Can you tell if this embolus on Optos is real?

Leo Sheck
minute read

As an ophthalmologist and a medical retina specialist, I rely on advanced retinal imaging to give the best possible care for my patients. However, being an expert means that I need to be aware of the limitations of different retinal imaging modalities. Here is a cautionary tale on the interpretation of Optos imaging.

The controversy

This case is on a 59-year-old woman with Sorsby's macular dystrophy, and she has been receiving intravitreal Eylea injections to her right eye for macular neovascularisation. She has already lost vision in her left eye due to a disciform scar. Her medical history includes paroxysmal atrial fibrillation, and she recently had an ablation procedure. She has been on rivaroxaban to prevent embolism due to her history of atrial fibrillation, and a decision was made to stop this medication by the cardiologist to prevent macular haemorrhages in the right eye as her risk of thromboembolism was thought to be low.

Four weeks after stopping rivaroxaban, she returned for a follow-up appointment. The below image was cropped from her left eye Optos imaging.

Left fundus Optos imaging showing a possible filling defect just nasal to the disc

When I looked at this imaging, my eye was immediately drawn to the white defect in the retinal arteriole nasally in the left eye. Given her recent cardiac history, I was concerned regarding an embolic event, and this patient may have to restart rivaroxaban, which will increase her risk of a macular haemorrhage.

On the other hand, I am aware that sometimes artefacts can occur on Optos imaging...

Verifying Optos imaging finding

Rather than just believing what I see on the Optos imaging, as all good ophthalmologists will do, I examine the patient thoroughly after dilatation of the pupils. When I examined the area concerned, to my surprise, I did not see an embolus.

I then repeated the imaging on Optos at a slightly different angle, as shown below.

Repeat Optos imaging on the same day, no longer showing a filling defect

The defect noted on the first image is now gone, confirming that it was an artefact and no treatment modification is needed.

Take home message

When you see an unexpected abnormality on Optos, you must verify it by examining the patient clinically. Artefacts can occur even with advanced retinal imaging, and your diagnostic and treatment decision must be based on accurate information.

About Dr Leo Sheck

Dr Sheck is a RANZCO-qualified, internationally trained ophthalmologist. He combined his initial training in New Zealand with a two-year advanced fellowship in Moorfield Eye Hospital, London. He also holds a Doctorate in Ocular Genetics from the University of Auckland and a Master of Business Administration from the University of Cambridge. He specialises in medical retina diseases (injection therapy), cataract surgery, ocular genetics, uveitis and electrodiagnostics.