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Laser photocoagulation is one of the important methods for treating retinal diseases, and retinal laser technology continues to advance. For decades, researchers have been striving to find a laser treatment that can minimize tissue damage while achieving optimal results. With low toxicity, low scattering light, strong penetrating power, small compared with the traditional laser damage, light reaction and no pain, the 577 nm subthreshold micropulse laser(SML)turns this goal into reality and ushers in a new era of laser treatment for fundus diseases. This article reviews the concept, mechanism, related parameters and clinical application progress of 577 nm SML in a variety of retinal diseases, aiming to provide references for clinical treatments.
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Central serous chorioretinopathy(CSC)is a common macular degeneration that primarily affects young patients. While the disease may resolve on its own to some extent, delayed or inadequate treatment can result in recurrence and progression to chronic CSC. This can lead to complications such as retinal pigment epithelium(RPE)atrophy and choroidal neovascularization, ultimately causing irreversible damage to central vision. Subthreshold micropulse laser photocoagulation(SMLP)is a type of laser therapy that differs from traditional lasers in that it does not cause damage or thermal injury to RPE cells and photoreceptors. SMLP has become widely used in clinical treatment of CSC due to its effectiveness, safety, and reproducibility, particularly in cases where verteporfin is not available in photodynamic therapy(PDT). The purpose of this review is to explain the mechanism of SMLP in CSC and summarize the effector cells, cytokines, and mechanisms of action involved in its treatment. This will provide a theoretical basis for promoting and rationalizing the use of SMLP in clinical practice.
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Central serous chorioretinopathy (CSC) is a common macular disease, which can lead to the loss of central vision in young patients. Although the disease is self-limited to some extent, there is no shortage of patients with prolonged course and recurrent attacks, eventually leading to irreversible visual impairment. Therefore, taking reasonable treatment in a certain period is particularly important for the visual prognosis of patients. Although thermal laser photocoagulation of leakage points and photodynamic therapy (PDT) have achieved good effects, there are risks of retinal damage and retinal pigment epithelium atrophy. Subthreshold micropulse laser (SMLP) is a kind of subthreshold short pulse laser, which does not cause visible damage to the retina and is safer. In the era of lack of PDT drugs, SMLP has gradually become an important means of clinical treatment for CSC, especially for patients with no obvious leakage point or subfoveal leakage point. An in-depth understanding of the mechanism of action of SMLP and its efficacy and safety in the treatment of CSC is helpful for the promotion and application of SMLP in the clinical treatment of CSC.
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Central serous chorioretinopathy (CSC) is a common macular disease, mainly manifested as a plasma detachment of the macula. Photodynamic therapy (PDT) is an effective treatment for CSC, but with the shortage of the photosensitizer Verteporfin, the effective treatment of CSC has become a common concern for ophthalmologists. In this paper, based on the latest research results on the relationship between the changes in the thickness of the outer nuclear layer and the natural course of the disease and PDT therapy, we propose that patients with CSC should receive effective treatment as early as possible to prevent irreversible damage to visual function due to the thinning of the outer nuclear layer. In addition to PDT, it is recommended that laser photocoagulation or subthreshold micropulse laser treatment of the leaking spot should be considered first, depending on the presence of the leaking spot and its location in relation to the macula center. Anti-vascular endothelial growth factor therapy can be considered if there is a combination of choroidal neovascularization and/or polypoidal choroidal vasculopathy. Other treatments that have not been demonstrated to be effective in evidence-based medicine are not recommended.
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AIM: To analyze the clinical effect of 577nm subthreshold micropulse laser(SML)photocoagulation combined with intravitreal injection of Conbercept in the treatment of diabetic macular edema(DME)after vitrectomy in patients with proliferative diabetic retinopathy(PDR).METHODS:A retrospective analysis was performed on 29 cases(30 eyes)of PDR patients who had DME after vitrectomy in our hospital from January 2019 to June 2021. They were divided into two groups according to different treatment methods: 14 cases(14 eyes)in the single injection group received intravitreal injection of Conbercept, and 15 cases(16 eyes)in the combined treatment group received 577nm SML photocoagulation in the macular area combined with intravitreal injection of Conbercept. The changes in best corrected visual acuity(BCVA)and central macular thickness(CMT)before and at 6 and 12mo after treatment, as well as the changes of multifocal electroretinogram(mfERG)before and at 12mo after treatment were compared between the two groups.RESULTS: The BCVA(LogMAR)of patients in both groups improved and CMT decreased after treatment for 6 and 12mo(all P<0.001). There were no significant differences in BCVA(LogMAR)and CMT before treatment and 6mo, 12mo after treatment between single injection group and combined treatment group(all P>0.05). Compared with the combined treatment group, the amplitude was slightly lower(23.02±3.13 vs. 26.50±3.33 μV/deg2)and the latency time was prolonged(38.75±1.62 vs. 34.21±3.06ms)in single injection group at 12mo(all P≤0.001). The average injection times in single injection group was 8.14±1.46, and 5.05±1.51 in combined treatment group at 12mo after treatment(P<0.05).CONCLUSION: 577nm SML photocoagulation combined with intravitreal injection of conbercept can effectively relieve macular edema, improve BCVA and visual function of macular area and reduce the injection times of conbercept for DME patients.
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Purpose: To study the effect of subthreshold micropulse yellow laser treatment on central serous chorioretinopathy (CSC) and to compare two laser protocols. As per our knowledge, there are no studies comparing the two protocols of subthreshold laser. Methods: Twenty-three patients with non-resolving CSC of at least three months duration were treated with subthreshold laser (577 nm). Ten patients were treated with 5% duty cycle (group A) and 13 patients with 10% duty cycle (group B). At one month, best corrected visual acuity (BCVA), central macular thickness (CMT), subretinal fluid (SRF), choroidal thickness (CT) and choroidal vascularity index (CVI) were evaluated. Results: In group A, BCVA improved from 0.508 ± 504 to 0.174 ± 0.171 (P = 0.0058), CMT improved from 349.8 ± 168.9 micrometers (mm) to 183.3 ± 70.312 mm (P = 0.0093) and SRF reduced from 202.4 ± 158.024 to 43.8 ± 46.599 mm (P = 0.0069). In group B, BCVA improved from 0.437 ± 0.426 to 0.289 ± 0.470 (P = 0.0026), CMT improved from 280.846 ± 72.668 to 196.769 ± 72.62 mm (P = 0.0002) and SRF reduced from 110.385 ± 57.687 mm to 52.538 ± 52.111 mm (P = 0.0064). No significant difference was found in BCVA and CMT between the groups (P = 0.8716 and P = 0.8523, respectively). CSC completely resolved in 50% of cases in group A and in 69.2% of cases in group B. This difference was not statistically significant (0.423); however, the odds ratio of resolution was 2.25 times more with 10% duty cycle. No change was observed on fundus autofluorescence (FAF) following laser. Conclusion: Subthreshold micropulse laser can lead to resolution of SRF in 60.87% of cases (groups A and B combined). Ten per cent duty cycle had higher odds of resolution without causing any RPE damage.
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@#Subthreshold micropulse laser(SML)consists of short repetitive pulses of laser. This kind of treatment is safe and cheap, and contrary to conventional laser photocoagulation(LPC), SML doesn't involve destruction of retinal cells and leave no scars. The possible mechanism of SML is to stimulate retinal pigment epithelium(RPE)cells for the production of heat shock proteins(HSPs)and regulate its metabolism and improve its function. The clinical indication of SML includes central serous chorioretinopathy(CSC), diabetic retinopathy edema(DME), nonproliferative diabetic retinopathy(NPDR)and proliferative diabetic retinopathy(PDR)and macular edema(ME)secondary to retinal vein occlusion(RVO). This article discussed the mechanism and safety of SML and reviewed the updates of its application.
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?AIM:To analyze the morphological changes of macular soft drusen and drusenoid pigmental epithulium detachment ( DPED ) after subthreshold micropulse laser treatment ( SMLT) .?METHODS: Fourteen patients ( 20 affected eyes ) with soft drusen and DPED clinically confirmed from August 2016 to October 2018, were included in this study. 577 nm yellow laser of SMLT was applied for soft drusen and DPED. The changes of soft drusen and DPED in best corrected visual acuity ( BCVA ) ( LogMAR ) and height, diameter and cross-sessional area according to fundus autofluorescence and SD - OCT examinations were observed after SMLT.?RESULTS: BCVA was not significant difference after treatment of soft drusen (P=0.260), and the DPED (P=0. 736 ) than that of the baseline. Compared with the baseline values, the height and cross-sessional area of soft drusen were reduced at the 6mo after treatment ( P=0. 008, P=0.034) . Compared with the baseline values, the differences were not statistically significant in height, diameter and cross - sectional area of DPED after treatment.?CONCLUSION: BCVA was not reduced for drusen and DPED after SMLT, however, the height and cross -sessional area of soft drusen was reduced compared with those before treatment, and the differences were not statistically significant in height, diameter and cross -sectional area of DPED before and after treatment. The results indicated that SMLT was effective for soft drusen, but was not effective for short-term treatment of DPED. SMLT caused no damage to the visual acuity in treatment of soft drusen and DPED, but prospective, controlled, large sample and long-term follow-up studies should be required.
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@#AIM: To analyze the morphological changes of macular soft drusen and drusenoid pigmental epithulium detachment(DPED)after subthreshold micropulse laser treatment(SMLT).<p>METHODS: Fourteen patients(20 affected eyes)with soft drusen and DPED clinically confirmed from August 2016 to October 2018, were included in this study. 577 nm yellow laser of SMLT was applied for soft drusen and DPED. The changes of soft drusen and DPED in best corrected visual acuity(BCVA)(LogMAR)and height, diameter and cross-sessional area according to fundus autofluorescence and SD-OCT examinations were observed after SMLT.<p>RESULTS: BCVA was not significant difference after treatment of soft drusen(<i>P</i>=0.260), and the DPED(<i>P</i>=0.736)than that of the baseline. Compared with the baseline values, the height and cross-sessional area of soft drusen were reduced at the 6mo after treatment(<i>P</i>=0.008, <i>P</i>=0.034). Compared with the baseline values, the differences were not statistically significant in height, diameter and cross-sectional area of DPED after treatment.<p>CONCLUSION: BCVA was not reduced for drusen and DPED after SMLT, however, the height and cross-sessional area of soft drusen was reduced compared with those before treatment, and the differences were not statistically significant in height, diameter and cross-sectional area of DPED before and after treatment. The results indicated that SMLT was effective for soft drusen, but was not effective for short-term treatment of DPED. SMLT caused no damage to the visual acuity in treatment of soft drusen and DPED, but prospective, controlled, large sample and long-term follow-up studies should be required.
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@#AIM: To analyze the morphological changes of macular soft drusen and drusenoid pigmental epithulium detachment(DPED)after subthreshold micropulse laser treatment(SMLT).<p>METHODS: Fourteen patients(20 affected eyes)with soft drusen and DPED clinically confirmed from August 2016 to October 2018, were included in this study. 577 nm yellow laser of SMLT was applied for soft drusen and DPED. The changes of soft drusen and DPED in best corrected visual acuity(BCVA)(LogMAR)and height, diameter and cross-sessional area according to fundus autofluorescence and SD-OCT examinations were observed after SMLT.<p>RESULTS: BCVA was not significant difference after treatment of soft drusen(<i>P</i>=0.260), and the DPED(<i>P</i>=0.736)than that of the baseline. Compared with the baseline values, the height and cross-sessional area of soft drusen were reduced at the 6mo after treatment(<i>P</i>=0.008, <i>P</i>=0.034). Compared with the baseline values, the differences were not statistically significant in height, diameter and cross-sectional area of DPED after treatment.<p>CONCLUSION: BCVA was not reduced for drusen and DPED after SMLT, however, the height and cross-sessional area of soft drusen was reduced compared with those before treatment, and the differences were not statistically significant in height, diameter and cross-sectional area of DPED before and after treatment. The results indicated that SMLT was effective for soft drusen, but was not effective for short-term treatment of DPED. SMLT caused no damage to the visual acuity in treatment of soft drusen and DPED, but prospective, controlled, large sample and long-term follow-up studies should be required.
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@#AIM: To compare the efficacy and safety of 577nm subthreshold micropulse laser(SML)and photodynamic therapy(PDT)in patients with chronic central serous chorioretinopathy(cCSC).<p>METHODS: Thirty patients(30 eyes)with cCSC were treated in our hospital from February 2015 to April 2018. And 15 patients(15 eyes)were treated with SML(577 nm)while the others were treated by PDT. The BCVA and CMT as well as complications were observed at 1, 3, 6mo after treatment.<p>RESULTS: At 1mo after treatment, BCVA was increased to 0.37±0.13 in SML group and 0.20±0.11 in PDT group(<i>t</i>=-3.93, <i>P</i><0.001); CMT was decreased to 382.80±76.54μm in SML group and 247.60±28.46μm in PDT group(<i>t</i>=-6.41, <i>P</i><0.001). Although improvements of BCVA and CMT were both achieved in two groups, improvements in PDT group were better than those in SML group. At 3mo and 6mo after treatment, both BCVA and CMT were no significant difference between the two groups(<i>P</i>>0.05). During the follow-up period, there were no obvious complications or recurrence observed.<p>CONCLUSION: Both SML(577nm)and PDT were effective and safe in the treatment of cCSC, but the theraputic effects of PDT was slightly quicker than SML. Further, with the prolongation of recovery time, the curative effects of these treatments were similar. Additionally, SML(577nm)costs was much cheaper than PDT and had no risk of injury or allergy for patients, and patients with cCSC could also be treated repeatedly using it.
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AIM: To observe the changes of MMP-9 expression in rabbit retina after laser irradiation at different thresholds of 577nm.METHODS: Twenty-six pigmentation rabbits were randomly divided into normal control group(n=2), conventional photocoagulation group (n=6) and subliminal micropulse laser photocoagulation group (n=18).The conventional photocoagulation group was treated with 577nm laser photocoagulation, subcutaneous micro-pulsed laser photocoagulation at a working loading rate of 9%, 12% and 15%, respectively.Eighteen rabbits were again divided into three subgroups according different powers of subthreshold working loading rate of 9%(n=6), 12%(n=6) and 15%(n=6) that undertook, respectively.The expression of MMP-9 on the retina of rabbit eyes was detected by immunohistochemistry.RESULTS: In the conventional photocoagulation group, the expression of MMP-9 in the RPE layer and the visual cell layer was strongly positive, which was significantly higher than that in the sub-micro pulse group(P0.05).CONCLUSION: The 577nm subliminal micro-pulsed photocoagulation has high selectivity to retinal pigment epithelium at working load rate of 9%, 12% and 15%, and no damage to retinal nerve fiber layer, which is safer than conventional 577nm laser photocoagulation.
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Photocoagulation is the standard of care for several ocular disorders and in particular retinal conditions. Technology has off ered us newer lasing mediums, wavelengths and delivery systems. Patt ern scan laser in proliferative diabetic retinopathy and diabetic macular edema allows laser treatment that is less time consuming and less painful. Now, it is possible to deliver a subthreshold micropulse laser that is above the threshold of biochemical eff ect but below the threshold of a visible, destructive lesion thereby preventing collateral damage. The advent of solid-state diode yellow laser allows us to treat closer to the fovea, is more eff ective for vascular structures and off ers a more uniform eff ect in patients with light or irregular fundus pigmentation. Newer retinal photocoagulation options along with their advantages is discussed in this review.