Eye and Vision OSCE Examination

1. Introduction
2. General Inspection
3. Visual Acuity
4. Colour Vision
5. Pupillary Reflexes
6. Visual Fields
7. Eye Movements
8. Fundoscopy
9. Completing the Examination
10. Quiz

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. A useful framing is to say you would like to check the patient’s vision, how their eyes move and look at the back of the eyes.

Position the patient sitting comfortably in a chair, ideally facing you at roughly the same eye level for the parts of the examination performed face-to-face.

Ask the patient whether they normally wear glasses or contact lenses, particularly distance glasses, as these will be needed for an accurate assessment of visual acuity. Also ask if they have any eye pain before you begin.

Begin with a general inspection of the patient and the area around them. Look for obvious clues to the underlying diagnosis such as a white stick or guide dog (suggesting significant visual impairment), glasses or contact lens equipment, an eye patch, a magnifier or large-print material, or a prosthetic eye. These adaptations give an immediate sense of how the patient’s vision affects their daily function.

Inspect the face and eyes for any asymmetry. A facial droop may indicate a previous stroke or facial nerve palsy, which is relevant because incomplete eyelid closure can threaten the cornea. Look at the position of the eyes for any obvious squint (strabismus) or proptosis (bulging of the eye), the latter classically associated with thyroid eye disease.

Inspect the eyelids for ptosis (drooping of the upper eyelid). Ptosis can be caused by a third cranial nerve (oculomotor) palsy or Horner’s syndrome, and the associated features help to distinguish them – a third nerve palsy tends to cause a complete ptosis with a ‘down and out’ eye and a dilated pupil, whereas Horner’s syndrome causes a partial ptosis with a constricted pupil.

Look at the eyes themselves for any redness (suggesting conjunctivitis, scleritis or an acute red eye), discharge, abnormal pupil size or shape, and the presence of corneal arcus (a pale ring around the iris caused by lipid deposition, which can indicate hyperlipidaemia in younger patients).

Visual acuity is the sharpness of central vision and is the single most important measurement in an eye examination. It is assessed using a Snellen chart positioned at 6 metres from the patient (or at 3 metres using a mirror). If the patient normally wears distance glasses, these should be worn, as you are testing their best corrected vision.

Test each eye separately, asking the patient to cover the other eye and read down the chart until the letters can no longer be made out. Record each eye individually, noting whether glasses were worn.

Visual acuity is recorded as a fraction, for example 6/6. The top number is the distance the patient was from the chart (6 metres), and the bottom number is the distance at which a person with normal vision could read that same line. So 6/6 is normal vision, while 6/60 means the patient can only read at 6 metres what a normal-sighted person could read at 60 metres – markedly reduced acuity.

If the patient cannot read the top letter of the chart even at 6 metres, the assessment is stepped down: move the patient to 3 metres, then 1 metre, then test counting fingers, hand movements, and finally perception of light. This grading describes exactly how poor the vision is and is important for documentation and for assessing severe disease.

If acuity is reduced, repeat the test with the patient looking through a pinhole. A pinhole allows only the central, most focused rays of light to reach the retina. If vision improves with a pinhole, the cause is most likely a refractive error (the eye is simply out of focus, correctable with glasses). If it does not improve, this points towards a pathological cause such as cataract, macular disease or optic nerve pathology.

Image - A Snellen chart, used to assess distance visual acuity. The patient reads down the chart at a set distance, and acuity is recorded as a fraction such as 6/6

Creative commons source by Jeff Dahl [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Near vision should also be assessed, using a near reading chart held at a comfortable reading distance with the patient wearing any reading glasses. Reduced near vision with preserved distance vision is common in presbyopia, the age-related loss of accommodation.

Colour vision is assessed using Ishihara plates. Each plate is made up of coloured dots arranged so that a number is visible to those with normal colour vision but is difficult or impossible to identify for those with a colour vision deficit.

The patient is asked to identify the number on each plate, testing one eye at a time. The first plate is usually a ‘test plate’ visible to everyone, including those with colour blindness, which checks the patient has understood the task and has adequate acuity to see the dots.

Ishihara plates primarily assess red-green colour discrimination. Test each eye separately; reduced performance in a symptomatic eye may support acquired colour impairment from optic nerve disease, such as optic neuritis, even when visual acuity is relatively preserved. Assess red desaturation separately by comparing the same red target between the eyes and asking whether it looks washed out or less vivid on one side. Colour-plate testing and red-target comparison assess different aspects of colour perception; neither alone establishes a diagnosis of optic neuritis.

Image - An Ishihara red-green colour-discrimination plate. People with typical colour vision read 74; people with red-green colour deficiency may read a different number or no number. This plate is not a direct test of red vividness

Creative commons source by Shinobu Ishihara [Public domain]

Before testing the reflexes, inspect the pupils at rest for their size, shape and symmetry. Most people have pupils of roughly equal size; a difference between the two is termed anisocoria.

Understanding the light reflex pathway makes interpreting the findings straightforward. The pathway has two limbs. The afferent limb carries the signal from the retina to the brainstem along the optic nerve when light is shone into an eye. The efferent limb carries the signal back to both pupils via the oculomotor nerve (cranial nerve III) and the parasympathetic fibres, causing both pupils to constrict. Crucially, light shone into one eye normally causes both pupils to constrict because the signal crosses to supply both sides.

To test the direct reflex, dim the room lights and shine a pen torch into one pupil from the side. The pupil into which the light is shone should constrict. To test the consensual reflex, shine the light into one eye but watch the opposite pupil, which should also constrict. The direct reflex tests the afferent limb of the eye being lit and the efferent limb of that same eye; the consensual reflex tests the afferent limb of the lit eye and the efferent limb of the contralateral eye.

The swinging light test is used to detect a relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil. Move the torch rhythmically from one eye to the other, pausing on each. In a normal response, both pupils stay constricted as the light swings across. If there is a defect in the afferent pathway of one eye – for example from optic neuritis, a central retinal artery occlusion or a large retinal detachment – that eye senses less light. When the torch swings onto the affected eye, the reduced afferent signal causes both pupils to paradoxically dilate, because the brain perceives the overall light input has fallen. An RAPD is therefore a sensitive sign of unilateral or asymmetrical optic nerve or retinal disease.

Finally, test the accommodation reflex. Ask the patient to look at a distant point and then quickly switch their gaze to a target held close to their nose. The eyes should converge and the pupils should constrict to bring the near object into focus. The classic abnormality is the Argyll Robertson pupil, which accommodates but does not react to light (‘accommodation-reaction dissociation’), historically associated with neurosyphilis.

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