Key distinguishing features of the most common diagnoses
|Acute Glaucoma||Vitreous Haemorrhage||Retinal Artery Occlusion||Migraine||TIA/CVA|
|Preceded by Spots and Flashing Lights||No||Possible||No||Yes||Possible|
|Followed by Headache||Possible||No||No||Yes||Possible|
|Absent Red Reflex||No||Yes||No||No||No|
|Affected Pupil Dilated and Fixed||Yes||No||Yes||No||No|
- In practice, there are none worth doing at the time, as the vast majority of cases will be referred urgently. Virtually all tests will therefore be arranged by the specialist, usually after the event, to look for underlying causes. Such investigations include the following.
- Screening for diabetes: Undetected retinopathy may have preceded vitreous haemorrhage.
- FBC: PCV may be raised in central retinal vein occlusion.
- ESR: Raised in temporal arteritis.
- Multiple microbiological investigations are needed for posterior uveitis.
- Posterior pole ultrasound may be useful in vitreous haemorrhage to identify treatable causes.
- CT scan only useful to investigate cerebral causes (CVA or cortical blindness).
- Acute visual disturbance is often difficult to diagnose accurately and very alarming for the patient. If in doubt, refer urgently, or, at the very least, review in a few hours.
- The patient’s assessment of visual loss, and its severity, is highly subjective – if at all possible, test it with a Snellen chart.
- Always keep spare batteries handy for your ophthalmoscope!
- Don’t forget that the visual disturbance may be the presenting symptom of some other pathology, such as hypertension, temporal arteritis or diabetes.
- Don’t miss a heart murmur or carotid bruit. These may be present in retinal artery occlusion and TIA/CVA.
- A cherry red spot on the fovea is pathognomic of retinal artery occlusion.
- Never use mydriatics to aid examination at the bedside – these will cloud the clinical picture and may even precipitate acute glaucoma.