Non-contact, two-dimensional measurement of tissue circulation in choroid and optic nerve head using laser speckle phenomenon

Assessment of subchondral bone blood flow in the rabbit femoral condyle using the laser speckle method

The laser speckle method is a new form of flowmetry that can obtain a two-dimensional distribution of blood flow in tissue. This method is a noncontact, simple, and rapid technique that may aid in the diagnosis of osteonecrosis. We investigated whether the subchondral bone blood flow within the femoral condyles of rabbits could be measured by the laser speckle method. The hydrogen washout method was chosen as a comparison technique because of its ability to allow repetitive measurements of blood flow in various conditions in one rabbit and because of its reliability, which already has been established. We simultaneously measured the bone blood flow in 20 femoral condyles of 10 rabbits with the laser speckle and hydrogen washout methods and found a significant correlation between the blood flow levels with use of these two methods. For the clinical application of the laser speckle method, we also investigated the influence of cartilage thickness on the measurements and the depth in the bone to which blood flow could be measured with this method. A cartilage thickness of 0.2 mm did not influence the measurement of the bone blood flow, and the depth in the bone to which the laser speckle method could be used was approximately 2 mm.

Acute effects of cigarette smoking on tissue circulation in human optic nerve head and choroid-retina

OBJECTIVE

To study the acute effects of cigarette smoking on tissue circulation in the human optic nerve head (ONH) and choroid-retina.

DESIGN

Nonrandomized, comparative trial (sequential self-controlled).

PARTICIPANTS

Nine healthy habitual smokers (age, 28 +/- 4 years; number of cigarettes smoked per day, 27 +/- 10; length of smoking history, 10 +/- 4 years; mean +/- standard deviation).

INTERVENTION

Using the laser speckle method, normalized blur (NB) value, a quantitative index of tissue blood velocity, was measured every 0.125 second and averaged over three pulses across an area located in the temporal site of the ONH free of visible surface vessels (NB(ONH)) and across an area located halfway between the macula and the ONH with no discrete vessels visible (NB(ch-ret)). NB(ONH), NB(ch-ret), and intraocular pressure (IOP) in one randomly chosen eye, and blood pressure (BP) and pulse rate (PR) were measured before and 1, 5, 10, 15, 20, 25, 30, 45, 60, and 90 minutes after sham smoking using a short drinking straw as a cigarette substitute (control). One week later, NB(ONH), NB(ch-ret), and IOP in the same eye, and BP and PR were measured after cigarette smoking according to the same time schedule as in the control experiment.

MAIN OUTCOME MEASURES

NB(ONH) and NB(ch-ret).

RESULTS

In the control experiment, all parameters examined showed no significant change during the experimental period. Differences in NB(ONH) and NB(ch-ret) before and after actual smoking were significantly greater than those in the control experiment (analysis of variance, P = 0.0000, 0.0000). BP and PR were significantly increased between 1 and 30 minutes after actual smoking as compared with control data, while IOP showed no significant change at any time of measurement.

CONCLUSIONS

These results indicated that cigarette smoking increased tissue blood velocity in the ONH and possibly in the choroid in habitual smokers.

Coherent optical techniques for diagnostics of retinal blood flow

Up to now, a variety of coherent optical techniques have been proposed and extensively studied for diagnostics of the retinal blood flow. These techniques are mainly based on dynamic laser light-scattering phenomena such as the laser Doppler effect and the laser speckle fluctuation. This paper reviews, first, spectral reflectance properties of the ocular fundus tissue layers and, then, principles of the techniques with the comparison of the Doppler and the speckle methods. Some physical phenomena are also discussed in the origin of the techniques such as heterodyne and homodyne beatings, and time-varying speckles. Developing processes of each technique are briefly outlined. Peculiarities of blood flow measurements at the retina are finally examined from the methodological point of view. © 1999 Society of Photo-Optical Instrumentation Engineers.

Effects of topical adrenergic agents on tissue circulation in rabbit and human optic nerve head evaluated with laser speckle tissue circulation analyzer

The effects of topical adrenergic agents on the tissue circulation of the optic nerve head (ONH) were studied in animal and human eyes with use of a laser speckle tissue circulation analyzer. Drugs studied were nipradilol, a beta1-2-blocker with weak alpha-blocking and nitroglycerinlike activities; bunazosin, a selective alpha1-blocker; carteolol, a beta1-2-blocker with intrinsic sympathomimetic activity; and betaxolol, a selective beta1-blocker. In the animal experiment, one eye each of nine albino rabbits received 0.25% nipradilol (N = 9) twice daily for 15 days or 0.01% bunazosin (N = 10) twice daily for 20 days; the fellow eye received the vehicle of each drug in a randomized masked design. Normalized blur (NB) in an area of ONH free of visible surface vessels, a quantitative index of peripheral blood velocity in ONH, was measured under general anesthesia before treatment and 2 hours after the last instillation on the 15th or 20th day. At 15 days, intraocular pressure and NB in the nipradilol-treated eyes decreased by 4.3 mm Hg (P < 0.01) and increased by 15.9% (P < 0.01), respectively, while those in the vehicle-treated eyes showed little change. At 20 days NB in both bunazosin- and vehicle-treated eyes showed little change, while intraocular pressure decreased only in the bunazosin-treated eyes (P < 0.01). In the human volunteer experiment NB was averaged over five pulses (mean NB) in both eyes before and 1.5, 3.0 and 4.5 hours after a 30 microL instillation of the vehicle of carteolol or betaxolol to serve as a control. Intraocular pressure, blood pressure and pulse rate were also measured. One week later a 30 microL drop of 2.0% carteolol (N = 6) or 0.5% betaxolol (N = 10) was instilled in one randomly chosen eye and the vehicle for each drug in the other eye, and those parameters were measured as above in a double-masked manner. In the carteolol experiment, mean NB in both eyes was significantly higher at 3 hours than it was in the control experiment (P < 0.05), while intraocular pressure was significantly lower in both eyes and blood pressure and pulse rate showed little change. In the betaxolol experiment, intraocular pressure at 1.5 hours and blood pressure at 4.5 hours were significantly lower than those in the control experiment (P < 0.05), while mean NB and pulse rate showed little change. In summary, using the laser speckle method we found that topical nipradilol and carteolol increase ONH blood velocity in rabbits and humans, respectively. This finding suggests that some topical beta-blockers used clinically may influence the ONH tissue circulation in patients and that this method may be used in clinical situations to assess the effect of various drugs on ONH circulation.

Effect of topical beta-blockers on tissue blood flow in the human optic nerve head

PURPOSE

To study the effect of topical 0.5% timolol and 2% carteolol on tissue blood flow in the human optic nerve head (ONH).

METHODS

Using a laser speckle tissue blood flow analyzer, normalized blur (NB), a quantitative index of tissue blood velocity, was measured every 0.125 s in the temporal site of the ONH free of visible surface vessels and averaged over 3 cardiac pulses (NBONH). To serve as a baseline, NBONH and intraocular pressure (IOP) in both eyes, blood pressure (BP) and pulse rate (PR) were recorded in healthy volunteers before, 1.5, 3 and 4.5 hrs after a 30L instillation of the vehicle of timolol or carteolol. From the following day and twice daily for 3 weeks, 30L of either 0.5% timolol or 2% carteolol was instilled into one eye and the respective vehicle into the fellow eye in a masked manner. NBONH, IOP, BP and PR were again recorded on the 21st and last experiment day. IOP was also recorded on the 7th and 14th days. Carteolol concentration in the plasma was also recorded after instillation of carteolol on the 21st day.

RESULTS

During the baseline experiments, all the parameters recorded showed no significant change. After topical timolol, IOP was significantly reduced bilaterally with more reduction in the timolol-treated eye. Bilateral NBONH, BP and PR showed little change on the 21st day. After topical carteolol, IOP was significantly reduced bilaterally with more reduction in the carteolol-treated eyes on the 21st day. NBONH in the carteolol- and vehicle-treated eyes was significantly higher on the 21st day than recorded in the same eye in the baseline experiment (P = 0.013 and 0.047), while BP and PR showed little change. The maximum carteolol concentration in plasma at 3 hrs on the 21st day averaged 1294 pg/ml.

CONCLUSIONS

Results indicated that 3-week twice daily topical timolol treatment had no deleterious effect on the ONH tissue blood flow in the human eye, and that 3-week twice daily topical carteolol treatment may increase the tissue blood flow in the human ONH.

Time change of nicardipine effect on choroidal circulation in rabbit eyes

PURPOSE

To investigate the time course of effects of intravenous administration of a calcium antagonist, nicardipine, on the choroidal circulation of rabbit eyes using a laser speckle tissue circulation analyzer.

METHOD

The rabbit fundus was illuminated by a diode laser spot and its image speckle was detected by an image sensor. The difference between the average of the speckle intensity (Imean) and the speckle intensity for successive scannings was calculated, and the ratio of Imean to this difference was defined as normalized blur (NB); a quantitative index of tissue blood velocity. The average NB over the field measured (0.620.62 mm in the choroid) was calculated to give Nb(av). Under general anesthesia, 0.4 ml/kg of 0.01% nicardipine hydrochloride dissolved in physiological saline was injected intravenously in a group of albino rabbits (control group) for measurement in the choroid (nicardipine groups). To serve as control, 0.4 ml/kg of physiological saline was injected in other groups of albino rabbits (control groups). Nb(av) was recorded at 1-min intervals for the first 5 min and at 5-min intervals for the next 85 min. During the experiment mean femoral arterial blood pressure (FABPm), pulse rate (PR), arterial blood pH, Pco2 and Po2 body temperature (BT) and intraocular pressure (IOP) were also monitored. Before and 45 min after nicardipine administration, the choroidal blood flow measurement using the microsphere technique and the Nb(av) measurement were carried out in the same eye in another group of rabbits.

RESULTS

Only the rabbits which did not show any significant change in the PR, pH, Pco2, Po2 and BT during the experiment were accepted. FABPm in the nicardipine group dropped to the minimum at 1 min postadministration and this level remained significantly lower than that in the control group up to 15 min post-injection, while te 10P did not show any significant change. The Nb(av) in the nicardipine group showed a significant increase after the FABPm return to the baseline, which was maintained throughout the experiment. The averaged increase between 30 and 90 minutes after administration was 27 +/- 1% (mean +/- S.E.M., n = 10). Relative increase in choroidal blood flow determined by the microsphere technique showed a good correlation (r = 0.90, P < 0.001, n = 12) with those determined by Nb(av) after nicardipine administration.

CONCLUSIONS

The present result indicates that the time course of drug effects on the choroidal circulation can be noninvasively and sensitively followed by Nb(av) measurements. Further, it was shown that nicardipine may have considerable potential for the treatment of ocular diseases associated with insufficient choroidal blood flow and that nicardipine's effects here observed deserve to be further studied in humans.