Clinical Study on Retinal Vein Occlusion Treated by Argon Ion Laser
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To observe the clinical effects of treating retinal vein occlusion by argon ion Laser and medicine,72 case with retinal vein occlusion were analyzed respectively.Keywords:
Retinal Vein
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Abstract. This study highlights the comparative efficacy of three different laser wavelengths ‐ argon green, argon blue‐green, and krypton red ‐ for sector photocoagulation in fresh cases of branch retinal vein occlusion. The mean Logarithm of minimal angle of resolution (LogMAR) improved in the argon green and argon blue‐green groups but decreased in the krypton red group. Statistical analysis of the automated visual fields in these eyes showed a mean change in corrected pattern standard deviation value, with increase in all three groups ‐ minimal increase in the argon blue‐green group and maximal in the krypton red group, suggesting maximum visual field defect in the krypton laser group. To conclude, the green and the blue‐green wavelengths gave results that were decidedly superior to those given by krypton red: further, argon blue‐green had an edge over the green wavelength.
Krypton
Green laser
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The breakdown and repair of the blood-retinal barrier following argon laser photocoagulation were studied in pigmented rabbits by kinetic vitreous fluorophotometry using carboxyfiuorescein as a tracer
Blood–retinal barrier
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Objective To study the histopathological effect of retinal lesions and restoration induced by micropulse diode laser and argon laser in rabbits.Methods Under the parameter of diabetic macular edema micropulse diode laser and argon laser was used to produce retinal lesions in rabbit eyes.The histopathological alterations were observed.Results The subthreshold spots were undetectable and argon spots were detectable. The photoreceptor cells did not change but there was vascular engorgement in the choroid and it was disappear in 4 week after photocoagulation.The outer membranous discs were arranged disorder and the hydroncus of retinal pigment epithelial(RPE) and nodal cells was observed in argon spots by transmission electron microscope. The heterochromatin became multy in outer nuclear layer. The hyperplasia of RPE and collagen were obviously in 4 week and the hyperplasia of pigment grains were seen in chorioid.But no changes were seen in micropulse spots.Conclusion The retinal lesions produced by micropulse diode laser were slightly than produced by argon laser.
Green laser
Outer nuclear layer
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Objective To explore the optimal parameter of 532 nm wavelengthed laser in penetrating the whole retina (including Bruch′s membrane) of dog′s eyes and to provide experimental data for improving the successful rate laser-induced chorioretinal venous anastomosis Methods Different retinal sites were photocoagulated with different parameters , and the effect was assessed by histological examination and the KS 400 image pattern analytic system Results The penetrated retinal level was influenced by the power, the size of spot and the photocoagulated sites ( P =0 0001) The combined parameters of 532 nm wavelengthed laser application for penetrating full-thickness retinal including Buch′s membrane are 1 2～1 8 W, 50 μm, 0 1 s, 1 8 W, 100 μm, 0 1 s Conclusions The optimal parameter of penetrating full-thickness retina is as follows : power ranging from 1 2～1 5 W, the size of spot at 50 μm and duration at 0 1 s
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Purpose: To investigate intravenous femtosecond laser surgery in models of branch retinal vein occlusion. Materials and Methods: Non-amplified near infrared femtosecond laser was used to ablate polyamide sutures and human hairs inserted into the vascular lumina of porcine retinal veins in vitro. Specimens were subjected to multiphoton laser scanning microscopy and electron microscopy. Results: Regular laser cuts within sutures and hairs were detected with laser microscopy and electron microscopy. Neither laser microscopy nor histology revealed collateral damage of the vascular wall. Conclusions: Non-amplified femtosecond lasers may allow precise atraumatic non-contact intravenous retinal surgery controlled by high-resolution imaging of the target.
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The argon continuous wave laser was used to inflict experimental injuries of an order similar to that which might be achieved in clinical situations. These lesions differed markedly from previously reported retinal injuries induced by ruby and neodymium lasers and by the xenon photocoagulator. It was found possible to fundamentally change the structural patterns of the media and adventitia of retinal arteries and to consistently thrombose choroidal vessels but not retinal arteries under the conditions employed.
Adventitia
Retinal Artery
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Photoacoustic microscopy (PAM) can be an effective imaging modality to visualize retinal vein occlusion during laserinduced photocoagulation on major retinal veins. Developments in the vessels could be observed before and after laser irradiation due to the change of the optical absorption spectrum of the target vessels. However, the suitable wavelength to achieve high contrast PAM images of occluded vessels is unclear. This study evaluates the effect of wavelength on PAM imaging to evaluate the photocoagulation lesions on the rabbit to optimize the wavelength for imaging. Retinal vein occlusion (RVO) was created using a 532 nm millisecond pulse duration green light with concurrent intravenous administration of Rose Bengal (5 mg/kg) in New Zealand rabbits. Imaging was acquired by the PAM system at various wavelengths ranging from 520 nm to 590 nm. In addition, the thermal lesion was also confirmed using optical coherence tomography (OCT). A group of 20 retinal veins was irradiated for 0.5 s at a laser fluence of 850 W/cm2 (power = 150 mW, beam diameter = 75 μm). Twenty shots of the laser were applied to each major vein. PAM results showed that the thermal lesion was obviously visualized and exhibited lower contrast in comparison with untreated vessels posttreatment. Photoacoustic spectroscopy exhibited that the highest PA contrast of vessels treated with Rose Bengal laserinduced RVO occurred at a wavelength of 563, 570, and 578 nm, which was higher than the PA amplitude at lower and longer wavelengths respectively. The use of multi-wavelength PAM can provide a better method for visualization and evaluation of retinal vein occlusions.
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