Impairment Of Vision

CLINICAL APPROACH AND DIFFERENTIAL DIAGNOSIS (contd) Examine the posterior segment of the eye with an ophthalmoscope.

Pupil dilatation may be required.

Papillomacular bundle

Papillomacular bundle

In the normal fundus, the disc is pale with a central cup and reddish-brown surrounding retina. Arteries and veins emerge from the optic disc. The macula is darker than the rest of the fundus and lies on the temporal side of the disc. One-third of all retinal fibres arise from the small macular region and pass to the optic nerve head (disc) as the papillomacular bundle. The macula is the region of sharpest vision (cone vision), whereas peripheral vision (rod vision) serves the purpose of perception of movement and directing central/macular vision. The optic nerve head contains no rods or cones and accounts for the physiological blind spot in normal vision. The macular fibres being so functionally active, are the most susceptible to damage and produce a specific defect in the visual field - a scotoma.

Retinal abnormality voith acute impairment of vision

Arteries: narrow - branch occlusion, one vessel absent, embolus may be visualised -ยป

Retina: pale and oedematous After a few days the macular area becomes cherry red in appearance (Retina thinned here and the choroid shows through.)

An upper arterial branch occlusion is associated with a lower field defect in one eye.

arterial occlusion

Confirm with visual field examination.

Altitudinal field defect

Altitudinal field defect

Look for embolic source, e.g. carotid stenosis.

Loss of retinal colour (bccomes milky white) and macular blush. -> CENTRAL RETINAL ARTERY

Disc margin blurred sfi"--------Loss of physiological

Jtfpl 'central cup'

Veins enlarged

Radial streaks and corrugated appearance of the retina Haemorrhages may appear

OCCLUSION

Papillitis: visual acuity severely affected due to associated inflammation of the optic nerve (retrobulbar neuritis).

Papilloedema does not affect visual acuity (unless the macular area is affected by haemorrhage) although the blind spot is enlarged.

CLINICAL APPROACH AND DIFFERENTIAL DIAGNOSIS (contd)

N.B. Distinguish:

HYPERMETROPIC patients who have a pale indistinct disc often difficult to differentiate from early papilledema. HYPERTENSIVE RETINOPATHY - superficial haemorrhages and 'cotton wool' exudates.

PSUEUDOPAPILLOEDEMA - 'DRUSEN' - hyaline bodies near the optic disc which raise the disc and blur the margin. This normal variant may be inherited.

Separation of the superficial retina from the pigment layer-RETINAL

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