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
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
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
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
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
For pupillary dilatation, the sympathetic pathway originates
in the hypothalamus, passing down to the ciliospinal centre
Internal carotid arteries Abducens nerve
Fig. 8.3 Cavernous sinus (coronal view). Neuroanatomy of cranial nerves III, IV and VI.
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
Fig. 8.6 Pupillary innervation. A Parasympathetic pathway.
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.
• if the eye is painful or photophobic
• if there has been any recent trauma
• whether there is any discharge
• whether there has been any recent contact lens wear or
Box 8.4 summarises the features of the common causes of
a red eye on history and examination.
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).
• 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
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.
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
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.
• whether the discharge is clear or opaque
• whether there is associated pain, foreign body sensation
• whether the patient has noticed other abnormalities, such
There are many causes of eye discharge, and their clinical
features are summarised in Box 8.6.
The orbit is an enclosed structure, except anteriorly. Any swelling
inside the orbit can lead to proptosis or anterior displacement
• the swelling is unilateral or bilateral
• the changes were acute or gradual
• there is any itchiness or irritation
• the swelling is associated with any double vision.
Box 8.7 summarises the common causes of swollen eyes.
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.
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
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
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
When patients present with a change in vision, ask:
• Did the change in vision start suddenly or gradually?
• How is the vision affected (loss of vision, cloudy vision,
• Is it one or both eyes that are affected?
• Is the whole or only part of the visual field affected?
• If partial, which part of the visual field is affected?
• whether anything started the pain
• about the character of the pain
• if the pain is exacerbated or relieved by any factors
• whether the pain is associated with any other symptoms.
The cornea is one of the most highly innervated regions of the
body. When the corneal nerves are activated, this leads to pain,
the sensation of foreign body, reflex watering and photophobia.
There are, however, many other causes of a painful eye. Box
8.3 summarises the history and examination findings associated
8.1 Common causes of an acute change in vision
Cause Clinical features Cause Clinical features
• Risk in proliferative diabetic retinopathy
• History of flashing lights or floaters may precede
haemorrhage in posterior vitreous detachment
• Poor fundus view on examination
• Reduction or loss of the red reflex
• Usually no RAPD if retina is intact
• Acute, painless loss of vision
• Greater risk if hypertensive
• Haemorrhages, exudates and tortuous retinal veins
• Sudden painless loss of central vision
• Haemorrhage at the macula (Fig. 8.7E)
• Association with flashing lights or floaters
• History of a curtain coming across vision
• Myopic patients at greater risk
• Pale raised retina usually with a retinal tear (Fig. 8.7B)
• Painless loss of upper or lower visual field
• Increased risk in vasculopaths
• Examination may reveal optic disc swelling
• Acute, painless loss of vision
• Increased risk in vasculopaths
• Examination: pale retina with a cherry red spot at the
• Pain exacerbated by eye movement
• Swollen optic disc in optic neuritis (Fig. 8.7F) or
normal appearances in retrobulbar neuritis
• Corneal opacity may be visible (e.g. Fig. 8.7D)
• Painless loss of vision for minutes
• History of cardiovascular disease
• May have associated atrial fibrillation or carotid bruit
Cerebral infarct • May have associated headache and/or neurological
• Usually specific field defects dependent on how the
visual pathway is affected (Fig. 8.5)
• If post chiasmal visual pathway affected, bilateral
Migraine • Gradually evolving usually bilateral visual loss
• Vision loss is usually preceded by visual aura
• Vision usually returns to normal after hours
RAPD, relative afferent pupillary defect (p. 162).
8.2 Common causes of a gradual loss of vision
Refractive error • No associated symptoms
• Vision can be improved by pinhole (Fig. 8.4D)
Glaucoma • Usually bilateral but asymmetric loss of visual field
• Cupped optic discs on examination
Cataract • Gradual clouding of vision
• May be associated with glare
• Examination: clouding of the pupil and altered red
• Central vision reduced or distorted
• Haemorrhages and exudates at the macula on
• Gradual unilateral loss of vision
• Pale optic disc on examination (Fig. 8.8D)
• Gradual bilateral symmetric loss of peripheral
• Nyctalopia (poor vision in dim light)
• Examination: bone spicule fundus, attenuated
blood vessels and waxy optic disc (Fig. 8.8E)
E Wet age-related macular degeneration. F Swollen optic nerve head in acute optic neuritis.
peripherally in association with a ring scotoma and symptoms of night blindness.
8.2 Common causes of a gradual loss of vision – cont’d
• Gradual loss of central vision
• Examination: drusen, atrophy and pigmentation at
Ocular examination: redness and swelling of lid
Ocular examination: foreign body visible or found
Ulcer on cornea, which can be highlighted with
fluorescein staining (see Fig. 8.7D)
Ocular examination: white infiltrate may be visible
Scleritis Severe pain that keeps the patient awake at night
Association with recent infection, surgery or
Ocular examination: scleral injection
Possibly, haloes seen around lights
Association with nausea and vomiting
Ocular examination: fixed mid-dilated pupil, hazy
RAPD, relative afferent pupillary defect (p. 162).
Conjunctivitis Increased clear or purulent discharge
Ocular examination: ciliary flush
Optic neuritis Reduction in vision
Reduction in colour sensitivity
Constant pain worsened by eye movement
Ocular examination: swollen disc in optic neuritis
(see Fig. 8.7F), normal disc in retrobulbar neuritis
Orbital cellulitis Constant ache around the eyes
Association with a recent viral infection
Ocular examination: conjunctival chemosis and
injection, restricted eye movements; in severe cases,
Symptoms of hyperthyroidism (p. 197)
Ocular examination: lid retraction, proptosis,
restricted eye movements and conjunctival injection,
conjunctival chemosis (see Fig. 10.4)
8.4 Common causes of a red eye
Possibly, more frequent occurrence at certain times
Viral conjunctivitis Watery discharge
Ocular examination: gland swelling and follicles
Ocular examination: may reveal subconjunctival
Acute-onset reduction in vision
Ocular examination: fixed, mid-dilated pupil with a
Ocular examination: ciliary flush
Episcleritis Focal or diffuse injection
Possible association with a nodule
Scleritis Focal or diffuse injection
Association with recent infection, surgery or
Severe pain that keeps the patient awake at night
Dry eyes Gritty or burning sensation
Ocular examination: corneal fluorescein staining
Comments
Post a Comment
اكتب تعليق حول الموضوع