Sudden, painless monocular visual loss presents a significant diagnostic challenge. Although CRAO and NAION are the most common vascular causes in the elderly, GCA must not be missed.  According to a national survey, 53% of US institutions offer intravenous tissue plasminogen activator for CRAO, which can sometimes occur without an eye examination in some centers without access to an ophthalmologist on call.  Therefore, the relative frequency and characteristics of these causes of acute monocular vision loss are important to determine.

This retrospective population-based study reviewed records of patients with CRAO, NAION, or GCA between 1/1/90 and 12/31/16 using a geographically restricted medical records linkage system.

We identified 105 patients with NAION, 63 with CRAO, and 14 with GCA (13 AAION and 1 CRAO). Mean ages were 66±12.1, 74.25±12.2, and 81.2±8.1 years and female representation was 44.3%, 43.8%, and 71.4% for NAION, CRAO, and GCA respectively. Mean presenting LogMAR visual acuity (VA) was 0.7, 1.82, and 1.53 for NAION, CRAO, and GCA respectively, with 34%, 85.7%, and 64.3% presenting with a VA of 20/200 or worse.  Therefore, CRAO accounted for 54.5% of patients presenting with acute severe unilateral vision loss.  In addition, GCA accounted for 9.1% of patients with acute severe unilateral vision loss.  

While acute severe painless vision loss is most likely to be caused by CRAO, there is still a substantial frequency of NAION.  GCA must be in the differential diagnosis as well.  As increasingly high-risk therapeutics are offered for suspected CRAO, these findings suggest a more cautionary approach and emphasize the need for appropriate diagnostic evaluation prior to administration.