Examination of the Eye

Patients presenting with an ophthalmological complaint may strike fear in some practitioner's hearts as they recall student days standing in dimly lit rooms looking at incomprehensible machines which obscure both patient and doctor, wondering what on earth was going on. History taking in ocular complaints is actually very similar to that taken with other problems and examination need not be difficult if you keep it simple and remember what it is you are looking for. The eye is one of the few organs of the body which can be looked at both outside and in and whose basic function can be assessed using simple desk-top tools.

As with any physical examination, you need not carry out every test - functional ones should be directed by history and anatomical examination - but as with everything, practice will increase your confidence, improve your speed and you may well even derive some excitement at eliciting signs from a little organ that has a lot to say.

Obviously, not all the examinations described below need be carried out on every patient. The table makes suggestions but be guided by the individual patient and examine more rather than less if uncertain.

The basic structure is no different than for other systems but take particular note of the following:

• History of presenting complaint - the time and speed of onset, ocular associations (e.g. red eye pain, photophobia, blurry vision etc), systemic associations (e.g. headaches, nausea, rash on the forehead) and what the fellow eye is up to - a surprising number of patients fail to tell you about symptoms in there.
• Past ocular history - similar episodes, other episodes, surgery, 'lazy eye'.
• Social history - independence: this may tip the balance one way or another when deciding on whether to operate on a borderline cataract.

Work systematically from front to back.

Lids

Basic examination

Note position (with regards to fellow eye), redness, swelling, lacerations (full thickness vs. partial thickness, involvement of the puncta) and lumps / bumps (chalazion, sebaceous cysts): it is sometimes helpful to get patient to close lids and simultaneously run finger over upper, then lower, lids to assess very small lumps. Note any skin abnormality - rashes (varicella zoster), ulcerations (basal cell carcinoma), ill-defined thickening (squamous cell carcinoma). Note eyelashes - if you have access to a slit lamp, look at them under magnification (blepharitis).

Further examination

Lid eversion:

• Indication: suspicion of foreign body (FB), examination of papillae / follicles.
• Requirements: drop of local anaesthetic (LA), two clean cotton buds.
• Procedure: explain to patient what you are going to do and place an anaesthetic drop in lower fornix. Ask them to look down, firmly hold eyelashes with index/ thumb of one hand and place cotton bud at base of tarsus (top of lid) with the other. The trick is to gently pull the lid down and towards you whilst keeping the cotton bud firmly in place, before lifting the lid directly up whilst reminding patient to keep looking down. Hold lid in place with the 'eyelash hand' and examine tarsus and fornix. Use your clean cotton bud to 'dust' off any foreign material (it is usually quite firmly embedded). See cornea re. removing corneal FB.

Lacrimal system

Basic examination

Examine lids as above and look at puncta in particular (these are the openings to the canaliculi - tear drainage channels): are they sitting against globe, turned in (entropion) or drooping out (ectropion)? Look for swellings medial to the canthus - where the lids meet (blocked tear ducts) and any evidence of redness, pain or discharge (dacrocystitis).

Further examination

Assessing for dry eye:

• Requirements: fluorescein stain (dilute drops), cobalt blue light.
• Procedure: instill a drop of fluorescein and look at the cornea using cobalt blue light. Ask the patient to close their eyes, then open them. For each eye, count the number of seconds it takes for the tear film (visualized as a hazy diffuse spread of fluorescein over the cornea) to break up. It should take at least 10 seconds. There is also the Schirmer test which involves strips of filter paper and waiting for several minutes for tear absorption but it is difficult to get this test right and therefore not always reliable.

Conjunctiva

Basic examination

Look at its colour - is it injected (conjunctivitis), pale (anaemia), are there cysts (clear blebs), concretions (yellow deposits) or ulcerations? Look for FBs embedded up (or down) in the fornices or even hidden in folds (get patient to look far left then right). Note any discharge.

Further examination

Lid eversion (as above) may be necessary to assess the presence of follicles (raised, gelatinous pale bumps) or papillae (vascular bulges) and to rule out conjunctival FBs. Fluorescein staining of the conjunctiva will highlight small lacerations.

Cornea

Basic examination

Check first: is the patient wearing their contact lens? If you are suspecting a bacterial keratitis, the lens needs to be sent to the microbiology labs (check with your lab with regards to local policy about how to store the lens). Is the cornea hazy (all over e.g. acute angle closure glaucoma vs. localised e.g. band keratopathy) or clear? Are there any white dots visible before fluorescein staining (infiltrates suggestive of infective keratitis).

Before instilling fluorescein

• Check sensation (neuropathic keratopathy): twist a clean cotton bud / tissue to a tip and lightly touch cornea - brisk reaction should immediately follow! Fluorescein drops are mixed with anaesthetic and this cannot be tested once instilled.
• If you suspect a penetrating injury, you may wish to carry out a Seidel test (see below). If this is positive, stop right there, apply hard protective shield and send the patient (nil by mouth) to your closest eye unit. In the absence of a shield, pad the eye with gauze and tape and strict instructions not to rub the eye or the structures around it.

Fluorescein staining

A dab from the fluorescein strip applicator (ask patient to blink a few times after this) or a single drop will do. Look for diffuse tiny spots (punctate epithelial erosion from dry eye) or presence of ulcers (e.g. herpes simplex keratitis). If your suspicions are strong but you cannot see anything, refer up as some of these lesions are tiny but must not go untreated.

Further examination

Seidel test:

• Indication: suspicion of penetrating injury.
• Requirements: 10% fluorescein (this is dark orange - a dry fluorescein strip will do), cobalt blue light source, a rigid eye shield.
• Procedure: apply the fluorescein to the suspicious area, asking the patient not to blink. If it turns from a dark non fluorescent orange to a swirly bright fluorescent orange / yellow, aqueous is leaking out (diluting it). The patient should be made nil by mouth, an eye shield should be applied and an urgent referral made.

Removing a corneal FB:

• Requirements: drop of local anaesthetic (LA), two clean cotton buds ± 25G needle and a burr (electrical device like a mini electric toothbrush on which a sterile round-tipped metal extension is applied).
• Procedure: evert the lid as above and attempt to remove the FB with cotton first. Some FBs (metallic ones in particular) can become quite embedded and if you have access to a slit-lamp and have a steady hand, use the needle to gently pry the FB out. Once it is removed, use the burr to remove any underlying rust ring (a gentle small rotary motion will do). If you do not have access to a slit lamp or if the patient complains of a persistant foreign body sensation 24 hours after apparently complete removal, refer to an opthalmology unit.

Anterior chamber

Assessment is limited without a slit lamp but a note can be made of the presence of hypopyon - a collection of pus sitting inferiorly (e.g. ophthalmitis) or hyphaema - blood in the anterior chamber. If you have a slit lamp, further assess by narrowing the beam to 1mm and putting it on its brightest light setting. Angle it at 30-45° to the cornea and focus in, past the cornea. If the iris comes into focus, you have focused too far, so go back again - you are effectively focusing into a space. Look for cells (like particles of dust passing through the shaft of light) and flare (slight cloudiness) of anterior uveitis.

Pupils

Look at their relative size - if you think that there may be anisocoria (different sized pupils), stand back from the patient, darken the room and look through the ophthalmoscope. You can elicit the red reflex in both eyes and compare the size of these directly rather than shifting from one to the other close up. Look for change in shape (typically oval in acute angle closure glaucoma, asymmetry in a penetrating injury) and any abnormal oscillations (Adie's tonic pupil syndrome).

Lens and the red reflex

A cataract is not always easy to spot without a slit lamp unless it is very mature (brunescent or even white - rare these days). However, you may notice an opacity by examining the red reflex: this is best seen with a dilated pupil when the patient is looking at the light of the ophthalmoscope which is held about an arm's length away from the patient. Look through the ophthalmoscope and turn the dial until you see the reflex. This may be attenuated as a result of any opacity between the cornea and the fundus but a clue may lie in that a corneal opacity is visible externally and a vitreous opacity may be mobile.

The red reflex is part of the routine neonatal check. Use a direct ophthalmoscope in a dimly lit room and hold your ophthalmoscope about 2/3 of an arm's length away from the baby. If the baby is screwing their eyes shut, ask the mother to feed them and check it during the feed. Very occasionally, a neonate may need dilating to check the red reflex. If this is the case, it is best to refer to an ophthalmologist who may use cyclopentolate 0.5% in both eyes.

Fundus

A basic fundus examination can be carried out with the ophthalmoscope. The key to success is practice and a systematic approach. In the first instance, become familiar with the ophthalmoscope. Try out the different light sources; most commonly used are the white and where available, the blue filter. The green filter highlights vessels more clearly. The dial changes the lens through which you look and what suits you best depends on whether you have a refractive error, the type and whether you keep your spectacles on during the examination.

When examining the patient, sit them comfortably, explain what you are going to do (including "I'm going to get very close to your face and shine a bright light in your eye. Don't look directly at the light unless I tell you to."). It helps to stand on the side you are going to do the examination. Always examine both eyes.

Elicit the red reflex and 'home in' through the pupil, looking for the disc. Once you have found it, adjust the focus by turning the dial until you are happy with what you see. Look for pallor (atrophy) or oedema (blurred margins). Then work your way along each of the four main vascular branches, looking for attenuation (embolus), aneurysms or exudates (diabetic eye disease). Look at the background retina - are there any haemorrhages (e.g. retinal vein occlusion) or areas of pallor (e.g. retinal artery occlusion) or unusual pale patches (e.g. chorioretinitis)? Lesions are noted as being a number of disc diameters away (nasally or temporally) from the disc. Finally, ask the patient to look at the light to assess the macula which lies about two disc diameters temporally to the disc (it may be seen as a slightly darker area than the surrounding retina - more so in darker people - with blood vessels arching over and under it but not on top of it) - this part of the examination should be swift as it may be uncomfortable. Look for the presence of haemorrhage or the loss of a pin-point yellow foveal reflex (macular oedema).

The visual acuity is the most basic of functions that should be examined in every patient. Beyond this, functional testing is guided by the symptoms and findings so far. An outline of some of the further tests available in a specialist department has been given - there are of course a vast array that fill volumes of textbooks but here is a sample ...

Visual Acuity

This essential examination should be carried out on every patient presenting with an eye problem.

Snellen Chart

The most common method is using a Snellen chart which comprises of random letters arranged in rows, decreasing in size in each row. Charts are designed to be read at 3 or 6 metres. The row corresponds to the distance at which a normal eye could read that row. For example, the top row could be read by the normal eye 60 metres away. The patient should be tested one eye at a time using their normal distance glasses (or distance portion of their bifocals) and then using a pin hole - you cannot assume that their glasses are of the correct prescription and the pinhole will correct any refractory errors unless there is media opacity e.g. corneal oedema.

The reading is recorded as 6/60 - this means that the patient was tested at 6 metres (or equivalent if you used a 3 metre chart) and were able to read the top row only. If they score 6/4 (i.e. read the lowest row), they were tested at 6 metres but their eyesight was so good that they actually saw what a 'normal' person would usually need to be 4 metres away to read. If the patient is unable to read the top row, try counting fingers (CF) at 1 metre in a well lit room, then hand movements (HM), then perception of light (PL). If the patient sees nothing at all, they are said to be NPL (no perception of light). If the patient reads most of a line right but gets 1 or two wrong at the 12 metre row for example, this is recorded as 6/12-2. If they get more than two wrong, assume they can only read the line above.

Non-standard testing

There are variations of the Snellen chart for patients who are illiterate: capital 'E's are rotated in different directions which the patient has to identify. Children may use the Sheridan-Gardiner test where they have to match up letters or pictures of different sizes with those presented on a card in front of them. Very young children are examined by assessing their preferential looking of cards of various pictorial complexity (Cardiff card test) and babies may be assessed by their ability to pick up very small objects such as the 'hundreds and thousands' cake decorations. Infants are watched for tracking of a light source.

Visual fields

The best way to examine these in the primary care setting tis to do a confrontational visual field test. This only works with a 'co-operative' patient and as it is a comparison with your own visual field, it is important to be aware of any defects of your own (which will limit the test). There are various ways to carry out this test but the principle is always the same.

Sit yourself directly opposite the patient, about a metre away from each other. Ask the patient to cover one eye and cover your contralateral eye (so that effectively, your covered eyes are opposite to each other). Tip: this test requires the patient to concentrate and some people get flustered over their left and right, and possibly getting it wrong in front of the doctor. Just say "cover one eye with your hand" and then follow their cue as to which eye you should cover.

Hold your arm out so that your hand is equidistant between you and the patient and place in one of the four quadrants. "I want you to keep your eye looking into mine and I'm going to test how well it can see out at the edges" - keep reminding them to look into your eye or the test is meaningless. Depending on the patient, either instruct them to say how many fingers you are holding up (do this 3 or 4 times for each quadrant) or - for a more accurate measurement - use a white hat pin. If their visual acuity is very poor, use a moving finger. Progressively work your way in towards the centre if there is a defect.

Repeat for fellow eye, giving time for the patient to rest between the two, particularly if they are elderly.

Intraocular pressure

Quick examination

A very low intra-ocular pressure (IOP) may manifest itself as a soft eyeball on palpation of the globe over the closed lids and a very high IOP may feel hard. However, these are very crude measures (and a globe thought to be soft on account of perforation should not be palpated) and are not a substitute for proper tonometry where there is a concern over IOP.

Tonometry

IOP can very easily measured using a slit-lamp and an applanation tonometer. The principle is that the tonometer measures the degree of resistance provided by the cornea to gentle indentation and converts this into a figure. Most tonometers are mounted on the slit lamp and some use a disposable head, others a washable one. Apply a drop of fluorescein / anaesthetic and put the blue light filter. "Look at the blue light which is going to get very close to your eye. It won't hurt but it is important that you keep looking ahead with your eyes wide open." (If you tell patients not to blink, they will). Gently move forwards and when the tonometer is just about touching the surface of the cornea, look through the eyepiece. You will see two semicircles. Rotate the dial on the side so that the semicircles are only just overlapping. Tell the patient to sit back and take the reading off the side of the tonometer (normal readings should be between 9 and 21mmHg).

Pupillary reactions

Examination conditions

It is important to get these right as they will influence the results of your tests. Sit the patient in a dimly lit room (to avoid pupillary constriction from the room light over-riding that from your torch) and tell them to look at a far wall to overcome the accommodation reflex. Use a bright light source which should be directed from below to avoid the shadow from the nose.

Direct response to light

Light directly shone on the eye for 3 seconds should elicit a prompt pupillary constriction of the pupil. Failure to do so is known as an afferent pupillary defect and indicates severe optic nerve pathology (e.g. transected nerve). There will also be failure of the fellow pupil to constrict. If there is no pupillary reaction but the fellow pupil does constrict, consider a traumatic iris paresis.

The swinging flashlight test

This identifies the presence of a relative afferent pupillary defect (RAPD). Shine the light source from one eye to the other in rapid succession. Stimulation of the normal eye should elicit a brisk constriction of both pupils but when the light is shone on the diseased eye, both pupils dilate. What happens is that the dilatation produced by withdrawing the light from the normal eye outweighs the weak constriction produced by shining light on the diseased eye - this is why it is called a relative afferent pupillary defect.

Light-near dissociation

If the reactions to light are normal, you can go on to test for the accommodation reflex.The room light should be turned on again and the patient asked to gaze to a far wall. Tell them that as soon as they see the watch / pen / other object, they should focus straight on it. As they gaze to the distance, hold your object above the level of their eyes, making sure that your arm is not in the way. Then, drop it into their line of view and observe the pupillary reactions as they look at it - there should be a brisk constriction. Failure to do so is known as light-near dissociation.
If all these pupillary tests are normal, the patient can be said to have Pupils Equally Reacting to Light and Accommodation - PERLA.

Optic nerve function

There are several essential components to examining the function of the optic nerve if you suspect pathology at this level:

• Check visual acuity
• Check for an RAPD
• Check for colour impairment (dyschromatopsia). Ideally, this is done using an Ishihara colour test booklet: cover the good eye first and flick through the book, allowing about 5 seconds per number, then compare with the fellow eye. If the booklet is not available, ask the patient to look at a bright red object (such as a child's toy) and compare the intensity of the colour when viewed with each eye seperately - descriptions of things looking "washed out" should ring alarm bells.
• Assess brightness sensitivity: shine a light in each eye and ask the patients to compare the brightness. A useful measure is to suggest: "If I were to give you a pound for this brightness" (shine light in good eye), "how much would you give me for this ..." (shine light in bad eye).
• Do a confrontational field test and assess the blind spot: in the same examination position and conditions as for confrontational visual field, bring a bright red object horizontally across their central field of vision, asking you to tell them if / when it disappears and then when it re-appears - if the blind spot is any bigger than yours, examine its margins, moving the pin around until you have an idea of its size.

Macular function

The most effective method of assessing macular function in an office setting is using an Amsler grid.It consists of a piece of paper on which a 10cm x 10cm grid box is printed with a black dot in the centre. The patient is asked to cover one eye and fix their gaze on the central dot. They are asked if they can see the four corners of the box. They are then told to comment on how straight the lines of the grid are and to draw over them as they see them in the parts that seem curved. Finally, they are asked to outline any areas missing within the box. This should be repeated for the fellow eye. This gives a reasonable indication of macular function. This simple tool can be used by the patient who can self test at home and report early if changes are detected.

Eyelids

Examination of the function of the eyelids is usually done in the context of assessing a ptosis. There are several simple measurements that can be made using a simple ruler with millimeter calibrations (a see-through ruler is ideal):

• The palpebral fissure (PF) - the distance between the upper and lower eyelid in vertical alignment with the centre of the pupil
• The marginal reflex distance-1 (MRD-1) - the distance between the centre of the pupillary light reflex and the upper eyelid margin with the eye in primary gaze
• MRD-2 - the distance between the center of the pupillary light reflex and the lower eyelid margin with the eye in primary gaze
• Levator function - the distance the eyelid travel from downgaze to upgaze while the frontalis muscle is held inactive at the brow: ask the patient to look down and press your finger firmly on the eyebrow. Put the ruler near the eye and ask the patient to look as far up as they can. Measure the distance covered from down to upgaze by the lid margin.
• The margin fold distance (MFD) - the distance from the upper eyelid margin to the fold of skin.
• Examine the pupils for evidence of Horner's syndrome.

Extraocular muscles

Eye alignment

This is important as a 3D image cannot be correctly formed if both foveas are not simultaneously fixed on the object. Hold a light source about an arm's length away from the patient and look at the position of the light reflection. This is usually in the centre of each pupil. If one side or the other is towards the outer edge, this indicates an inward deviation of the globe (esotropia) and if there is a reflex more towards the inner edge of the pupil, there is an outward deviation of the globe (exotropia).

The cover/uncover test helps further assess squints. An object to focus on is held in front of the patient who is instructed to focus on it. One eye is completely occluded for several seconds and the uncovered eye is observed for movement as it focuses on the object. This eye is the covered and the other eye is observed for movement. Movement of the eye outwards confirms that there is an esotropia (i.e. the eye was turned inwards initially) and vice versa for exotropia. The test is repeated for objects at 6 metres and far distance which may also reveal a vertical squint.

A modified version of this test (the alternate cover test) is used to detect a exo / endophoria (as opposed to exo / endotropia described above) which is a latent squint that only manifests itself in the absence of bifoveal stimulation. Most normal people have this to a very mild degree.

An epicanthus or facial asymmetry may mimic a squint.

Eye movement

This examination is necessary in a number of orbital problems (e.g. orbital floor fracture) as well as neuromuscular problems (e.g. myasthenia gravis). Sit the patient in front of you and explain that you want them to follow this (show bright object) with their eyes only and that you will help them keep their head still. Gently but firmly place a hand on their forehead and with the other, test all the positions of gaze in that hemifield. Swap hands and do the same in the other hemifield. Look for limitation of globe movement, presence of nystagmus and ask for diplopia, blurring or loss of the image.

There are a variety of other tests that are routinely performed in specialist units, examples of which are:

• Visual field assessment - using static and kinetic perimeters
• Ultrasound scan - to visualise the lens, vitreous and retina
• Exophthalmometre - to assess proptosis (e.g. thyroid eye disease)
• Keratometry - to assess the gradient of the cornea, rather like an ordinance survey map
• Hess chart - to accurately map extraocular muscle movement
• Fluorescein angiography - to map retinal vessels and identify leaks
• And so the list goes on ...