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.

Imaging video plethysmography shows reduced signal amplitude in glaucoma patients in the area of the microvascular tissue of the optic nerve head

“…An advantage of LSF, compared with OCT-A, is the possibility to measure the waveform of the pulsatile signal, which can be changed in diseased eyes. This was shown for patients with glaucoma [ 28 , 31 ].…”

“…Shiga et al [ 31 ] described a delay in the peak of the MBR waveform, a flattened waveform, and reduced MBR amplitude for normal tension glaucoma (NTG) subjects in the ONH capillary area only. Mursch-Edlmayr et al [ 28 ] found a reduced blood flow in the vessels supplying the retina assessed by MBR from ONH in NTG subjects. They also evaluated the shape of the MBR curve using several specific parameters and found a flatter waveform for NTG subjects, which means a lower MBR avg and a lower flow acceleration index.…”

“…MBR shows a pulsatile behaviour that reflects the pulsatile blood flow. From the waveform of MBR, additional parameters can be calculated—average MBR (MBR avg ), the flow index, and the flow acceleration index [ 27 , 28 ]. LSF shows a reduction in the microcirculation in the ONH in glaucoma patients [ 29 , 30 ].…”

Ocular and Systemic Factors Affecting Laser Speckle Flowgraphy Measurements in the Optic Nerve Head

“…In fact, many studies have compared the MT between normal and glaucoma eyes or glaucoma eyes with different stages of the disease. 9 – 17 With regard to MV, in vitro experiments and comparison with laser Doppler velocimetry indicate that MV is a quantitative parameter of blood velocity in the large retinal vessels at the ONH. 18 – 20 …”

Waveform analysis of human retinal and choroidal blood flow with laser Doppler holography

“…First, blood flow monitoring is important to evidence retinal hypoperfusion inherent to many ocular diseases. For example laser speckle flowgraphy can measure abnormal perfusion in some types of glaucoma [5,6], and Doppler ultrasound is able to detect decrease of the ocular circulation [7]. Going further into the study of blood flow dynamics, a time-resolved analysis of blood flow changes contains a wealth of information as the arterial waveform profile is influenced by the arterial compliance and peripheral resistance [8][9][10].…”