Ophthalmology - Assessment and history taking

Question 1

What are the important features of an ocular history?

Answer 1

Side or side affected (laterality), time course, and periodicity are particularly important features. Specific ocular symptoms that one should elicit include:

• visual disturbance
• pain
• floaters
• flashing lights
• halos
• visual field loss
• diplopia

Past ocular history is an additional and useful component of an ophthalmic history and should include:

• contact lens wearer
• glasses wearer
• ocular/head injury
• ocular surgery
• lazy eye/ squint/ patching of the eye as a child

Question 2

What is the examination routine for examining the eye?

Answer 2

1) Visual acuity
2) Colour vision
3) Eye movements/ diplopia
4) Visual fields
5) Pupil reflexes
6) General external examination including eyelids e.g. ectropion, entropion, skin laxity, scars, evidence of trauma
7) Conjunctiva - e.g. colour, blood vessel injection, swelling/ oedema (chemosis)
8) Cornea - e.g. clarity (should be obtained with fluorescein and examined under a cobalt blue light for epithelial defects)
9) Anterior chamber - (typically examined using a slit lamp, but with pen torch fluid level may be visible)
10) Pupil size, shape, symmetry and reflexes
11) Direct ophthalmoscopy - red reflex to check for lens opacity, fundus examination

Also consider trigeminal nerve assessment, and facial nerve function (eye closure).

Question 3

How should one examine colour vision?

Answer 3

Bright red target - simple check for optic nerve damage; ask patient to comment on the appearance of the target with each eye
- impaired perception of colour/ brightness of the target or red desaturation can indicate early optic nerve pathology

Ishihara test plates - test for congenital red-green colour blindess.

• patients asked to read coloured numbers that are presented individually to each eye
• optic nerve damage can result in red green colour vision impairment so this can be used to detect such pathology

Question 4

How should one examine pupillary reflexes?

Answer 4

1) Comment on the size and symmetry
2) Ask the patient to focus on a distant target
3) Hold an object at about 15cm from the patients eye, ask them to focus on the object to observe accommodation (pupil constriction)
4) Ask the patient to fixate on a distant object again
5) Shine the beam of light from a pen torch into one pupil, observe THAT pupil for constriction (direct light reflex)
6) Repeat the process whilst observing the opposite pupil to which the light is being shone (consensual light reflex)
7) Now shine the beam into the other pupil and elicit direct and consensual reflexes
8) Swinging light test (to test for relative afferent pupillary defect) - the light beam is shone from one pupil and then to the other and back again. The pupil onto which the light beam is being swung over to is observed for paradoxical dilatation

Question 5

What technique is used to test visual fields?

Answer 5

Confrontation. There are various different methods for doing this.

1) Examiner holds up one or two fingers, in a quadrant of the peripheral visual field. Patient is asked how many fingers are being held up. Each quadrant is tested in this way
2) Examiner slowly brings their fingers into the visual field from outside the field towards a central point. The patient is asked to say “yes” when the tip of the finger first comes into view
3) A further method involves a hat pin
- white hat pin is brought in from the periphery by the examiner instead of a finger
- red hat pin can then be used to map out the patients blind spot

Question 6

How should eye movements be assessed?

Answer 6

When examining the eyes, a history of double vision should be elicited. There are various aspects of eye movements to assess:

1) Is there a head tilt or turn?
2) Is there any obvious exo/eso deviation
3) Eye movements: the patient is asked to follow a target, such as a pen torch, held by the examiner. The pen is then moved from the centre to peripheral positions whilst both eyes are observed for any abnormalities such as restriction, nystagmus, double vision and pain. If there is double vision a check should be made to see whether this is monocular or binocular. If diplopia persists after covering one eye, this is monocular diplopia and suggests an underlying refractive cause.

Most people check movements using a “H” pattern.

Question 7

How is visual acuity checked?

Answer 7

A Snellen chart is used. One eye is occluded and the patient asked to read down the chart. If the patient can read more than 50% of a line then visual acuity can be recorded as at that line. The distance that the patient is away from the chart is written on the top of the ‘fraction’ and the line which they can read is recorded below the ‘fraction’, e.g. if a patient can read the ‘36’ line at 6 metres then visual acuity should be recorded as 6/36 in that eye.

Question 8

If a patient does not achieve 6/6 vision then how should the be examined further?

Answer 8

If normal vision is not attained, then the vision should be tested with the patient looking through a pinhole. This will reduce the adverse effect of a simple refractive error and may give a better indication of potential visual acuity. For example, a glasses wearer may have extremely poor vision when tested on the Snellen chart if tested without their glasses (unaided) and this would be misleading.
If the patient cannot read the top line of the chart (i.e. vision is worse than 6/60) then the chart can be brought closer, for example to 1 meter. This new distance must be recorded at the top of the ‘fraction’,e.g. if the top line of the chart can be read at 1 meter then visual acuity can be recorded at 1/60. If a patient can still not read the letters, then the patient can be asked if they can count fingers (CF). The distance at which this is possible is recorded.
If a patient cannot count fingers, they should be asked to detect hand movements (HM).