Examination

In addition to a general and standard eye examination, particular features to look for in a patient with a sudden visual loss include:

Visual acuity

Examination of the patient’s visual acuity should be undertaken using a Snellen chart.

If the patient is unable to see the top line of the chart then the assessments should be undertaken, moving to the next step if failure occurs.

Visual acuity assessment steps

Step 1: Move the patient to three metres from the chart and recheck (recorded as 3/x)

Step 2: Assess ability to count fingers (recorded as CF)

Step 3: Assess ability to perceive hand motion (recorded as HM)

Step 4: Assess ability to perceive light and dark (recorded as LP)

Pupillary reactions

When examining pupillary reactions the clinician should be looking for:

• Appearance – is it regular and is there a red reflex?
• Reaction to direct and consensual light
• Reaction to accommodation
• Presence of a relative afferent pupillary defect

Ophthalmoscopy, slit lamp and tonometry

The patient should undergo ophthalmoscopy, slit lamp examination and tonometry if available. Remember to visualise the retina adequately, the pupils must be dilated with a topical mydriatic such as tropicamide. This carries a negligible risk of precipitating acute angle closure glaucoma. [11]

Learning bite

Particular attention should be paid to bilateral accurate assessment and documentation of visual acuity for cases of sudden visual loss. The eye may well look macroscopically normal, even on fundoscopy. Visual acuity assessment then proves the only objective marker of pathology.