Research conducted in Sunshine Hospital, Melbourne, has highlighted the importance of testing for vision loss in patients following a stroke.
Acute Ischemic Stroke (AIS) is a medical emergency requiring immediate hospital treatment to reduce future complications and improve the prognosis for recovery in the patient.
Current medical practice considers that stroke can best be identified by evaluating three aspects of motor function, as captured in the pneumonic F.A.S.T. which stands for Facial Droop, Arm weakness, Speech slur and Time to act, fast.
However, the use of motor functions to identify the effects of stroke, as specified by F.A.S.T., limits consideration to processes comprising smaller brain volumes than those involved in processing vision (including visual attention and cognition), eye movements and visually driven motor actions. UK studies indicate that 92% of 915 stroke patients referred to ophthalmic centres for vision loss or suspected oculo-motor abnormality had some form of visual deficit, though these studies did not exclude existing ocular co-morbidity (age-related macular degeneration, glaucoma).
The research undertaken in Melbourne, by Chamini Wijesundera, Professor Sheila G. Crewther, Professor Tissa Wijeratne and Professor Algis J. Vingrys wanted to overcome any potential referral biases by recruiting 160 consecutive presenting cases of stroke to a hospital emergency ward. Ocular co-morbidities were identified from past medical records and excluded from participation. This left 60 cases of AIS who completed all the team’s vision tests without stress or fatigue. The purpose of the trial was to identify whether visual defects were common to uncomplicated stroke cases, and whether these could be identified using simple tests presented on a modern smart device (iPad tablet).
For this purpose, the researchers used the Melbourne Rapid Fields – neural application (MRFn), which presents a visual acuity test, an acuity in luminance-noise (AiN) test, a central visual field test, and an eye-hand coordination test. All tests were administered on an iPad at the patient’s bedside within one week of hospital admission. This battery of tests took, on average, about seven minutes per eye for completion and patients wore their habitual reading glasses during testing.
Sixty cases of AIS could complete all vision tests. The majority (90%) were graded as having a mild defect by their NIHSS score (<9) and the rest moderate. Despite this modest motor loss, the researchers reported that about two thirds of the stroke cases failed at any vision test, except visual acuity, which was either very mildly affected (one line loss) in five cases (8%), or normal in most others. They also found a poor correlation with the usual NIHSS stroke score, indicating near normal somato-sensory and motor capacity, suggesting that F.A.S.T. fails to identify cases of stroke reliably. More importantly, 93% of the stroke cases, who had their lesion confirmed by MRI or CT-scan and who may have had normal motor capacity, were abnormal on one of the three vision tests. Consistent with their good acuity, 44% of these cases were not aware of their visual deficit, despite the presence of substantial visual field losses (hemianopia or quadrantanopia) that could impede mobility or safe driving.
This indicates that vision testing is an essential element of stroke evaluation and should be used by eye care practitioners as part of a differential diagnosis in suspect cases, or in cases of unexplained headache, to ensure the absence of any sinister cause.
- Wijesundera C, Vingrys AJ, Wijeratne T, Crewther SG. Acquired Visual Deficits Independent of Lesion Site in Acute Stroke. Front Neurol. 2020;11:705, doi: 10.3389/fneur.2020.00705.
- Wijesundera C, Crewther SG, Wijeratne T, Vingrys AJ. Vision and Visuomotor Performance Following Acute Ischemic Stroke. Front Neurol. 2022;13:757431, doi: 10.3389/fneur.2022.757431.