An unusual cause of "floaters"
I recently discussed this case in the 2023 Retina Specialists annual education evening. The case illustrates the importance of taking a detailed history and understanding the patient's symptoms to get the correct diagnosis. Furthermore, having the right equipment (in this case, high-quality OCT scans and Optos imaging) and the in-depth expertise to pick up subtle abnormalities on imaging is essential in challenging retinal cases.
Is this just a floater?
A 77-year-old European man presented to me with a two-week history of a blurred spot in the vision of his right eye. The blurred spot moved around with eye movement. There was no photopsia. He also had a history of age-related macular degeneration, with drusen only in the right eye but neovascular complications in the left eye. He had been receiving anti-VEGF injections in the left eye every six weeks.
Two weeks ago, another ophthalmologist saw him and was diagnosed with a posterior vitreous detachment.
Examination findings
His visual acuity was 6/7.5 right and 6/9 left. He had bilateral early cataracts. Fundoscopy showed bilateral age-related macular degeneration changes.
Does he have a floater?
Yes, indeed, there is a floater, but as my routine practice, I spent extra time understanding his symptoms. Upon further questioning, the blurred spot in the right eye was always in the same position in relation to his fixation. On an Amsler grid, he reported that the lines were missing inferior to fixation in his right eye. So, rather than the blur from a floater, this patient has a relative scotoma in the right eye.
OCT imaging was carried out to investigate this further.
Diagnosis - paracentral acute middle maculopathy (PAMM) from cilioretinal artery occlusion
The distribution of PAMM corresponds to the location of the cilioretinal artery in the right eye. This patient also has an extensive cardiac history. A diagnosis of cilioretinal artery occlusion was made, and giant cell arteritis was excluded on clinical grounds. An acute referral was made to the stroke team with his cardiac medication optimised.
Commentary
Suppose one starts with the incorrect mental model with a suboptimal history. In that case, it is easy to conclude that a posterior vitreous detachment is the cause of this patient's symptoms, given that there is a detectable Weiss ring. However, getting a clear and detailed history takes time, and it is impossible to do so with an overloaded clinic. In my practice, all patients are booked with a 30-minute slot so I can take the time to understand their symptoms and their concerns. Taking this extra time here meant I clinched the diagnosis and reduced the patient's risk of a further thromboembolic event.
All patients with floaters get both OCT and Optos imaging in my practice. Optos imaging is instrumental in documenting a Weiss ring's presence and the retina's status. However, the visualisation of the far peripheral retina is suboptimal on Optos imaging, so a detailed retinal examination (including a three-mirror exam) is still mandatory. OCT imaging is vital to check the status of the posterior vitreous, to look for the presence of cells (which may be red cells or pigments) at the posterior vitreous, and in this case, to check if there is any occult pathology not visible otherwise.
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.
