21: Pupil and eye assessment – March 2015
The assessment of pupils is a routine element of any patient physical assessment. It is commonly considered part of the conscious state assessment though it is in fact not. Changes to pupils can occur without change to consciousness. Similarly, changes to consciousness are not always accompanied by pupil changes. That said, pupils can provide significant clues in assessment. To correctly identify them, a standard approach to eye assessment is required.
The first part of eye assessment is to examine the external surrounds of the eye. Bruising and swelling are looked for. They may indicate injury to the eye(s), surrounding orbit or the skull itself. Where swelling precludes one or both eyes from being opened, it should not be forced open.
Where the eye can be opened, a visual inspection of the eye can be performed. The white of the eye (sclera) may be yellowed by jaundice. It may be bloodshot. There may be visible bleeding into the iris. The conjunctiva may be its normal pink, inflamed red or cyanosed. This may be useful in darker skinned patients. It can be examined by gently pulling down on the cheek just below the eye.
The pupil is the main focus (excuse the pun) to assess within the eye itself. Size is important and is often expressed in millimetres. However for pre-hospital assessment it is usually sufficient to note whether the pupil is dilated, normal size, small or pinpoint. The expected size will vary with ambient light.
Other key observations of the pupil are its shape and reactivity to extra light. The pupil is normally round. It may become oval at times including raised ICP. Occasionally it may be deformed and look more like a keyhole. If the lenses have cataracts the pupil may look cloudy. Typically pupils react to light and constrict briskly to reduce entry. Slow or no response is abnormal. Within the brain there is a meeting point of optic nerve impulses called the chiasma. This means that if one eye is stimulated by light and the brain returns a message to respond, it will be answered by both pupils. Pupils are normally equal and reactive to light – PEARL.
The pupils should normally be equal in size. The occasional person has a small difference as normal. Finding unequal pupils can indicate serious neurological injury including infection, stroke, or head trauma. In serious cases rising ICP can squeeze the optic nerve and stop nerve impulses being passed along it. The pupil will dilate and be unreactive.
To test each pupil the patient closes their eyes for a few seconds then reopens them one at a time. A light is shone for a couple of seconds on the face just to the side of the eye. It doesn’t have to shine directly on the eye itself. Each eye is assessed individually and compared. If the ambient light is very bright the pupils will already be very small. Eyes can be closed and reopened one at a time and the ambient light allowed to do the job of the torch.
The final part of eye assessment is to question the patient for such complaints as double vision (diplopia) or photophobia.
Jeff Kenneally – www.Prehemt.com