Case 35: Sudden blurred vision
Monday, October 31st, 2011
A 56 year female presented to the Emergency department with a 2 day history of blurred vision. This was severe enough to stop her driving. There was no pain or other symptoms. She has suffered with glaucoma for 12 years which has been stable on her regular medication. She had recently been diagnosed with hypothyroidism and started on levothyroxine. Her drug history also included gabapentin and latanoprost eye drops (prostaglandin analogue for glaucoma), both of which she had been taking for some time.
On examination both eyes looked normal, with no redness, clear anterior chambers and normal pupils. Visual acuity was reduced in both eyes. On fundoscopy both retinae looked normal, as did the discs.
1. There was no change in this patient’s glaucoma. Can you think of other causes for sudden blurring of vision in both eyes?
Click to see the answerMain causes of sudden painless bilateral blurred vision are: a) papilloedema, b) cerebrovascular accident (usually causes homonymous blurring), c) drugs (eg atropine-like, particularly in eye drops), and d) sudden refractive changes associated with diabetes.
With this patient the visual impairment was not homonymous (ie in part of the visual field), her only new treatment was thyroxine (which should not affect vision), and her retina was normal.
2. So what is the likely cause for her symptoms, and what test would you organise?
Click to see the answerThe likely cause was diabetes. Her blood glucose was 24.4 mmol/l. (Her urine dip stick showed maximum glucose and ketones).
3. Can you link this new diagnosis with her existing diagnoses?
Click to see the answerDiabetes and thyroid disease are linked. This may partly be explained by autoimmune factors. Diabetics are three times as likely as others to have hypothyroidism.