20 Disorders of the eye
Clinical assessment of the eye
Most eye disorders can be diagnosed by history and examination; special investigations are rarely necessary. Causes of eye symptoms are summarised in Table 20.1.
| Nature | Type | Causes |
|---|---|---|
| Pain |
Examination
The important features of eye examination are shown in Table 20.2.
| Property examined | Tests and abnormal findings |
|---|---|
| Visual acuity (normal = 6/6) |
Visual fields
The rules of interpretation of acuity and field tests are:
• lesions anterior to the chiasma affect one eye only
• lesions at the chiasma usually damage the crossing nasal fibres from each eye to give rise to bitemporal field defects
• lesions posterior to the chiasma damage the temporal fibres from one eye plus the nasal fibres from the other eye, causing a homonymous defect.
Pupils
Abnormal pupillary responses are summarised in Table 20.3. The light reflex (parasympathetic) is intact when a light shone on one eye constricts both pupils at an equal rate and to a similar degree.
| Abnormality | Common causes |
|---|---|
| Dilatation |
