Experiments on the absorption of argon and krypton laser by blood

Efficacy of knee osteoarthritis by use of laser acupuncture: A systematic review and meta-analysis

BACKGROUND

Previous studies need to be aggregated and updated. We aim to assess the efficacy of laser acupuncture (LA) in knee osteoarthritis (OA) through a meta-analysis.

METHODS

Electronic databases were searched for studies investigating laser acupuncture's efficacy in managing OA. Data were collected from the beginning of each database to 2022 (up to March). The "WOMAC total score," "WOMAC stiffness score," "WOMAC pain score," "WOMAC physical function score," and "VAS score" were the key outcomes of interest. The Der Simonian-Laird method for random effects was used.

RESULTS

Twenty-five randomized controlled clinical trials met our criteria and were included (2075 patients). Comparisons of interest is the LA versus Sham LA (efficacy), LA versus. A (Acupuncture) (comparative effectiveness), LA combined with A versus A (effectiveness as an adjunct), and any other research used LA in their treatment. Laser irradiation is effective in patients with Knee OA. LA is also effective and has almost the same outcome as laser irradiation. LA can achieve almost the same effect as manual acupuncture, even better than acupuncture in some studies.

CONCLUSION

Laser acupuncture is more or less effective in patients with OA; better efficacy will be achieved under appropriate laser parameters (810 nm, 785 nm) in the LA versus Sham LA group. Many studies have diverse results, possibly due to unstaged analysis of patients' disease, inappropriate selection of acupoints, lack of remote combined acupoints, and unreasonable laser parameters. Furthermore, a combination of acupoints was found to be more effective, which aligns with the combined-acupoints application of traditional Chinese medicine.

Theoretical and practical aspects relating to the photothermal therapy of tumors of the retina and choroid: A review

Photothermal treatment of tumors of the retina and choroid such as retinoblastomas, malignant melanomas, benign tumors as well as of vascular malformations can be performed by using laser radiation. A number of basic physical laws have to be taken into account in this procedure. Of particular importance thereby are: Arrhenius' law to approximate the kinetics of protein denaturation and photocoagulation, furthermore the electromagnetic radiation field, the distribution of both radiant and thermal energy induced in tumors and vascular structures, the influence of the wavelength and laser pulse duration (exposure time), as well as of the optical properties of the tissue. Strict confinement of the extent of the photothermal damage is critical since such pathological entities are frequently located close to the macula or optic nerve head.The conditions for tumor destruction are best fulfilled when using radiation in the near-infrared range of the electromagnetic spectrum such as that emitted from the diode (810 nm) and the Nd: YAG (1064 nm) laser, because of the good optical penetration properties of these radiations in tissue. Short wavelength sources of radiation, such as the argon ion (488, 514 nm) or the freqeuency-doubled Nd: YAG (532 nm) laser are less well suited for the irradiation of large vascular structures due to their poor penetration depths. However, for vascular formations with a small thickness (1 mm or less), short wavelength sources appear to be the most appropriate choice. Optical coupling of radiant energy to the eye by means of indirect ophthalmoscopic systems or positive contact lenses is furthermore of importance. Strong positive lenses may lead to severe constrictions of the laser beam within the anterior segment, that leads to high irradiance increasing the probability for structures to be damaged; with negative contact lenses, such as the -64 D Goldmann type lens, this danger is largely absent.

Transmission of retinal laser wavelengths through blood

PURPOSE

Treatment of retinal and choroidal diseases may be influenced by overlying blood. We compared the penetration through blood of various laser wavelengths used in thermal photocoagulation, photodynamic therapy, and transpupillary thermotherapy.

METHODS

Laser light of wavelengths 514 nm, 568 nm, 647 nm, 689 nm, and 810 nm was directed through normal saline (control), whole blood with a hematocrit of 40%, and serial dilutions of whole blood until a steady-state reading of laser power output was obtained. Laser power output was measured with an Orion Laser Power/Energy monitor (Ophir Optronics LTD). Laser power was measured in milliwatts and expressed as a percentage of control.

RESULTS

Five hundred fourteen-nanometer and 568-nm laser wavelengths penetrated the least through all dilutions of blood tested (>60% attenuation through the highest dilution tested); 647-nm, 689-nm, and 810-nm laser wavelengths penetrated most effectively through blood but were still significantly attenuated ( approximately 46%, 49.6%, and 47.0% attenuation, respectively, at the highest dilution tested).

CONCLUSIONS

The presence of hemorrhage may have a significant effect on the delivery of laser energy to underlying structures/tissue. This may affect parameters used in thermal and nonthermal laser treatment of ocular diseases such as choroidal neovascularization.

Laser energy and dye fluorescence transmission through blood in vitro

PURPOSE

Because of the potential usefulness of evaluating and treating choroidal neovascularization obscured by blood, we designed this study to quantify the transmission of dye fluorescence and laser energy through blood.

METHODS

Blood preparations anticoagulated with ethylenediaminetetraacetic acid with hematocrits of 0% (plasma), 46%, and 99% were placed in open cuvettes with path lengths of 100, 200, or 500 microns and were exposed for one minute to either 100% oxygen or 100% carbon dioxide. Each cuvette was then sealed. Photographs of the cuvettes of blood in front of a flask of fluorescein or indocyanine green solution were decoded and used to calculate the percent transmission of fluorescence through blood. Cuvettes of blood were also placed in the path of argon, krypton, and diode lasers for energy transmission measurements.

RESULTS

Plasma transmission of fluorescein and indocyanine green fluorescence and argon, krypton, and diode laser energy was 89% to 100% for all samples tested. Transmission of fluorescein fluorescence and argon laser energy through 99% hematocrit samples were both less than 5%. Transmission of indocyanine green fluorescence through 100-, 200-, and 500-microns-thick cuvettes filled with 99% hematocrit blood was 57%, 34%, and 4%. Transmission of krypton laser energy was 50%, 25%, and 6%; and transmission of diode laser energy was 60%, 35%, and 12% through 99% hematocrit blood. Intermediate transmission values were obtained for 46% hematocrit samples.

CONCLUSIONS

Krypton and, to a slightly greater degree, diode laser energy penetrate a thin film of blood. Indocyanine green fluorescence also penetrates a thin film of blood. If a layer of blood appears thinner than 500 microns, then indocyanine green angiography may be useful in imaging underlying pathologic features. If a lesion can be imaged with indocyanine green, then it can probably be treated with a krypton or diode laser.

Dye laser photocoagulation through experimentally induced retinal hemorrhage

The histological effects of photocoagulation obtained by using each of 4 wavelengths of the dye laser (577, 590, 610, and 630 nm) on experimentally induced retinal hemorrhage in cat eyes were examined. Energy from 577, 590, and 610 nm laser was directly absorbed by red blood cells in the retinal hemorrhage and destroyed the inner layers of the retina. Red blood cells were not directly coagulated with the use of 630 nm laser, and the retinal pigment epithelial cells (RPE cells) and choroidal melanocytes were coagulated. These results suggest that the use of yellow or orange dye lasers for photocoagulative therapy in a retinal hemorrhage is dangerous, because of the risk for destruction of the inner layers of the retina. A 630 nm dye laser is useful for photocoagulation of a retinal hemorrhage, while the laser energy is unable to reach the RPE cells and the choroid with the use of other wavelengths.

Photocoagulation of raised new vessels by long-duration low-energy argon laser photocoagulation--a preliminary study

Direct laser treatment of retinal neovascularisation is indicated when regression has not been brought about by retinal photocoagulation. Current treatment regimens involve multiple laser applications to the neovascular complex. Long-duration low-energy burns have the advantage of slowly heating the tissue without engendering disruption. We report the use of this treatment as a means of occluding the feeder vessels to a neovascular network. The application of argon blue-green laser treatment at 0.1 watt for 60 seconds at two adjacent points on a feeder vessel was found to give rise to permanent vascular occlusion without causing complications.

Krypton red laser photocoagulation for branch retinal vein occlusion

Krypton red (647 nm) laser photocoagulation may offer distinct advantages in the treatment of branch retinal vein occlusion (BRVO), particularly in eyes with extensive intraretinal hemorrhage or in the presence of media opacities such as vitreous hemorrhage or cataract. Twenty-three eyes were followed for a minimum of 6 months (range, 6-38). Of 19 eyes treated for macular edema, 17 (89%) had complete resolution of their edema, one (5%) had reduction of its edema, and one (5%) was unchanged. Of five eyes treated for retinal neovascularization of the disc or retina, all eyes had complete elimination of neovascularization. The authors were unable to demonstrate any statistical correlation between final visual acuity and the following factors: duration of symptoms, cystoid macular edema (CME), degree of paramacular nonperfusion, and contiguous intraretinal hemorrhage extending into the foveal avascular zone (FAZ).

Wavelength selection in macular photocoagulation. Tissue optics, thermal effects, and laser systems

The therapeutic effects of macular photocoagulation result from focal heating of the retina and choroid. The magnitude, spatial extent, and duration of temperature increases produced by laser exposures are influenced by light scattering in intraocular and intraretinal transit; light absorption by melanin, hemoglobin, and xanthophyll in target tissues; and beam parameters, such as wavelength, spot size, and exposure duration. Tissue optics and thermodynamics provide a useful guide for selecting new laser systems of potential value in macular photocoagulation, but laser-tissue interactions and subsequent chorioretinal responses are poorly understood, and therapeutic efficacy can be established only by controlled clinical trials.

Histology of macular photocoagulation

The histology of macular photocoagulation is reviewed. This information may be helpful in selecting the best available laser for retinal vascular and choroidal disorders in the macular region, as providing an experimental method to better understand the effects of photocoagulation on retinal disease processes.