Objective: Increased pulsatile pressure induces as well as aggravates microvascular damage. Scanning laser Doppler flowmetry allows the noninvasive assessment of both retinal capillary flow (RCF) and arteriolar structural parameters of the retinal circulation. Moreover, pulsatile characteristics of the retinal arterioles can be assessed.
Methods: In study 1, reliability of pulsatile RCF and structural parameters were examined in randomly selected patients. In study 2, pulsatile RCF as well as the structural parameters of retinal arterioles were assessed in hypertension grade 1–2 (HT1–2; n = 20) and treatment-resistant hypertension (TRH; n = 19).
Results: In study 1, test–retest, interobserver and intraobserver reliability of all parameters showed coefficients of variation of less than 10%. In study 2, it was shown that patients with TRH had higher pulse pressure (P = 0.003) and pulsed RCF values (P < 0.001) as patients with HT1–2. Patients with HT1–2 had no change in the vessel diameter, but a significant difference in lumen diameter, resulting in an altered wall thickness (P = 0.001) between systole and diastole. In contrast, patients with TRH showed differences in vessel diameter (P = 0.005) as well as lumen diameter (P = 0.001), resulting in an unaltered wall thickness between systole and diastole. Hence, wall thickness change as a result of pulsed flow regulation observed in HT1–2 was missing in TRH.
Conclusion: We suggest a new reliable tool for evaluating the pulsatility in the retinal circulation in humans, and found significant differences in pulsatile RCF and structural parameters between patients with HT1–2 and those with TRH.
aDepartment of Nephrology and Hypertension, University of Erlangen–Nuremberg, Erlangen–Nuremberg, Germany
bDepartment of Pathophysiology
cDepartment of Nephrology and Hypertension, University of Warmia and Masury, Olsztyn, Poland
dDepartment of Ophthalmology, University of Erlangen–Nuremberg, Erlangen–Nuremberg, Germany
Correspondence to Dr Roland E. Schmieder, Professor, Department of Nephrology and Hypertension, University Hospital Erlangen, Ulmenweg 18, 91054 Erlangen, Germany. Tel: +49 9131 8536245; fax: +49 9131 8536215; e-mail: firstname.lastname@example.org
Abbreviations: AFFPIA, automatic full-field perfusion imaging analyses; BP, blood pressure; GCP, good clinical practice; HT1–2, primary hypertension grade 1–2; M/L, media-to-lumen ratio; PCR, pulse curve run; PP, pulse pressure; RCF, retinal capillary flow; RCFd, retinal capillary flow during diastole; RCFm, mean retinal capillary flow; RCFs, retinal capillary flow during systole; SLDF, scanning laser Doppler flowmetry; TRH, treatment-resistant hypertension; WLR, wall-to-lumen ratio
Received 6 February, 2014
Revised 11 June, 2014
Accepted 11 June, 2014