Relationship Between Daytime Variability of Blood Pressure or Ocular Perfusion Pressure and Glaucomatous Visual Field Progression

In their recent study, Lee and associates studied the relationship between daytime variability of blood pressure (BP) or ocular perfusion pressure and glaucomatous visual field progression. Joe and associates had earlier performed a study on 24-hour blood pressure patterns in patients with normal-tension glaucoma (NTG) and defined NTG patients as non-dippers, dippers, and over-dippers, wherein over-dippers had the greatest degree of reduction in their nocturnal mean arterial pressure (MAP) as compared to dippers and non-dippers. They found that nocturnal BP reduction estimated in habitual position was associated with structural damage in eyes with NTG. Lee and associates have done a similar study on 24-hour variation in MAP and found similar results. However, the title of the original article by Lee and associates, “Daytime variability of blood pressure or ocular perfusion pressure,” is misleading, as the authors have studied 24-hour variation and not simply a daytime variability, as stated in title. As nocturnal dip is an established risk factor and a work without study of nocturnal MAP would be incomplete and insufficient, we therefore agree with the authors in doing a 24-hour variation. If the authors at all desire to emphasize that daytime variability is also as significant as nocturnal dip, then it would have been better if the Results section had described the difference between daytime variability and nighttime variability of blood pressure and ocular perfusion pressure and also whether this difference was statistically significant. It is similar to the case of Lombardi and Parati, who stated that the nocturnal blood pressure dipping regularly exceeds 10% of mean daytime values in normotensive and primary hypertensive subjects, and it is established that this nocturnal dipping itself predisposes to an early-morning surge of blood pressure predisposing to vascular accidents. Additionally, a habitual position has been described by Lee and associates, but it is not clarified whether subjects also went to sleep through the daytime during the time of measurement of blood pressure and ocular perfusion pressure, and whether this sleep further created more daytime variability in their subjects, as such an occurrence would have pointed out that it is the sleep posture itself, whether during day or night, that is the risk factor. It would also clarify that it is perhaps not night but the act of sleep per se that reduces blood pressure, as sleep onset induces characteristic changes in autonomic and endocrine functions, with a reduction in sympathetic outflow to the heart and muscle vascular bed combined with a reduced activity of the rennin-angiotensin system. Simultaneously, parasympathetic activity to the heart is also increased during sleep.

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Jan 6, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Relationship Between Daytime Variability of Blood Pressure or Ocular Perfusion Pressure and Glaucomatous Visual Field Progression

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