From the Department of Ophthalmology (HE), Clinical Research Institute, National Hospital Organization, Kyushu Medical Center; Softcare, Ltd. (KO), Iizuka; the Department of Computer Science and Electronics (HF), Kyushu Institute of Technology, Iizuka; and the Department of Ophthalmology (HE, TI), Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Supported in part by a matching fund from the New Energy and Industrial Technology Development Organization (NEDO).
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Hiroshi Enaida, MD, Department of Ophthalmology, Clinical Research Center, National Hospital Organization, Kyushu Medical Center, 1-8-1 Jigyohama, Chuo-ku, Fukuoka, 810-8563, Japan. E-mail: firstname.lastname@example.org
Although fluorescein angiography and indocyanine green angiography have significant usefulness, it is difficult to quantify the blood flow in real time. Laser speckle flowgraphy (LSFG), which was developed at Kyushu Institute of Technology, demonstrated that it was possible to visualize a microcirculation map of the human retina and choroid using a dynamic laser speckle effect to move erythrocytes. By using LSFG, chorioretinal blood flow can be measured continuously and quantitatively in a non-invasive manner in areas that can be freely selected after measurement.1–3
Intravitreal bevacizumab has been reported to induce regression of the retina and iris neovascularization of proliferative diabetic retinopathy.4,5 In this report, we investigate the changes of chorioretinal blood flow using LSFG for a patient with proliferative diabetic retinopathy after intravitreal injection of bevacizumab and examine the usefulness of the method for investigation of chorioretinal hemodynamics in the drug intervention of quantitative LSFG analysis as a pilot study.
This pilot study was performed with approval from the Institutional Review Board and performed in accordance with the ethical standards of the 1989 Declaration of Helsinki. The possible advantages and risks of the current treatment were explained to the patient and written informed consent was obtained.
A 27-year-old man with insulin-dependent diabetes mellitus presented with a history of panretinal photocoagulation to his left eye with a best-corrected visual acuity of 12/20. Proliferative diabetic retinopathy with active neovascularization elsewhere (NVE) and neovascularization of the disc (NVD) was noted. The patient had experienced two instances of vitreous hemorrhage to date. He underwent off-label intravitreal bevacizumab (Avastin; Genentech, Inc., South San Francisco, CA) 1.25-mg injection according previous reports4,5 without complication. Ophthalmic examinations before and after injection included slit-lamp microscopy, ophthalmoscopy, best-corrected visual acuity, intraocular pressure, fluorescein angiography, and LSFG.
The LSFG (LSFG-NAVI; Softcare Ltd., Iizuka, Fukuoka, Japan) that was used for this study is the next generation instrument and has the capacity for higher resolution than previously reported instruments. The blood flow velocity (in relative values) was calculated at each pixel point from the square blur rate. In this system, the new blur rate was calculated from the volume of 2 × 2 × 3 pixels and was defined as the mean blur rate for critical analysis as previously reported.6 In this study, mean blur rate was measured in five areas of neovascularization from fluorescein angiography findings before the injection of bevacizumab. In addition, one area without neovascularization was selected and the mean blur rate was measured as a reference.
We measured six times consecutively under the same conditions and calculated the average mean blur rate in each area at pre-injection and 7, 14, and 50 days post-injection. The average mean blur rate was compared before and after injection in each area. The data were analyzed with image-processing software (Form Layer View; Softcare Ltd., Iizuka, Fukuoka, Japan) in each area.
After 7 days, almost all neovascularization had regressed by analysis with fluorescein angiography (Figs. 1A–1D). Changes in the velocity of the blood flow were examined using LSFG. A reduction in velocity was observed sequentially in the areas of neovascularization, as shown on the change of color pattern. An increase of the green and blue area on the average mean blur rate color map was observed with the regression of a neovascularization. Green and blue color area gradually increased from 7 days until 50 days in the neovascularization areas. Moreover, the change in vascular pattern and diameter was observed at the same time sequentially (Figs. 1E–1H).
Figure 1. (A–D) The Neovascularization Regressed Rapidly, Apparently, and Sequentially with Fluorescein Angiography After Bevacizumab Injection. (E–H) From the Change in the Velocity of Blood Flow by Laser Speckle Flowgraphy, a Reduction in Velocity Was Observed Sequentially as the Color Change in the Area of Neovascularization on the Average Mean Blur Rate Color Map. (E) Moreover, the Change in Vascular Pattern and Diameter Was Observed (asterisk) (A and E: Pre-Injection; B and F: After 7 Days; C and G: After 14 Days; D and H: after 50 Days).
In previously confirmed areas of neovascularization (Fig. 2), the mean blur rate decreased quickly by the seventh day after injection. In the four areas of NVE, the mean blur rate was reduced by an average of 32.7% (range: 24.5% to 42.4%) compared with pre-injection observations. The area of NVD and the areas of NVE showed a similar reduction pattern of mean blur rate. In this area, mean blur rate was reduced by 31.9% (Fig. 3).
Figure 2. Mean Blur Rate Was Measured in the Previously Confirmed Areas According to Fluorescein Angiography in an Average of the Four Areas of Neovascularization Elsewhere (NVE-1 to NVE-4) and in One Area of Neovascularization of the Disc (NVD) and One Area Without Neovascularization (nonNV).
Figure 3. Mean Blur Rate (MBR) Reduced an Average of 32.7% in the Area of Neovascularization Elsewhere (NVE) Compared with Pre-Injection (NVE-AVE = the Average MBR of the NVE-1 to NVE-4). In Neovascularization of the Disc (NVD) Area, MBR Was Finally Reduced to 31.9% (NVD). However, the Reduction in MBR Was not Observed in the Area in Which Neovascularization Did not Exist (without Neovascularization [nonNV]). The Significance Between Pre-Injection and After 50 Days Was Calculated by the Student’s t Test (asterisk: P < .01).
However, a reduction in mean blur rate was not observed in the area in which neovascularization did not exist (Fig. 3). Postoperative best-corrected visual acuity was up to 20/20 at 50 days post-injection without any complications.
The new LSFG system that was used for this study is the next generation instrument and has the capacity for higher resolution than previous systems. The resolution of the area sensor was improved to 1.7 × 104 pixels/mm2. Furthermore, improvements were made to the tracking and navigation system. In 4 seconds, an area of 5.3 × 2.9 mm could be analyzed.
Intravitreal bevacizumab has been reported to induce rapid regression of retinal and iris neovascularization in proliferative diabetic retinopathy.4,5 In this pilot report, we confirmed the dynamic changes in the velocity of the chorioretinal blood flow in the area of neovascularization quantitatively using a new LSFG instrument for a patient with proliferative diabetic retinopathy treated with an intravitreal injection of bevacizumab.
The advantages of LSFG analysis include that quantitative observation of the blood flow in the point or the area can be set up beforehand without any direct invasive interventions as imaging agent injection for the patients and can evaluate the influence of the chorioretinal blood flow sequentially on various drug interventions or surgeries. Such quantitative evaluation is difficult to detect in only fluorescein angiography or indocyanine green angiography analysis.
Although LSFG has several advantages, it is still under development. In fact, some disadvantages do exist with LSFG. The measurement angle of view (21°) is small and resolution is still low compared with fluorescein angiography or indocyanine green angiography. Moreover, measurements are impossible in an eye with an implanted intraocular lens, because the laser light is too scattered. Additionally, because mean blur rate does not provide an absolute value of the blood flow, comparison between patients is difficult.
Therefore, for LSFG to become increasingly useful for diagnostic purposes, further improvements are necessary and additional investigations are required before any clinical recommendations can be given. From this report, LSFG will offer new information on chorioretinal hemodynamics after any interventions.
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