Modern retinal laser therapy

Subthreshold laser treatment in retinal diseases: a mini review

PURPOSE

To summarize the mechanism and the clinical applications of subthreshold laser (STL) in retinal practice. Subthreshold or "non-destructive" laser includes all types of laser treatments that produce minimal or no damage to the tissues and no visible signs after application.

METHODS

A descriptive review of articles from literature databases (PubMed, Medline, Embase, Cochrane, Web of Science) published before August 2023, which discuss current STL treatments of retinal diseases.

RESULTS

This review provides evidence for STL as a treatment option for central serous chorioretinopathy, diabetic retinopathy, age-related macular degeneration, macular edema due to retinal vein occlusion, and other maculopathies. In most published reports, STL has shown a therapeutic effect without damage to the underlying tissue.

CONCLUSION

Subthreshold laser treatment has shown safety and efficacy in the management of some retinal and macular diseases. Stimulation of the retinal pigment epithelium without destroying adjacent neuroretina has been shown to be sufficient in inducing retinal repair in many clinical cases. Recent research and clinical studies continue to explore the mechanisms and improving therapeutic benefits of this technology as well as extend the range of retinal disorders treatable by this modality.

Autonomous screening for laser photocoagulation in fundus images using deep learning

BACKGROUND

Diabetic retinopathy (DR) is a leading cause of blindness in adults worldwide. Artificial intelligence (AI) with autonomous deep learning algorithms has been increasingly used in retinal image analysis, particularly for the screening of referrable DR. An established treatment for proliferative DR is panretinal or focal laser photocoagulation. Training autonomous models to discern laser patterns can be important in disease management and follow-up.

METHODS

A deep learning model was trained for laser treatment detection using the EyePACs dataset. Data was randomly assigned, by participant, into development (n=18 945) and validation (n=2105) sets. Analysis was conducted at the single image, eye, and patient levels. The model was then used to filter input for three independent AI models for retinal indications; changes in model efficacy were measured using area under the receiver operating characteristic curve (AUC) and mean absolute error (MAE).

RESULTS

On the task of laser photocoagulation detection: AUCs of 0.981, 0.95, and 0.979 were achieved at the patient, image, and eye levels, respectively. When analysing independent models, efficacy was shown to improve across the board after filtering. Diabetic macular oedema detection on images with artefacts was AUC 0.932 vs AUC 0.955 on those without. Participant sex detection on images with artefacts was AUC 0.872 vs AUC 0.922 on those without. Participant age detection on images with artefacts was MAE 5.33 vs MAE 3.81 on those without.

CONCLUSION

The proposed model for laser treatment detection achieved high performance on all analysis metrics and has been demonstrated to positively affect the efficacy of different AI models, suggesting that laser detection can generally improve AI-powered applications for fundus images.

Insights Into Visual Rehabilitation: Pan-Retinal Photocoagulation for Proliferative Diabetic Retinopathy

This review comprehensively explores pan-retinal photocoagulation (PRP) as a pivotal intervention in visually rehabilitating individuals afflicted with proliferative diabetic retinopathy (PDR). The review begins by elucidating the significance of PDR within the spectrum of diabetic retinopathy (DR), emphasizing the progressive nature of the disease and the consequential impact on visual health. A detailed analysis of PRP follows, encompassing its definition, purpose, and historical development, shedding light on the procedural intricacies and mechanisms of action. The postoperative care and follow-up section underscores the necessity of vigilant monitoring for complications, visual recovery, and the importance of regular ophthalmic check-ups. The subsequent discussion delves into patient education and counseling, stressing the need to manage expectations, encourage lifestyle modifications, and highlight the significance of follow-up appointments. The review concludes with insights into future directions, including advancements in laser technology and emerging therapies, offering a glimpse into the evolving landscape of DR management. By addressing ongoing challenges and embracing innovative approaches, this review provides a comprehensive guide for clinicians, researchers, and healthcare practitioners who visually rehabilitate individuals struggling with PDR.

Vision protection therapy for prevention of neovascular age-related macular degeneration

To access the effect of vision protection therapy on neovascular conversion in age-related macular degeneration (AMD). Patient unidentified data aggregated by Vestrum Health, LLC (VH) from over 320 US retina specialists was analyzed to compare the conversion rate from dry to neovascular (wet) AMD in a practice employing VPT (VPT group) compared to those employing standard care alone (SCA group) between January 2017 through July 2023. 500,00 eyes were filtered then matched for neovascular conversion risk factors by propensity scoring and compared in a 10/1 ratio of 7370 SCA and 737 VPT treated eyes. SCA eyes had significantly fewer clinical encounters and shorter follow up than the VPT group. Despite this, the risk of neovascular conversion by PS was significantly lower in the VPT group compared to SCA (HR 5.73, p < 0.0001). Analysis matching the encounter frequency of both groups as a post-randomization variable produced a similar HR (HR 5.98, p < 0.0001). Because 9% of eyes in the VPT group were not treated with VPT due to bilateral early (low-risk) AMD, analysis comparing the SCA group to VPT-treated eyes was done that also showed significantly lower conversion rates in the VPT-treated eyes, with or without encounter frequency matching (HR 5.84, 5.65, p < 0.0001). Visual acuity was consistently better in VPT eyes compared to SCA eyes throughout the study time window. The advantage of VPT over SCA increased with increased SCA encounter frequency and higher conversion risk factors, including age and ICD10 coded dry AMD severity. Neovascular (wet) AMD is the main cause of irreversible visual loss worldwide. Consistent with two prior studies, the current study finds Vision Protection Therapy markedly more effective at both recognizing and preventing neovascular AMD than the current standard of care, benefiting the highest risk dry AMD eyes the most.

Micropulse Laser Therapy as an Integral Part of Eye Disease Management

Ocular diseases can significantly impact vision and quality of life through pathophysiological alterations to the structure of the eye. The management of these conditions often involves a combination of pharmaceutical interventions, surgical procedures, and laser therapy. Laser technology has revolutionized many medical fields, including ophthalmology, offering precise and targeted treatment options that solve some of the unmet needs of other therapeutic strategies. Conventional laser techniques, while effective, can generate excessive thermal energy, leading to collateral tissue damage and potential side effects. Compared to conventional laser techniques, micropulse laser therapy delivers laser energy in a pulsed manner, minimizing collateral damage while effectively treating target tissues. The present paper highlights the advantages of micropulse laser therapy over conventional laser treatments, presents the implications of applying these strategies to some of the most prevalent ocular diseases, and highlights several types and mechanisms of micropulse lasers. Although micropulse laser therapy shows great potential in the management of ocular diseases, further research is needed to optimize treatment protocols, evaluate long-term efficacy, and explore its role in combination therapies.

TRPV4 channels promote vascular permeability in retinal vascular disease

This study aimed to determine the role of transient receptor potential vanilloid 4 (TRPV4), a calcium (Ca²⁺)-permeable cation channel, in the pathophysiology of retinal vascular disease. The retinal vein occlusion (RVO) murine model was created by irradiating retinal veins using lasers. TRPV4 expression and localization were evaluated in RVO mice retinas. In addition, we examined the effects of TRPV4 antagonists (RQ-00317310, HC-067047, GSK2193874, and GSK2798745) on retinal edema, blood flow, and ischemic areas in RVO mice. Furthermore, changes in the retinal expression of tumor necrosis factor (TNF)-α and aquaporin4 (AQP4) by RQ-00317310 were analyzed using Western blot. We also assessed the barrier integrity of epithelial cell monolayers using trans-endothelial electrical resistance (TEER) in Human Retinal Microvascular Endothelial Cells (HRMECs). The expression of TRPV4 was significantly increased and co-localized with glutamine synthetase (GS), a Müller glial marker, in the ganglion cell layer (GCL) of the RVO mice. Moreover, RQ-00317310 administration ameliorated the development of retinal edema and ischemia in RVO mice. In addition, the up regulation of TNF-α and down-regulation of AQP4 were lessened by the treatment with RQ-00317310. Treatment with GSK1016790A, a TRPV4 agonist, increased vascular permeability, while RQ-00317310 treatment decreased vascular endothelial growth factor (VEGF)- or TRPV4-induced retinal vascular hyperpermeability in HRMECs. These findings suggest that TRPV4 plays a role in the development of retinal edema and ischemia. Thus, TRPV4 could be a new therapeutic target against the pathological symptoms of retinal vascular diseases.

Development of a Computer System for Automatically Generating a Laser Photocoagulation Plan to Improve the Retinal Coagulation Quality in the Treatment of Diabetic Retinopathy

In this article, the development of a computer system for high-tech medical uses in ophthalmology is proposed. An overview of the main methods and algorithms that formed the basis of the coagulation plan planning system is presented. The system provides the formation of a more effective plan for laser coagulation in comparison with the use of existing coagulation techniques. An analysis of monopulse- and pattern-based laser coagulation techniques in the treatment of diabetic retinopathy has shown that modern treatment methods do not provide the required efficacy of medical laser coagulation procedures, as the laser energy is nonuniformly distributed across the pigment epithelium and may exert an excessive effect on parts of the retina and anatomical elements. The analysis has shown that the efficacy of retinal laser coagulation for the treatment of diabetic retinopathy is determined by the relative position of coagulates and parameters of laser exposure. In the course of the development of the computer system proposed herein, main stages of processing diagnostic data were identified. They are as follows: the allocation of the laser exposure zone, the evaluation of laser pulse parameters that would be safe for the fundus, mapping a coagulation plan in the laser exposure zone, followed by the analysis of the generated plan for predicting the therapeutic effect. In the course of the study, it was found that the developed algorithms for placing coagulates in the area of laser exposure provide a more uniform distribution of laser energy across the pigment epithelium when compared to monopulse- and pattern-based laser coagulation techniques.

Advances in targeted retinal photocoagulation in the treatment of diabetic retinopathy

AIM

Targeted retinal photocoagulation (TRP) is an emerging laser technology for retinal targeted therapy. TRP can specifically act on unperfused retinal capillaries and retinal intermediate ischemic areas, reduce damage to tissue perfusion areas and panretinal photocoagulation (PRP) complications or adverse events. In this regard, this review discusses the treatment options, efficacy, and latest progress of TRP for diabetic retinopathy (DR) based on randomized controlled trial (RCT), meta-analysis, case review, and other existing studies.

METHODS

In-depth research was conducted on articles about the proposal and development of TRP, its simple application in DR, and combined therapy. In order to review the new progress, application methods, effects, and prospects of TRP in the treatment of DR, the articles related to TRP in the databases of PubMed and Web Of Science since this century were comprehensively analyzed.

RESULTS

TRP is effective in treating DR and may become a substitute for PRP in the future. In addition, the treatment regimen of TRP combined with intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) drugs can also be used as a new therapeutic approach to expand the treatment regimen for the treatment of DR, and this combination therapy also has effects on other retinal vascular diseases.

CONCLUSIONS

With the advancement of technology, TRP has been continuously applied in clinical practice, and its potential benefits have opened up broad prospects for the treatment of DR. The combination therapy of TRP and anti-VEGF is expected to become a new option for patients with DR an retinal diseases.

Real World Data Comparison of Standard Care vs SDM Laser Vision Protection Therapy for Prevention of Neovascular AMD

Purpose

To access the impact of regular periodic subthreshold diode micropulse laser (SDM) as Vision Protection Therapy on the rate of neovascular conversion of dry age-related macular degeneration (AMD).

Methods

Patient unidentified clinical data aggregated by Vestrum Health, LLC (VH) from 300 retina specialists across the United States was analyzed to examine the effect of a program of regular periodic panmacular low-intensity/high-density subthreshold diode micropulse laser as vision protection therapy (VPT) compared to standard care alone, on the incidence of neovascular conversion in patients with dry age-related macular degeneration (AMD), between January 4, 2016, and September 30, 2020, producing 392,250 eyes for study.

Results

After applying inclusion and exclusion criteria, eyes were matched by propensity scoring for key risk factors. This produced 830 eyes managed by standard care plus VPT, performed on average every 108 days per eye; and 8300 eyes managed with standard care alone (SCA) in a 1/10 ratio for comparison. Comparison found that VPT eyes had a markedly lower rate of neovascular conversion than SCA eyes (hazard ratio 13.04) overall, and for each propensity score matched quintile. VA worsened over time in the SCA group but improved in the VPT group.

Conclusion

Our findings suggest that, compared to standard care alone, VPT may markedly reduce the rate of neovascular conversion in AMD, the main cause of irreversible visual loss worldwide.

Application of Artificial Intelligence in Ophthalmology for the Diagnosis and Treatment of Eye Diseases

In this paper, we present the main aspects of artificial intelligence application in ophthalmology for the diagnosis and treatment of eye diseases on the example of developing a computer system for personalizing retinal laser photocoagulation. Approaches to the automation of eye disease prediction and treatment based on fundus images are described. Four problems of applying the neural network approach are highlighted. Decision support information technology for personalizing laser treatment of diabetic macular edema and identifying prognostic factors of surgical outcome using methods of intellectual analysis of large unstructured data is described. The system allows the doctor to form a plan of optimal coagulation arrangement for retinal laser coagulation for each case, to predict the quality of laser coagulation depending on the initial data on the localization and severity of edema and to improve his skills by comparing the result of coagulation performed and the coagulation plan proposed by the system.

Polymyositis and dermatomyositis: ocular manifestations and potential sight-threatening complications

Dermatomyositis (DM) and polymyositis (PM) are idiopathic inflammatory myopathies characterized by progressive, symmetric, mainly proximal muscle weakness. DM is also characterized by cutaneous involvement. However, other clinical features, systemic involvement, histopathological findings, response to treatment, and prognosis, differ significantly. Although uncommon, ocular manifestations in DM and PM may potentially affect any structure within the eye. Notwithstanding being generally mild, ocular involvement in DM and PM may result in significant morbidity. Left untreated, significant retinal inflammation associated with hemorrhage and detachment may occur, leading to significant vision loss. This review aims to present an up-to-date overview for rheumatologists about the ocular involvement and potential complications of DM and PM and when to refer to the ophthalmologist to avoid sight-threatening complications.

Optical dosimeter for selective retinal therapy based on multi-port fiber-optic interferometry

Selective retinal therapy (SRT) employs a micro-second short-pulse lasers to induce localized destruction of the targeted retinal structures with a pulse duration and power aimed at minimal damage to other healthy retinal cells. SRT has demonstrated a great promise in the treatment of retinal diseases, but pulse energy thresholds for effective SRT procedures should be determined precisely and in real time, as the thresholds could vary with disease status and patients. In this study, we present the use of a multi-port fiber-based interferometer (MFI) for highly sensitive real-time SRT monitoring. We exploit distinct phase differences among the fiber ports in the MFI to quantitatively measure localized fluctuations of complex-valued information during the SRT procedure. We evaluate several metrics that can be computed from the full complex-valued information and demonstrate that the complex contour integration is highly sensitive and most correlative to pulse energies, acoustic outputs, and cell deaths. The validity of our method was demonstrated on excised porcine retinas, with a sensitivity and specificity of 0.92 and 0.88, respectively, as compared with the results from a cell viability assay.

Modeling of Fundus Laser Exposure for Estimating Safe Laser Coagulation Parameters in the Treatment of Diabetic Retinopathy

A personalized medical approach can make diabetic retinopathy treatment more effective. To select effective methods of treatment, deep analysis and diagnostic data of a patient’s fundus are required. For this purpose, flat optical coherence tomography images are used to restore the three-dimensional structure of the fundus. Heat propagation through this structure is simulated via numerical methods. The article proposes algorithms for smooth segmentation of the retina for 3D model reconstruction and mathematical modeling of laser exposure while considering various parameters. The experiment was based on a two-fold improvement in the number of intervals and the calculation of the root mean square deviation between the modeled temperature values and the corresponding coordinates shown for the convergence of the integro-interpolation method (balance method). By doubling the number of intervals for a specific spatial or temporal coordinate, a decrease in the root mean square deviation takes place between the simulated temperature values by a factor of 1.7–5.9. This modeling allows us to estimate the basic parameters required for the actual practice of diabetic retinopathy treatment while optimizing for efficiency and safety. Mathematical modeling is used to estimate retina heating caused by the spread of heat from the vascular layer, where the temperature rose to 45 °C in 0.2 ms. It was identified that the formation of two coagulates is possible when they are located at least 180 μm from each other. Moreover, the distance can be reduced to 160 μm with a 15 ms delay between imaging.

Effect of 532 nm argon laser pan retinal photocoagulation on corneal thickness and corneal endothelial cell parameters among proliferative diabetic retinopathy patients

Background

Laser photocoagulation has been the mainstay treatment for diabetic retinopathy (DR). However, the applied laser light must pass through multiple ocular structures such as the cornea to reach the retina, potentially causing thermal injury to non-target tissues. The purpose of this study was to examine the effects of 532 nm Argon laser pan-retinal photocoagulation (PRP) on corneal thickness and corneal endothelial cell parameters by comparing central corneal thickness (CCT), endothelial cell density (ECD), and endothelial cell area coefficient of variation (CoV) before and after PRP for proliferative diabetic retinopathy (PDR). The effect of laser PRP on these corneal parameters may help in adapting treatment protocols to reduce corneal damage and thereby improve patient outcome.

Methods

This was a prospective cohort study involving newly diagnosed PDR patients. All patients underwent specular microscopy examination (CCT, ECD and endothelial cell area CoV) both pre-PRP and at 1-week and 6-weeks after the final PRP session (post-PRP). A Carl Zeiss Visulas Argon laser (532 nm) was used to perform PRP.

Results

A total of 33 newly diagnosed PDR patients were included in this study. There were no significant differences in mean CCT, ECD, and endothelial cell area CoV at 1-week and 6-weeks following PRP compared to pre-treatment baseline (p > 0.05). Further, there were no significant correlations between laser energy delivered and CCT, ECD and endothelial cell area CoV at either post-PRP examination time.

Conclusion

Argon laser (523 nm) energy delivered within recommended ranges for PRP had no adverse effects on corneal structure.

Comparison of Pain Scores Among Patients Undergoing Conventional and Novel Panretinal Photocoagulation for Diabetic Retinopathy: A Systematic Review

PURPOSE

To summarize key findings from a systematic review focusing on pain as an adverse outcome of panretinal photocoagulation (PRP) among patients with diabetic retinopathy.

DESIGN

Systematic review.

METHODS

We systematically searched articles in major databases from July to September 2020. Studies that compared pain outcomes of PRP among diabetic patients who underwent conventional single-spot laser (SSL), conventional multi-spot laser (MSL), and/or novel navigated laser (NNL) were included. The Cochrane RoB 2 tool and ROBINS-I tool were used to evaluate the risk of bias of the included randomized controlled trials (RCTs) and controlled clinical trials (CCTs), respectively.

RESULTS

We included 13 RCTs and 4 CCTs. Thirteen studies were included for Comparison 1 (Conventional SSL versus Conventional MSL), 3 studies were included for Comparison 2 (NNL versus Conventional MSL), and 3 studies were included for Comparison 3 (NNL versus Conventional SSL). A total of 783 patients and 1961 eyes were included in this review. The review showed that NNL yielded the lowest pain scores, followed by conventional MSL, then by conventional SSL.

CONCLUSION

This review summarizes findings of multiple studies that reported pain as an adverse outcome of PRP among patients with advanced diabetic retinopathy. Data from RCTs with mostly some concerns for bias (RoB 2 tool) and CCTs with mostly moderate risk of bias (ROBINS-I tool) show benefit of using MSL over SSL, and NNL over conventional systems for PRP in diabetic retinopathy, considering pain as the primary outcome.

Dual-Acting Antiangiogenic Gene Therapy Reduces Inflammation and Regresses Neovascularization in Diabetic Mouse Retina

Intravitreal injections of anti-vascular endothelial growth factor drugs have become the gold standard treatment for diabetic retinopathy (DR). However, several patients are classified as non-responders or poor responders to treatment. Therefore, it is essential to study alternative target molecules. We have previously shown that the progression of DR in the Ins2^Akita mouse reflects the imbalance between pro- and anti-angiogenic molecules found in the human retina. We report, for the first time, the therapeutic potential of a dual-acting antiangiogenic non-viral gene therapy. We have used an expressing vector encoding both the pigment epithelium-derived factor gene and a short hairpin RNA (shRNA) targeted to the placental growth factor to restore the balance between these factors in the retina. Twenty-one days after a single subretinal injection, we observed a marked decrease in the inflammatory response in the neural retina and in the retinal pigment epithelium, together with reduced vascular retinal permeability in the treated diabetic mouse. These results were accompanied by the restoration of the retinal capillary network and regression of neovascularization, with significant improvement of DR hallmarks. Concomitant with the favorable therapeutic effects, this approach did not affect retinal ganglion cells. Hence our results provide evidence toward the use of this approach in DR treatment.

Safety and efficacy of the use of navigated retinal laser as a method of laser retinopexy in the treatment of symptomatic retinal tears

PURPOSE

To investigate the safety and efficacy of the use of navigated retinal laser as a delivery method of laser retinopexy in the treatment of symptomatic retinal tears.

METHODS

We conducted a retrospective observational study of 69 patients presenting to a district general hospital in the United Kingdom with a diagnosis of symptomatic retinal tear who underwent retinopexy using a navigated retinal laser (Navilas 577s). Patients were followed up at two weeks or later to assess the efficacy and safety of the use of navigated retinal laser for retinopexy treatment.

RESULTS

In total, 72 retinal tears in 69 patients were identified in our cohort. Of these cases, 70 (97.2%) retinal tears were treated with retinopexy using a navigated laser with a median treatment time 200 seconds. Two retinal tears could not be imaged on the navigated laser system and so underwent cryopexy. In 67/70 (95.7%) of retinal tears, one session of laser treatment using the navigated laser system was sufficient for primary management. The remaining three tears required a second session. No retinal tears treated with navigated laser treatment progressed to retinal detachment. There were no other complications seen with the use of this laser.

CONCLUSIONS

The use of navigated retinal laser as a method of laser retinopexy for the treatment of retinal tears shows comparable safety and efficacy with other studies using traditional retinal laser systems.

Comparison of Subthreshold 577 and 810 nm Micropulse Laser Effects on Heat-Shock Protein Activation Kinetics: Implications for Treatment Efficacy and Safety

Purpose

To compare the safety and efficacy of 810 versus 577 nm laser wavelengths for micropulse subthreshold (sublethal) laser treatment by mathematical analysis.

Methods

Two different representative laser parameter sets for micropulsed subthreshold diode laser treatment, one employing 810 nm and the other 577 nm, are compared with regard to efficacy by analysis of the kinetics of laser-induced heat-shock protein (HSP) activation; and for safety, by scaling law analysis.

Results

Kinetics analysis of laser-induced HSP activation shows that the primary therapeutic effect of laser is thermal incitement of a long-term wavelength-independent increase in the rate of HSP-mediated protein repair specific to sick and dysfunctional cells, rather than from short-term increases in free intracellular HSP concentrations. Scaling law analysis of the same 810 and 577 nm laser parameters, however, finds treatment safety highly wavelength-sensitive, favoring 810 over 577 nm.

Conclusions

Mathematical analyses of the effects retinal laser-induced HSP activation provide important insights into the mechanism of action and the importance of wavelength selection in modern retinal laser therapy. Our analyses find 810 and 577 nm to be equally effective, but 810 nm having a significantly wider therapeutic range/safety margin, and thus less likely to cause inadvertent, and thus unpredictable, laser-induced retinal damage, than 577 nm.

Translational Relevance

Mathematical analysis of enzyme reaction kinetics provides important insights into the mechanism of action and clinical implications of wavelength selection in modern retinal laser therapy.

19th EURETINA Congress Keynote Lecture: Diabetic Retinopathy Today

In the last decades, significant changes have been taking place regarding the pathogenesis of diabetic retinopathy (DR) and the complex mechanisms that eventually lead to the various manifestations of the disease, including diabetic macular edema (DME). DR was first considered a pure microvascular disease, due to the evident capillary structural changes (microaneurysms), fluid extravasation, and lipid exudation. With the advent of fundus fluorescein angiography, the concept of ischemia and the correlation between peripheral nonperfusion and neovascularization has been introduced, which was eventually followed by the advent of new therapeutic strategies, such as peripheral photocoagulation. Nowadays, thanks to more advanced imaging techniques, namely optical coherence tomography (OCT), OCT angiography, and wide-field imaging (imaging up to 200° of the retina in a single shot), it became clear that other elements participate in the occurrence of DR and DME, including inflammation and neurodegeneration. In the future, integration of standard investigations with new diagnostic devices would allow the prompt recognition of DR even before clinical signs of the disease are ophthalmoscopically evident, and the development of personalized treatment for both retinopathy and DME will be available.

Comparison of navigated laser and conventional single-spot laser system for induced pain during panretinal photocoagulation

To compare the panretinal photocoagulation (PRP)-induced pain response between novel navigated laser (Navilas) and conventional single-spot laser. The eyes were randomly assigned to Navilas or conventional laser. Contralateral eyes underwent PRP with the other system with 30 min resting interval. Pulse duration was 100 ms in conventional laser and 30 ms or 100 ms in Navilas and power setting was enough to create gray-white light burn on both devices. Pain response was evaluated by verbal scale (VS) (0-4) and visual analog scale (VAS) (0-10) after each PRP application. The mean age of 70 patients (140 eyes) was 62.52 ± 9.49 years. Mean power and spot numbers for Navilas and conventional laser were 291.9 ± 85.3 mW vs 368.4 ± 72.0 mW, and 375.4 ± 108.4 vs 374.2 ± 105.0 (p < 0.001 and p = 0.53, respectively). Pain scores for Navilas and conventional laser were 1.19 ± 0.73 and 1.99 ± 0.84 for VS and 2.41 ± 1.65 and 4.74 ± 2.17 for VAS (p < 0.001 and p < 0.001). More comfortable PRP is achieved with Navilas system in comparison with conventional single-spot laser system. However, small number of patients treated with same pulse duration and different contact lenses used for two systems should be taken into consideration. Besides, we did not report comparative clinical efficiency of either laser system.

Bevacizumab versus ziv-aflibercept in branch retinal vein occlusion

Purpose:

To compare the effectiveness of treatment with intravitreal bevacizumab (IVB) and ziv-aflibercept (IVZ) in patients with macular edema (ME) post-branch retinal vein occlusion (BRVO).

Methods:

Patients with treatment naïve ME post-BRVO were included retrospectively if they received either IVB (0.05 ml/1.25 mg) or IVZ (0.05 ml/1.25 mg) monotherapy with a follow up of 12 months.

Results:

Thirty-two and 17 eyes received IVB and IVZ, respectively. The mean improvement in best corrected visual acuity (BCVA) was 0.36 ± 0.3 logarithm of minimum angle of resolution (logMAR) in the IVB group and 0.27 ± 0.3 in the IVZ group (P = 0.35). The mean change in central macular thickness was 178.9 ± 180.9 and 173.5 ± 344.4 μm in IVB and IVZ groups, respectively (P = 0.94). The mean number of injections was higher in the IVB group (4.0 ± 1.8) compared with 1.82 ± 0.8 in the IVZ group (P < 0.0001). The IVZ group had significantly fewer number of visits (P < 0.0001) and longer maximum treatment-free intervals (P = 0.0081).

Conclusion:

IVZ appears to be cost-effective with the similar visual outcome and less number of visits in comparison to IVB.

Safety and efficacy of 532 nm frequency-doubled Nd-YAG green laser photocoagulation for treatment of retinopathy of prematurity

Purpose

To evaluate the safety and efficacy of 532 nm frequency-doubled Nd-YAG green laser for treatment of retinopathy of prematurity (ROP).

Methods

This retrospective interventional case series included infants undergoing treatment for ROP with 532 nm green laser between January 2012 and March 2017 at a single tertiary-care referral center. Review of clinical records was done to identify baseline ROP characteristics, procedural difficulties, complications related to the laser procedure and outcome of treatment at ≥ 1 year of follow-up.

Results

There are about 347 eyes of 182 infants were included in this present study. ROP presented in zone I in 76 eyes (21.9%) and zone II in 271 eyes (78.1%). Tunica vasculosa lentis (TVL) was present in 43.8% and pre-existing vitreous hemorrhage in 4.6% of the eyes. 532 nm green laser could be performed as a primary procedure in all eyes, including those with TVL. 322 eyes completed a minimum follow up of 1 year with a mean follow up of 22.8 months (range, 12-54 months). At the last follow-up visit, 298 (92.5%) of the 322 eyes had a favorable outcome. On logistic regression analysis, pre-existing fibrovascular proliferation (p = 0.04) and new-onset fibrovascular proliferation after treatment (p = 0.001) were the most significant independent predictors of poor outcome. Complications encountered were new-onset hemorrhage in 36 eyes (11.2%), anterior segment ischemia in two eyes (0.006%) and cataract in one eye (0.003%).

Conclusion

532 nm frequency-doubled Nd-YAG green laser appears to be safe and effective in the treatment of ROP.

En-Face Optical Coherence Tomography Angiography for Longitudinal Monitoring of Retinal Injury

A customized Optical Coherence Tomography Angiography (OCTA) algorithm and Orthogonal OCT (en-face and B-Scans) were used for longitudinal assessment of retina murine vascular and tissue remodeling comparing photoreceptor ablation and laser-induced Choroidal Neovascularization (CNV). In the mouse model, we utilized a combined OCTA/OCT technique to image and quantify morphological and vascular features of laser lesions over time. This approach enabled us to monitor and correlate the dynamics of retina vascular and tissue remodeling as evidenced by swelling, edema, and scarring. From the OCT B-Scans, three stages of inflammatory progression were identified: the early response occurring within hours to day 3, the transition phase from 3-7 days, and the late stage of 7-21 days entering either the resolving phase or chronic phase, respectively. For the case of CNV, en-face OCTA revealed a transient non-perfusion of inner retina capillaries, specifically Deep Vascular Plexus (DVP), which corresponded to growth in lesions of a height of 200 μm or greater. Non-perfusion first occurred at 24 hours, persisted during edema and CNV formation days 7-14. In contrast, the acute inflammation induced photoreceptor damage, but no detectable alterations to the microvasculature were observed. We demonstrated that the en-face OCTA system is capable of visualizing capillary networks (~5 μm) and the corresponding tissue remodeling and growth dynamics allowing for separating acute injury from CNV. For the first time, by using OCTA we observed the presence of the 5-10 μm capillary non-perfusion present in DVP as part of CNV formation and the associated wound healing in the retina.

Retinal cell regeneration using tissue engineered polymeric scaffolds

Degenerative retinal diseases, such as age-related macular degeneration (AMD), can lead to permanent sight loss. Although intravitreal anti-vascular endothelial growth factor (VEGF) and steroid injections are effective for the management of early stages of wet and/or neovascular AMD (nAMD), no proven treatments currently exist for dry AMD or for the advanced geographic atrophy of the retina that follows. Tissue engineering (TE) has recently emerged as a promising alternative to repair retinal damaged and restore its functions. Here, we review recent advances in TE, with a particular emphasis on retinal regeneration. We provide an overview of retinal diseases, followed by a comprehensive review of TE techniques, cells, and polymers used in the fabrication of scaffolds for retinal cell regenerations, in particular the retinal pigment epithelium (RPE).

Novel stem cell and gene therapy in diabetic retinopathy, age related macular degeneration, and retinitis pigmentosa

Degenerative retinal disease leads to significant visual morbidity worldwide. Diabetic retinopathy and macular degeneration are leading causes of blindness in the developed world. While current therapies for these diseases slow disease progression, stem cell and gene therapy may also reverse the effects of these, and other, degenerative retinal conditions. Novel therapies being investigated include the use of various types of stem cells in the regeneration of atrophic or damaged retinal tissue, the prolonged administration of neurotrophic factors and/or drug delivery, immunomodulation, as well as the replacement of mutant genes, and immunomodulation through viral vector delivery. This review will update the reader on aspects of stem cell and gene therapy in diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa and other less common inherited retinal dystrophies. These therapies include the use of adeno-associated viral vector-based therapies for treatment of various types of retinitis pigmentosa and dry age-related macular degeneration. Other potential therapies reviewed include the use of mesenchymal stem cells in local immunomodulation, and the use of stem cells in generating structures like three-dimensional retinal sheets for transplantation into degenerative retinas. Finally, aspects of stem cell and gene therapy in diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, and other less common inherited retinal dystrophies will be reviewed.

Selective laser trabeculoplasty vs micropulse laser trabeculoplasty in open-angle glaucoma

Aim

The aim of this study was to prospectively compare the efficacy, safety, and tolerability of selective laser trabeculoplasty (SLT) vs micropulse laser trabeculoplasty (MLT) in reducing intraocular pressure (IOP) in open-angle glaucoma patients.

Patients and methods

In all, 38 patients were randomized to 360° MLT and 31 patients were randomized to 360° SLT. IOP was measured at intervals of 1 hour and 1, 1–6, 6–12, 6–24, 24–36, and 36–52 weeks. Patients completed a survey 1 week after the procedure. Patients with end-stage, neovascular, uveitic, or angle-closure glaucoma were excluded. Treatment response was defined as an IOP reduction of ≥20.0% or ≥3 mmHg from baseline.

Results

IOP was lowered to ≥3 mmHg from baseline among 37.0% of the micropulse patients and 36.0% of patients in the selective laser group at 24–52 weeks. Similarly, 29.6% of the micropulse patients and 36.0% of the selective laser patients experienced a 20.0% IOP decrease from baseline during the 24–52-week interval (P=0.77). Both groups revealed similar reductions in IOP as absolute values and percentage decreases from baseline at all intervals up to 52 weeks post treatment. There were more treatment failures in the micropulse group up to 52 weeks post laser treatment; however, this was not statistically significant. The micropulse group reported less pain both during and after the procedure (P=0.005).

Conclusion

Micropulse trabeculoplasty has demonstrated similar efficacy to SLT over a 52-week follow-up period with less discomfort experienced both during and after the procedure.

Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

Selective treatment of the retinal pigment epithelium (RPE) by using short-pulse lasers leads to a less destructive treatment for certain retinal diseases in contrast to conventional photocoagulation. The introduction of selective retina therapy (SRT) to clinical routine is still precluded by the challenges to reliably monitor treatment success and to automatically adjust dose within the locally varying therapeutic window. Combining micrometer-scale depth resolving capabilities of optical coherence tomography (OCT) with SRT can yield real-time information on the laser-induced changes within the RPE after a laser pulse or even during treatment with a laser pulse train. In the present study, SRT and OCT were combined to treat ex-vivo porcine eyes demonstrating closed-loop dose-control. We found a reliable correlation of specific signal changes in time resolved OCT images and physiological lesions in the RPE. First experiments, including 23 porcine eyes, prove the feasibility of the novel treatment concept.

Subthreshold microsecond laser for proliferative diabetic retinopathy: a randomized pilot study

Aim

To compare the outcomes of subthreshold microsecond (STM) and continuous-wave laser (CWL) panretinal photocoagulation (PRP).

Methods

In this randomized, prospective, pilot study, 20 eyes of 10 subjects with symmetric severe non-proliferative (NPDR) or low-risk proliferative diabetic retinopathy (PDR) were included. Each eye of the subject was randomized into either CWL or STM PRP group. Patients were evaluated at baseline and at months 3, 6, and 9 with color fundus photographs and visual field tests at each visit; however, electroretinography (ERG) was conducted at baseline and at month 9. The primary outcome measure was the difference in disease progression between the groups. Secondary outcome measures included change in visual acuity, contrast visual acuity, retinal sensitivity on visual field test, and change in ERG parameters.

Results

During the 9-month follow-up, one eye of the STM group progressed to vitreous hemorrhage at the month 6 follow-up and required rescue conventional laser. The CWL group showed a drop in low-contrast visual acuity, visual field index, and scotopic b/a ratio in comparison to the STM group, although the difference was statistically insignificant (p>0.05).

Conclusion

This prospective pilot study proposes microsecond PRP is non-inferior to CWL PRP and could be an alternative to CWL PRP to avoid associated complications in cases of severe NPDR and early PDR.

Advances in Retinal Laser Therapy

Since the 1960s, laser therapies have played a critical role in the treatment of numerous retinal diseases. Significant advances have been made in laser technology and the molecular understanding of laser-tissue interactions over the past 55 years to maximize the therapeutic effect while minimizing side-effects. While pharmacologic therapies (e.g., anti-vascular endothelial growth factor or anti-VEGF) are playing a larger role, laser therapy remains an important treatment modality for proliferative diabetic retinopathy (PDR), diabetic macular edema (DME), sickle cell retinopathy, retinal vein occlusions, central serous chorioretinopathy, tumors, polypoidal choroidal vasculopathy, and retinal tears. With the development new laser technologies such as selective retinal therapy, subthreshold micropulse laser, nanosecond laser, photomediated ultrasound therapy, and navigated laser, the risk of adverse events has been significantly reduced. This review summarizes the latest developments in retinal laser therapy.

Panretinal Photocoagulation: A Review of Complications

Panretinal photocoagulation (PRP) is a mainstay of therapy for retinal ischemic disease. The procedure involves creating thermal burns in the peripheral retina leading to tissue coagulation, the overall consequence of which is improved retinal oxygenation. While highly effective, there have been concerns historically regarding the anatomic effects and visual complications following PRP, the most common of which include choroidal effusions, exudative retinal detachments, macular edema, visual field deficits, and night vision defects. The occurrence of these complications is closely tied to laser parameters such as increased duration and power and intensive treatment in a single sitting, all of which cause increased dispersion of thermal energy within the retina and choroid. The advent of newer laser delivery systems, such as the multispot pattern laser, has greatly mitigated but not eliminated these issues. The following article reviews the most common complications following PRP treatment, including reported occurrences, inciting factors, and underlying pathophysiology.

Potentiating angiogenesis arrest in vivo via laser irradiation of peptide functionalised gold nanoparticles

BACKGROUND

Anti-angiogenic therapy has great potential for cancer therapy with several FDA approved formulations but there are considerable side effects upon the normal blood vessels that decrease the potential application of such therapeutics. Chicken chorioallantoic membrane (CAM) has been used as a model to study angiogenesis in vivo. Using a CAM model, it had been previously shown that spherical gold nanoparticles functionalised with an anti-angiogenic peptide can humper neo-angiogenesis.

RESULTS

Our results show that gold nanoparticles conjugated with an anti-angiogenic peptide can be combined with visible laser irradiation to enhance angiogenesis arrest in vivo. We show that a green laser coupled to gold nanoparticles can achieve high localized temperatures able to precisely cauterize blood vessels. This combined therapy acts via VEGFR pathway inhibition, leading to a fourfold reduction in FLT-1 expression.

CONCLUSIONS

The proposed phototherapy extends the use of visible lasers in clinics, combining it with chemotherapy to potentiate cancer treatment. This approach allows the reduction of dose of anti-angiogenic peptide, thus reducing possible side effects, while destroying blood vessels supply critical for tumour progression.

Photothermal enhancement of chemotherapy in breast cancer by visible irradiation of Gold Nanoparticles

Photothermal Therapy (PTT) impact in cancer therapy has been increasing due to the enhanced photothermal capabilities of a new generation of nanoscale photothermal agents. Among these nanoscale agents, gold nanoshells and nanorods have demonstrated optimal properties for translation of near infra-red radiation into heat at the site of interest. However, smaller spherical gold nanoparticles (AuNPs) are easier to produce, less toxic and show improved photoconversion capability that may profit from the irradiation in the visible via standard surgical green lasers. Here we show the efficient light-to-heat conversion of spherical 14 nm AuNPs irradiated in the visible region (at the surface plasmons resonance peak) and its application to selectively obliterate cancer cells. Using breast cancer as model, we show a synergistic interaction between heat (photoconversion at 530 nm) and cytotoxic action by doxorubicin with clear advantages to those of the individual therapy approaches.

A Review of Subthreshold Micropulse Laser and Recent Advances in Retinal Laser Technology

The role of retinal photocoagulation as a first line therapy for various retinal pathologies has decreased with the introduction of anti-vascular endothelial growth factor therapy. However, retinal laser therapy remains an important treatment modality, especially with the emergence of micropulse subthreshold treatment and the integration of newer technology such as augmented reality and semi-automated delivery. This review summarizes current evidence for micropulse laser as a treatment modality and discusses the role of new technology such as augmented reality in the future of laser therapy.

Multi-Modal Longitudinal Evaluation of Subthreshold Laser Lesions in Human Retina, Including Scanning Laser Ophthalmoscope-Adaptive Optics Imaging

BACKGROUND AND OBJECTIVE

Subthreshold retinal laser therapy is efficacious for a variety of retinovascular disorders. Currently, it is unknown which laser parameters can ensure no detectable damage to human retina tissue.

MATERIALS AND METHODS

One informed physician participant with a normal retina was treated with three levels (75%, 50%, and 25%) of subthreshold 577-nm laser (PASCAL; Topcon, Santa Clara, CA) at 20-millisecond (ms) duration and 100 µm spot size. Several high-resolution retinal imaging modalities, including spectral-domain optical coherence tomography (SD-OCT) and scanning laser ophthalmoscope-adaptive optics (SLO-AO), were used to longitudinally image retinal laser lesions during a 9-month period.

RESULTS

SLO-AO and SD-OCT imaging of subthreshold laser therapy in human retina showed no cone cell or RPE damage at all time points during a 9-month period using the 25% threshold power 577-nm laser in the human retina.

CONCLUSION

It is likely that subthreshold laser therapy with 577-nm laser at 20-ms duration in the human retina is safe at the 25% of threshold power level.

Argon Laser Photoablation for Treating Benign Pigmented Conjunctival Nevi

PURPOSE

To evaluate the outcomes of argon laser photoablation of benign conjunctival pigmented nevi with different clinical presentations.

PATIENTS AND METHODS

This interventional case series was conducted between July 2014 and January 2015. Patients presenting with benign conjunctival nevi were included. Data were collected on the clinical features at presentation, argon laser photoablation, and follow-up at 8 and 24 weeks. Postoperative photography allowed recording of the success of each case and the overall success rate. Complete removal of conjunctival pigments was considered an absolute success. Partial pigmentation requiring repeat laser treatment was considered a qualified success.

RESULTS

There were 14 eyes (four right eyes and ten left eyes) with benign pigmented conjunctival nevi. There were three males and eight females in the study sample. The median age was 36 (25% percentile: 26 years). Three patients had bilateral lesions. The nevi were located temporally in nine eyes, nasally in three eyes, and on the inferior bulbar conjunctiva in two eyes. The mean horizontal and vertical diameters of nevi were 5 ± 2 mm and 4 ± 2.7 mm, respectively. The mean follow-up period was 5 months. Following laser treatment, no eyes had subconjunctival hemorrhage, infection, scarring, neovascularization, recurrence, or corneal damage. The absolute success rate of laser ablation was 79%. Three eyes with elevated nevi had one to three sessions of laser ablation resulting in a qualified success rate of 100%.

CONCLUSIONS

Argon laser ablation was a safe and effective treatment for the treatment of selective benign pigmented conjunctival nevi in Arab patients.

Short-pulse duration retinal lasers: a review

The development of lasers for biological use was an important medical advance in the 20th century with numerous evidence-based therapeutic applications to retinal disease, including capillary leakage at the macula. Although the role of photocoagulative laser in the treatment of macular oedema has diminished, there is evidence for a modified role in clinical management, particularly for extrafoveal leakage. Additionally, it may reduce the frequency of required intravitreal injections and assist in visual stabilization when used as an adjunct. The tissue destructive effect of photocoagulative lasers has motivated the development of safer macular lasers and the search for novel therapeutic applications, including treatment of drusen and regeneration of dysfunctional retinal pigment epithelium.

Novel strategies for the treatment of diabetic macular edema

Macular edema such as diabetic macular edema (DME) and diabetic retinopathy are devastating back-of-the-eye retinal diseases leading to loss of vision. This area is receiving considerable medical attention. Posterior ocular diseases are challenging to treat due to complex ocular physiology and barrier properties. Major ocular barriers are static (corneal epithelium, corneal stroma, and blood-aqueous barrier) and dynamic barriers (blood-retinal barrier, conjunctival blood flow, lymph flow, and tear drainage). Moreover, metabolic barriers impede posterior ocular drug delivery and treatment. To overcome such barriers and treat back-of-the-eye diseases, several strategies have been recently developed which include vitreal drainage, laser photocoagulation and treatment with biologics and/or small molecule drugs. In this article, we have provided an overview of several emerging novel strategies including nanotechnology based drug delivery approach for posterior ocular drug delivery and treatment with an emphasis on DME.

Determination of pulse profile characteristics of multi spot retinal photocoagulation lasers

A system is described for determination of discrete pulse train characteristics of multi spot laser delivery systems for retinal photocoagulation. While photodiodes provide an ideal detection mechanism, measurement artifacts can potentially be introduced by the spatial pattern of the delivered beam relative to a discrete photodiode element. This problem was overcome by use of an integrating sphere to produce a uniform light field at the site of the photodiode detector. A basic current driven photodiode detection circuit incorporating an operational amplifier was used to generate a signal captured by a commercially available USB interface device at a rate of 10 kHz. Studies were undertaken of a Topcon Pascal Streamline laser system with output at a wavelength of 577 nm (yellow). This laser features the proprietary feature of 'Endpoint Management' ™ where pulses can be delivered as 100% of set energy levels with visible reaction on the retina and also at a reduced energy level to create potentially non visible but clinically effective lesions. Using the pulse train measurement device it was identified that the 'Endpoint Management' ™ delivery mode of pulses of lower energy was achieved by reducing the pulse duration of pulses for non-visible effect pulses while maintaining consistent beam power levels within the delivered pulse profile. The effect of eye geometry in determining safety and effectiveness of multi spot laser delivery for retinal photocoagulation is discussed.