Medical Ophthalmology: Case three

This 70 year-old woman presented to the eye casualty with a sudden onset right visual loss. Examination revealed a right inferior retinal artery occlusion from an embolus.

a. What does her chest X-ray show?

 
The X-ray shows the presence of a mechanical mitral valve.

The most common indication for mitral valve replacement is mitral stenosis resulting from rheumatic fever. Mechanical valve causes thrombus formation and therefore a source of embolus. Life-long anti-coagulation with warfarin is required. Biological valve is now commonly used and had a lower incidence of thrombus formation.
 
 

b. What other ocular signs may be associated with this X-ray appearance?
 
Embolus to the eye can cause:
• retinal artery occlusion (both central and branch)
• ophthalmic artery occlusion


Embolus to the visual pathway can cause:

• homonymous hemianopia/quadrantinopia


Bacteria endocarditis of the valve can cause:

• Roth's spots in the retina


Mechanical valve can cause haemolysis of the red blood cells and therefore jaundice
 
 

c. The patient was on warfarin therapy. If she were to undergo a cataract extraction, should the warfarin be stopped?
 
No. Stopping the warfarin increases the risk of thrombus formation and may lead to fatal cerebrovascular accident.

The recommended INR (international normalized ratio) for prosthetic valve is between 2.5 to 3.5. Patients who have an embolic episode on adequate oral anticoagulation should receive additional aspirin.


d. Is prophylactic antibiotic needed if she were to have cataract surgery?
 

No. Cataract surgery does not appear to increase the risk of bacterial endocarditis unlike oral, dental, respiratory and gastrointestinal procedures.