Disturbance of vision

When taking the history it is important to establish time sequences, associated features and whether the disturbance

TABLE 7.1

Examples of abnormal appearance of head, face and eyes

Site

Appearance

Associated features

Cause

Head

Abnormal head posture

Squint and diplopia on straightening head

Vertical muscle palsy

Face

Asymmetry and fullness of supraorbital ridge

Cranial nerve palsies

Sphenoidal ridge meningioma

Eyes

Proptosis

Lid lag and lid retraction

Dysthyrold eye disease

Lids

Xanthelasma

Corneal arcus

Hypercholesterolaemia

is unilateral or bilateral. Apparent sudden loss of vision may have only been noticed suddenly when the normal eye was covered. The main disturbances of vision are:

• blurred vision

• double vision (diplopia)

• flashing lights (photopsia) and haloes

Blurred vision. Blurring is usually due to an ocular problem. When the media (cornea, lens, aqueous or vitreous) are hazy, vision blurs and there is often dazzle in bright light. Cataracts cause such symptoms. The blur caused by refractive errors is cured by spectacles.

Loss of vision. Sudden visual loss suggests a vascular aetiology. The nature of the loss may help localise the lesion. Loss of vision in one eye indicates that the problem is anterior to the chiasm; hemianopie field defects in both eyes that it is post chiasmal (Fig. 6.13, p. 200). Patients often state that they cannot see out of the right eye when they cannot see the right side of the visual field (right hemianopia), and likewise those with a left hemianopia may equate this with loss of vision in the left eye. Scotomas or blind spots are often observed accurately by the patient, who will describe the defect in the field of vision.

DISORDERS

Causes of reduced visual acuity

• Uncorrected refractive errors

Retinal disease

• Optic nerve disease

Psychological,

Diplopia. Patients may complain of double vision when they mean blurred vision. True double vision becomes single when one eye is covered. Sudden onset of double vision usually indicates a neurological problem (p. 202).

DISORDERS

Causes of diplopia

• Neurological disorders, e.g. disseminated sclerosis

• Muscle and neuromuscular junction disorders, e.g. myasthenia gravis

• Decompensating long-standing squint

• Refractive errors

• Incorrect spectacles

• Media opacities

• Macular disease.

Photopsia and haloes. Seeing flashes and zigzags of light is called photopsia. It occurs when the retina is stimulated by the vitreous tugging on it. Very similar sensations are noted in both eyes in migraine. Haloes are due to prismatic effects, usually water drops in the cornea or lens in corneal oedema or cataract.

Floaters. Seeing occasional small 'lloalers' is physiological, but patients may be alarmed when they are first noticed. A sudden rash of many floaters or large black "tadpoles' suggest a vitreous haemorrhage.

KEY POINTS

• Patients with eye and visual disorders are often very anxious.

• Sudden loss of vision Is usuaily vascular.

• Sudden onset of diplopia Is often neurological.

« Patients may mistake hemianopia for loss of vision In one eye

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