Effect of Green Light from Doubled Frequency Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) Laser in the Nanosecond Range on Rabbit’s Lens –In Vitro Study

 INTRODUCTION: The unprotected eye is extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. The area of the eye damaged by laser energy is dependent upon the wavelength of the incident laser beam, duration of exposure and tissue characteristics. This study aims to investigate the effect of intense green light from doubled frequency Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) (532nm) in the nanosecond range on the protein of rabbits lenses after short and prolonged (6, 18 seconds) exposures.METHODS: The fundamental wavelength (1064 nm) was frequency doubled in β- Barium Borate (BBO) crystal for second harmonic generation (SHG). Rabbits’ lenses were irradiated in vitro, and the effect of the laser was evaluated by comparing the protein concentration, structure and conformation by sodium dodecyle sulphate polyacrylamide electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR).RESULTS: The results indicated a significant change in the soluble protein content, the molecular weights and the backbone structure of different lens crystallin fractions. These effects were more distinct when using laser with prolonged irradiation for 18 seconds than for 6 seconds.CONCLUSION: Irradiation with frequency doubled Nd-YAG green laser seem to be cataractous if the lens is exposed to laser that is intense enough to warrant thermal protein aggregation, folding and denaturatio

Histopathological Changes of the Retina After Nd: YAG Laser Thrombolysis in Branch Retinal Vein Occlusion: An Experimental Study

Introduction: The efficacy of many therapeutics techniques for treatment of branch retinal vein occlusion (BRVO) has been the subject of many investigations. The aim of the present work is to evaluate the transluminal Nd: YAG laser thrombolysis as a new therapeutic approach used for treatment of BRVO in rabbits as an experimental model.Methods: Four rabbits were considered as a control (n=8 eyes); occlusion of the branch retinal veins was performed by using a dye enhancing thrombus formation in right eyes of 10 rabbits (n=10 eyes). Thrombi in the retinal veins were induced by intravenous injection of rose bengal solution as a photosensitizer immediately before the argon laser application with a power of 1200 mW, a spot size of 100 μm, and a duration of 20 ms. One week later, transluminal Nd: YAG laser thrombolysis (30 mJ, 3 pulses/4 ns) was employed to the site of occluded veins, until the thrombi were partially or completely shattered. The rabbits were followed up after 4 days, 1 week and 2 weeks for slit lamp fundus examination and the treated retinas were isolated for histopathological examination.Results: Argon laser photothrombosis induced complete BRVO with some vitreous hemorrhage, destruction, and necrosis in the surrounding retinal layers. Moreover, one week later, Nd: YAG laser thrombolysis showed complete venous flow, minimal vitreous hemorrhage, reperfused retina, complete veins improvement. Follow up after 2 weeks revealed more improvement of all retinal layers.Conclusion: Treatment with transluminal Nd: YAG laser thrombolysis represented a novel therapeutic modality in BRVO

Histological Evaluation of Retina after Photo Disruption for Vitreous Humor by Q-Switched Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) Laser

Introduction: Rabbits’ eyes were exposed to vitreous humor liquefaction with Q - switched (sometimes called " giant pulses") Neodymium-Doped Yttrium Aluminium Garnet (Nd: YAG) laser using two different energy protocols (5 mJ X 100 pulse and 10 mJ X 50 pulse) with and without vitamin C administration . The histological changes in the retina were investigated to evaluate the protective role of vitamin C.Methods: The rabbits were divided into four main groups (n= 12 each). The first group was divided into three subgroups (n=4) and then treated with 5 mJ X 100 pulse (X means times) delivered to the anterior, middle and posterior vitreous humor respectively. The second group received a daily dose of 25 mg/Kg vitamin C for two weeks then was divided into three subgroups and treated with laser in the same manner as the first group. The third group was divided into three subgroups (n=4) and then treated with 10 mJ X 50 pulse delivered to the anterior, middle and posterior vitreous respectively. The fourth group received a daily dose of 25 mg/Kg vitamin C for two weeks then was divided into three subgroups and treated with laser in the same manner as the third group. After two weeks, rabbits were decapitated and histological examination for the retina was performed.Results: The results showed that, the anterior vitreous group exposed to 5mJX100 pulse and supplemented with vitamin C, showed no obvious change. Furthermore, all other treated groups showed alteration in retina's tissues histology after laser.Conclusion: Application of Q-switched Nd: YAG laser in vitreous humor liquefaction induces changes in retina's layers. Although there were some sorts of improvements in retinas supplemented with vitamin C, it cannot protect them against laser oxidative damage

Histopathology of Corneal Lenticules Obtained from Small Incision Lenticule Extraction (SMILE) versus Microkeratome Excision

Purpose: To study the alterations on the lenticules extracted after femtosecond (Femto) small incision lenticule extraction (SMILE) versus the corneal free cap removed using a microkeratome. Methods: The visuMax (500 kHz; laser energy: 180 nJ) was used for small-incision lenticule extraction. Free caps from human cadaveric corneas were excised by microkeratome. The collected lenticules were examined with the light and transmission electron microscope (TEM) for histological analysis, DNA fragmentation was assessed by agarose gel electrophoresis, DNA damage was evaluated using comet assay, and corneal proteins secondary structure was assessed by Fourier transform infrared spectroscopy (FTIR). Results: Light microscopic examination showed the presence of more edematous stroma under Femto SMILE than under free cap with a percentage change of 101.6%. In the Femto SMILE group, TEM examination showed pyknotic keratocytes, disruption, and cavitation of the collagen arrays stromal area under Femto SMILE. The DNA fragmentation for the Femto SMILE group revealed one undefined band with a size of 1.1 Kbp. The comet assay analysis indicated the presence of 3% and 8.0% tailed cells for the free cap and Femto SMILE groups, respectively. The tail lengths were 1.33 ± 0.16 and 1.67 ± 0.13 μm (P < 0.01), the percentage of tail DNA was 1.41 ± 0.18% (P < 0.01) and 1.72 ± 0.15%, and the tail moments were 1.88 ± 0.12 AU and 2.87 ± 0.14 AU (P < 0.001) for the free cap and Femto SMILE groups, respectively. FTIR spectroscopy of the Femto smile group revealed disorders in the secondary and tertiary structure of the proteins. Conclusion: Femto SMILE technique induced more structural changes, DNA fragmentation, DNA damage, and corneal proteins secondary structure alteration than those induced by a microkeratome cutting. These changes may be attributed to the deep penetration of high energy levels to the corneal layer. These findings may highlight the potential impact of the Femto SMILE on the cornea and the necessity for managing the laser parameters used

Photothrombosis of Corneal Neovascularization by Photodynamic Therapy Utilizing Verteporfin and Diode Laser

Introduction: The aim of the present study was to evaluate the effect of photodynamic therapy in the treatment of experimental corneal neovascularization (NV) with benzoporphyrin derivative (BPD).Methods: One group was considered as control (n=6 eyes) then, corneal NV was induced in 30 New Zealand male rabbits (n=60 eyes) by placing 7.0 silk sutures at midstromal depth approximately1mm from the limbus. Fifteen rabbits with corneal NV were left without any treatment, and 15 rabbits were subjected to photodynamic therapy (PDT) by intravenous injection with Verteporfin at a dose of 1.5 mg /Kg. Diode laser (660 nm) was applied after 15minutes for 5 minutes with a power of 50 mW/cm2. All rabbits were successively followed up by slit lamp examination for periods of 1 day, 1, 2, 3 and 4 weeks. Three rabbits were selected and sacrificed weekly (n=6 eyes each) and the corneas were isolated for histopathological examination.Results: The results of slit lamp examination indicated the gradual regression of the cornea neovascularization 4 weeks of PDT. Furthermore, regression of corneal neovascularization was documented clinically by decrease number and length of blood vessels and by histopathological examination.Conclusion: PDT with Verteporfin can provide efficacious treatment of corneal neovascularization

The Effect of Anterior Stromal Puncture Using Q-Switched Nd:YAG Laser on Corneal Wound Healing

Introduction: Recurrent corneal erosion occurs when the wounded corneal epithelium failed to adhere to the underlying stroma. Therefore, this work aimed to assess the effect of treatment of corneal injury using Q- switched Nd:YAG laser.  Method: Twenty one New Zealand male rabbits weighing 2-2.5 kg and 3 months old were classified into three main groups. The control group: did not received any treatment (n=3 rabbits). The rest of the animals (n= 18 rabbits), corneal epithelium was injured by syringe needle and blade 15 and divided into:(A) Normal healing group: which was divided into three subgroups (n=3 rabbits each), and the animals were left for normal healing for1 day, 1 week, and 4 weeks respectively, (B) Laser treated group: divided into three subgroups (n=3 rabbits each) and subjected to anterior stromal puncture using Q-switched Nd: YAG laser on corneal sub-epithelium or superficial stroma, and the animals were left for 1 day, 1 week, and 4 weeks respectively. After the demonstrated periods, the corneas were isolated for estimation of total protein content, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), total antioxidative capacity (TAC), total oxidative capacity (TOC) and oxidative stress index (OSI).Results: The present results of corneal total protein showed increment in the percentage change in normal healed groups after 1 day, 1 week and 4 weeks by values of 93%, 68% and 39%. In Q-switched Nd: YAG laser treated group the results showed better improvement in corneal protein than normal healed group with percentage changes of 58%, 29%, and 7.5% respectively. In SDS- PAGE, a protein band at 110 KD appeared in the migrating epithelium for both normal healed group and Q-switched Nd:YAG laser treated group with changes in the peaks intensities at middle and  low molecular weight regions. Moreover, after 4 weeks the peak at 110 KD disappeared in the wounded epithelium treated with Q-switched Nd:YAG. After four weeks, the OSI in laser treated corneas showed pronounced balance between antioxidative capacity and oxidative capacity.Conclusion: Anterior stromal puncture by Q-switched Nd:YAG laser is an effective, simple, safe and promising procedure to treat recurrent corneal erosion than normal healing

Effect of intense pulsed light therapy on tear proteins and lipids in meibomian gland dysfunction

Purpose: To assess the effect of a novel intense pulsed light (IPL) therapy on tear proteins and lipids in eyes with Meibomian gland dysfunction (MGD). Methods: Twenty-four eyes of 12 patients with MGD were recruited and received five overlapping flashes (565-1400 nm) directed at the lower eyelid. The IPL parameters include intensity: 2.5 to 6.5 J/cm2, voltage: 100 to 240 V, frequency: 50 to 60 Hz, input: 16 W, maximum optical energy: 23 J, pulse duration: <2.0 ms, and repetition time: 1-3.5 s. Tear samples were evaluated immediately before and 2 weeks after IPL therapy and included measurements of protein concentration, electrophoretic mobility by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, lipid profile assessments, and thin-layer chromatography (TLC) for phospholipids. Results: Significant improvements were observed in tear protein concentrations and molecular weight after IPL therapy. The most pronounced effect was in the molecular weight of tear lysozyme, lactoferrin, and albumin. Tear lipids showed an improvement in the concentrations of total lipids, triglycerides, cholesterol, and phospholipids. On TLC, the tears in patients with MGD had significantly lower amounts of anionic phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine but amounts zwitterionic neutral phospholipid phosphatidylcholine were normal. These anionic phospholipids showed obvious recovery after IPL therapy. Conclusion: IPL therapy is effective in eyes with MGD. It improved tear protein and lipid content and composition. The anionic phospholipids were more responsive to IPL therapy than were the other zwitterionic phospholipids

Light-Emitting Diode Laser Therapy for HyperoxiaInduced Retinal Abnormalities: LED Laser Therapy for Retinal Hyperoxia

Introduction: Hyperoxygenation is linked to numerous effects in a variety of organ systems. It can cause tissue damage by generating reactive oxygen species (ROS), increasing oxidative stress, and inducing cell death by apoptosis. The present study aimed to evaluate the effects of low-level laser therapy on the retina in response to acute hyperoxia in animals.Methods: A total of 70 Wistar albino rats were evaluated in the present study: 10 rats were designated as a control group, and the rest were exposed to hyperoxia (O2, 90%) for 3 days, 1 week, and 2 weeks (20 rats each). Each group was divided into two subgroups (n=10), one of which was designated as hyperoxia only. The other was treated with a 670 nm light-emitting diode laser (2 sessions/one week, ~ 9.0 J/cm2) in each eye. The animals were euthanized, and their retinas were dissected for analysis of protein content, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), total antioxidant capacity (TAC), hydrogen peroxide (H2O2), malondialdehyde (MDA), and histological examination.Results: We found that two weeks of hyperoxia-induced an increase in retinal protein content (P&lt;0.001), an alteration in the intensities and molecular weights of protein fractions, a significant decrease in the TAC level (P&lt;0.01), and a noticeable increase in H2 O2 and MDA levels (P&lt;0.001). Histological examination revealed fragmentation of the photoreceptors and neovascularization in the outer and inner plexiform layers. Furthermore, the data showed remarkable improvement in the retinal protein contents, oxidative state, and retinal structure after light-emitting diode laser therapy.Conclusion: Light-emitting diode laser therapy was found to be a useful treatment paradigm for reducing hyperoxia-induced retinal damage. DOI: 10.34172/jlms.2021.6