Emergency Medicine

SUDDEN LOSS OF VISION IN THE UNINFLAMED EYE

Ophthalmic Emergencies 423

2 There is sudden blindness associated with a relative afferent pupillary defect
(RAPD), known as a Marcus Gunn pupil.

3 Testing for a relative afferent pupillary defect (RAPD), Marcus Gunn pupil:
(i) Direct a swinging light into one eye then briskly into the other.
This produces apparent dilation of the pupil in the affected eye,
as the relaxing consensual reflex in the good eye is dominant.
(ii) It is an excellent sign of a unilateral or asymmetrical optic nerve
or retinal lesion.

4 The fundus is milky white, the optic disc is pale and oedematous, and a
cherry-red spot develops at the macula in 1–2 days.

5 A preceding history of transient episodes of monocular visual loss ‘amauro-
sis fugax’ suggests embolic branch retinal artery occlusion.
(i) Perform a work-up for a transient ischaemic attack including a
duplex carotid ultrasound, and commence aspirin – see page 93.

6 Alternatively, a prodromal history of headache, scalp tenderness and malaise
suggest temporal arteritis causing anterior ischaemic optic neuropathy
(AION).
(i) Measure an urgent ESR and, if raised, immediately give the
patient prednisolone 60 mg orally to prevent the other eye
becoming involved (see p. 101).

MANAGEMENT

1 Commence acetazolamide 500 mg slowly i.v. or orally to reduce intraocular
pressure.

2 Give gentle pulsed ocular massage with sustained pressure on the globe for
5–10 s, followed by sudden release repeated for 10–15 min.

3 Refer the patient urgently to the ophthalmology team, as treatment within
1–2 h including anterior chamber paracentesis may restore the retinal
circulation.

Central retinal vein occlusion

DIAGNOSIS

1 This condition is most common in elderly patients with atherosclerosis,
hypertension and simple glaucoma. Diabetes and hyperviscosity also predis-
pose to this.

2 Visual loss is less abrupt but may be noticed suddenly. An RAPD (Marcus
Gunn pupil) occurs in more extensive cases.

3 The fundus is dramatic and shows congested veins with scattered f lame
haemorrhages and optic disc swelling.