Author: Law, Kwai Mei
Title: Effect of caffeine on ocular circulation in high myopes
Advisors: Lam, Andrew (SO)
Degree: DHSc
Year: 2023
Subject: Caffeine -- Physiological effect
Eye -- Blood-vessels
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Health and Social Sciences
Pages: xiii, 95 pages : color illustrations
Language: English
Abstract: Introduction
Caffeine, an ingredient commonly found in beverages such as coffee and tea, can cause vasoconstriction. Choroid is a major vascular structure responsible for delivering blood and nutrients to the outer retina. Impaired choroidal blood flow is associated with several ocular diseases. Myopia is prevalent in populations worldwide. Globally, the prevalence of myopia is expected to increase to 50 % in 2050, with almost 10 % of the population projected to have high myopia. If the consumption of caffeine reduces ocular blood supply, such effect may be more damaging to high myopes because they usually have thinner choroid than those without myopia. With advancements in technology, ocular blood supply can be evaluated through optical coherence tomography (OCT) in terms of choroidal thickness. A few recent studies involving individuals with low to moderate ametropia revealed that caffeine can reduce subfoveal choroidal thickness (SFChT). Choroidal volume (ChV) can be derived from OCT measurement, which can be used to examine a large choroidal region. Retinal vasculature can now be evaluated noninvasively through OCT angiography (OCTA). No study has incorporated both OCT and OCTA to investigate the effect of caffeine on ocular circulation.
The study aim was to investigate the acute effects of 200 mg of caffeine on ocular circulation in terms of SFChT and ChV (through OCT) as well as vessel length density (VD) and perfusion area density (PD) (through OCTA) in high myopes.
This was a cross-over, self-controlled, randomized trial. Healthy high myopes were enrolled. Participants received a 200 mg caffeine capsule or a placebo capsule, randomly assigned in 2 visits, which were separated by at least 1 week. After baseline measurements during each visit, blood pressure (BP), intraocular pressure (IOP), and SFChT were measured. The automated retinal thickness and volume measurements were used to calculate the ChV using a semi-automated image segmentation method. The superficial retinal vasculature was examined on the basis of VD and PD and monitored using an OCTA machine. All the parameters were monitored at 30, 60, 120, and 180 minutes following capsule consumption in the morning.
Eighteen subjects completed the study. After the consumption of caffeine capsules, significant differences in systolic blood pressure (SBP) were found at 60 and 120 min, but significant differences in diastolic blood pressure (DBP) were identified only at 60 min. IOP and axial length (AL) were stable throughout the study. Reductions in SFChT and ChV were noted. VD demonstrated a decreasing trend at the central 1-mm circle and 1-to-3 mm parafoveal region. Additionally, a trend of reduced PD was noted at the central 1-mm circle, the 1-to-3 mm parafoveal region, and the entire 3-mm foveal region. Significant reductions in VD and PD were noted 180 minutes after caffeine consumption at the central 1-mm circle. However, the reductions in VD and PD were small. For other regions, no significant changes were found. All parameters were stable following consumption of the placebo capsule.
The current study revealed reductions in SFChT, ChV, VD, and PD in high myopes after consumption of 200 mg caffeine capsule. The reduction was small but persisted for several hours.
Rights: All rights reserved
Access: restricted access

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