Department of Ophthalmology, University Hospital Dresden, Dresden, Germany.
Acta Ophthalmol. 2012 Nov;90(7):e524-8. doi: 10.1111/j.1755-3768.2012.02486.x. Epub 2012 Aug 3.
To investigate the effect of caffeine on retinal vessel diameter before and during flicker light stimulation in young healthy subjects.
Seventeen healthy subjects (mean age: 29.6 ± 3.73 years, range: 22-35 years) were included in this study. The diameter of retinal vessels was measured continuously with the retinal vessel analyzer (RVA) before and 1 hr after 200 mg oral caffeine intake. After baseline assessment, a green luminance flicker of 20-second duration was applied to stimulate retinal activity. The diameter of a segment of an arteriole and of a venule were measured during stimulation and 80 second after cessation of the stimulus. Flicker stimulation and 80-second measurement interval were carried out three times. Blood pressure parameters, systemic mean arterial pressure (MAP), ocular perfusion pressure (OPP) and intraocular pressure (IOP) were obtained before and after oral caffeine intake.
The mean diameter of the arterioles at baseline before caffeine intake was 123.30 ± 14.0 μm (arithmetic mean standard deviation) and after caffeine 117.30 ± 13.0 μm which was significantly different (p=0.004). The mean diameter of the venules at baseline before caffeine intake was 147.60 ± 19.5 μm and after caffeine 137.73 ± 19.9 μm which was significantly different (p = 0.005). The mean diameter of the arterioles during flicker light stimulation before caffeine intake was 126.65 ± 13.24 μm and after caffeine intake 121.59 ± 12.12 μm (p = 0.012). The mean diameter of the venules during flicker light stimulation before caffeine intake was 151.87 ± 18.63 μm and after caffeine intake was 145.14 ± 19.82 μm (p = 0.027). The flicker response of the arterioles increased from 2.8% before caffeine to 3.8% after caffeine intake (p = 0.010). The flicker response of the venules increased from 3.4% before caffeine to 5.5% after caffeine intake (p = 0.0001). Baseline diameters and diameters during flicker light stimulation after caffeine intake showed a significant negative correlation to the MAP for the arterioles (baseline: r = -0.338, p = 0.049 and flicker: r = -0.345, p = 0.046) and the venules (baseline: r = -0.496, p = 0.003 and flicker: r =-0.479, p = 0.004).
The present study showed a significant vasoconstrictory response of the retinal vessels 1 hr after caffeine intake in young healthy subjects. Retinal vessel diameter changes were negatively correlated with MAP after caffeine consumption. These effects seem to be elicited by an autoregulatory response of the retinal vessels to the increased blood pressure changes after caffeine.
观察健康年轻人在闪烁光刺激前后摄入咖啡因对视网膜血管直径的影响。
本研究纳入了 17 名健康受试者（平均年龄：29.6±3.73 岁，范围：22-35 岁）。在口服 200mg 咖啡因 1 小时前后，使用视网膜血管分析仪（RVA）连续测量视网膜血管直径。在基线评估后，给予绿色亮度闪烁 20 秒以刺激视网膜活动。在刺激期间和刺激停止后 80 秒测量一段动脉和静脉的直径。闪烁刺激和 80 秒测量间隔进行了 3 次。在口服咖啡因前后获得血压参数、系统平均动脉压（MAP）、眼灌注压（OPP）和眼内压（IOP）。
咖啡因摄入前基线时动脉的平均直径为 123.30±14.0μm（均数标准差），咖啡因摄入后为 117.30±13.0μm，差异有统计学意义（p=0.004）。咖啡因摄入前基线时静脉的平均直径为 147.60±19.5μm，咖啡因摄入后为 137.73±19.9μm，差异有统计学意义（p=0.005）。咖啡因摄入前闪烁光刺激时动脉的平均直径为 126.65±13.24μm，咖啡因摄入后为 121.59±12.12μm（p=0.012）。咖啡因摄入前闪烁光刺激时静脉的平均直径为 151.87±18.63μm，咖啡因摄入后为 145.14±19.82μm（p=0.027）。咖啡因摄入后动脉的闪烁反应从 2.8%增加到 3.8%（p=0.010）。咖啡因摄入后静脉的闪烁反应从 3.4%增加到 5.5%（p=0.0001）。咖啡因摄入后基线和闪烁光刺激期间的直径与动脉的 MAP 呈显著负相关（基线：r=-0.338，p=0.049；闪烁：r=-0.345，p=0.046）和静脉（基线：r=-0.496，p=0.003；闪烁：r=-0.479，p=0.004）。
本研究显示，在年轻健康受试者中，摄入咖啡因 1 小时后视网膜血管明显收缩。咖啡因摄入后视网膜血管直径变化与 MAP 呈负相关。这些影响似乎是由视网膜血管对咖啡因引起的血压变化的自动调节反应引起的。
