Cranial nerve examination

• Ask about sense of smell and taste (I).

• Assess visual acuity (using a Snellen chart) and visual fields (by confrontation) (II).

• Observe pupils and test pupillary reactions bilaterally: direct and consensual (II).

• Observe both eyes in the neutral position. Are they orthotropic (both pointing in the same direction)? Test eye movements, observing

for completeness of movement in pursuit and looking for nystagmus (III, IV, VI).

• Test facial sensation (V) and corneal reflex (V and VII).

• Observe for facial asymmetry and test facial muscles of the upper and lower parts of the face (VII).

• Perform a bedside test of hearing (VIII).

• Assess speech, swallow and palatal movement (IX, X, XI).

• Inspect the tongue and assess movement (XII).

Neurological examination of the upper limb

• Expose the upper limbs ensuring maintenance of dignity and privacy; request a chaperone if appropriate.

• Inspect for wasting, fasciculations.

• As a screening test ask the patient to hold the arms out (palms up) and close their eyes – watch for pronator drift.

• Assess tone.

• Test muscle power: shoulder abduction (axillary nerve C5), elbow flexion (musculocutaneous nerve, C5, C6) and extension (radial nerve, C7), finger

extension (posterior interosseus nerve, C7), index finger abduction (ulnar nerve, T1), little finger abduction (ulnar nerve, T1), thumb abduction

(median nerve, T1).

• Assess reflexes at biceps (C5), triceps (C7) and supinator (brachioradialis, C6).

• Test coordination with finger – nose test and look for dysdiodokinesia.

• Test sensory modalities: pinprick, temperature, vibration sense, joint position sense.

Neurological examination of the lower limb

• Undress the patient to expose both lower limbs fully, ensuring maintenance of dignity and privacy; request a chaperone if appropriate.

• Carry out a general inspection, noting walking aids and other associated neurological signs, such as facial droop or ipsilateral arm flexion.

• If the patient is able to do so, ask them to stand and walk so that you can assess stance and gait. Assess tandem gait.

• Inspect both legs, noting any scars, muscle wasting or fasciculations, abnormal postures or movements.

• Assess tone at the hip, knee and ankle. Test for ankle clonus.

• Test muscle power. As a simple screen, assess hip flexion (iliofemoral nerve, L1, 2) and extension (sciatic, L5/S1), knee flexion (sciatic, S1) and

extension (femoral, L3, 4), and ankle plantar flexion (tibial, S1, 2) and dorsiflexion (deep peroneal, L4, 5).

• Assess reflexes at the knee (L3) and ankle (S1), comparing sides. Test the plantar response.

• Test coordination via heel-to-shin tests.

• Test sensory modalities: pinprick, temperature, vibration and joint position sense. Map out any symptomatic areas of disturbed sensation.

OSCE example 2: Tremor – cont’d

Summarise your findings

The patient has an asymmetric pill-rolling rest tremor of the right arm, which briefly disappears on movement but quickly returns (re-emergent tremor).

He also has a tremor affecting the jaw/chin. There is a lack of facial expression, drooling, monotonous, hypophonic speech, bradykinesia (reduced fine

finger movements, difficulty with repetitive movements), increased tone with cog wheeling, and loss of the right arm swing and increased tremor when

walking, with short stride length.

Suggest a diagnosis

These findings are typical of Parkinson’s disease.

Suggest initial investigations

A diagnosis of Parkinson’s disease is usually based on the clinical features and investigation unnecessary. In selected cases, structural imaging (MR or

CT) to rule out the rare mimics of PD, or functional imaging (DaTscan) may be appropriate. Blood tests are rarely helpful, but a strong family history

may precipitate consideration of genetic testing.

8

The visual system

Shyamanga Borooah

Naing Latt Tint

Anatomy and physiology 152

Eye 152

Extraocular muscles 152

Refractive elements of the eye 153

Visual pathway 153

Pupillary pathways 153

The history 155

Common presenting symptoms 155

Past ocular history 159

Past medical history 159

Drug and allergy history 159

Family history 159

Social history 159

The physical examination 160

General examination 160

Visual acuity 160

Orbit and periorbital examination 161

Pupils 161

Visual fields 162

Ocular alignment and eye movements 163

Ophthalmoscopy 164

Retinopathies 165

Investigations 165

OSCE example 1: Gradual visual loss 168

OSCE example 2: Double vision 169

Integrated examination sequence for ophthalmology 169

152 • The visual system

Eye

The eyeball is approximately 25 mm in length and comprises

three distinct layers. From outside in (Fig. 8.1), these are the:

• Outer fibrous layer: this includes the sclera and the clear

cornea. The cornea accounts for two-thirds of the

refractive power of the eye, focusing incident light on to

the retina.

• Middle vascular layer (uveal tract): anteriorly this consists

of the ciliary body and the iris, and posteriorly the choroid.

• Inner neurosensory layer (retina): the retina is the structure

responsible for converting light to neurological signals.

Extraocular muscles

The six extraocular muscles are responsible for eye movements

(Fig. 8.2). Cranial nerve III innervates the superior rectus, medial

rectus, inferior oblique and inferior rectus muscles. Cranial nerve

IV innervates the superior oblique muscle and cranial nerve VI

innervates the lateral rectus muscle. The cranial nerves originate

Anatomy and physiology

The eye is a complex structure situated in the bony orbit. It is

protected by the eyelid, which affords protection against injury

as well as helping to maintain the tear film. The upper lid is

elevated by the levator palpebrae superioris, innervated by cranial

nerve III, and Müller’s muscle, innervated by the sympathetic

autonomic system. Eyelid closure is mediated by the orbicularis

oculi muscle, innervated by cranial nerve VII.

The orbit also contains six extraocular muscles: the superior

rectus, medial rectus, lateral rectus, inferior rectus, superior

oblique and inferior oblique. In addition, the orbit houses the

lacrimal gland, blood vessels, autonomic nerve fibres and cranial

nerves II, III, IV and VI. The contents are cushioned by orbital

fat, which is enclosed anteriorly by the orbital septum and the

eyelids (Fig. 8.1).

The conjunctiva is a thin mucous membrane lining the posterior

aspects of the eyelids. It is reflected at the superior and inferior

fornices on to the surface of the globe. The conjunctiva is coated

in a tear film that protects and nourishes the ocular surface.

Retina

Fovea centralis

Central retina vein

Central retina artery

Optic nerve

Optic disc

Inferior rectus muscle

Superior rectus muscle

Levator palpebrae superioris muscle

Cornea

Orbicularis oculi muscle

Septum

Skin

Frontalis muscle

Orbital fat

Müller’s muscle Frontal sinus

Iris

Pupil

Sclera

Inferior oblique

Lens

Anterior chamber

Meibomian glands

Tarsal plate

Ciliary body

Vitreous body

Zonules

Ora serrata

Hyaloid canal

Fig. 8.1 Cross-section of the eye and orbit (sagittal view).

Right eye

Superior

rectus

Lateral

rectus

Lateral

rectus

Inferior

rectus

Inferior

rectus

Superior

oblique

Superior

oblique

Inferior

oblique

Inferior

oblique

Medial

rectus

Superior

rectus

Left eye

Fig. 8.2 Control of eye movements. The direction of

displacement of the pupil by normal contraction of a particular

muscle can be used to work out which eye muscle is paretic. For

example, a patient whose diplopia is maximal on looking down and

to the right has either a weak right inferior rectus or a weak left

superior oblique muscle.

Anatomy and physiology • 153

8

of Budge at the level of T1. Fibres then pass to, and synapse

in, the superior cervical ganglion before joining the surface of

the internal carotid artery and passing to the pupil along the

nasociliary and the long ciliary nerves (Fig. 8.6B).

in the midbrain and pons and then pass through the cavernous

sinus (Fig. 8.3).

Refractive elements of the eye

The major refracting elements of the eye are the tear film, the

cornea and the crystalline lens. The cornea possesses the greatest

refractive power and is the main refracting element of the eye;

the lens provides additional controllable refraction, causing the

light to focus on to the retina. When light is precisely focused on

to the retina, refraction is called emmetropia (Fig. 8.4A). When

the focus point falls behind the retina, the result is hypermetropia

(Fig. 8.4B, long-sightedness). When rays focus in front of the

retina, the result is myopia (Fig. 8.4C, short-sightedness). These

refractive errors can be corrected with lenses or with a pinhole

(Fig. 8.4D).

Visual pathway

The visual pathway consists of the retina, optic nerve, optic

chiasm, optic tracts, lateral geniculate bodies, optic radiations

and visual cortex (Fig. 8.5). Deficits in the visual pathway lead

to specific field defects.

Pupillary pathways

The pupil controls the amount of light entering the eye. The

intensity of light determines the pupillary aperture via autonomic

reflexes. Pupillary constriction is controlled by parasympathetic

nerves, and pupillary dilatation is controlled by sympathetic

nerves.

For pupillary constriction, the afferent pathway is the optic

nerve, synapsing in the pretectal nucleus of the midbrain. Axons

synapse in both cranial nerve III (Edinger–Westphal) nuclei, before

passing along the inferior division of the oculomotor nerve to

synapse in the ciliary ganglion. The efferent postganglionic

fibres pass to the pupil via the short ciliary nerves, resulting in

constriction (Fig. 8.6A).

For pupillary dilatation, the sympathetic pathway originates

in the hypothalamus, passing down to the ciliospinal centre

Cavernous sinus

Arachnoid mater

Subarachnoid space

Third ventricle Optic tracts

Anterior cerebral arteries

Oculomotor nerve

Trochlear nerve

Ophthalmic division

of trigeminal nerve

Maxillary division

of trigeminal nerve

Temporal

lobe

Anterior pituitary

Sphenoidal air sinuses

Internal carotid arteries Abducens nerve

Dura mater

Fig. 8.3 Cavernous sinus (coronal view). Neuroanatomy of cranial nerves III, IV and VI.

B

A

C

D

Fig. 8.4 Normal and abnormal refraction by the cornea and lens.

A Emmetropia (normal refraction). Cornea and lens focus light on the

retina. B Hypermetropia (long-sightedness). The eye is too short and the

image on the retina is not in focus. A convex (plus) lens focuses the image

on the retina. C Myopia (short-sightedness). The eye is too long and the

image on the retina is not in focus. A concave (minus) lens focuses the

image on the retina. D Myopia corrected using a pinhole. This negates

the effect of the lens, correcting refractive errors by allowing only rays from

directly in front to pass.

154 • The visual system

Fig. 8.5 Visual field defects. 1, Total loss of vision in one eye because of a lesion of the optic nerve. 2, Bitemporal hemianopia due to compression of

the optic chiasm. 3, Right homonymous hemianopia from a lesion of the optic tract. 4, Upper right quadrantanopia from a lesion of the lower fibres of the

optic radiation in the temporal lobe. 5, Lower quadrantanopia from a lesion of the upper fibres of the optic radiation in the anterior part of the parietal lobe.

6, Right homonymous hemianopia with sparing of the macula due to a lesion of the optic radiation in the occipital lobe.

Light source

Short ciliary nerve

Ciliary ganglion

III nerve

Edinger–Westphal nucleus

Lateral geniculate body

Posterior commissure Superior

colliculus

Midbrain

Optic nerve

A B Posterior

hypothalamus

First-order neuron

Second-order neuron

Internal carotid artery

Superior cervical ganglion

External carotid artery

Carotid plexus

Trigeminal nerve

Long ciliary

nerve

Müller’s muscle

Pupil dilator

Ciliospinal centre of Budge

(C8–T2)

Fig. 8.6 Pupillary innervation. A Parasympathetic pathway.

B Sympathetic pathway.

The history • 155

8

Red eye

The eye is covered in a network of vessels in the conjunctiva, episclera

and sclera. Ciliary vessels are also found around the cornea. Dilatation

or haemorrhage of any of these vessels can lead to a red eye.

Additionally, in uveitis, acute angle-closure glaucoma and corneal

irritation the ciliary vessels around the cornea become more prominent

(a ‘ciliary flush’). The appearance is distinct from conjunctivitis, in

which there is a relative blanching of vessels towards the cornea.

Ask:

• if the eye is painful or photophobic

• if vision is affected

• if there has been any recent trauma

• whether the eye is itchy

• whether there is any discharge

• whether there has been any recent contact lens wear or

foreign body exposure.

Box 8.4 summarises the features of the common causes of

a red eye on history and examination.

Double vision (diplopia)

Decipher whether the diplopia is monocular or binocular. Binocular

diplopia is caused by an imbalance in eye movement. Monocular

diplopia results from intraocular disease in one eye. There are

several causes of double vision (Box 8.5 and Figs 8.9 and 8.10).

Ask:

• whether the double vision occurs in one or both eyes

• about the character of the double vision, and whether the images

are seen side by side, one above the other or at an angle

• whether the double vision is associated with any recent

trauma.

Test the eye movements (see Fig. 8.11), and use your

knowledge of the function of the extraocular muscles (see Fig. 8.2)

to work out which cranial nerve is affected in binocular diplopia.

Discharge

Increasing discharge from the eye results from either an increase

in production or a decrease in drainage from the ocular surface.

Irritation of corneal nerves activates cranial nerve V(I) and results

in a reflex tearing response.

Tears normally drain through the punctum at the medial end of

the lower eyelid into the nasolacrimal duct, which opens below the

inferior turbinate into the nasal cavity. Blockage of tear drainage

or abnormal lid position can also result in excessive discharge.

Ask:

• whether the discharge is clear or opaque

• whether there is associated pain, foreign body sensation

or itchiness

• whether the patient has noticed other abnormalities, such

as red eye.

There are many causes of eye discharge, and their clinical

features are summarised in Box 8.6.

Swollen eyes

The orbit is an enclosed structure, except anteriorly. Any swelling

inside the orbit can lead to proptosis or anterior displacement

of the globe.

Ask if:

• the swelling is unilateral or bilateral

• the changes were acute or gradual

• the swelling is painful

• there is any itchiness or irritation

• the swelling is associated with any double vision.

Box 8.7 summarises the common causes of swollen eyes.

The history

When taking an ophthalmic history, bear in mind the anatomy

of the eye and visual pathways. This will enable you to work

from ‘front to back’ to include or exclude differential diagnoses.

Common presenting symptoms

Start the ophthalmic history with open questions. This builds rapport

with the patient by allowing them to describe the condition in their

own words, and provides clues for more directed questions later.

The visual system has its own set of presenting symptoms,

which prompt specific sets of questions. The most common

are described here.

Altered vision

Vision may be altered by an intraocular disease that leads

to a change in the optical or refractive properties of the eye

and prevents incident light rays from being clearly focused on

the retina. Alternatively, it may result from extraocular factors

associated with damage to the visual pathway, which runs from

the optic nerve to the occipital lobe (see Fig. 8.5).

Establish whether the change in vision is sudden or gradual,

as these will have their own specific set of differential diagnoses

(Box 8.1 and Fig. 8.7; Box 8.2 and Fig. 8.8).

Vision may be not just reduced but also distorted. This

results from disruption to the normal structure of the macula,

the central part of the retina. The most common cause is macular

degeneration but it may also frequently stem from an epiretinal

membrane, vitreous traction or central serous retinopathy.

Flashes and floaters result from disturbance of the vitreous and

the retina, occurring most commonly in posterior vitreous detachment. This is usually found in older patients as the vitreous

gradually degenerates and liquefies, causing it to peel off from the

retina. The vitreous is attached to the retina in certain regions; in

these regions the vitreous either detaches with traction, resulting

in flashing lights, or detaches by tearing the retina, releasing

retinal pigment cells. Patients will see either of these as floaters.

Haloes are coloured lights seen around bright lights. They

occur with corneal oedema and are most commonly associated

with angle-closure glaucoma.