In the first article of a new series, Sophia Pathai and Andrew McNaught explain how to take an ophthalmic history and do an ophthalmic examination

• What do you do when called to see a patient with new onset atrial fibrillation who suddenly wakes up in the morning with loss of vision in one eye?
• An elderly woman is admitted with nausea and vomiting. The working diagnosis is small bowel obstruction. You notice she has a rather red eye. Is it just conjunctivitis?
• A patient with rheumatoid arthritis has been complaining of gritty, sore eyes for a week. You've tried chloramphenicol ointment, and it's not getting better. Is there something else going on?

The answers to these problems, and more, will be outlined in this series of articles. Although ophthalmology is a specialist subject, we hope to show you that you don't need amazing ophthalmic knowledge or specialist equipment to elicit the clinical signs that often point to the diagnosis. Most of the time you will need to refer the patient to the ophthalmologist for further management, but imagine how impressive your referral will be when you can give a differential list rather than just "red eye--possible conjunctivitis?" Seriously, having some basic practical ophthalmic knowledge and skills will ensure that you are able to assess the severity of an eye condition and the need for, or urgency of, referral. It means that you will hopefully consider the possibility of acute angle closure glaucoma in your elderly patient with acute abdominal pain and a red eye.

The ophthalmic and medical history

It's important to remember that it's not just the ophthalmic history that is important; the patient's current medical problem and past medical history are often highly relevant to the ophthalmic diagnosis.

On the ward the presenting complaint will often be of an acute nature such as sudden loss of vision, or an acutely red eye. It's useful to try to ask about associated symptoms that will help point towards the diagnosis--painless loss of vision with a headache would mean that temporal arteritis would be high on the differential list. It is also worth inquiring about the patient's past ophthalmic history; he or she may have an acute or chronic problem. For example, patients with another attack of anterior uveitis are often aware of the symptoms signalling a recurrence.

The medical history is also important. Patients with cardiovascular or cerebrovascular disease are at increased risk of vascular damage to the retina and optic nerve. So, in a patient with atrial fibrillation and an embolus could easily reach the central retinal artery, clinically manifest as sudden loss of vision. Diabetes and hypertension are also important medical conditions to exclude. Also take note of any systemic disease, from sarcoid to inflammatory bowel disease, as these conditions often have ocular manifestations that can present at any time. Medicines prescribed for non-ocular conditions can also lead to eye problems in susceptible individuals. For example, anticholinergic drugs may precipitate an episode of acute closed angle glaucoma.

Examination

Ophthalmic examination can often instil a sense of fear and confusion about shining pen torches around and waving hatpins in a haphazard manner. In fact, many important clinical signs can be elicited without specialist ophthalmic equipment and often just require simple items found on the ward.

Visual acuity

Always make an attempt to measure the visual acuity of each eye separately. You may not have a full size Snellen chart on the ward, but many pocket clinical handbooks have reduced Snellen charts that are held at one third of a metre, making them easy to use. If a Snellen chart is not available, then an assessment of the ability to read standard newspaper print gives an estimate of near visual acuity. Next, measure the acuity through a pinhole, which can be made by sticking a pin through a piece of cardboard. Testing with a pinhole is important, as a reduction in vision with the pinhole can be a sign of ophthalmic pathology rather than a refractive error (the patient requires distance glasses).

Colour vision

Colour vision is important to assess as it is a sensitive indicator of the function of the optic nerve. Acquired defects of colour vision can be roughly determined by comparing the depth of colour of a red target between the two eyes. Hold the target in front of a white background and ask the patient to look at it with each eye separately. A "duller red" with one eye suggests optic nerve damage, even though the patient may have good acuity in that eye.

Visual fields

Test the fields by confrontation. You do not need lots of hatpins to do this. Initially, assess for gross homonymous defects by sitting 1 metre away from the patient. Ask him or her to look at your nose. Hold one finger of each hand in the superior quadrants and make a small movement with one finger. Ask the patient to point towards the movement. Repeat with the other finger and then both fingers together. Assess the inferior quadrant by repeating the process. A normal response should exclude gross homonymous hemianopia.

Eye movements

The patient may complain of diplopia in varying positions of gaze. Try to establish whether the diplopia is monocular or binocular by asking the patient to fixate on an object and then covering one eye. If the diplopia disappears it is true binocular diplopia; if it remains it is monocular. Repeat this for the other eye. Assess the extraocular movements by asking the patient to follow a target held 1 metre directly in front of him/her. Slowly move the target in an "H" shape, keeping it vertical when moving to the left and right, and horizontal when moving up and down.

Pupils

The pupils are often just examined for their reaction to light and accommodation, and "PERLA" written in the notes. Many other visible signs can give valuable information.

Look at the size and shape of the pupils and the iris. A difference in iris colour (heterochromia) may be a sign of inflammation, tumour, or congenital Horner's syndrome. The pupil may have an odd shape; causes include posterior synechiae where the iris sticks to the lens due to inflammation, as sometimes seen in anterior uveitis. Ocular trauma or recent surgery may also lead to an irregularly shaped pupil, illustrating the importance of the history. Variation in pupil size between the two eyes (anisocoria) may indicate neurological pathology. Neuro- ophthalmic signs are important to elicit; examples include Horner's syndrome, where there is a small pupil and a mild ptosis, and a third nerve palsy, where the pupil may be dilated with a mild or complete ptosis.

Test the pupil's reactions. Ask the patient to fix on a distant object (to avoid the accommodation reflex that causes constriction of the pupil). Shine a pen torch into one eye and assess if the pupil constricts. Then repeat this in the other eye. Observe for the direct and consensual response. Of more significance is the "swinging flashlight" test used to identify a relative afferent pupillary defect (RAPD). Ask the patient to fixate on an object in the distance, and then direct a bright light to one eye. Move the light quickly to the other eye and repeat the process, swinging the light from eye to eye. A normal reaction would be a brisk pupil constriction of the stimulated eye; as the light is moved to the fellow eye it should constrict (or stay constricted). If it dilates rather than constricts, this is known as an RAPD. A positive finding is a strong indicator of retinal or optic nerve pathology.

Optic disc

The best way to become familiar with abnormal looking discs is to practise looking at as many normal ones as possible. Becoming comfortable with the ophthalmoscope and the close proximity between you and the patient takes time. Before attempting to get a view of the retina and disc (fundus), stand at arm's length from the patient and shine the light from the ophthalmoscope into the pupil. You should see a yellow/orange glow known as the red reflex; this represents the reflection from the fundus. If you do not see this, it means there is an opacity in the lens, vitreous, or cornea. The commonest cause is acquired cataract, but other ocular pathology can also be responsible. If there is no red reflex, no fundal view will be possible. If you do get a red reflex, move in closer and try to get a view of the disc. If you are having trouble locating it, "track" on to a retinal vessel, and follow it back; it should lead to the disc. If it seems out of focus, turn the lens dial up or down until the image is clear. Examine the disc, then the retina, moving your head around and asking the patient to look in different directions to improve the view of the periphery. Complete the examination by asking the patient to look directly into the light; this should give a view of the macula.

Iris loboloma: a congenital abnormality

External eye

It's easiest to be systematic and work from the front to back. Look at the eyelids; the appearance of the skin, any erythema or swelling, and the position of the lids, noting any ptosis. Assess the conjunctiva--if it looks red (injected), is there a diffuse redness, or a localised pattern? Next would be the cornea and anterior chamber, but these are difficult to examine without more specialised equipment.

Further reading

Elkington AR, Khaw PT. ABC of Eyes. 3rd ed. London: BMJ Books, 1999.

Key points

• Remember to think about the general medical history as well as the eye problem
• Ophthalmic examination is not as difficult as it seems, and you often don't need specialist equipment
• Always test visual acuity even if you don't have a Snellen chart available
• Assess the pupils for a direct and consensual response and a relative afferent pupillary defect
• Ophthalmoscopy does get easier--with practice!