COMPARISON OF LASER PHOTOCOAGULATION FOR DIABETIC RETINOPATHY USING 532-NM STANDARD LASER VERSUS MULTISPOT PATTERN SCAN LASER

Laser Treatment for Diabetic Retinopathy: History, Mechanism, and Novel Technologies

Background: Diabetic retinopathy (DR), as a complication of diabetes mellitus (DM), remains a significant contributor to preventable vision impairment in the working-age population. Laser photocoagulation is essential in treating DR in conjunction with anti-vascular endothelial growth factor (VEGF) injection, steroids, and vitrectomy. This review summarizes the history of laser photocoagulation and highlights its current role and long-term effectiveness in real-world conditions. Methods: The National Clinical Trial (NCT), PubMed, Google Scholar, and China National Knowledge Infrastructure (CNKI) databases were searched utilizing combined or individual keywords, and a total of 121 articles were reviewed by the authors. Results: Several novel laser photocoagulation technologies, such as patterned scanning laser, subthreshold micropulse laser, navigated laser, multimodal imaging-guided laser, and retina rejuvenation therapy, substantially decrease the adverse effects and improve the accuracy and security of laser therapy. Numerous studies have demonstrated the outstanding clinical efficacy of combination therapies with pharmacologic treatments like anti-VEGF in treating DR and diabetic macular edema (DME). A 20-year follow-up retrospective study in our center preliminarily demonstrated the long-term effectiveness of conventional laser photocoagulation. Conclusions: More clinical trials are required to confirm the clinical effectiveness of novel laser technologies. Better treatment protocols for the combination therapy may be detailed. Anti-VEGF treatment has better effects, especially for DME and in a short period. But in real-world conditions, given the long-term effectiveness and economic advantages of conventional laser treatment, it should be prioritized over anti-VEGF injection in certain situations.

Recent advances in the treatment and delivery system of diabetic retinopathy

Diabetic retinopathy (DR) is a highly tissue-specific neurovascular complication of type 1 and type 2 diabetes mellitus and is among the leading causes of blindness worldwide. Pathophysiological changes in DR encompass neurodegeneration, inflammation, and oxidative stress. Current treatments for DR, including anti-vascular endothelial growth factor, steroids, laser photocoagulation, and vitrectomy have limitations and adverse reactions, necessitating the exploration of novel treatment strategies. This review aims to summarize the current pathophysiology, therapeutic approaches, and available drug-delivery methods for treating DR, and discuss their respective development potentials. Recent research indicates the efficacy of novel receptor inhibitors and agonists, such as aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, peroxisome proliferator-activated receptor alpha agonists, and novel drugs in delaying DR. Furthermore, with continuous advancements in nanotechnology, a new form of drug delivery has been developed that can address certain limitations of clinical drug therapy, such as low solubility and poor penetration. This review serves as a theoretical foundation for future research on DR treatment. While highlighting promising therapeutic targets, it underscores the need for continuous exploration to enhance our understanding of DR pathogenesis. The limitations of current treatments and the potential for future advancements emphasize the importance of ongoing research in this field.

Retinal Oxygenation With Conventional 100-ms Versus Short-Pulse Pan-Retinal Laser Photocoagulation

BACKGROUND AND OBJECTIVE

Conventional (100 ms) pan-retinal photocoagulation (PRP) laser burns are larger than short-pulse (10 ms to 20 ms) PRP burns. This study investigates the effect of PRP burns of different sizes on retinal oxygenation.

METHOD

A mathematical model using COMSOL Multiphysics 6 was used to create a three-dimensional abstraction of the coupled biology of the choroid, photoreceptor, and retinal tissues. Laser burn sizes were varied in the model, specifically considering burn diameters of 500 μm, 250 μm, and 125 μm, while keeping the total burn area constant.

RESULTS

Total increase in retinal oxygenation was the same for different burn sizes, but the oxygen distribution differed. Smaller burns resulted in a more even lateral oxygen distribution but with reduced penetration into the inner retina.

CONCLUSIONS

Conventional and short-pulse PRP may affect retinal oxygenation differently, even when total burn area is the same. Further investigation into optimum burn size and pattern is required. [Ophthalmic Surg Lasers Imaging Retina 2024;55:40-45.].

Quantitative Evaluation of Fundus Autofluorescence in Laser Photocoagulation Scars for Diabetic Retinopathy: Conventional vs. Short-Pulse Laser

Short-pulse laser is popular for its advantages like less pain. However, its effectiveness is still debated. The aim of this study was to compare fundus autofluorescence (FAF) luminosity changes of laser photocoagulation scars between the conventional laser (0.2 s) and the short-pulse laser (0.02 s) for diabetic retinopathy. Conventional and short-pulse laser photocoagulations were performed in six and seven eyes, respectively. FAF images were captured at 1, 3, 6, 12, and 18 months after the treatments. To evaluate FAF, individual gray-scale values of the laser scars adjacent to the retinal arcade vessels were recorded; then, the mean gray values of the scars were divided by the luminosity of arcade vein. The average luminosity ratio of laser scars at 1, 3, 6, 12, and 18 months were 1.51 ± 0.17, 1.26 ± 0.07, 1.21 ± 0.03, 0.95 ± 0.11, and 0.89 ± 0.05 with conventional laser and 1.91 ± 0.13, 1.50 ± 0.15, 1.26 ± 0.08, 1.18 ± 0.06, and 0.97 ± 0.04 with short-pulse laser, respectively. Findings suggest the short-pulse laser displayed delayed hypoautofluorescence progression. This implies potential postponement in post-irradiation atrophic changes, as well as metabolic amelioration delay in the ischemic retina, when compared to conventional laser treatment.

The Role of Laser Photocoagulation in Treating Diabetic Macular Edema in the Era of Intravitreal Drug Administration: A Descriptive Review

Background and Objectives: This study aimed to elucidate the role of laser photocoagulation therapy in the treatment of diabetic macular edema (DME) as an alternative to, or in conjunction with, the first-line treatment, anti-vascular endothelial growth factor (VEGF). Materials and Methods: A comprehensive literature search to identify studies that evaluated the efficacy of laser photocoagulation therapy in the management of DME was performed. The relevant findings of the efficacy of focal/grid laser therapy from data in randomized, controlled trials were synthesized, and the potential of new laser technologies, such as navigated laser systems, pattern scan lasers, and subthreshold lasers, was explored. The usefulness of multimodal imaging-guided laser therapy was also evaluated, with a focus on the potential contribution to anti-VEGF therapy. Results: Focal laser photocoagulation targeting microaneurysms remains an effective therapeutic approach to chronic refractory edema, despite the widespread use of anti-VEGF therapy. To achieve the best possible treatment outcomes, precise identification of microaneurysms is essential. This requires the use of multimodal imaging-guided, highly accurate, minimally invasive coagulation techniques. Subthreshold laser therapy can also reduce the frequency of anti-VEGF injections and minimize treatment burden. Conclusions: Further studies are needed to determine the optimal timing and settings for laser photocoagulation therapy and the potential of new laser technologies in the management of DME. Nevertheless, laser photocoagulation therapy plays an important role in the management of DME, in conjunction with anti-VEGF therapy.

Conventional and Pattern Scanning Pan-Retinal Photocoagulation Laser in Diabetic Patients' Visual Field

Introduction: In this study, we aimed to compare visual field defects in two different laser methods, namely conventional pan-retinal photocoagulation (PRP) and pattern scanning PRP, in patients with either proliferative diabetic or very severe non-proliferative diabetic retinopathy. Methods: This study was a randomized, single-blind, prospective clinical trial. Twenty patients with either proliferative or very severe non-proliferative diabetic retinopathy were enrolled in this study. Notably, only those patients with the same severity scores in both eyes were included. One eye underwent the conventional PRP laser and another eye underwent the pattern scanning PRP laser simultaneously. Swedish interactive threshold algorithms (SITA) standard perimetry was performed at baseline and one month after the treatment, and visual field defects were evaluated. Results: The pattern standard deviation (PSD) significantly increased in both the pattern and conventional PRP laser groups after one month. The change of the PSD at baseline and after the treatment was not significant between the groups. The mean deviation (MD) level significantly decreased in the conventional group after one month. The change in the MD level at baseline and after the treatment was not significant between the pattern and conventional groups. The change in the mean best corrected visual acuity (BCVA) between the groups was not significant. Conclusion: Changes in visual acuity and visual fields of the patients between the pattern and conventional PRP laser methods showed no significant difference; however, the pattern PRP method caused a smaller reduction in overall sensitivity in the patient's visual field.

Diabetic retinopathy with extensively large area of capillary non-perfusion: characteristics and treatment outcomes

Background

Capillary non-perfusion is an important characteristic for diabetic retinopathy (DR) indicating microvascular damage and ischemia. Data on the description and treatment outcomes of DR with large area of non-perfusion are lacking to date. We aim to describe the characteristics and treatment outcomes in a series of patients with DR who presented extensively large area of capillary non-perfusion (LACNP).

Methods

Fundus fluorescein angiograms from medical charts in patients diagnosed with DR between Jan 2017 and Dec 2019 were retrospectively reviewed. Clinical data in eyes with LACNP including imaging and laboratory findings at the first presentation were analyzed. The LACNP was defined as over 70% area of capillary non-perfusion throughout the whole image retina. The mean follow-up duration was 12.4 ± 16.7 months. Follow-up data including extensive pan-retinal photocoagulation and surgical intervention and treatment outcomes were evaluated.

Results

A total of 43 eyes in 24 patients with LACNP were included, accounting for 3.3% of DR populations in the same period. The overall percentage of non-perfusion area was 79.1 ± 8.1%. All patients received proper control of diabetes and hypertension, and extensive pan-retinal laser photocoagulation. During the follow-up periods, 20 eyes (46.5%) developed severe neovascular complications, of which 15 eyes (34.9%) underwent vitrectomy and/or anti-glaucoma surgeries. Conservative therapies including glycemic control and supplemental laser photocoagulation were conducted in 23 eyes (53.5%) without neovascular complications. In the final follow-up, best corrected visual acuity improved or maintained stable in 19 eyes (44.2%) while deteriorated in 24 eyes (55.8%).

Conclusions

The presence of LACNP is the hallmark of advanced DR and often indicates a poor visual outcome, although aggressive treatments may slow DR progression and maintain central vision for some time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02508-6.

Predictive factors associated with anatomical and functional outcomes following panretinal photocoagulation in people with proliferative diabetic retinopathy

PURPOSE

To determine effects of baseline characteristics and laser type performed on outcomes in people with proliferative diabetic retinopathy (PDR) undergoing panretinal photocoagulation (PRP).

METHODS

Medical records of all consecutive patients with PDR naïve to PRP, identified using an electronic database, evaluated at the Macula Clinic, Belfast Health and Social Care Trust, receiving their first PRP between 1st January 2016 and 30th June 2017, and followed for a minimum of 6 months following stabilization of PDR, were retrospectively reviewed. Outcomes included time to stabilization following PRP, progression of PDR, and mean change in best-corrected visual acuity from baseline to last follow-up. Cox regression was used to estimate hazard ratios (HRs) for the effect of baseline characteristics and type of laser on outcomes following treatment.

RESULTS

One hundred and fourteen patients (135 eyes) with a mean age of 57.6 (SD: 13.1) years were included, 67% males. People receiving pattern or mixed laser had a statistically significantly delayed stabilization (HR: 0.54, p=0.004; and HR: 0.41, p=0.001, respectively) and increased risk of progression (HR: 1.83, p=0.028; and HR: 2.04, p=0.018, respectively) when compared to those receiving standard laser. Among other potential predictors in multivariable regression analysis, only vitreous hemorrhage and fibrosis or traction at baseline increased risk of progression (HR: 1.70, p=0.017; and HR: 4.14, p<0.001 respectively). Baseline characteristics and type of laser had no statistically significant effect on vision.

CONCLUSION

These findings should be considered when selecting laser treatment, planning surveillance, and counselling patients with PDR undergoing PRP.

Steering light in fiber-optic medical devices: a patent review

INTRODUCTION

Steering light is relevant to many medical applications that require tissue illumination, sensing, or modification. To control the propagation direction of light beams, a great variety of innovative fiber-optic medical devices have been designed.

AREAS COVERED

This review provides a comprehensive overview of the patent literature on light beam control in fiber-optic medical devices. The Web of Science Derwent Innovation Index database was scanned, and 81 patents on fiber-optic devices published in the last 20 years (2001-2021) were retrieved and categorized based on the working principle to steer light (refraction/reflection, scattering, diffraction) and the design strategy that was employed (within fiber, at fiber end, outside fiber).

EXPERT OPINION

Patents describing medical devices were found for all categories, except for generating diffraction at the fiber end surface. The insight in the different designs reveals that there are still several opportunities to design innovative devices that can collect light at an angle off-axis, reduce the angular distribution of light, or split light into multiple beams.

Diabetic retinopathy: Looking forward to 2030

Diabetic retinopathy (DR) is the major ocular complication of diabetes mellitus, and is a problem with significant global health impact. Major advances in diagnostics, technology and treatment have already revolutionized how we manage DR in the early part of the 21^st century. For example, the accessibility of imaging with optical coherence tomography, and the development of anti-vascular endothelial growth factor (VEGF) treatment are just some of the landmark developments that have shaped the DR landscape over the last few decades. Yet, there are still more exciting advances being made. Looking forward to 2030, many of these ongoing developments are likely to further transform the field. First, epidemiologic projections show that the global burden of DR is not only increasing, but also shifting from high-income countries towards middle- and low-income areas. Second, better understanding of disease pathophysiology is placing greater emphasis on retinal neural dysfunction and non-vascular aspects of diabetic retinal disease. Third, a wealth of information is becoming available from newer imaging modalities such as widefield imaging systems and optical coherence tomography angiography. Fourth, artificial intelligence for screening, diagnosis and prognostication of DR will become increasingly accessible and important. Fifth, new pharmacologic agents targeting other non-VEGF-driven pathways, and novel therapeutic strategies such as gene therapy are being developed for DR. Finally, the classification system for diabetic retinal disease will need to be continually updated to keep pace with new developments. In this article, we discuss these major trends in DR that we expect to see in 2030 and beyond.

Pain Perception of Patients Undergoing Laser Panretinal Photocoagulation: Comparison of Single-Spot Versus Multispot Techniques

BACKGROUND AND OBJECTIVE

To compare pain intensity with single-spot versus multispot technique in laser panretinal photocoagulation, using a 532-nm, solid-state laser system.

MATERIALS AND METHODS

This was a prospective, interventional, randomized, single-masked comparison trial. Patients received two types of intervention: conventional single-spot technique, with an exposure time of 150 ms, and multispot technique, done with an exposure time of 20 ms, Both techniques used power sufficient to produce visible gray-white burns, and spot size of 20 μm. Participants received both treatments in the same eye, each one in one hemiretina, and were randomized to receive first single- or multispot technique and to the initial site of treatment. We assessed pain intensity using a numerical pain scale immediately after completion of each treatment.

RESULTS

A significantly lower pain scale was observed with the multispot when compared with the single-spot technique (coefficient [Coef]: -1.61; 95% CI, -2.49 to -0.74; P < .001), which was not affected by treatment order, the hemiretina treated, or treatment duration (P > .05). Among demographic characteristics, multiracial patients had a pain scale 1.25 greater than that of White patients (Coef: 1.25; 95% CI, 0.47 to 2.04; P = .002), but there is no effect of age or sex on the pain scale (P > .05). Regarding treatment duration, a shorter procedure was also observed in the multispot technique (Coef: -1.13; 95% CI, -1.43 to -0.82; P < .001), and it was not affected by order of treatment (P = .098), hemiretina (P = .327), pain (P = .141), or demographic data, such as age, sex, and race (P > .05).

CONCLUSION

The use of the multispot technique, with a short pulse duration (20 ms), is significantly less painful and less time-consuming for patients with proliferative retinopathy compared with the conventional single-spot technique using an exposure time of 150 ms. [Ophthalmic Surg Lasers Imaging Retina. 2022;53:40-45.].

Laser Therapy in the Treatment of Diabetic Retinopathy and Diabetic Macular Edema

PURPOSE OF REVIEW

This review highlights indications and evidence on laser therapy in the management of diabetic retinopathy and diabetic macular edema. Particular focus is placed upon the benefits and limitations of conventional laser photocoagulation versus more modern laser photocoagulation techniques, as well as the role of laser photocoagulation in treatment of diabetic retinopathy and diabetic macular edema with the frequent utilization of pharmacologic, including anti-vascular endothelial growth factor (VEGF), therapy.

RECENT FINDINGS

Laser photocoagulation remains the gold-standard therapy for the effective, definitive treatment of PDR, and also is highly effective in the management of DME. However, numerous recent studies have demonstrated the clinical efficacy and improved functional and anatomic outcomes of combination therapy with pharmacologic treatment. Continuing innovations in laser technology and improved understanding of laser-retinal interactions and pathophysiology demonstrate that laser therapy will continue to play a critical role in the treatment of diabetic retinopathy and diabetic macular edema for many years to come.

COMPARATIVE EVALUATION OF ANTERIOR SEGMENT OPTICAL COHERENCE TOMOGRAPHY, ULTRASOUND BIOMICROSCOPY, AND INTRAOCULAR PRESSURE CHANGES AFTER PANRETINAL PHOTOCOAGULATION BY PASCAL AND CONVENTIONAL LASER

PURPOSE

To compare intraocular pressure, anterior segment optical coherence tomography, and ultrasound biomicroscopy parameters over 3 months after panretinal photocoagulation (PRP) for proliferative diabetic retinopathy after 1 of 2 sittings by conventional laser (half PRP) and a single sitting of Pattern Scan Laser (PASCAL) PRP.

METHODS

This was a prospective, randomized, interventional study. All tests were performed at baseline, and at 1, 6, and 24 hours, and 1, 4, 8, and 12 weeks after PRP.

RESULTS

The intraocular pressure at 1 hour and 6 hours after PRP was significantly raised in both groups. Mean intraocular pressure was 21.17 ± 4.01 mmHg after PASCAL and 17.48 ± 3 mmHg after conventional laser at 1 hour, P < 0.001. On anterior segment optical coherence tomography, conventional laser PRP caused a more significant narrowing of angle-opening distance (AOD750) and trabecular-iris space area (TISA 500), P = 0.03 and 0.04, respectively, on Day 1. Ultrasound biomicroscopy showed a significantly narrow angle in both groups on Day 1. A significant increase in ciliary body thickness was observed in both groups, with 57.1% of PASCAL and 100% of conventionally treated eyes showing ciliary effusion on Day 1 that decreased but persisted for the next 3 months.

CONCLUSION

Performing PRP in sittings, prescribing previous glaucoma medications in patients at risk, and recording intraocular pressure an hour after the PRP could decrease complications.

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.

Changes of visual fields in treatment of proliferative diabetic retinopathy: a systematic review

The aim of this systematic review was to compare certain side-effects [visual fields (VF), dark adaptation, colour vision (CV) and contrast sensitivity (CS)] of conventional panretinal photocoagulation (PRP) with those of other treatments in proliferative diabetic retinopathy (PDR). A systematic literature search was conducted on 30 November 2018 in PubMed and Embase. The search comprised the keywords 'proliferative diabetic retinopathy', 'laser', 'treatment' and 'anti-vegf'. We included prospective studies and randomized controlled trials that investigated certain side-effects (VF, dark adaptation, CV, CS) in treatment of PDR (primary outcome). In total, 1867 articles were screened, and 10 studies were included (2176 eyes of 2086 patients examined in the VF studies and 1360 eyes of 1360 patients examined in the CV and CS studies). Visual fields (VF) were investigated in 10 studies, CV in one study and CS in one study. Treatment modalities included conventional PRP, other modalities of laser treatment and vascular endothelial growth factor (VEGF) inhibitors. Four studies demonstrated a worse VF impact of PRP than VEGF inhibitors. Seven studies reported of an overall worsening in VF after laser with no differences between different laser approaches. No differences were found in CV or CS. Overall, we found a trend, confirmed in four large studies, towards VEGF inhibitors causing less harm to VF compared to conventional PRP. Whilst VF was generally depressed after laser, it did not differ between different treatment approaches. Furthermore, it was not possible to make certain conclusions of CV or CS, with only one study in each field.

Choroidal Detachment Following Multi-spot Double Frequency Nd-YAG Retinal Photocoagulation - A Case Report

Introduction: Panretinal photocoagulation (PRP) remains the gold standard treatment for severe non-proliferative and proliferative diabetic retinopathy (PDR), as it reduces the risk of severe visual loss by more than 50%. In the conventional single-spot laser, the procedure involves the application of moderate-intensity burns of 200-500 microns, placed one spot-size apart to achieve a total of 1200-2000 applications in 2 or 3 sessions. The more advanced retina lasers like the Pattern Scan Laser (PASCAL) and the VITRA multi-spot laser are 532 nm frequency-doubled (Nd: YAG) solid-state lasers. These modern lasers enable the application of multiple laser burns in a rapid pre-determined sequence with reduced pulse duration (10-20 ms) to facilitate the PRP to be completed in a single sitting with lesser collateral tissue damage. Case Report: Though multi-spot lasers have significantly reduced the adverse events when compared with the conventional single-spot lasers, we report a case of rare adverse events (serous choroidal detachment) following PRP with the VITRA multi-spot double frequency NdYAG (532 nm) laser. Conclusion: Most of the serious choroidal detachments following PRP are self-limiting. We recommend complete retinal evaluation post laser procedure even with modern multisport laser to look for such adverse events.

Emerging drugs for the treatment of diabetic retinopathy

INTRODUCTION

Diabetic retinopathy (DR) is one of the main pathological features of the diabetes mellitus spectrum. It is estimated that in 2020 about 4 million people worldwide suffered from blindness or visual impairment caused by DR. Many patients cannot access treatment, mostly because of high costs, while others discontinue it prematurely due to the high number of intravitreal administrations required, or the occurrence of ocular complications, or discomfort in quality of life.

AREAS COVERED

The aims of this paper are to summarize the current understanding of the pathogenesis and treatment of diabetic retinopathy, focus on the most promising new approaches to treatment that are being evaluated in clinical trials, and outline the potential financial impact of new drugs in future markets.

EXPERT OPINION

Slow-release systems with steroids, anti-VEGF or sunitinib are promising. Oral imatinib would avoid the ocular complications of intravitreal drugs. Brolucizumab and abicipar pegol may be superior to aflibercept and ranibizumab with the advantage of less frequent administrations. Faricimab, active on Tie-2 receptors, is being evaluated in two phase 3 clinical trials. Further knowledge of the efficacy and safety of these drugs is necessary before their final approval for the treatment of diabetic retinopathy.

Changes in choroidal thickness in advanced diabetic retinopathy treated with pan-retinal photocoagulation using a pattern scanning laser versus a conventional laser

Background

To compare the effect of pan-retinal photocoagulation (PRP) using pattern scanning or conventional laser on subfoveal choroidal thickness (SFChT).

Methods

Thirty-eight patients (64 eyes) with advanced diabetic retinopathy (DR) who underwent PRP using pattern scanning or conventional laser were included. Changes in SFChT were compared with baseline values at 1, 3, 6, and 12 months after PRP using swept-source optical coherence tomography.

Results

The conventional laser group showed a statistically significant decrease in SFChT at 1, 3, 6, and 12 months after PRP (P < 0.001). SFChT was significantly decreased at 3 (P = 0.025), 6 (P = 0.004), and 12 (P < 0.001) months after treatment in the pattern laser group.

Conclusion

Eyes with advanced DR showed a significant reduction in SFChT over 12 months regardless of the type of laser used; however, the reduction was sooner after conventional laser than after pattern laser.

Comparison of pain experience and time required for pre-planned navigated peripheral laser versus conventional multispot laser in the treatment of diabetic retinopathy

PURPOSE

To compare the pain and the duration of a panretinal photocoagulation (PRP) session using a conventional multispot laser (Quantel Medical) versus the Navilas^® laser.

METHODS

Treatment-naïve patients requiring bilateral PRP for diabetic retinopathy were included. For each patient, PRP was carried out using a conventional multispot laser (Quantel Medical, 577 nm) in one eye and the other eye was treated with the Navilas laser (OD-OS, 577 nm). For both PRP treatments, similar parameters (same power, exposure time, number, size and spacing of the spots) were used. For each eye, the duration of the session and the pain, measured using respectively a chronometer and a visual analogic scale (VAS), were recorded.

RESULTS

Thirty-two eyes of sixteen patients (mean age 57 ± 13 SD, range 28-74), 11 men and 5 women, have been included. A mean of 1289 (1000-1500) spots with a mean power of 352 mW (300-450 mW) and an exposure time of 27 ms (20-30 ms) were delivered. The PRP session with the Navilas laser (mean time of 5.2 ± 0.8 min) was faster than with the conventional multispot laser (6.6 ± 1.1 min) (p = 0.02). Laser-induced pain was significantly reduced (VAS of 2.4 ± 1.6) using the Navilas laser compared to conventional laser (VAS: 7.1 ± 2) (p < 0.001).

CONCLUSION

The PRP sessions using the Navilas laser were significantly faster and less painful than with a conventional multispot laser in our series.

American Society of Retina Specialists Clinical Practice Guidelines on the Management of Nonproliferative and Proliferative Diabetic Retinopathy without Diabetic Macular Edema

Purpose

Nonproliferative (NPDR) and proliferative diabetic retinopathy (PDR) without diabetic macular edema (DME) affect millions of individuals living with diabetes throughout the world. There is increasing data on various management strategies for such patients, but there is limited consensus on how the data should be adopted into clinical practice.

Methods

This literature review and editorial presents and synthesizes the current evidence for various management paradigms for NPDR and PDR without DME.

Results

Retina specialists are an integral member of the diabetes management team, and should encourage patients on the importance of glycemic and cardiovascular optimization for both systemic and retinopathy risk factor reduction. The diabetic retinopathy severity scale (DRSS) is now an approvable endpoint for clinical trials in the United States, therefore becoming more clinically relevant. For PDR without DME, the Diabetic Retinopathy Study (DRS) and the Early Treatment Diabetic Retinopathy Study (ETDRS) established the standard of care with panretinal photocoagulation (PRP). Laser parameters have since evolved to include less intense and earlier intervention. Studies have recently demonstrated that anti-vascular endothelial growth factor (VEGF) treatment of PDR is effective at regressing neovascularization and improving DRSS levels in many patients. Further evidence is required to determine optimal treatment frequency, duration, and retreatment criteria, in the real world. There are concerns for adverse events in patients being lost to follow up during anti-VEGF treatment. For NPDR without DME, the standard of care has been a wait-and-watch approach. Data within the DRS and the ETDRS suggest that PRP for severe NPDR can be an option for select patients as well. Multiple clinical trials have now demonstrated that anti-VEGF treatment can improve the DRSS score in NPDR. Further studies are required to assess whether this positively affects long-term visual outcomes, and whether the benefits outweigh the risks in the real world for routine use.

Conclusions

There is cumulative evidence demonstrating the efficacy of various treatment options for NPDR and PDR without DME. Currently, patients would most likely benefit from thoughtful management strategies that are tailored to the individual patient.

Single session of pattern scanning laser versus multiple sessions of conventional laser for panretinal photocoagulation in diabetic retinopathy: Efficacy, safety and painfulness

Purpose

To evaluate the clinical efficiency, safety and painfulness of retinal laser photocoagulation employing a pattern scanning laser system Pascal given in a single-session versus conventional laser multiple-session treatment of the same patient with diabetic retinopathy during 12-month follow-up.

Methods

The cohort included 60 eyes in 30 patients treated at the Ophthalmology Clinic, Faculty Hospital Ostrava, from 2008 to 2013. Panretinal laser coagulation was performed on one eye using the multispot panretinal photocoagulation given in a single-session system Pascal (OptiMedica, Santa Clara, California). On the other eye laser treatment was carried out by the classic conventional multiple-session method.

Results

The performance of Pascal panretinal laser coagulation was evaluated as significantly less painful (visual scale of pain was 3.28 ± 1.9) than the performance of conventional photocoagulation (visual scale of pain was 3.93 ± 1.88) with similar efficiency. Distribution of progression of diabetic retinopathy in individual patients was very similar in both groups under comparison, and was strictly paired in 24 of the 30 patients at the end of 1-year follow-up.

Conclusion

Laser photocoagulation of the retina with the use of short impulse durations and patterns in patients with diabetic retinopathy given in one session possesses similar efficiency to that of conventional retinal photocoagulation in multiple sessions. The single session treatment is also better tolerated by patients and in addition to this, it shortens the performance of the whole therapy, which potentially saves considerable funds of all subjects participating in the process of treatment.

Trial registration

ClinicalTrials.gov NCT03672656.

The impact of spot size, spacing, pattern, duration and intensity of burns on the photocoagulation index in a geometric simulation of pan-retinal laser photocoagulation

PURPOSE

To evaluate the impact of spot size, spacing, pattern, duration and intensity of burns on the photocoagulation index, using a geometric simulation of pan-retinal laser photocoagulation.

METHODS

Simulations of full-scattered pan-retinal laser photocoagulation were performed on a retinal map, using a geometry-based method. Simulations consisted of 300-, 400- or 500-μm diameter equidistant spots on the retina with 1.0-spot width spacing, as well as 400-μm diameter spots on the retina in an equidistant pattern or grid pattern, with 1.0-, 0.75-, 0.50-, 0.25- or 0-spot width spacing. For each simulation, we calculated the ratio of the total photocoagulated retinal area to the whole retina, termed the photocoagulation index. We recalculated the photocoagulation indexes using the expansion ratios of photocoagulated lesions by different duration and intensity of burns from a previous study.

RESULTS

The photocoagulation indexes of the simulated pan-retinal laser photocoagulation with 300-, 400- and 500-μm diameter spots were 20.8%, 20.6% and 21.0%, respectively. The photocoagulation indexes of the 1.0-, 0.75-, 0.50-, 0.25- and 0-spot width spacing configurations of pan-retinal laser photocoagulation burns for the equidistant pattern were 20.6%, 27.1%, 36.7%, 53.2% and 83.1%, respectively, and those for the grid pattern were 17.9%, 23.5%, 31.8%, 46.1% and 72.0%, respectively. The photocoagulation indexes obtained with the equidistant and grid patterns changed (range, 1.7-84.7% and 1.5-73.4%, respectively) when the duration or burn intensity of the pan-retinal photocoagulation was changed.

CONCLUSION

This geometric simulation method could evaluate the impact of a range of conditions on the photocoagulation index.

Single-Session Low Duration Panretinal Photocoagulation Using Conventional Laser on Central Subfield Macular Thickness in Diabetic Retinopathy

Objective:

To compare the change in central subfield macular thickness following single-session and multiple-session laser panretinal photocoagulation in subjects with diabetic retinopathy.

Methods:

A single-center, randomized controlled trial study was performed on 28 eyes of 16 patients with severe non-proliferative diabetic retinopathy or proliferative diabetic retinopathy. Eyes were randomly assigned for treatment with panretinal photocoagulation performed either in single-session or multiple-session divided into three sessions during two-week period. Central subfield macular thickness was quantified using spectral domain optical coherence tomography and changes at four weeks follow-up were compared to the baseline measurement.

Result:

Mean baseline central subfield macular thickness of 12 eyes underwent single-session and 16 eyes underwent multiple-session panretinal photocoagulation were 342.91+109.51 micrometers and 354+171.79 micrometers (p> .05), respectively. Mean post laser central subfield macular thickness in the single-session group was 305.83+81.95 micrometers and 389.75+229.51 micrometers in the multiple-session group (p> .05). Mean central subfield macular thickness changes four weeks post laser was 37.08+94.21 micrometers for eyes treated with single-session and -35.75+123.62 micrometers for the multiple-session treated eyes (p= .101).

Conclusion:

There was no significant difference in change of central subfield macular thickness at four weeks post laser from treatment with single-session and multiple-session panretinal photocoagulation. Single-session panretinal photocoagulation can be used as effective multiple-session panretinal photocoagulation for the treatment of diabetic retinopathy.

PASCAL laser platform produces less pain responses compared to conventional laser system during the panretinal photocoagulation: a randomized clinical trial

Background

Most of patients experience pain during the panretinal photocoagulation(PRP). Laser photocoagulation delivery has advanced with the introduction of pattern-scanning laser systems (PASCAL). Shorter pulse duration and less choroidal penetration believed to reduce pain during the laser treatment.

Objectives

To compare the severity of expressed pain scores in patients with PDR who underwent PRP either with PASCAL laser or conventional laser.

Methods

A total of 28 patients with a diagnosis of PDR who were scheduled for bilateral PRP therapy were enrolled into the prospective study. Both eyes were treated within the same session and while one eye was treated with PASCAL the other was treated with conventional laser randomly. Pulse duration was adjusted to 100-ms in conventional laser and 30 ms in PASCAL. The severity of pain was graded using a verbal scale and a visual analog scale (VAS).

Results

Mean age was 61.36±9.10 years. Mean verbal and VAS scores were 1.32±0.47 and 2.86±1.21 in the PASCAL laser and 2.39±0.49 and 5.75±1.35 in the conventional laser group, respectively. Differences between expressed pain scores obtained by both two scales were statistically significant (p<0.001).

Conclusion

PASCAL laser significantly alleviates pain levels possibly due to the shorter laser pulse duration and lower intensity.

Comparison of 577-nm Multispot and Standard Single-Spot Photocoagulation for Diabetic Retinopathy

OBJECTIVE

To compare two different laser strategies of panretinal photocoagulation for diabetic retinopathy.

METHODS

Single-center, randomized study including 41 eyes treated with 577-nm multispot laser with a 20-ms pulse duration (group 1) or a 532-nm single-spot laser with a 100-ms pulse duration (group 2). The outcomes included best-corrected visual acuity (BCVA) and imaging changes at baseline, 6 and 12 months, laser parameters, and results of subjective pain analysis.

RESULTS

At 12 months, the treatments did not differ significantly in BCVA, central retinal thicknesses (CRTs), improved macular edema, vitreomacular interface changes, patient-reported pain scores, or angiographic responses. Group 1 had significantly fewer treatment sessions but used more laser spots (p < 0.001).

CONCLUSION

The multispot laser required fewer applications with more spots delivered to compensate for lower fluency, showing similar patient tolerance to single-spot laser. Both groups maintained the initial visual acuities and CRTs; about 50% of cases had vitreomacular interface changes and improved macular edema, with similar angiographic improvements after 12 months.

Clinical outcomes of patterned laser trabeculoplasty as adjuvant therapy in open angle glaucoma and ocular hypertension

AIM

To assess the efficacy and safety of patterned laser trabeculoplasty (PLT) as an adjunctive treatment in open angle glaucoma (OAG) or ocular hypertension (OHT) patients who were under antiglaucoma medical treatment.

METHODS

This study was a retrospective review of primary or secondary OAG patients and OHT patients with medically uncontrolled (≥18 mm Hg) intraocular pressure (IOP) who underwent 360° PLT from June 2016 to August 2016. Follow-up visits at week 1, and 1, 3 and 6mo were performed. IOP, best corrected visual acuity (BCVA), complications and eye drop glaucoma medication were recorded at each follow-up visit. Success was defined as IOP reduction ≥20% from baseline.

RESULTS

Forty-one eyes of 25 patients were included in this study. Pre-treatment mean IOP was 20.2±1.6 mm Hg. After PLT, IOP was 19.3±5.2, 16.1±2.7, 17.1±3.7 and 16.3±3.5 mm Hg, at 1wk, 1, 3 and 6mo, respectively. IOP reduction from baseline was statistically significant from the first month, remaining stable at 6mo (P<0.001). PLT success at 6mo of follow-up was 48.78%. The number of glaucoma medication per eye (P=0.10) and the mean BCVA both remained constant (P=0.37). Complications included transient IOP spikes in 4 eyes (9.8%) and peripheral anterior synechiae in 7 eyes (17.1%).

CONCLUSION

PLT is an effective and safe method for the management of patients with OHT or OAG as an adjunctive therapy. Additional larger studies should be designed to verify the long-term stability of IOP reduction with this laser technology.

Less Expansion of Short-Pulse Laser Scars in Panretinal Photocoagulation for Diabetic Retinopathy

Purpose

To compare the expansion rates of laser photocoagulation scars between the conventional laser and short-pulse laser using fundus autofluorescence (FAF).

Methods

Retrospective chart review. Conventional laser was performed on 6 eyes of 6 patients, and short-pulse laser was performed on 11 eyes of 8 patients with diabetic retinopathy. FAF images were obtained by Optos® 200Tx (Optos, Dunfermline, Scotland, UK) at 1, 3, 6, and 12 months after treatment. The average area of 20 photocoagulation scars was measured by using ImageJ software. The expansion rates were calculated from the proportion of the averaged area against the optic disc area. Regression of retinopathy and central macular thickness were also evaluated.

Results

The expansion rates of the conventional laser scars compared with the size at 1 month after treatment were 1.12 ± 0.08 (3 M), 1.27 ± 0.12 (6 M), and 1.39 ± 0.11 (12 M). The expansion rates of the short-pulse laser scars were 1.04 ± 0.05 (3 M), 1.09 ± 0.04 (6 M), and 1.13 ± 0.05 (12 M). The expansion rates of the short-pulse laser were significantly lower than those of the conventional laser (p < 0.01).

Conclusion

FAF images were useful to evaluate the changes in the photocoagulation scar sizes. The scars with the short-pulse laser showed lower expansion rates than those of the conventional laser.

Different lasers and techniques for proliferative diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) is a chronic progressive disease of the retinal microvasculature associated with prolonged hyperglycaemia. Proliferative DR (PDR) is a sight-threatening complication of DR and is characterised by the development of abnormal new vessels in the retina, optic nerve head or anterior segment of the eye. Argon laser photocoagulation has been the gold standard for the treatment of PDR for many years, using regimens evaluated by the Early Treatment of Diabetic Retinopathy Study (ETDRS). Over the years, there have been modifications of the technique and introduction of new laser technologies.

OBJECTIVES

To assess the effects of different types of laser, other than argon laser, and different laser protocols, other than those established by the ETDRS, for the treatment of PDR. We compared different wavelengths; power and pulse duration; pattern, number and location of burns versus standard argon laser undertaken as specified by the ETDRS.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 5); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov and the ICTRP. The date of the search was 8 June 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of pan-retinal photocoagulation (PRP) using standard argon laser for treatment of PDR compared with any other laser modality. We excluded studies of lasers that are not in common use, such as the xenon arc, ruby or Krypton laser.

DATA COLLECTION AND ANALYSIS

We followed Cochrane guidelines and graded the certainty of evidence using the GRADE approach.

MAIN RESULTS

We identified 11 studies from Europe (6), the USA (2), the Middle East (1) and Asia (2). Five studies compared different types of laser to argon: Nd:YAG (2 studies) or diode (3 studies). Other studies compared modifications to the standard argon laser PRP technique. The studies were poorly reported and we judged all to be at high risk of bias in at least one domain. The sample size varied from 20 to 270 eyes but the majority included 50 participants or fewer.Nd:YAG versus argon laser (2 studies): very low-certainty evidence on vision loss, vision gain, progression and regression of PDR, pain during laser treatment and adverse effects.Diode versus argon laser (3 studies): very-low certainty evidence on vision loss, vision gain, progression and regression of PDR and adverse effects; moderate-certainty evidence that diode laser was more painful (risk ratio (RR) troublesome pain during laser treatment (RR 3.12, 95% CI 2.16 to 4.51; eyes = 202; studies = 3; I² = 0%).0.5 second versus 0.1 second exposure (1 study): low-certainty evidence of lower chance of vision loss with 0.5 second compared with 0.1 second exposure but estimates were imprecise and compatible with no difference or an increased chance of vision loss (RR 0.42, 95% CI 0.08 to 2.04, 44 eyes, 1 RCT); low-certainty evidence that people treated with 0.5 second exposure were more likely to gain vision (RR 2.22, 95% CI 0.68 to 7.28, 44 eyes, 1 RCT) but again the estimates were imprecise . People given 0.5 second exposure were more likely to have regression of PDR compared with 0.1 second laser PRP again with imprecise estimate (RR 1.17, 95% CI 0.92 to 1.48, 32 eyes, 1 RCT). There was very low-certainty evidence on progression of PDR and adverse effects.'Light intensity' PRP versus classic PRP (1 study): vision loss or gain was not reported but the mean difference in logMAR acuity at 1 year was -0.09 logMAR (95% CI -0.22 to 0.04, 65 eyes, 1 RCT); and low-certainty evidence that fewer patients had pain during light PRP compared with classic PRP with an imprecise estimate compatible with increased or decreased pain (RR 0.23, 95% CI 0.03 to 1.93, 65 eyes, 1 RCT).'Mild scatter' (laser pattern limited to 400 to 600 laser burns in one sitting) PRP versus standard 'full' scatter PRP (1 study): very low-certainty evidence on vision and visual field loss. No information on adverse effects.'Central' (a more central PRP in addition to mid-peripheral PRP) versus 'peripheral' standard PRP (1 study): low-certainty evidence that people treated with central PRP were more likely to lose 15 or more letters of BCVA compared with peripheral laser PRP (RR 3.00, 95% CI 0.67 to 13.46, 50 eyes, 1 RCT); and less likely to gain 15 or more letters (RR 0.25, 95% CI 0.03 to 2.08) with imprecise estimates compatible with increased or decreased risk.'Centre sparing' PRP (argon laser distribution limited to 3 disc diameters from the upper temporal and lower margin of the fovea) versus standard 'full scatter' PRP (1 study): low-certainty evidence that people treated with 'centre sparing' PRP were less likely to lose 15 or more ETDRS letters of BCVA compared with 'full scatter' PRP (RR 0.67, 95% CI 0.30 to 1.50, 53 eyes). Low-certainty evidence of similar risk of regression of PDR between groups (RR 0.96, 95% CI 0.73 to 1.27, 53 eyes). Adverse events were not reported.'Extended targeted' PRP (to include the equator and any capillary non-perfusion areas between the vascular arcades) versus standard PRP (1 study): low-certainty evidence that people in the extended group had similar or slightly reduced chance of loss of 15 or more letters of BCVA compared with the standard PRP group (RR 0.94, 95% CI 0.70 to 1.28, 270 eyes). Low-certainty evidence that people in the extended group had a similar or slightly increased chance of regression of PDR compared with the standard PRP group (RR 1.11, 95% CI 0.95 to 1.31, 270 eyes). Very low-certainty information on adverse effects.

AUTHORS' CONCLUSIONS

Modern laser techniques and modalities have been developed to treat PDR. However there is limited evidence available with respect to the efficacy and safety of alternative laser systems or strategies compared with the standard argon laser as described in ETDRS.

Electroretinogram evaluation for the treatment of proliferative diabetic retinopathy by short-pulse pattern scanning laser panretinal photocoagulation

Panretinal photocoagulation (PRP) is a standard method for proliferative diabetic retinopathy (PDR) treatment. However, conventional PRP usually significantly damages the retinal structure and vision. Retinal pattern scanning laser (PASCAL) photocoagulation has emerged as a new technique with fewer complications for the treatment of retinal disorders. This study compares the therapeutic effects of short-pulse PASCAL to conventional single-spot PRP for PDR. Fifty-two PDR patients (104 eyes) were randomly assigned into a short-pulse PASCAL-PRP treatment (SP) group and a conventional PRP treatment (TP) group. The best corrected visual acuity (BCVA) and full-field flash electroretinogram (ERG) data were evaluated before and after the two treatments. The BCVA data between before and after the PRP treatments did not show any significant difference. After the PRP treatment, the b-wave amplitude (b-A) in the dark-adapted 3.0 ERG (p = 0.0005) and the amplitude in the light-adapted 3.0 flicker ERG (p = 0.009) were significantly higher in the SP group compared with that of the TP group. In addition, after the PRP treatment, the a-wave implicit time (a-T) of light-adapted 3.0 ERG prolonged significantly in the TP group compared to the SP group. Compared with the parameters before the treatments, the a-A and b-A under dark-adapted 3.0 ERG and the b-A under the light-adapted 3.0 ERG in both TP and SP groups after the treatments decreased significantly (p < 0.05). Short-pulse PASCAL-PRP significantly attenuated partial vision damage compared to conventional PRP, although it still caused limited retinal injury and mild reduction in retinal function. These findings suggest that short-pulse PASCAL-PRP is a promising technique for PDR treatment.

Patient Comfort with Yellow (577 nm) vs. Green (532 nm) Laser Panretinal Photocoagulation for Proliferative Diabetic Retinopathy

PURPOSE

Pain associated with panretinal photocoagulation (PRP) can adversely affect the number and quality of retinal burns delivered and subsequently increase the number of treatment sessions required to achieve regression of proliferative diabetic retinopathy (PDR). We assessed comfort in patients undergoing treatment with yellow (577 nm) vs. green (532 nm) PRP for PDR.

DESIGN

Prospective, single-center, randomized crossover clinical trial.

SUBJECTS

Patients with PDR with high-risk characteristics.

METHODS

Subjects were equally randomized to first receive PRP with a laser indirect ophthalmoscope with either green (IQ 532; IRIDEX, Mountain View, CA) or yellow (IQ 577; IRIDEX) laser, followed by additional treatment with the opposite laser using standardized settings in the superior hemisphere of a single treatment eye per patient. Topical anesthetic was used in all study eyes before each treatment and power was titrated until moderate grey-white retinal burns were achieved.

MAIN OUTCOME MEASURES

The primary outcome measure was patient's perceived pain as measured with a standardized 10-point pain scale. Secondary outcome measures included laser power, treatment time, number of treatment shots with each laser, and physician ease-of-use score with each laser on a 10-point scale.

RESULTS

Forty patients (40 eyes) with a mean age of 54.0 years were enrolled. Mean pain scores were similar when comparing treatment with yellow and green laser (3.1 ± 2.3 vs. 2.8 ± 2.6; P = 0.40). No significant difference was seen in visual acuity (P = 0.44) or central macular thickness (P = 0.39) 1 month after PRP. Additionally, there were no significant differences when comparing minimum power required (243.2 ± 74.2 vs. 234.0 ± 59.6 mW; P = 0.55), treatment time (5.1 ± 3.6 vs. 5.6 ± 3.9 minutes; P = 0.384), and number of treatment shots (257.6 ± 12.6 vs. 258.0 ± 2.3; P = 0.68). Six of 7 co-investigators (85%) preferred using yellow laser over green and reported ease-of-use scores of 9.0 ± 1.2 and 7.6 ± 1.4, respectively (P = 0.07). No severe adverse events occurred.

CONCLUSIONS

Patient comfort during PRP for PDR utilizing laser indirect ophthalmoscopy is similar for green and yellow wavelengths.

Evolution of Concepts and Technologies in Ophthalmic Laser Therapy

Ophthalmology was the first medical specialty to adopt lasers right after their invention more than 50 years ago, and they gradually revolutionized ocular imaging, diagnostics, therapy, and surgery. Challenging precision, safety, and selectivity requirements for ocular therapeutic and surgical procedures keep advancing the laser technologies, which in turn continue enabling novel applications for the preservation and restoration of sight. Modern lasers can provide single-cell-layer selectivity in therapy, submicrometer precision in three-dimensional image-guided surgery, and nondamaging retinal therapy under optoacoustic temperature control. This article reviews the evolution of laser technologies; progress in understanding of the laser-tissue interactions; and concepts, misconceptions, and accidental discoveries that led to modern therapeutic and surgical applications of lasers in ophthalmology. It begins with a brief historical overview, followed by a description of the laser-tissue interactions and corresponding ophthalmic applications.

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.

Early intraocular pressure change after peripheral iridotomy with ultralow fluence pattern scanning laser and Nd:YAG laser in primary angle-closure suspect: Kowloon East Pattern Scanning Laser Study Report No. 3

PURPOSE

Our purpose was to assess the early intraocular pressure (IOP) changes of ultralow fluence laser iridotomy using pattern scanning laser followed by neodymium:yttrium-aluminum-gamet (Nd:YAG) laser.

METHODS

This is a prospective interventional study. Thirty-three eyes of 33 adult Chinese primary angle-closure suspect subjects were recruited for prophylactic laser peripheral iridotomy. Sequential laser peripheral iridotomy was performed using pattern scanning laser followed by Nd:YAG laser. Visual acuity (VA) and IOP were measured before treatment, at 1 h, 1 day, 1 week, 1 month, 3 months and 6 months after laser. Laser energy used and complications were documented. Corneal endothelial cell count was examined at baseline and 6 months. Patency of the iridotomy was assessed at each follow-up visit.

RESULTS

All subjects achieved patent iridotomy in a single session. The mean energy used was 0.335+/-0.088 J for the pattern scanning laser, and 4.767+/-5.780 mJ for the Nd:YAG laser. The total mean energy was 0.339+/-0.089 J. None of the eyes developed a clinically significant IOP spike (≥ 8 mmHg) at 1 h and 1 day after laser use. Only four eyes developed higher IOP at 1 h and all were ≤3 mmHg compared to baseline. The mean IOP was 13.8+/-2.5 mmHg at 1 h and 11.5+/-2.2 mmHg at 1 day, both were significantly lower than baseline (15.8+/-2.1 mmHg) (P < 0.001). Mean VA (logMAR) was similar at 1 h post laser compared to baseline (0.23 vs 0.26). There was also no statistically significant difference in mean VA at other follow-up visits compared to baseline. Peripheral iridotomy closure was encountered in two (6.1%) eyes, one at 1 month and another at 6 months follow-up. There were no complications including hyphema, peripheral anterior synechia formation nor prolonged inflammation throughout the follow-up period. There was no significant loss in corneal endothelial cell counts at 6 months (2255+/-490) compared to baseline (2303+/-386) (P = 0.347).

CONCLUSIONS

Sequential LPI using an ultralow fluence pattern scanning laser, followed by a Nd:YAG laser, is safe and efficacious, and produces no IOP spike in dark irides of primary angle-closure suspects. Further studies to investigate its role in the treatment of other angle-closure conditions are warranted.

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.

Bullous Exudative Retinal Detachment after Retinal Pattern Scan Laser Photocoagulation in Diabetic Retinopathy

Laser retinal photocoagulation is the gold standard treatment for diabetic retinopathy. We describe 3 cases in which bullous exudative retinal detachment (ERD) developed after pattern scan laser photocoagulation (PASCAL) in diabetic retinopathy. ERD spontaneously resolved in all 3 cases with various visual courses. This case series highlights 2 key points: first, ERD can occur regardless of gender, age, glycemic control, or vitreous status and despite a moderate number of laser shots, even with PASCAL; second, ERD in nonvitrectomized eyes may cause irreversible visual loss, even if the ERD resolves within 1 month.

Effect of Topical Nepafenac on Central Foveal Thickness following Panretinal Photocoagulation in Diabetic Patients

Purpose

To evaluate effectiveness of topical nepafenac in reducing macular edema following panretinal photocoagulation (PRP).

Design

Prospective randomized double-blinded controlled study.

Methods

Sixty eyes of 60 patients having proliferative or severe nonproliferative diabetic retinopathy had PRP. Patients were then divided into two groups: nepafenac group (30 eyes) receiving 1% topical nepafenac eye drops for 6 months and control group (30 eyes) receiving carboxymethylcellulose eye drops for 6 months. Best-corrected visual acuity (BCVA) and macular optical coherence tomography were followed up at 1, 2, 4, and 6 months after PRP.

Results

BCVA was significantly better in nepafenac group than in control group at all follow-ups (P < 0.01). At 6 months post-PRP, logMAR BCVA was 0.11 ± 0.04 (equivalent to 20/26 Snellen acuity) in the nepafenac group and 0.18 ± 0.08 (equivalent to 20/30 Snellen acuity) in the control group (P < 0.01). Central foveal thickness (CFT) increased in both groups from the first month after PRP. Increase in CFT was higher in control group than in nepafenac group throughout follow-up, but the difference became statistically significant only after 4 months. No significant ocular adverse events were reported with topical nepafenac.

Conclusion

Topical nepafenac can minimize macular edema and stabilize visual acuity following PRP for diabetic patients.

Structural and functional changes to the retina and optic nerve following panretinal photocoagulation over a 2-year time period

PurposeTo evaluate long-term structural and functional changes to the retina and optic nerve following panretinal photocoagulation (PRP) in diabetic retinopathy (DR) patients.MethodsParticipants were patients with DR requiring PRP and control patients with DR not requiring PRP. The Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT) were performed to analyze the optic nerve and macula. Best-corrected visual acuity (BCVA) and visual field (VF) testing were done to measure central and peripheral vision. Wide-field fluorescein angiogram was performed to monitor the progression of diabetic ischemia. The primary outcome measure was to determine the degree of retinal and optic nerve changes before and after PRP.ResultsThere was a non-significant thickening of the macula and retinal nerve fiber layer at 6 months post laser that recovered by 24 months. Mean perfused ratio was significantly increased (P=0.02) at 12 and 24 months post laser. Independently grading patient stereophotographs, grader 1 indicated there was a non-significant increase in cup to disk ratio post laser, while grader 2 indicated a significant increase at 6 (P=0.04), 12 (P=0.02), and 24 months (P=0.005). There was a significant VF decrease (P≤0.02) at 12 and 24 months post laser with BCVA showing a non-significant trend of deteriorating results.ConclusionDespite an improvement in peripheral perfusion, there was a significant progressive decline of peripheral VF over the study period. Clinical grading of the optic nerve was more unreliable following PRP, despite the absence of significant morphological changes as detected by the OCT and HRT.

A Novel Method for Laser Suture Lysis Using Multispot Laser System

Although often uncomplicated, the current technique for laser suture lysis after filtration surgery requires patient cooperation and appropriate care taken by the surgeon. In cases with suboptimal cooperation, steadying the 50-µm laser aiming beam exactly over a thin 10-0 nylon suture, can be exhausting, difficult for both the patient and the surgeon; it may prove to be ineffective or even precipitate complications. We describe a novel method for laser suture lysis using a multispot laser system, which requires less patient cooperation and surgeon skills and yields excellent results.

Comparison of Efficacy and Side Effects of Multispot Lasers and Conventional Lasers for Diabetic Retinopathy Treatment

Panretinal photocoagulation (PRP) is a standard treatment for proliferative diabetic retinopathy. Conventional laser (CL) therapy is performed in one or more sessions in single spot mode. Visual disabilities have been reported after treatment with CL, including central vision loss due to macular edema and peripheral visual field loss resulting from extensive inner retinal scarring. Multispot laser (MSL) photocoagulation has recently been introduced to clinical practice. Studies comparing PRP conducted with MSL and CL have reported that MSLs resulted in less retinal tissue damage and pain, and greater patient comfort compared to CL. The aim of this review was to compare the efficacy and side effects of MSLs and CLs for diabetic retinopathy treatment.

A Computational Model of Peripheral Photocoagulation for the Prevention of Progressive Diabetic Capillary Occlusion

We developed a computational model of the propagation of retinal ischemia in diabetic retinopathy and analyzed the consequences of various patterns and sizes of burns in peripheral retinal photocoagulation. The model addresses retinal ischemia as a phenomenon of adverse local feedback in which once a capillary is occluded there is an elevated probability of occlusion of adjacent capillaries resulting in enlarging areas of retinal ischemia as is commonly seen clinically. Retinal burns of different sizes and patterns, treated as local oxygen sources, are predicted to have different effects on the propagation of retinal ischemia. The patterns of retinal burns are optimized with regard to minimization of the sum of the photocoagulated retina and computer predicted ischemic retina. Our simulations show that certain patterns of retinal burns are effective at preventing the spatial spread of ischemia by creating oxygenated boundaries across which the ischemia does not propagate. This model makes no statement about current PRP treatment of avascular peripheral retina and notes that the usual spot sizes used in PRP will not prevent ischemic propagation in still vascularized retinal areas. The model seems to show that a properly patterned laser treatment of still vascularized peripheral retina may be able to prevent or at least constrain the propagation of diabetic retinal ischemia in those retinal areas with intact capillaries.

Changes in pupil size following panretinal retinal photocoagulation: conventional laser vs pattern scan laser (PASCAL)

PurposeTo evaluate and compare the possible changes in pupil size subsequent to panretinal laser photocoagulation (PRP) via conventional laser and pattern scan laser (PASCAL).Patients and methodsForty eyes of 40 patients with diabetic retinopathy were included. 20 eyes had a PRP via conventional laser and formed Group 1. 20 eyes had a PRP via PASCAL laser and formed Group 2. The participants underwent standard ophthalmologic examination at baseline. Automated infrared pupillometry were performed at baseline and month 1.ResultsThe mean pupillary measurements (mm) for Group 1 (in the order photopic, mesopic, and scotopic conditions) were 2.88±0.34, 3.38±0.40, and 3.95±0.38, and changed to 3.64±0.42, 4.18±0.42, and 4.58±0.48, respectively. There was significant increase in pupil size at month 1 (P<0.001, P<0.001, and P<0.00, respectively). For Group 2, they were 2.90±0.38, 3.43±0.36, and 3.90±0.40, and changed to 3.18±0.42, 3.74±0.36, and 4.10±0.38, respectively. There was significant increase in pupil size at month 1 (P=0.018, P=0.014, and P=0.014, respectively). The pupil size increased significantly in both groups in all illumination conditions.ConclusıonWe have demonstrated via automated infrared pupillary measurements that PRP may significantly increase pupil size whether it is performed with conventional laser or PASCAL laser.

Pan-retinal photocoagulation and other forms of laser treatment and drug therapies for non-proliferative diabetic retinopathy: systematic review and economic evaluation

BACKGROUND

Diabetic retinopathy is an important cause of visual loss. Laser photocoagulation preserves vision in diabetic retinopathy but is currently used at the stage of proliferative diabetic retinopathy (PDR).

OBJECTIVES

The primary aim was to assess the clinical effectiveness and cost-effectiveness of pan-retinal photocoagulation (PRP) given at the non-proliferative stage of diabetic retinopathy (NPDR) compared with waiting until the high-risk PDR (HR-PDR) stage was reached. There have been recent advances in laser photocoagulation techniques, and in the use of laser treatments combined with anti-vascular endothelial growth factor (VEGF) drugs or injected steroids. Our secondary questions were: (1) If PRP were to be used in NPDR, which form of laser treatment should be used? and (2) Is adjuvant therapy with intravitreal drugs clinically effective and cost-effective in PRP?

ELIGIBILITY CRITERIA

Randomised controlled trials (RCTs) for efficacy but other designs also used.

DATA SOURCES

MEDLINE and EMBASE to February 2014, Web of Science.

REVIEW METHODS

Systematic review and economic modelling.

RESULTS

The Early Treatment Diabetic Retinopathy Study (ETDRS), published in 1991, was the only trial designed to determine the best time to initiate PRP. It randomised one eye of 3711 patients with mild-to-severe NPDR or early PDR to early photocoagulation, and the other to deferral of PRP until HR-PDR developed. The risk of severe visual loss after 5 years for eyes assigned to PRP for NPDR or early PDR compared with deferral of PRP was reduced by 23% (relative risk 0.77, 99% confidence interval 0.56 to 1.06). However, the ETDRS did not provide results separately for NPDR and early PDR. In economic modelling, the base case found that early PRP could be more effective and less costly than deferred PRP. Sensitivity analyses gave similar results, with early PRP continuing to dominate or having low incremental cost-effectiveness ratio. However, there are substantial uncertainties. For our secondary aims we found 12 trials of lasers in DR, with 982 patients in total, ranging from 40 to 150. Most were in PDR but five included some patients with severe NPDR. Three compared multi-spot pattern lasers against argon laser. RCTs comparing laser applied in a lighter manner (less-intensive burns) with conventional methods (more intense burns) reported little difference in efficacy but fewer adverse effects. One RCT suggested that selective laser treatment targeting only ischaemic areas was effective. Observational studies showed that the most important adverse effect of PRP was macular oedema (MO), which can cause visual impairment, usually temporary. Ten trials of laser and anti-VEGF or steroid drug combinations were consistent in reporting a reduction in risk of PRP-induced MO.

LIMITATION

The current evidence is insufficient to recommend PRP for severe NPDR.

CONCLUSIONS

There is, as yet, no convincing evidence that modern laser systems are more effective than the argon laser used in ETDRS, but they appear to have fewer adverse effects. We recommend a trial of PRP for severe NPDR and early PDR compared with deferring PRP till the HR-PDR stage. The trial would use modern laser technologies, and investigate the value adjuvant prophylactic anti-VEGF or steroid drugs.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005408.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Prediction of regression of retinal neovascularisation after panretinal photocoagulation for proliferative diabetic retinopathy

PURPOSE

The purpose of this study was to evaluate the regression of neovascularization elsewhere (NVE) after panretinal photocoagulation (PRP) based on its location in relation to the internal limiting membrane (ILM).

METHODS

Participants in this retrospective case series were 47 patients with active NVE within the vascular arcade. All patients were treated with PRP and followed up for at least 12 months. The time to regression of NVE based on its location relative to the ILM on spectral domain-optical coherence tomography (SD-OCT) was analyzed.

RESULTS

The proportion of eyes, showing regression of NVE at the end of follow-up period was 19/25 (76 %) in the "below ILM" group and 13/22 (59 %) in the "above ILM" group. The "below ILM" group was associated with a twofold enhanced regression of NVE in comparison to the "above ILM" group (HR = 2.13, p = 0.038).

CONCLUSIONS

Regression of NVE is determined by its location relative to the ILM. Patients with "below ILM" NVE were found to show a twofold increased regression rate in comparison with the "above ILM" group, while the proportion of eyes showing regression of NVE at the end of the follow-up period was significantly greater in the "below ILM" than the "above ILM" group.

Changes in Pupil Size Following Panretinal and Focal/Grid Retinal Photocoagulation: Automatic Infrared Pupillometry Study

PURPOSE

To evaluate possible changes in pupil size subsequent to panretinal and focal/grid laser photocoagulation.

METHODS

Sixty-four eyes of 64 participants were included. Thirty-two eyes with planned panretinal photocoagulation formed Group 1, and 32 eyes with planned focal retinal photocoagulation formed Group 2. The participants underwent full ophthalmologic examination at baseline. Automated infrared pupillometry was performed at baseline and month 1.

RESULTS

The mean pupillary measurements (in millimeters) for Group 1 (in order photopic, mesopic, scotopic) were 3.09 ± 0.69 mm, 3.66 ± 0.85 mm, and 3.87 ± 1.01 mm and changed to 3.34 ± 0.74 mm, 3.82 ± 0.92 mm, and 4.03 ± 1.02 mm. There was a significant increase in pupil size at month 1 (P = 0.001, P = 0.001, P = 0.003). For Group 2, they were 2.65 ± 0.87 mm, 3.08 ± 1.08 mm, and 3.18 ± 1.19 mm and changed to 2.92 ± 0.72 mm, 3.45 ± 0.76 mm, and 3.57 ± 0.88 mm. There was no significant difference in pupil size at month 1 (P = 0.151, P = 0.106, P = 0.095).

CONCLUSION

We have demonstrated through automated infrared pupillary measurements that panretinal laser photocoagulation may significantly influence pupil size and focal/grid laser photocoagulation may not.

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.