Laser speckle flowgraphy derived characteristics of optic nerve head perfusion in normal tension glaucoma and healthy individuals: a Pilot study

Abstract

The purpose of this prospective, case control study was to investigate the differences in optic nerve head blood flow measured with Laser Speckle Flowgraphy (LSFG) between Caucasian patients with normal tension glaucoma and healthy subjects. It included 20 eyes from 20 Caucasian patients with diagnosis of normal tension glaucoma and 20 eyes from age- and sex-matched healthy individuals. In the glaucoma group the antiglaucomatous therapy was paused 3 weeks prior to the investigations. Measurement of optic nerve head blood flow was performed with LSFG. The mean blur rate was obtained for different vascular compartments of the optic nerve head. Parameters for the characterization of pulse-waveform of the mean blur rate were calculated. It was shown that the mean blur rate was significantly lower in the glaucoma group compared to the control group (P < 0.001). The significant differences in the pulse-waveform parameters blow out time (P = 0.028) and flow acceleration time index (P < 0.001) indicate a flatter curve in NTG patients. In conclusion, LSFG can detect differences in optic nerve head blood flow between eyes with normal tension glaucoma and healthy eyes.

Figure 1

ROC curve for mean blur rate (MBR) in the whole optic nerve head area (MA), in the area of the big vessels (MV) and the microvasculature (MT). An area under the ROC curve (AUROC) of 1.0 represents perfect discrimination, whereas an AUROC of 0.5 can be considered chance discrimination.

Figure 2

Calculation of the pulse-waveform parameters. Top left: Blow out time (BOT). Top center: blowout score (BOS). Top right: skew. Middle left: acceleration time index (ATI). Middle center: rising rate (RR). Middle right: falling rate (FR). Bottom left: the flow acceleration index (FAI). Bottom center: resistivity index (RI). Bottom right: fluctuation, (MOF) mean of fluctuation.