Paracentral acute middle maculopathy in giant cell arteritis versus non-arteritic anterior ischaemic optic neuropathy

Background/aims To compare the prevalence of paracentral acute middle maculopathy (PAMM) on optical coherence tomography (OCT) in patients with giant cell arteritis (GCA) and non-arteritic anterior ischaemic optic neuropathy (NAION) and to evaluate its association with steroid treatment and presenting visual function. Methods This retrospective observational study included patients with GCA (with or without visual symptoms) and NAION identified from two tertiary care neuro-ophthalmology practices. Clinical data, visual acuity (VA) and visual field mean deviation (VFMD) were collected. OCT imaging was reviewed for the presence of PAMM. Results A total of 80 patients with biopsy-proven GCA and 179 patients with NAION were included. PAMM was identified in 28% of patients with GCA versus 0% of patients with NAION (p<0.001). Among patients with GCA, PAMM was observed in 33% of those with persistent visual symptoms, 8% with transient symptoms and 29% without visual symptoms (p=0.23). PAMM was present in 29% of patients who received corticosteroids prior to OCT compared with 22% of those who had not (OR 1.43 (95% CI 0.41 to 4.94); p=0.76). There was no significant association between PAMM and presenting VA or VFMD. Conclusions PAMM occurs in over a quarter of GCA cases but not in NAION, persists after initiation of corticosteroid therapy and can detect subclinical retinal ischaemia in visually asymptomatic patients with normal visual function. These findings support the diagnostic utility of PAMM in differentiating between anterior ischaemic optic neuropathy and NAION and detecting GCA with subclinical ocular involvement.