Mesenchymal stem cells (MSCs) are multipotent cells present in adult bone marrow that replicate as undifferentiated cells and can differentiate to lineages of mesenchymal tissues. Here we show that blue laser (wave length; 405 nm) irradiation can influence the differentiation of mouse MSCs into osteoblasts by altering the intracellular localization of the circadian rhythm protein Cryptochrome 1 (mCRY1). Laser irradiation could provide a simple and effective means of controlling the fate of implanted MSCs as a therapeutic strategy. Furthermore, this model system may be useful for exploring the crosstalk between circadian rhythm and cell differentiation.

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Indocyanine green (ICG) has a wide optical absorption band extending from 600nm to above 800nm wavelength, and the maximum absorption near 800nm has been used for the fluorescence diagnosis in Ophthalmology, and for dye-enhanced photocoagulation. To clarify the effect of ICG irradiation, we investigated the singlet oxygen (¹O₂) generation in the ICG irradiation by means of a highly sensitive near infrared (NIR) detection system, and the activity in a HeLa tumor in a mouse by irradiation after an ICG injection.
We obtained the NIR spectrum at around 1270nm from irradiated ICG solutions dissolved in water, heavy water, and ethanol. The spectrum intensity was maximum in ethanol and minimum in water. Sodium azide (NaN₃, known as an ¹O₂ quencher) was added to a water solution of ICG, and the spectrum was diminished dose-dependently by the concentration of NaN₃, revealing that the spectrum was the result of ¹O₂. Laser irradiations (635nm, 670nm) to HeLa tumors in mice after an ICG injection resulted in tumor necrosis due to PDT. However, with irradiation at 823nm, the severe necrosis was caused by the combination of PDT and the thermal effect. When using an ICG injection to diagnose conditions of the choroid and the retina, we recommend the use of limited light power or energy during the irradiation to avoid the occlusion of veins.

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Laser speckle microscopy was developed to observe living cells and tissue without any troublesome labeling preparation. The system consists of an optical microscope, a laser source, and a video camera. The technique has an advantage that cell and tissue conditions can be instantaneously determined by observing speckle fluctuations. In the experiments, living and fixed HeLa cells were compared on the basis of speckle fluctuation. Cellular environmental effects on speckle fluctuations and long-term plant tissue observation were also investigated. By applying this technique to cell and tissue observations, it is expected to estimate not only their activities but also real-time movements of bio-materials inside cells and tissue without fluorescence observation.

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Singlet oxygen (¹O₂) generated in photodynamic therapy (PDT) plays a very important role in killing tumor cells. Using a new near infrared-photomultiplier tube (NIR-PMT) system, we monitored the real-time production of ¹O₂ during PDT and thus investigated the relationship between the ¹O₂ production and photodynamic effects. We performed PDT using 5-aminolevulinic acid (ALA) in 9L glioma cells in vitro and in rat in vivo subcutaneous tumor model inoculated 9L glioma cells, and monitored ¹O₂ production using NIR-PMT system. Moreover, based on the ¹O₂ monitoring, we investigated how ¹O₂ production would affect the tumor cell death following PDT. We could observe the temporal changes of ¹O₂ production during PDT in detail. At a low fluence rate the ¹O₂ signal gradually decreased with a low peak, while at a high fluence rate it decreased immediately with a high peak. Consequently, the cumulative ¹O₂ at a low fluence rate tended to be higher, which thus induced a strong photodynamic effect. A low fluence rate tended to induce apoptotic change, while a high fluence rate tended to induce necrotic change. The results of this study suggested that the monitoring of ¹O₂ enables us to predict the photodynamic effect and then allows us to select the optimal laser conditions for each patient.

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Optical coherence tomography (OCT) has facilitated an understanding of the pathogenesis of various retinal diseases. It also enables measurement of the thickness of the total retina and nerve fiber layer that aids in the diagnosis of early glaucoma, the monitoring of disease progression, and the evaluation of treatment effects. Recently, the acquisition speed and sensitivity of OCT have been dramatically improved with a novel detection technique known as Fourier-, spectral-, or frequency-domain detection that increases the imaging speed by ∼25- to 100-fold compared to that yielded by standard-resolution time-domain OCT (TD-OCT). Spectral-domain OCT (SD-OCT) enables three-dimensional (3D) analysis of retinal pathologies, 3D visualization of the vitreoretinal interface, and comprehensive observation of intraretinal structural changes. It allows the segmentation of some retinal layers such as the nerve fiber layer, inner retina, and photoreceptor outer segment, and this in turn enables the monitoring of the thickening or thinning of these structures. SD-OCT also allows the segmentation of 3D pathological lesions such as soft drusen, pigment epithelial detachment, and serous retinal detachment. Thus, disease progression can be monitored and the effects of treatment can be evaluated more precisely using SD-OCT than TD-OCT. Further, SD-OCT enables the registration of 3D volume images with other standard ophthalmic images such as color fundus photographs and angiograms. Thus, SD-OCT dramatically expands the potential use of OCT in the analysis of retinal diseases and glaucomas.

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ArF excimer laser is now applicable to refractive surgery in ophthalmology. Detailed observation of the cornea have been needed. We show the devices using laser in the examinations.

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Reduction of intraocular pressure (IOP) is the only evidence-based treatment against glaucoma. The major methods of IOP reduction are eye drops and surgical treatments. Selective Laser Trabeculoplasty (SLT) is besed on selective photohermolysis theory. SLT is without tissue impairment, and is capable of re-treatment. SLT uses Q-switched frequency-doubled Nd:YAG laser, and it needs a few minutes for the treatment. Response rate is about 70%. IOP reduction rate is 20-30%. The IOP lowering effect of SLT is as much as that of the most effetive eye drop, and the effect lasts for a long time. And then, some group has investigated the efficacy and safety of SLT as primary treatment. SLT is expected to become a common treatment of glaucoma.

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Photodynamic therapy (PDT) on exudative age-related macular degeneration has been performed since 2004 in Japan and now undergone in about 179 institutions. The number of patients received PDT is estimated to be about 16,000. Good visual prognosis has been reported by PDT, while in contrast there are some problems such as postoperative hemorrhage and high recurrence rate. Direct injury on the retina is spared by PDT, but damage on the normal tissue surrounding the choroidal neovascularization such as the choriocapillaris and retinal pigment epithelium occurs. PDT combined with triamcinolone acetonide or the other anti-vasucular endothelial growth factor agents is tried in order to get lower recurrence rate. The effectiveness on visual prognosis by combined therapy is still controversial. The effectiveness of PDT based on the diagnosis with indocyanine green angiography (IA guided PDT) has been investigated. Retinal angiomatous proliferation and choroidal neovascularization with large serous detachment of the retinal pigment epithelium resist to PDT. PDT has possibilities as a treatment to occlude the choroidal neovascularization, though it has merits and demerits.

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Purpose: The purpose of this study is to report the clinical outcome of a pilot study of subthreshold diode laser micropulse photocoagulation (SDM) for diabetic macular edema. Methods: Twenty two patients 25 eyes with clinically significant macular edema were investigated after SDM. Primary outcome measurers were visual acuity, foveal macular thickness and macular volume measured by OCT scan. Results: After more than 6 months follow-up, no obvious laser scar was found at treated area. Visual acuity was improved or maintained within 0.2 Log MAR level change in 92% of treated eyes. In 19 eyes which macular thickness parameters had been measured with OCT scan, average foveal thickness which was 340.6μm preoperatively had been significantly decreased after treatment; 313.5μm at 1 month (P=0.019), 295.3μm at 3 months (P=0.013), 286.3μm at 6 months (P=0.006). Average foveal volume which was 8.245mm³ preoperatively had also decreased after treatment; 8.235 mm³ at 1 month, 8.117mm³ at 3 months, 7.897mm³ at 6 months (P=0.04). Conclusion: Subthreshold diode laser micropulse photocoagulation is effective treatment for clinically significant macular edema to decrease macular edema and improve or maintain visual acuity with minimal damage to macular retinal tissue, which has important visual function.

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