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Retinal imaging could help predict likelihood of stroke
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Risk for stroke is elevated in people with hypertensive retinopathy, even if their BP is controlled. Retinal imaging could help detect those at risk, according to a new report.
Population-based study data suggest that “closely monitoring BPs and medication compliance may not be sufficient for stroke prevention in patients with hypertension,” Mohammad Kamran Ikram, MD, PhD, of the Singapore Eye Research Institute and National University of Singapore, and colleagues wrote. “Retinal assessment may be useful especially in those with good control of hypertension.”
Researchers investigated whether hypertensive retinopathy, as classified by a new, simpler system, can be a predictor of stroke for people with hypertension. They aimed to detect retinopathy with retinal photography instead of a clinical ophthalmoscopic examination, as previous research suggested the former has better reliability and reproducibility.
The analysis included 2,907 participants from the ARIC study who were aged 50 to 73 years at the 1993 to 1995 examination. The participants had prevalent hypertension (systolic BP ≥140 mm Hg, diastolic BP ≥ 90 mm Hg, or use of antihypertensive medication within 2 weeks before the exam) and no history of stroke, CHD or diabetes at baseline. Participants with diabetes were excluded because hypertensive retinopathy can be difficult to distinguish from diabetic retinopathy. Each participant had gradable retinal photographs that were assessed for signs of hypertensive retinopathy (classification: none, mild, moderate/severe).
During a mean follow-up of 13 years, 165 participants experienced a stroke; 146 were cerebral infarctions and 15 were hemorrhagic strokes. After adjusting for age, sex, BP and other risk factors, the researchers determined that those with moderate hypertensive retinopathy were more likely to experience a stroke compared with those with no hypertensive retinopathy (multivariable HRs=2.37; 95% CI, 1.39-4.02).
The elevated risk for stroke was present even in participants whose BP was well controlled with medication (mild retinopathy: HR=1.96; 95% CI, 1.09-3.55; moderate retinopathy: HR=2.98; 95% CI, 1.01-8.83).
The association between hypertensive retinopathy and stroke risk suggests that “the presence of these retinal microvascular changes is indicative of additional vascular risk beyond that conferred by traditional CV risk factors,” Ikram and colleagues wrote. “Retinal photography is a potential clinical tool to indirectly assess potential microvascular damage in the cerebral vasculature.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Philip B. Gorelick, MD, MPH
The study is important because it shows that retinal microvascular changes in hypertensive patients are not only associated with the long-term risk for incident stroke, which was predominantly ischemic in nature and stroke risk was greater in those with more advanced retinal microvascular changes, but also retinal microvascular changes conferred elevated stroke risk even when BP was controlled and, therefore, added risk beyond that to be expected of traditional CV risk factors.
Although retinal photographs are available in practice, these findings are not likely to substantially change clinical practice, as gradable retinal photographs are not a customary and usual office practice in many primary care settings. In addition, the findings should be validated in other studies or appropriate existent data sets. Finally, should the validation data support the findings, they could be added to risk prediction models to determine whether the risk for stroke changes. If it changes significantly and the change will then alter treatment or prevention in a cost-effective manner, the findings then might be more reasonably recommended in practice.
The retina is viewed by some as a ‘window’ to the brain. Hypertensive retinal microvascular disease is believed to mirror other small vessel hypertensive disease in various systemic vascular beds (e.g. brain, kidney). The relationship of stroke risk with hypertensive retinal changes is consistent with my practice observations.
The researchers rely on a baseline BP determination at the time the retinal photographs were taken. Thus, BP determination at a point in time is studied, but it is not known what BPs were years later or leading up to stroke occurrence. This is a study limitation that the researchers acknowledge. Furthermore, peripheral arm or cuff BP may only represent a portion of the BP story. For example, aortic or central BP is believed to be the pressure head read by the brain, heart and kidneys, but is rarely measured in practice. In addition, visit-to-visit office BP variability may be important in conferring stroke and other CV risk, but it is often ignored. Such information is not available in this study. Therefore, when one claims that BP is controlled, can one say that central BP and BP variability are under control? Assuming that BP is truly under control suggests that chronic retinal microvascular changes in persons with hypertension confers additional risk beyond traditional CV risks.
After validation of the findings in other data sets or studies, and proof that the findings will change treatment or prevention efforts, one can more clearly advocate for the strategy proposed by the authors.
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