Does Nocturnal Blood Pressure Matter in Retinal Small Vessels? A Systematic Review and Meta-Analysis of the Literature.

Purpose of the review: Τhe association between nocturnal blood pressure (BP) and alterations in the retinal microvasculature remains understudied, with few available studies to provide conflicting results. Therefore, we conducted a systematic review and meta-analysis to determine whether an association exists between retinal microvascular alterations and nocturnal BP patterns, determined by 24h ambulatory BP measurement.

Recent findings: Our search concluded to 1002 patients (6 studies). A total of 3 studies (411 patients) were enrolled in the meta-analysis. Central retinal arteriolar equivalent found to be not different between patients with and without dipping status (mean differences [MD]: -0.01; 95% CI: -0.23 to 0.20; I²=0%; P < 0.610). Regarding central retinal venular equivalent, dippers showed significantly lower values compared to non-dippers (MD: -0.25; 95% CI: -0.47 to -0.03; I²=0%; P < 0.024). For the comparison between nighttime and daytime BP regarding the damage in small retinal vessels, we identified only 5 studies. Due to different evaluated outcomes as well as due to the heterogeneity of outcomes and different grouping of patients based on different BP cut-off values, these results couldn't be analyzed quantitatively. In summary, this is the first effort to summarize evidence on the effects of day-to-night variation of BP on the retinal small vessels. According to the findings of the present systematic review and meta-analysis, non-dipping status may be associated with retinal venular dilatation, and elevated nighttime BP with retinal arteriolar narrowing. Further studies are warranted to elucidate the impact of nocturnal BP patterns in the retinal microvasculature.