Here is a selection and amalgamation of five readers' collected wisdom on using an ophthalmoscope--from senior house officer to consultant ophthalmologist

The ophthalmoscope seems a simple tool. But, in reality, "fundi NAD" written in the notes often means "not actually discerned." The ophthalmoscope is not difficult to use but it requires some practice. Try to get in the habit of using it in every neurological examination--you'll soon get the hang of it.

Prepare your equipment

Does it work?

Check that the ophthalmoscope actually works--the batteries may be flat or it may not have been charged. Some ophthalmoscopes have a small cover over their aperture which, if closed, may lead you to think that it is not working.

How does it work?

There are different types of ophthalmoscope, and it always pays (with the lights still on) to familiarise yourself with the various dials and levers. When switched on, the emitted light should be:

• Bright--turn it to maximum
• White--ignore all other colours
• Circular--again, ignore all the slits and crosses; turn the dial until you get a round circle.

Many people find it confusing to have to think about their own glasses and the patient's glasses. Don't worry about this--set all the numbers on the ophthalmoscope to "0." Ask the patient to remove his or her glasses--you can keep your own on or remove them as you prefer. Contact lenses do not need to be removed.

Room lighting

Switch the room lights off or dim them, but don't make the room too dark.

Prepare your patient

Dazzling examination

Explain what you are going to do to the patient. Warn the patient that the bright light can temporarily dazzle them.

Position

Position the patient so that he or she is comfortable but sitting up (if possible).

To dilate or not to dilate?

Pupil dilatation (with one drop tropicamide 1% in each eye and wait for 15 minutes) is useful to acquaint yourself with the normal fundus but may not always be possible, especially in neurology patients or those with a head injury.

Even with dilatation, only about a third of the fundus is visible with a direct ophthalmoscope. Fortunately, the area most visible is the posterior pole (including the disc and the macula), where you should be able to see
the ocular findings of many systemic diseases such as hypertension and diabetes.

Where the patient should look

It is important to get your patient to fixate on a precise area (for example, the corner of the room or curtain rail). If you are too vague about this they will move their eyes. Instruct the patient to look at this spot no matter what--even if you get in the way. This spot should be located so that they are looking slightly away from you when they are examined--that is, to the left when you examine the right eye and vice versa.

Get your own position right

Eye to eye

It is best to examine the patient's left eye with your own left eye and right eye with your own right eye--this takes practice. Try to keep your other eye open. Certainly, in an examination, such as for membership of the Royal College of Physicians part 2, you shouldn't close your other eye while examining the retina.

Place your hand on the patient's forehead so that your fingers are splayed but your thumb is on the upper lid. This is important as you will use your thumb to hold the patient's lid open and also the joint of your flexed thumb is exactly where your forehead needs to end up.

Begin at arm's length

Begin at arm's length by shining the ophthalmoscope light into the patient's pupil (you will then see the red reflex). Follow this reflex until your forehead rests on your thumb--you should immediately see the optic disc. It will probably be out of focus so, without moving your head, turn the lens dial either way--if the disc becomes clearer keep turning. If it becomes more blurred, turn the dial the other way.

To look at the macula, ask the patient to look directly into the ophthalmoscope light. The ophthalmoscope can also be used for examining the anterior part of the eye by turning the lens dial to about +10.

What am I looking for?

Follow a routine: red reflex, anterior segment, disc, vessels, and lastly macula (see box). In an exam, once you have found an abnormality, keep looking for a second one.

When examining the vascular arcades, ask the patient to look in the appropriate direction to extend your field of view. The red-free (don't call it "green") filter is useful for enhancing the appearance of blood vessels and haemorrhages by making blood show up black.

Record your findings

Record any abnormalities in a diagram, using the disc diameter as a reference measure. Remember, the image is not inverted, so you can draw it as you see it. Seek expert advice if needed.

Common mistake

The biggest mistake doctors make when using the ophthalmoscope is not getting near enough to the patient. Don't be shy. Make sure you are very close to the patient, almost cheek to cheek, and that you maintain this throughout the examination. The closer you get, the wider your field of view.

If you dilate the patient's pupils remember that he or she should not drive for at least one or two hours after dilatation, and longer if they feel their vision has not returned to normal.

What am I looking for?
Red reflex
Media opacities obscure the red reflex (corneal scars, cataract and vitreous haemorrhage, and asteroid hyalosis).

Optic disc
Look for optic disc size, colour (pallor, congestion), cup disc ratio, margins, haemorrhages, new vessels, collaterals. Pale and clearly demarcated disc: optic atrophy. Pathological cupping: glaucoma. New vessels on the disc: proliferative diabetic retinopathy is the most common cause. Yellow-grey disc with blurred margins ± haemorrhages: papilloedema--bilateral.

Vessels
Start at the disc and follow the vessels out to look for hypertensive and arteriosclerotic changes. Look as far as the mid-periphery for scars (inflammatory, laser), haemorrhages, exudates, pigment (white, black), and pigmented lesions. Examine arteries, veins (slightly thicker), and perivascular fundus. A-V nipping is seen in hypertension.
Look also for: microaneurysms, blot haemorrhages, hard exudates--background diabetic retinopathy; cotton wool spots (fluffy white patches), vessel changes such as venous beading, and venous loops are preproliferative changes; leashes of new vessels. Macula
You will find the macula temporal to the disc. The foveal reflex is seen better with a green (red-free) filter and is at two disc diameters away from the disc and 1.5 degrees below the horizontal (your whole field of view is 8 degrees). A circinate ring of hard exudates, haemorrhage (dot, blot, or flame), or pigment deposition are the most common things you will see.

Further information
www.opt.indiana.edu/riley/HomePage/Direct_Oscope/Text_Direct_Oscopt.html
www.academy.org.uk/
lectures/eperjesi3.htm
www.eyes.arizona.edu/FundOph.htm
www.mrcophth.com

Dear Student BMJ

I was fairly amused by the photograph on p321 of the September edition of Student BMJ. In an article entitled 'How to use an ophthalmoscope', the picture shows a man using the wrong eye (with his other eye closed), holding the instrument incorrectly and not resting his other hand on the patient's forhead! Furthermore, even if the ophthalmoscope is turned on (which it deons't look like it is), the patients appears to be looking away from the doctor in one final attempt to ensure that the elusive fundus remains out of view.

Quite amusing, I thought.

I did enjoy the article however (look how much i have learnt!)

Thanks
Mark Pinkham

To obtain a quick survey of the peripheral retina, a quick and easy tip that my students have often found helpful is to ask the patient to sequentially look into the different directions of gaze ie. "up", "up to the right", "right", "down to the right", "down", "down to the left", "left", "up to the left".

This avoids the need for the examiner to move his head and ophthalmoscope excessively when examining the peripheral fundus

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