem may present a diagnostic challenge. No cause may be found in some instances. However, it is important to remember that the more sinister causes of sudden visual loss, such as temporal arteritis, carotid or cardiac emboli that cause retinal vascular occlusion, retinal detachment, vitreous haemorrhage and orbital masses, need to be identified early. Using the duration of the visual loss as the primary differentiating factor, with associated symptoms and signs as supplementary factors, the causes can be narrowed down. A thorough history, goal-directed examination, proper investigation and appropriate referral should enable early diagnosis and adequate management. This will prevent further ocular morbidity, and even patient mortality. Peer reviewed. (Submitted: 2012-10-31 Accepted: 2012-12-15.) © Medpharm S Afr Fam Pract 2013;55(3):235-240 CPD Article: Sudden loss of vision 236 Vol 55 No 3 S Afr Fam Pract 2013 bilateral ocular or optic nerve disease, but more commonly is a sign of disease posterior to the optic chiasm, including the optic tract and cerebral cortex. It may indicate impaired posterior cerebral circulation or even a migraine.1 Transient loss of vision, particularly in patients with significant cardiovascular risk factors, may be owing to amaurosis fugax, resulting from atherosclerosis. These patients require further investigation. A floating, mobile scotoma is consistent with vitreous pathology, as the vitreous undulates relative to the retina when the globe moves.1 Testing visual fields to confrontation is of importance in cases where history points to a retinal or neurological cause of the loss of vision. Keeping in mind that normal pupil reactions require normal oculomotor and optic nerve functioning, it is important to assess the direct, as well as consensual, pupillary responses in each eye. Subtle differences between the two optic nerves may be detected by carrying out the swinging flashlight test for a relative APD. It is important to assess the red reflex in each eye. This may be obscured by media opacities, such as vitreous haemorrhage, as well as intraocular pathology, for example, retinal detachment.4 Fundoscopy should be performed after pupil dilation if acute angle closure glaucoma is not suspected. An examination of the cranial nerves may also help to diagnose orbital disease. In any setting, papilloedema requires prompt imaging.1 Loss of vision may be associated with migraine. Usually, the visual aura of a migraine presents as zigzag lights or shimmering colours and precedes the headache. Atypical cases should be referred to a neurologist. Using the duration of the visual loss as the primary differentiating factor, with associated symptoms and signs as secondary factors, the causes can be narrowed down, as indicated in Figure 1.