As in all clinical medicine, an accurate history and examination
are essential for correct diagnosis and treatment.
Most ocular
conditions can be diagnosed with a good history and simple
examination techniques.
Conversely, the failure to take a history
and perform a simple examination can lead to conditions being
missed that pose a threat to sight, or even to life.
The history may give many clues to the diagnosis. Visual
symptoms are particularly important.
The rate of onset of visual symptoms gives an indication of
the cause. A sudden deterioration in vision tends to be vascular
in origin, whereas a gradual onset suggests a cause such as
cataract.
The loss of visual field may be characteristic, such as
the central field loss of macular degeneration.
Symptoms such
as flashing lights may indicate traction on the retina and
impending retinal detachment. Difficulties with work, reading,
watching television, and managing in the house should be
identified.
It is particularly important to assess the effect of the
visual disability on the patient’s lifestyle, especially as conditions
such as cataracts can, with modern techniques, be operated on
at an early stage.
The patient should also be asked exactly what is worrying
them, as visual symptoms often cause great anxiety.
Appropriate
reassurance then can be given. Questions about particular symptoms
Some specific questions are important in certain circumstances.
A history of ocular trauma or any high velocity injury particularly a hammer and chisel injury should suggest an
intraocular foreign body.
Other questions, for example about
the type of discharge in a patient with a red eye, may enable
you to make the diagnosis.
Previous ocular history
Easily forgotten, but essential.
The patient’s red eye may be
associated with complications of contact lens wear for
example, allergy or a corneal abrasion or ulcer.
A history of
severe shortsightedness (myopia) considerably increases the
risk of retinal detachment.
A history of longsightedness
(hypermetropia) and typically the use of reading glasses before
the age of 40 increases the risk of angle closure glaucoma.
Patients often forget to mention eye drops and eye operations
if they are asked just about “drugs and operations.”
A purulent conjunctivitis requires much more urgent attention if the
patient has previously had glaucoma drainage surgery, because
of the risk of infection entering the eye.
Medical history
Many systemic disorders affect the eye, and the medical history
may give clues to the cause of the problem; for instance,
diabetes mellitus in a patient with a vitreous haemorrhage or
sarcoidosis in a patient with uveitis.
Family history
A good example of the importance of the family history is in
primary open angle glaucoma. This may be asymptomatic until
severe visual damage has occurred.
The risk of the disease may
be as high as 1 in 10 in first degree relatives, and the disease
may be arrested if treated at an early stage.
For any disease that has a genetic component (for example, glaucoma), the age of
onset and the severity of disease in affected family members
can be very useful information.
Drug history
Many drugs affect the eye, and they should always be considered
as a cause of ocular problems; for example, chloroquine may
affect the retina.
Steroid drugs in many different forms (drops,
ointments, tablets, and inhalers) may all lead to steroid induced
glaucoma.
Examination of the visual system
Vision
An assessment of visual acuity measures the function of the eye
and gives some idea of the patient’s disability.
It may also have
considerable medicolegal implications; for example, in the case
of ocular damage at work or after an assault.
In the United Kingdom, visual acuity is checked with a
standard Snellen chart at 6 m.
If the room is not large enough, a
mirror can be used with a reversed Snellen chart at 3 m.
The
numbers next to the letters indicate the distance at which a
person with no refractive error can read that line (hence the 6/60
line should normally be read at 60 m).
If the top line cannot be
discerned, the test can be done closer to the chart. If the chart
cannot be read at 1 m, patients may be asked to count fingers,
and, if they cannot do that, to detect hand movements.
Finally, it
may be that they can perceive only light. From the patient’s point
of view, the functional difference between these categories may be
the difference between managing at home on their own (count
fingers) and total dependence on others (perception of light).
In other areas of the world (for example, the United
States), visual acuity charts use a different nomenclature. Visual
acuity of 20/20 is equivalent to 6/6 and 20/200 is equivalent to
6/60.
A logarithmic chart (LogMAR) is also used, especially for
large scale clinical trials and orthoptic childhood screening.
The LogMAR system offers increased sensitivity in acuity
testing, but the tests take longer to perform.
Vision should be tested with the aid of the patient’s usual
glasses or contact lenses.
To achieve optimal visual acuity, the
patient should be asked to look through a pinhole.
This reduces the effect of any refractive error and particularly is
useful if the patient cannot use contact lenses because of a red
eye or has not brought their glasses.
If patients cannot read
English, they can be asked to match letters; this is also useful
for young children.
Reading vision can be tested with a standard reading type
book or, if this is not available, various sizes of newspaper print.
There may be quite a difference in the near and distance
vision.
A good example is presbyopia, which usually develops in
the late forties because of the failure of accommodation with
age.
Distance vision may be 6/6 without glasses, but the patient
may be able to read only larger newspaper print.
Colour vision can be tested by using Ishihara colour plates,
which may give useful information in cases of inherited and
acquired abnormalities of colour vision.
The ability to detect
relative degrees of image contrast (contrast sensitivity) is also
important and can be assessed with a Pelli-Robson chart.
Some
eye problems (such as cataract, for example) may cause a
significant reduction in contrast sensitivity, despite good Snellen
visual acuity.
Field of vision
Tests of the visual field may give clues to the site of any lesion
and the diagnosis.
It is important to test the visual field in any patient with unexplained visual loss.
Patients with lesions that
affect the retrochiasmal visual pathway may find it difficult to
verbalise exactly why their vision is “not right.”
Location of the lesion Unilateral field loss in the lower nasal
field suggests an upper temporal retinal lesion.
Central field
loss usually indicates macular or optic nerve problems.
A homonymous hemianopia or quadrantanopia indicates
problems in the brain rather than the eye, although the patient
may present with visual disturbance.
Diagnosis A bitemporal field defect is most commonly
caused by a pituitary tumour.
A field defect that arches over
central vision to the blind spot (arcuate scotoma) is almost
pathognomonic of glaucoma.
To test the visual field The patient should be seated directly
opposite the examiner and then should be asked to cover the
eye that is not being tested and to look at the examiner’s face.
It is essential to make sure that the other eye is covered
properly to eliminate erroneous results.
In case of a gross
defect, the patient will not be able to see part of the examiner’s
face and may be able to indicate this precisely: “I can’t see the
centre of your face.”
If no gross defect is present, the fields can be tested more
formally.
Testing the visual field with peripheral finger
movements will show severe defects, but a more sensitive test is
the detection of red colour, because the ability to detect red tends
to be affected earlier.
A red pin is moved in from the periphery
and the patient is asked when they can see something red.
The pupils
Careful inspection of the pupils can show signs that are helpful
in diagnosis.
A bright torch is essential. A pupil stuck down to
the lens is a result of inflammation within the eye, which always
is serious.
A peaked pupil after ocular injury suggests
perforation with the iris trapped in the wound.
A vertically oval
unreactive pupil may be seen in acute closed angle glaucoma.
The pupil’s reaction to a good light source is a simple way
of checking the integrity of the visual pathways.
When testing
the direct and consensual pupil reactions to light, the
illumination in the room should be reduced and the patient
should focus on a distant point.
By the time pupils do not react
to direct light, the damage is very severe.
A much more
sensitive test is the relative difference in pupillary reactions.
Move the torchlight to and fro between the eyes, not allowing
time for the pupils to dilate fully.
If one of the pupils continues
to dilate when the light shines on it, there is a defect in the
visual pathway on that side (relative afferent pupillary defect).
Cataracts and macular degeneration do not usually cause an
afferent pupillary defect unless the lesions are particularly
advanced.
Neurological disease must be suspected.
Other important and potentially life threatening conditions
in which the pupils are affected include Horner’s syndrome,
where the pupil is small but reactive with an associated ptosis.
This condition may be caused by an apical lung carcinoma.
The
well known Argyll Robertson pupils caused by syphilis (bilateral
small irregular pupils with light-near dissociation) are rare.
In a third nerve palsy there is ptosis and the eye is divergent.
The
pupil size and reactions in such a case give important clues to
the aetiology.
If the pupil is unaffected (“spared”), the cause is
likely to be medical for example, diabetes or hypertension.
If the pupil is dilated and fixed, the cause is probably surgical
for example, a treatable intracranial aneurysm.
Any differences in the colour of the two irides
(heterochromia iridis) should be noted as this may indicate
congenital Horner’s syndrome, certain ocular inflammatory
conditions (Fuch’s heterochromic cyclitis), or an intraocular
foreign body.
Eye position and movements
The appearance of the eyes shows the presence of any large
degree of misalignment.
This can, however, be misleading if the
medial folds of the eyelids are wide.
The position of the corneal
reflections helps to confirm whether there is a true “squint.”
Patients should be asked if they have any double vision.
If so, they should be asked to say whether diplopia occurs in any
particular direction of gaze.
It is important to exclude palsies of
the third (eye turned out) or sixth (failure of abduction)
cranial nerves, as these may be secondary to life threatening
conditions.
Complex abnormalities of eye movements should
lead you to suspect myasthenia gravis or dysthyroid eye disease.
The presence of nystagmus should be noted, as it may indicate
significant neurological disease.
A protruding globe (proptosis) or a sunken globe
(enophthalmos) should be recorded.
Proptosis is always an
important finding: its rate of onset and progression may give
clues to the underlying pathology, and the direction of globe
displacement indicates the site of the pathology.
Eyelids, conjunctiva, sclera, and cornea
Examination of the eyelids, conjunctiva, sclera, and cornea
should be performed in good light and with magnification. You
will need:
● a bright torch (with a blue filter for use with fluorescein) or
an ophthalmoscope with a blue filter
● a magnifying aid.
The lower lid should be gently pulled down to show the
conjunctival lining and any secretions in the lower fornix.
The anterior chamber should be examined, looking
specifically at the depth (a shallow anterior chamber is seen in
angle-closure glaucoma and perforating eye injuries) and for
the presence of pus (hypopyon) or blood (hyphaema).
All these signs indicate serious disease that needs immediate
ophthalmic referral.
If there are symptoms of “grittiness,” a red eye or any
history of foreign body, the upper eyelid should be everted.
This should not be done, however, if there is any question of
ocular perforation, as the ocular contents may prolapse.
Conjunctiva and sclera Look for local or generalised
inflammation and pull down the lower lid and evert upper lid.
Cornea Look at clarity and stain with fluorescein.
Anterior chamber Check for blood and pus; also check
chamber depth.
The drainage angle of the eye can be checked with a special
lens (gonioscope).
Intraocular pressure
Assessment of intraocular pressure by palpation is useful only
when the intraocular pressure is considerably raised, as in acute
closed angle glaucoma.
The eye should be gently palpated
between two fingers and compared with the other eye or with
the examiner’s eye.
The eye with acute glaucoma feels hard.
Consider acute angle closure in any person over the age of 50
with a red eye.
Ophthalmoscopy
Good ophthalmoscopy is essential to avoid missing many
serious ocular and general diseases. A direct ophthalmoscope
can be used to allow intraocular structures to be seen.
Specific
contact and non-contact lenses are used during the
examination, and the ophthalmologist should use a slit-lamp
microscope or head-mounted ophthalmoscope.
To get a good view, the pupil should be dilated.
There is an
associated risk of precipitating acute angle closure glaucoma,
but this is very small. The best dilating drop is tropicamide 1%,
which is short acting and has little effect on accommodation.
However, the effects may still last several hours, so the patient
should be warned about this and told not to drive until any
blurring of vision has subsided.
The direct ophthalmoscope should be set on the “0” lens.
The patient should be asked to fix their gaze on an object in
the distance, as this reduces pupillary constriction and
accommodation, and helps keep the eye still.
To enable a
patient to fix on a distant object with the other eye, the
examiner should use his right eye to examine the patient’s
right eye, and vice versa.
The light should be shone at the eye
until the red reflex is elicited.
This red reflex is the reflection
from the fundus and is best assessed from a distance of about
50 cm.
If the red reflex is either absent or diminished, this
indicates an opacity between the cornea and retina.
The most
common opacity is a cataract.
The optic disc should then be located and brought into
focus with the lenses in the ophthalmoscope.
If a patient has a high refractive error, they can be asked to leave their glasses on,
although this can cause more reflections.
The physical signs at
the disc may be the only chance of detecting serious disease
in the patient.
The retina should be scanned for abnormalities
such as haemorrhages, exudates, or new vessels.
The green
filter on the ophthalmoscope helps to enhance blood vessels
and microaneurysms.
Finally the macula should be examined for the pigmentary changes of age-related macular
degeneration and the exudates of diabetic maculopathy.
It is viewed using a slit-lamp microscope and lens or head
mounted indirect ophthalmoscope. However, these techniques
are specialised.
