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During any examination in an OSCE it is important to understand the pathology and reasoning behind each of the signs and symptoms elicited, even if the patient being examined is ‘normal’. This article explains how to perform a fundoscopy (ophthalmoscopy) examination and the key findings you should look for, showing you what each sign means and what conditions it may indicate.
Fundoscopy uses a focused beam of light and a series of lenses to inspect the fundus – the inner back surface of the eye. It is the only part of the body where blood vessels and a portion of the central nervous system (the optic nerve head) can be viewed directly, which makes it a uniquely valuable window onto systemic disease such as diabetes, hypertension and raised intracranial pressure.
Contents
Introduction
Gather your equipment – a direct ophthalmoscope (with charged batteries) and, where appropriate, mydriatic eye drops.
Wash your hands and don personal protective equipment if appropriate.
Introduce yourself to the patient and ensure to mention your grade e.g. 3rd year medical student/junior doctor/consultant.
Confirm the patient’s details taking 3 points of identification usually; full name, date of birth and NHS/hospital number.
Obtain consent for the examination, ensuring to explain what the examination will entail. It is worth warning the patient that you will need to dim the lights, that you will be working very close to their face, and that the light will be bright and may be uncomfortable.
Ask the patient if they have any pain in or around the eyes before you begin.
Position the patient seated in a chair at your eye level. It is important to seat the patient before dimming the lights to avoid trips and falls in the dark.
Ask the patient to remove their glasses if they wear them, as the frames get in the way; contact lenses can stay in. Any residual refractive error is corrected later using the ophthalmoscope’s lens dial.
Ask the patient to fixate on a distant target behind you (for example a spot on the wall) and to keep looking at it throughout, even when your head moves into their line of sight. Fixation on a distant point relaxes accommodation, keeps the eye still and helps bring the fundus into focus.
General Inspection
Begin with a general inspection of the patient and the bedside, as this often provides important clues before the ophthalmoscope is even picked up.
Inspect the patient for any obvious visual aids such as glasses, a white cane or a guide dog, which suggest significant visual impairment, and note any head turn or abnormal posture that a patient may adopt to compensate for a visual field defect.
Glance at the external eyes before reaching for the ophthalmoscope. Note the eyelids for ptosis (a drooping upper lid, seen in a third nerve palsy or Horner’s syndrome) and compare the pupils for size, symmetry and shape. A pupil that is fixed and dilated, or markedly unequal, is relevant both to the underlying pathology and to whether the eye has already been pharmacologically dilated.
Look around the bedside for objects relevant to the underlying diagnosis, such as capillary blood glucose monitors or insulin (suggesting diabetes), blood pressure equipment (suggesting hypertension), or eye drops. These are valuable because the most common abnormalities seen on fundoscopy – diabetic and hypertensive retinopathy – are complications of these systemic diseases.
Assess whether the patient appears comfortable or is in distress. A patient with a painful red eye, severe headache or vomiting may have an acute condition such as acute angle-closure glaucoma and should be assessed urgently.
Preparing for Fundoscopy
Good preparation is what separates a useful fundoscopy from a frustrating one, and examiners reward it.
Dilate the pupils. A small pupil is the single biggest obstacle to a good view of the fundus, as it acts like a narrow keyhole. Where appropriate, instil a short-acting mydriatic such as tropicamide 1% to widen the pupil and let in more light. The pupil typically takes around 15–20 minutes to dilate. It is essential to warn the patient that their vision will become blurred and light-sensitive for several hours and that they must not drive until it has worn off.
Before dilating, consider the risks. Mydriatics can precipitate acute angle-closure glaucoma in susceptible eyes, because widening the pupil bunches up the peripheral iris and can block drainage of aqueous humour at the iridocorneal angle, causing a sudden rise in intraocular pressure. Dilation also temporarily abolishes the pupillary response, which is unhelpful if you are monitoring a patient with a head injury or other neurological condition. In an OSCE you may simply be expected to state that you would dilate the pupil and acknowledge these considerations.
Set up the ophthalmoscope. Turn the light to its maximum brightness and select a medium, round white beam for a standard examination. Set the lens (dioptre) dial to 0 as a starting point; this dial can later be rotated to compensate for your own and the patient’s refractive error to bring the fundus into sharp focus. Most ophthalmoscopes also offer additional beam settings, including a red-free (green) filter that removes red wavelengths so that blood appears black against a green background. This sharpens the contrast of the blood vessels and small haemorrhages and is particularly useful when scrutinising the retinal vasculature and the centre of the macula in more detail.
Dim the room lights. A dark room causes the patient’s pupils to dilate naturally and greatly improves your view, complementing any pharmacological dilation.
Match eye to eye and hand to hand. Examine the patient’s right eye with your right eye, holding the ophthalmoscope in your right hand, and their left eye with your left eye and left hand. This keeps your head and the instrument out of the patient’s line of fixation and lets you get close without your noses colliding.
Assessing the Fundal (Red) Reflex
The first step of the examination proper is to assess the fundal reflex, also called the red reflex.
Hold the ophthalmoscope to your eye and, from approximately one arm’s length away and slightly to the side, shine the light onto the patient’s pupil. You should observe a reddish-orange reflection filling the pupil. This colour is produced by light reflecting back off the vascular, pigmented retina – it is the same effect that causes ‘red eye’ in flash photography.
An absent, diminished or abnormally coloured reflex indicates that something is obstructing the path of light between the cornea and the retina:
- A white reflex (leukocoria) is an important finding. In a child it must prompt urgent referral, as it can be caused by retinoblastoma (a malignant retinal tumour) or congenital cataract.
- A dark or absent reflex in an adult is most commonly due to a cataract (opacification of the lens), but can also reflect a dense vitreous haemorrhage.
Anterior Segment
As you move closer, take a moment to inspect the anterior structures of the eye through the ophthalmoscope before focusing on the retina. Increasing the positive (plus) lenses on the dioptre dial brings these more superficial structures into focus.
Look at the cornea and lens for any opacities. Lens opacities appear as dark shadows or specks silhouetted against the red reflex and represent cataract. Identifying media opacities at this stage explains why your subsequent view of the retina may be poor and prevents you from mistaking the obstruction for retinal pathology.
Quiz
- 200
