Evolution of retinal laser therapy: minimum intensity photocoagulation (MIP). Can the laser heal the retina without harming it?

Advancements in Imaging and Therapeutic Options for Dry Age-Related Macular Degeneration and Geographic Atrophy

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly, with dry AMD (d-AMD) leading to geographic atrophy (GA) and significant visual impairment. Multimodal imaging plays a crucial role in d-AMD diagnosis and management, allowing for detailed classification of patient phenotypes and aiding in treatment planning and prognosis determination. Treatment approaches for d-AMD have recently witnessed profound change with the development of specific drugs targeting the complement cascade, with the first anticomplement agents recently approved for GA treatment. Additionally, emerging strategies such as gene therapy and laser treatments may offer potential benefits, though further research is needed to fully establish their efficacy. However, the lack of effective therapies capable of restoring damaged retinal cells remains a major challenge. In the future, genetic treatments aimed at preventing the progression of d-AMD may emerge as a powerful approach. Currently, however, their development is still in the early stages.

Efficacy of anti-VEGF monotherapy versus anti-VEGF therapy with subthreshold micropulse laser (SML) in the management of diabetic macular oedema (DMO): a systematic review and meta-analysis

BACKGROUND

Intravitreal injection anti-vascular endothelial growth factor (IVI anti-VEGF) therapy serves as the primary treatment for centre involving diabetic macular oedema (DMO). Conventional laser therapy (CLT) adjunct has proven beneficial; however, it is not widely used due to significant risks of retinal scarring. Subthreshold micropulse laser (SML) therapy has, however, emerged as a comparable alternative to combination therapy, offering a distinct advantage by mitigating the risk of retinal scarring.

METHODS

A search of six databases was conducted. A meta-analysis of mean differences was performed including subgroup analyses where appropriate. Primary outcome was the number of injections at 12-14 months; secondary outcomes were changes in central macular thickness (CMT) and best corrected visual acuity (BCVA) at 6-8 months and 12-14 months.

RESULTS

A total of ten papers including six randomised clinical trials and four retrospective clinical studies were included in our study, capturing 563 eyes of 478 patients. Overall, the risk of bias was moderate for these studies. Significantly fewer anti-VEGF therapy injections were administered in the combination therapy versus anti-VEGF monotherapy patients at 12-14 months who had poor visual acuity (6/18 Snellen or worse) at baseline, mean difference - 2.25 (95% CI; - 3.35, - 1.15; p < 0.05). Combination therapy was not associated with significantly fewer intravitreal injections in patients with a higher visual acuity (6/15 Snellen or better) at baseline. Our analysis also showed significant improvements to both BCVA and CMT were reached at 6 - 8 month post-baseline at the 95% confidence intervals: - 1.13 (- 2.09, - 0.16) and - 4.04 (- 7.59, - 0.50). These improvements remained statistically significant at 12-14 months: - 0.94 (- 1.67, - 0.20) and - 1.92 (- 3.52, - 0.32) respectively with combination therapy.

CONCLUSION

Our findings demonstrate that combination therapy (SML + IVI anti-VEGF) is associated with fewer intravitreal injections. We report a better BCVA and a reduction in CMT at 6 and 12 months from baseline with combination treatment compared to the IVI anti-VEGF monotherapy comparator. SML is a proven non-scarring cost-effective therapy for DMO that should be readily available in the medical retinal therapy as it may reduce the burden of care.

Morphological Evaluation of Transscleral Laser Retinopexy in Rabbits: Comparison of Optical Coherence Tomography and Histologic Examinations

Transscleral retinopexy is a preventive technique used against retinal detachment. Fundus examination can allow the monitoring of morphological retinal changes in the progression of photocoagulation lesions, without offering details on the morphological changes by the retinal lesion. The aim of the study was to assess the progression of photocoagulation lesions induced by transscleral retinopexy (840 nm diode laser), by comparing the optical coherence tomography (OCT) and histological images over a period of six weeks on eight pigmented New Zealand healthy rabbits (four males and four females; n = 16 eyes). All rabbits underwent transscleral retinopexy on their left eye on day 0 (D0). Measurements of the photocoagulation lesions were obtained in vivo on D0, D7, D15, D21, and D42 by acquiring OCT images of both eyes from all rabbits. On D1, D7, D21, and D42, two rabbits were euthanized, and their eyes were enucleated. A significant effect by time on the decrease in the central retinal thickness of the photocoagulation lesion was observed from D1 to D7 (p = 0.001); however, no such effect was observed on the horizontal length ((HL) p = 0.584) of the lesion surface. The reliability between the OCT and histological measurements, which were evaluated using intraclass correlation coefficients, was excellent for measuring the retinal thickness at the center (ICC = 0.91, p < 0.001), moderate for the right side of the retinal lesions (ICC = 0.72, p = 0.006), and not significant for the left side and HL (p = 0.055 and 0.500, respectively). The morphological changes observed in the OCT and histopathological images of the photocoagulation lesions were qualitatively described over time. OCT is an effective tool for monitoring changes in photocoagulation lesions. Some measurements and qualitative changes showed an adequate correlation between the OCT and histological findings.

Yellow Subthreshold Micropulse Laser in Retinal Diseases: An In-Depth Analysis and Review of the Literature

Yellow subthreshold micropulse laser (YSML) is a retinal laser capable of inducing a biologic response without causing thermal damage to the targeted tissue. The 577-nm YSML is delivered to the retina abiding by different protocols in which wavelength, power, duration, spot size and number of spots can be properly set to achieve the most effective and safe treatment response in various chorioretinal disorders. The ultrashort trains of power modulate the activation of the retinal pigment epithelium cells and intraretinal cells, such as Müller cells, causing no visible retinal scars. Subthreshold energy delivered by YSML stimulates the production of the heat-shock proteins, highly conserved molecules that protect cells against any sort of stress by blocking apoptotic and inflammatory pathways that cause cell damage. YSML treatment allows resorption of the subretinal fluid in central serous chorioretinopathy and intraretinal fluid in various conditions including diabetic macular edema, postoperative cystoid macular edema and other miscellaneous conditions. YSML also seems to modulate the development and progression of reticular pseudodrusen in dry age-related macular degeneration. The aim of this review is to discuss and summarize the safety and efficacy of YSML treatment in retinal diseases.

Intravitreal Dexamethasone Implant (IDI) Alone and Combined with Navigated 577 nm Subthreshold Micropulse Laser (SML) for Diabetic Macular Oedema

Background: The anatomical and functional changes after intravitreal dexamethasone implant (IDI) alone and combined with navigated subthreshold micropulse laser (NSML) in diabetic macular oedema (DMO) were compared. Methods: Patients with a clinically confirmed diagnosis of non-proliferative diabetic retinopathy (NPDR) and DMO were enrolled in this prospective study and were randomly assigned to two different treatment groups: thirty patients were treated with IDI (IDI group), and the other 30 patients received IDI combined with NSML treatment (combined IDI/NSML group). All patients during a 6-month follow-up underwent best corrected visual acuity (BCVA) evaluation and spectral domain optical coherence tomography (SD OCT). The main outcome measures were: BCVA, central macular thickness (CMT); (3) choroidal vascularity index (CVI), subfoveal choroidal thickness (SCHT); and time to retreatment between IDI at baseline and the second implant in both groups. Results: BCVA, CMT, and SCHT significantly decreased starting from the 1-month follow-up and CVI from 3 months in both groups. The between-group differences were significantly different from 1-month follow-up for BCVA, from 5-month follow-up for CMT and SCHT, and from 4-month follow-up for CVI. The Needed to Treat analysis indicated that six patients would have to be treated with SML after IDI in order for just one person to receive a benefit. Conclusions: the combined treatment showed good anatomical and functional outcomes for the treatment of DMO. In addition, IDI/SML seems to reduce injection frequency over time, improving patients’ quality of life and reducing the socio-economic burden.

Pascal short-pulse plus subthreshold endpoint management laser therapy for diabetic macular edema: the "sandwich technique"

Background

Diabetic macular edema (DME) is the main cause of visual loss in diabetic patients. Despite the use of anti-VEGF therapy as first-line treatment, there are many patients whose response to treatment is poor or transient at best. Sophisticated laser techniques have emerged aiming at low-intensity retinal damage, avoiding excessive heat that causes tissue necrosis and related collateral effects.

Objective

To evaluate the effect of combined sublethal laser modalities from short-pulse duration (SPD) with endpoint management (EpM) subthreshold laser [named the “sandwich technique” (SWiT)] on central subfield thickness (CST) and best-corrected visual acuity (BCVA) in patients with DME.

Material and methods

In this consecutive retrospective study, 37 patients (37 eyes) with center-involved (CI) DME were treated with SWiT laser therapy from April 2017 to June 2021. The technique consisted of a mean number of 200 (range number 50–400) SPD laser burns OCT-guided thickened area performed on the juxta- and perifoveal area 500 µm away from the foveal center, overlapping with a mean number of 1000 (range number 800–1200) EpM laser burns focused on 6 mm macular diameter area but saving 300 µm toward the foveal center. All patients underwent ophthalmological evaluations, including BCVA and CST measurement by spectral-domain optical coherence tomography (SD-OCT), before and after SWiT laser therapy. The mean follow-up time was 19.2 months (range 2–60 months).

Results

Thirty-five out of 37 cases showed an improvement in CST and BCVA following treatment. At baseline, mean CST (µm) ± standard error (SE) and mean BCVA (logMAR) ± SE was 456.95 ± 37.00 and 0.71 ± 0.29, respectively. After a mean follow-up of 19.2 months, mean CST (µm) ± SE and BCVA (logMAR) ± SE were 272.09 ± 9.10 (p < 0.0001) and 0.54 ± 0.26 (p = 0.003), respectively. A statistically significant reduction in CST and improvement in BCVA was noted after laser therapy application. The anti-VEGF injection frequency was reduced during the mean 19.2 months of the study period.

Conclusions

The novel “sandwich” laser therapy aid reduced CST and improved BCVA in this retrospective case series. Further prospective studies are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40942-022-00381-5.

Comparison of the 1-Year Visual and Anatomical Outcomes between Subthreshold Red (670 nm) and Yellow (577 nm) Micro-Pulse Laser Treatment for Diabetic Macular Edema

We investigated the efficacy and safety of red (670 nm) subthreshold micropulse laser (SMPL) treatment for diabetic macular edema (DME) and compared the 1-year treatment outcomes of red and yellow (577 nm) SMPL for DME. A medical chart review was performed in 43 consecutive eyes of 35 patients who underwent red or yellow SMPL treatment for DME and were followed up for 12 months. There were 26 and 17 eyes in the yellow and red SMPL groups, respectively. The mean best-corrected visual acuity (BCVA) was maintained throughout the follow-up period of 12 months in the yellow and red SMPL groups (p = 0.39, p = 0.70, respectively). The central retinal thickness (CRT) measured by spectral-domain optical coherence tomography (SD-OCT) was significantly decreased at 12 months from baseline in the yellow and red SMPL groups (p = 0.047, p = 0.03, respectively). Although the amount of CRT reduction in the red SMPL group was significantly greater than that in the yellow SMPL group at 8 months from baseline (p = 0.02), the significance disappeared at the final follow-up period (p = 0.44). The red SMPL maintained the BCVA in patients with center-involving DME. The mean CRT in the red SMPL group significantly decreased, and the amount of CRT reduction was equivalent to that in the yellow SMPL group.

Subthreshold micropulse laser adjuvant to bevacizumab versus bevacizumab monotherapy in treating diabetic macular edema: one- year- follow-up

Purpose

To compare the therapeutic impact of combining intravitreal injections of bevacizumab (IVB) with micropulse laser (MPL) in central diffuse diabetic macular edema (DME) versus IVB monotherapy during 12 months follow-up.

Methods

We conducted a retrospective comparative study of 98 treatment-naive eyes (63 patients) with central diffuse DME. The first group of patients (IVB + MPL group, n = 49) was treated with 3 monthly IVB followed by MPL within 1 week after the third injection. Patients were then followed and treated on a pro re nata (PRN) basis, with MPL retreatment if necessary. The changes in best-corrected visual acuity (BCVA), central macular thickness (CMT), number of IVB injections and MPL sessions were evaluated at 4, 8, and 12 months. A control group of diabetic patients with treatment-naive DME was treated with standard protocol of 3 monthly IVB as monotherapy then followed on a PRN basis (IVB group, n = 49). Statistic comparaison of BCVA, CMT, and IVB number variation was interpreted at 12 months between both groups.

Results

In IVB + MPL group, baseline BCVA improvement was not significant at 4 and 8 months (p = 0.90, p = 0.08), and was statistically significant (p = 0.01) at 12 months. Mean CMT significantly decreased at 4, 8, and 12 months (p < 0.01) in IVB + MPL group. The difference in BCVA (p = 0.091) and CMT (p = 0.082) variation at 12 months between both groups was not significant but the number of injections was significantly lower in IVB + MPL group (4.1 ± 1.5 injections) compared to IVB group (7.2 ± 1.3 injections) (p < 0.005).

Conclusion

Combining intravitreal injections of bevacizumab and MPL in the treatment of DME is effective and safe. This protocol may decrease the number of IVB and its frequency. It offers the advantage of lasting therapeutic response with fewer recurrences.

Subthreshold Micropulse Laser Modulates Retinal Neuroinflammatory Biomarkers in Diabetic Macular Edema

Subthreshold micropulse laser treatment has become a recognized option in the therapeutic approach to diabetic macular edema. However, some yet undefined elements pertaining to its mechanism of action and most effective treatment method still limit its clinical diffusion. We reviewed the current literature on subthreshold micropulse laser treatment, particularly focusing on its effects on the modulation of retinal neuroinflammation. Subthreshold micropulse laser treatment seems to determine a long-term normalization of specific retinal neuroinflammatory metabolic pathways, contributing to the restoration of retinal homeostasis and the curtailing of local inflammatory processes. Optimized and standardized parameters ensure effective and safe treatment.

Physiological response of the retinal pigmented epithelium to 3-ns pulse laser application, in vitro and in vivo

BACKGROUND

To treat healthy retinal pigmented epithelium (RPE) with the 3-ns retinal rejuvenation therapy (2RT) laser and to investigate the subsequent wound-healing response of these cells.

METHODS

Primary rat RPE cells were treated with the 2RT laser at a range of energy settings. Treated cells were fixed up to 7 days post-irradiation and assessed for expression of proteins associated with wound-healing. For in vivo treatments, eyes of Dark Agouti rats were exposed to laser and tissues collected up to 7 days post-irradiation. Isolated wholemount RPE preparations were examined for structural and protein expression changes.

RESULTS

Cultured RPE cells were ablated by 2RT laser in an energy-dependent manner. In all cases, the RPE cell layer repopulated completely within 7 days. Replenishment of RPE cells was associated with expression of the heat shock protein, Hsp27, the intermediate filament proteins, vimentin and nestin, and the cell cycle-associated protein, cyclin D1. Cellular tight junctions were lost in lased regions but re-expressed when cell replenishment was complete. In vivo, 2RT treatment gave rise to both an energy-dependent localised denudation of the RPE and the subsequent repopulation of lesion sites. Cell replenishment was associated with the increased expression of cyclin D1, vimentin and the heat shock proteins Hsp27 and αB-crystallin.

CONCLUSIONS

The 2RT laser was able to target the RPE both in vitro and in vivo, causing debridement of the cells and the consequent stimulation of a wound-healing response leading to layer reformation.

Comparison of the efficacy and safety of anti-VEGF monotherapy versus anti-VEGF therapy combined with subthreshold micropulse laser therapy for diabetic macular edema

The purpose of this study is to compare the efficacy and safety of 577-nm subthreshold micropulse laser (SML) and intravitreal bevacizumab injection (IVB) combined therapy with IVB monotherapy in the treatment of diabetic macular edema (DME). This retrospective study included 80 eyes of 80 patients; 40 eyes were treated with IVB monotherapy, and 40 eyes were treated with SML-IVB combined therapy. The mean number of required IVB injections and changes of best corrected visual acuity (BCVA) and central macular thickness (CMT) values were compared between the groups. The mean age of the patients was 60.19±7.43 years. The baseline characteristics of the patients were similar between the groups. In the SML-IVB combined group, the mean number of required SML sessions was 2.1±0.81. The mean number of required IVB injections was 4.38±0.81 in the SML-IVB combined group and 5.65±1.51 in the IVB monotherapy group (p<0.05). The increase of the BCVA was significant in the SML-IVB combined group at the 3rd, 6th, 9th, and 12th months; however, in the IVB monotherapy group, it was only significant at the 3rd month (p<0.05). The mean CMT values of the 3rd, 9th, and 12th months were similar between the groups (p>0.05); only at the 6th month was it significantly lower in the SML-IVB combined group (p<0.05). When compared with baseline, the decrease of the CMT was statistically significant in both groups at the 3rd, 6th, 9th, and 12th months (p<0.05). In this study, a significant benefit of adding SML to IVB therapy was found with less IVB need, although a very significant increase in BCVA could not be achieved. The use of SML-IVB combined treatment may be an effective and safe alternative for DME.

Saudi Arabia Guidelines for diabetic macular edema: A consensus of the Saudi Retina Group

Diabetes mellitus (DM) and its complications are major public health burdens in Saudi Arabia. The prevalence of diabetic retinopathy (DR) is 19.7% and the prevalence of diabetic macular edema (DME) is 5.7% in Saudi Arabia. Diabetic macular edema is a vision-threatening complication of DR and a major cause of vision loss worldwide. Ocular treatments include retinal laser photocoagulation, anti-vascular endothelial growth factor (anti-VEGF) agents, intravitreal corticosteroids, and vitreoretinal surgery when necessary. The present consensus was developed as a part of the Saudi Retina Group's efforts to generate Saudi guidelines and consensus for the management of DME, including recommendations for its diagnosis, treatment, and best practice. The experts' panel stipulates that the treatment algorithm should be categorized according to the presence of central macula involvement. In patients with no central macular involvement, laser photocoagulation is recommended as the first-line option. Patients with central macular involvement and no recent history of cardiovascular (CVS) or cerebrovascular disorders can be offered anti-VEGF agents as the first-line option. In the case of non-responders (defined as an improvement of <20% in optical coherence tomography or a gain of fewer than 5 letters in vision), switching to another anti-VEGF agent or steroids should be considered after 3 injections. Within the class of steroids, dexamethasone implants are recommended as the first choice. In patients with a recent history of CVS events, the use of anti-VEGF agents is not recommended, regardless of their lens status. The experts' panel recommends that a future study be conducted to provide a cut-off point for early switching to steroid implants in pseudo-phakic eyes.

Micropulse laser in patients with refractory and treatment-naïve center-involved diabetic macular edema: short terms visual and anatomic outcomes

Purpose:

The purpose of the study is to describe visual and anatomic outcomes of 5774nm micropulse laser photocoagulation in eyes with either treatment-naïve or refractory diabetic macular edema (DME) at 3 months.

Methods:

This was a prospective case series that recruited 23 consecutive patients (33 eyes) with center-involved DME that was either treatment-naïve or had not responded to prior treatment. Micropulse therapy was performed with the Easy Ret 577 (Quantel Medical, Cournon d’Auvergne, France) diode laser in a high-density manner in eyes with treatment-naïve or refractory DME. The primary outcome was the change of best-corrected visual acuity (BCVA; logMAR) at 1 and 3 months. Secondary outcomes were changes in the central macular thickness (CMT), thickness area, macular volume, and macular capillary leakage at 1 and 3 months.

Results:

There were no significant changes in BCVA at 3 months, with mean ± standard deviation (SD) of −0.08 ± 0.01 (p = 0.228) and + 0.01 ± 0.01 (p = 0.969) for treatment-naïve and refractory groups, respectively. The change in CMT at 3 months was statistically but not clinically significant in the treatment-naïve group only (mean ± SD; –30 ± 130 µm; p = 0.011). The macular volume and area thickness change were not statistically significant (p = 0.173 and p = 0.148 for macular volume and area thickness, respectively) in the treatment-naïve group. There was no difference concerning the leakage area in both groups. No adverse events were reported.

Conclusion:

We concluded that micropulse 577nm laser therapy maintained the visual acuity and macular thickness at 3 months in both treatment-naïve and refractory DME.

Subthreshold yellow micropulse laser for treatment of diabetic macular edema: Comparison between fixed and variable treatment regimen

PURPOSE

To compare the efficacy between fixed and variable treatment regimens of subthreshold yellow micropulse laser for the treatment of diabetic macular edema.

METHODS

This is a retrospective, comparative, 12-month study of 39 eyes: 24 eyes received fixed treatment regimen of subthreshold micropulse laser treatment and 15 eyes underwent variable treatment regimen of subthreshold micropulse laser, all eyes were followed up for 12 months. Subthreshold micropulse laser was performed with the following parameters: 100 μm spot size on slit lamp, 5% duty cycle of 0.2 s, and 250 mW power. To choose the power of the variable treatment regimen of subthreshold micropulse laser group, continuous laser power was titrated to a barely visible burn and then switched to MicroPulse mode, multiplying the test burn power by 4 and using a 5% duty cycle of 0.2 s. Main outcomes included changes in central macular thickness and best-corrected visual acuity.

RESULTS

At baseline, the mean LogMAR best-corrected visual acuity was 0.297 ± 0.431 in the variable treatment regimen of subthreshold micropulse laser group and 0.228 ± 0.341 in the fixed treatment regimen of subthreshold micropulse laser group. At the end of follow-up, the mean LogMAR best-corrected visual acuity was 0.289 ± 0.473 (p = 0.785) and 0.245 ± 0.376 (p = 0.480) in the variable and fixed treatment regimens of subthreshold micropulse laser groups, respectively. Similarly, central macular thickness decreased in both groups after treatment; at baseline, the mean central macular thickness was 371.06 ± 37.8 in the variable treatment regimen of subthreshold micropulse laser group and improved to 325.60 ± 110.0 μm (p = 0.025) at the end of the follow-ups, while it was 342.30 ± 35.4 in the fixed treatment regimen of subthreshold micropulse laser group and improved to 308.51 ± 67.5 (p = 0.037).

CONCLUSION

Both treatment regimens are effective for the treatment of mild center-involving diabetic macular edema: fixed treatment appears more suitable minimizing treatment time and reducing the possible errors due to wrong titration in the switch from continuous to micropulse mode.

Aflibercept plus micropulse laser versus aflibercept monotherapy for diabetic macular edema: 1-year results of a randomized clinical trial

PURPOSE

To evaluate the role of adjuvant micropulse laser with aflibercept injections in the management of treatment naive center involving DME, looking at decreased treatment burden and increased efficacy as outcomes after 1 year.

METHODS

This was a prospective, single center, randomized trial that included 40 eyes (40 patients) with previously untreated center involved DME. Patients were randomly assigned to receive either aflibercept plus micropulse laser (group A) or aflibercept monotherapy (group B).

RESULTS

Overall, 40 patients were included in the study; they were randomized into either group A (aflibercept + micropulse; 20 patients) or group B (aflibercept monotherapy; 20 patients). The mean number of injections after the loading dose was 4.5 ± 1.4 in group A and was 5.4 ± 1.7 in group B, and the difference between both groups was statistically significant (P = 0.029).

CONCLUSION

Adding 577-nm micropulse laser to aflibercept is effective for treatment naïve DME and is associated with decreased number of injections.

A Model to Study Thermal Energy Delivery to the Choroid: A Comparison of Surgical Devices

Purpose

We measure and compare surgical devices using an ex vivo, temperature-controlled, choroidal incision model during thermal energy transfer with a high-resolution infrared camera.

Methods

Ex vivo porcine choroidal tissue specimens (n = 516) were isolated and placed on a temperature-regulated (37°C) perfusion platform. We tested the pulsed electron avalanche knife (PEAK), micropulse laser (MpL), continuous laser (CL), and bipolar cautery (BpC) at three energy settings (11 [low], 45 [medium], and 134 [high] mJ/mm). Each device was clamped to a stationary mechanical arm. Movement of tissue specimens beneath the surgical device was achieved using a stepping motor-driven x-y table. An infrared video camera measured orthogonal temperature variation in the surrounding tissue.

Results

Increased power resulted in greater lateral thermal spread using all modalities (P < 0.001). Mean (standard deviation) lateral thermal spread at low energy was smallest for the MpL at 0.0 (0.01) mm (P < 0.001), whereas BpC had the least collateral tissue damage at medium and high energies (0.02 [0.08] and 0.34 [0.22] mm, respectively; P < 0.001). Fluidics of the ex vivo system may limit thermal spread. The PEAK had the greatest thermal spread across all energy groups (P < 0.001), with clinically relevant variation between disposable blades.

Conclusions

Our ex vivo model enabled direct comparison of threshold thermal tissue injury across four devices. MpL and BpC showed the least thermal damage. PEAK had a higher variation in energy delivery, but also has the advantage of more effective tissue cutting.

Translational Relevance

Our ex vivo surgical device analysis provides thermal tissue injury predictions for choroidal surgery.

Visual outcomes and anatomic changes after sub-threshold micropulse yellow laser (577-nm) treatment for chronic central serous chorioretinopathy: long-term follow-up

PurposeTo analyze the long-term efficacy of 577 nm sub-threshold micropulse yellow laser (SMYL) in the treatment of chronic central serous chorioretinopathy (CCSC) and to evaluate the anatomic outcome, visual results and safety profile of the treatment.Patients and methodsThis prospective study assessed 39 eyes of 39 patients with non-resolving CCSC lasting more than three months. All eyes were treated by using 577 nm SMYL system with 5% duty cycle (DC) and each patients was monitored monthly. The main outcome measures were best-corrected visual acuity (BCVA), contrast sensitivity (CS) and subretinal fluid (SRF) height, central macular thickness (CMT), central macular volume (CMV), total macular volume (TMV), and subfoveal choroidal thickness (SFCT) measured by spectral domain optical coherence tomography (SD-OCT).ResultsThe median follow-up time period was 17.82±0.42 (13-23 months) months. The BCVA was improved significantly at final follow-up in comparison of baseline visit (P<0.01) in 35 eyes (89.7%) and in 4 eyes (10.3%) was stable. The median CMT, CMV, TMV before treatment was 369 μm, 0.30 mm3, and 9.86 mm3, in comparison to 250 μm, 0.19 mm3, and 8.76 mm3 at final follow-up, respectively (P<0.01 for all these parameters). Initial median SFCT was recorded as 364 μm and 342 μm at the final follow-up (P<0.001).DiscussionResults suggest that SMYL treatment is an effective method as response was rapid and procedure is safe to manage the non-resolving CCSC eyes.

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.

Bone Marrow-Derived Cell Recruitment to the Neurosensory Retina and Retinal Pigment Epithelial Cell Layer Following Subthreshold Retinal Phototherapy

Purpose

We investigated whether subthreshold retinal phototherapy (SRPT) was associated with recruitment of bone marrow (BM)–derived cells to the neurosensory retina (NSR) and RPE layer.

Methods

GFP chimeric mice and wild-type (WT) mice were subjected to SRPT using a slit-lamp infrared laser. Duty cycles of 5%, 10%, 15%, and 20% (0.1 seconds, 250 mW, spot size 50 μm) with 30 applications were placed 50 to 100 μm from the optic disc. In adoptive transfer studies, GFP⁺ cells were given intravenously immediately after WT mice received SRPT. Immunohistochemistry was done for ionized calcium-binding adapter molecule-1 (IBA-1⁺), CD45, Griffonia simplicifolia lectin isolectin B4, GFP or cytokeratin). Expression of Ccl2, Il1b, Il6, Hspa1a, Hsp90aa1, Cryab, Hif1a, Cxcl12, and Cxcr4 mRNA and flow cytometry of the NSR and RPE-choroid were performed.

Results

Within 12 to 24 hours of SRPT, monocytes were detected in the NSR and RPE-choroid. Detection of reparative progenitors in the RPE occurred at 2 weeks using flow cytometry. Recruitment of GFP⁺ cells to the RPE layer occurred in a duty cycle–dependent manner in chimeric mice and in mice undergoing adoptive transfer. Hspa1a, Hsp90aa1, and Cryab mRNAs increased in the NSR at 2 hours post laser; Hif1a, Cxcl12, Hspa1a increased at 4 hours in the RPE-choroid; and Ccl2, Il1b, Ifng, and Il6 increased at 12 to 24 hours in the RPE-choroid.

Conclusions

SRPT induces monocyte recruitment to the RPE followed by hematopoietic progenitor cell homing at 2 weeks. Recruitment occurs in a duty cycle–dependent manner and potentially could contribute to the therapeutic efficacy of SRPT.

A Review of Subthreshold Micropulse Laser for Treatment of Macular Disorders

Micropulse laser treatment is an alternative to the conventional continuous-wave laser for the treatment of retinal or macular diseases. In contrast to the conventional laser, the therapeutic effect of the subthreshold micropulse laser is not accompanied by thermal retinal damage. This fact is of particular importance when a treatment near the fovea is required. Micropulse treatment is applied in indications such as central serous chorioretinopathy (CSC), diabetic macular edema (DME), or macular edema due to retinal vein occlusion (RVO). This review outlines and discusses the published literature of subthreshold micropulse laser treatment for CSC, DME, and macular edema after RVO.

Biological Modulation of Mouse RPE Cells in Response to Subthreshold Diode Micropulse Laser Treatment

Many clinical trials have demonstrated the effectiveness of subthreshold phototherapy with no visible damage in retinal vascular diseases, such as diabetic retinopathy. We aimed primarily to investigate the effect of subthreshold diode micropulse laser (SDM) treatment on mouse retinal pigmented epithelium (RPE) cells. The expression of angiogenesis-modulating cytokines in response to SDM was also explored. The least toxic laser dose was selected by measuring cell viability with MTT assay and 5 % duty cycle (DC) was chosen for use in further experiments. RPE cells were treated with laser-induced radiation ranging from 0 to 400 mW for 24 h. The apoptotic rate of RPE cells was assessed by flow cytometry. Expressions of vascular endothelial growth factor A (VEGF-A), transforming growth factor beta (TGF-β), basic fibroblast growth factor (bFGF), and pigment epithelium-derived factor (PEDF) were determined by Western Blotting and real-time PCR, respectively. After 24 h of laser irradiation, cell viability was reduced dose dependently and the effect was significant compared to the controls (P < 0.05). In addition, laser treatment with intensities of 100 and 200 mW with DC of 5 % produced no significant effect on cell viability and apoptosis as compared with the control group (P > 0.05). The protein and mRNA expressions of angiogenic stimulators (VEGF-A, TGF-β, and bFGF) were significantly down-regulated (P < 0.05), whereas those of the angiogenic inhibitor (PEDF) were up-regulated (P < 0.05). No significant difference was found between the cells treated with different intensities of laser radiation (P > 0.05). Our results showed that SDM treatment of the RPE cells suppressed the expression of choroid neovasculization-promoting cytokines and up-regulated the angiogenic inhibitor, PEDF without damaging the cells. Further investigation is needed to understand the mechanism and to optimize the use of SDM as a novel method of treatment for retinal vascular diseases.

Diabetic Macular Edema

Diabetic macular edema (DME), one the most prevalent causes of visual loss in industrialized countries, may be diagnosed at any stage of diabetic retinopathy. The diagnosis, treatment, and follow up of DME have become straightforward with recent developments in fundus imaging, such as optical coherence tomography. Laser photocoagulation, intravitreal injections, and pars plana vitrectomy surgery are the current treatment modalities; however, the positive effects of currently available intravitreally injected agents are temporary. At this point, further treatment choices are needed for a permanent effect.

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.

Randomised clinical trial evaluating best-corrected visual acuity and central macular thickness after 532-nm subthreshold laser grid photocoagulation treatment in diabetic macular oedema

Purpose

To compare best-corrected visual acuity (BCVA) and central macular thickness (CMT) after 532-nm subthreshold laser grid photocoagulation and threshold laser grid photocoagulation for the treatment of diabetic macular oedema (DME).

Patients and methods

Twenty-three patients (46 eyes) with binocular DME were enroled in this study. The two eyes of each patient were divided into a subthreshold photocoagulation group and a threshold photocoagulation group. The eyes of the subthreshold group underwent 532-nm patter scan laser system (PASCAL) 50% end point subthreshold laser grid photocoagulation therapy, whereas the threshold photocoagulation group underwent short-pulse grid photocoagulation with a 532-nm PASCAL system. BCVA and CMT were assessed in all patients before treatment, 7 days after treatment, and 1, 3, and 6 months after treatment.

Results

After grid photocoagulation, the mean BCVA improved in both the subthreshold group, and the threshold group, and the two groups did not differ statistically significantly from each other. Similarly, the macular oedema diminished in both groups after treatment, and the two groups did not differ statistically significantly from each other with regard to CMT.

Conclusion

Both 532-nm subthreshold laser grid photocoagulation and threshold laser grid photocoagulation can improve the visual acuity and reduce CMT in DME patients.

The short-term efficacy of subthreshold Micropulse yellow (577-nm) laser photocoagulation for diabetic macular edema

Purpose

This pilot study aimed to evaluate the efficacy and safety of subthreshold micropulse yellow (577-nm) laser photocoagulation (SMYLP) in the treatment of diabetic macular edema (DME).

Methods

We reviewed 14 eyes of 12 patients with DME who underwent SMYLP with a 15% duty cycle at an energy level immediately below that of the test burn. The laser exposure time was 20 ms and the spot diameter was 100 µm. Laser pulses were administered in a confluent, repetitive manner with a 3 × 3 pattern mode.

Results

The mean follow-up time was 7.9 ± 1.6 months. The baseline-corrected visual acuity was 0.51 ± 0.42 logarithm of the minimum angle of resolution (logMAR), which was improved to 0.40 ± 0.35 logMAR (p = 0.025) at the final follow-up. The central macular thickness at baseline was 385.0 ± 111.0 µm; this value changed to 327.0 ± 87.7 µm (p = 0.055) at the final follow-up.

Conclusions

SMYLP showed short-term efficacy in the treatment of DME and did not result in retinal damage. However, prospective, comparative studies are needed to better evaluate the efficacy and safety of this treatment.

Diabetic macular edema: new concepts in patho-physiology and treatment

Diabetic macular edema (DME), a serious eye complication caused primarily by hyperglycemia, is one of the major causes of blindness. DME, which is characterized by cystic retinal thickening or lipid deposition, is prone to relapse after successful treatment. DME is a complex pathological process caused by multiple factors, including breakdown of the inner and outer blood-retinal barriers, oxidative stress, and elevated levels of vascular endothelial growth factor which have been demonstrated in both preclinical and clinical studies. Starling's law theory explains many of the features of DME. Early detection and treatment of DME can prevent vision loss. Current effective interventions for DME include treatment of systemic risk factors, such as elevated blood glucose, blood pressure and dyslipidemia. Ophthalmic treatments include laser photocoagulation, surgery and intraocular pharmacotherapy. New drugs, which are given by intraocular injection, have emerged in recent years to become first line treatment for DME that affects the central macula with loss of vision. Laser photocoagulation is still the gold standard of treatment for DME which does not involve the central macular. This review outlines these new treatments with particular emphasis on the optimal timing of how they are given.

Correlation with OCT and histology of photocoagulation lesions in patients and rabbits

PURPOSE

To examine spectral domain optical coherence tomographic (OCT) and histological images from comparable retinal photocoagulation lesions in rabbits, and to correlate these images with comparable OCT images from patients.

METHODS

508 rabbit lesions were examined by HE-stained paraffin histology. 1019 rabbit lesions versus 236 patient lesions were examined by OCT, all at the time-points 1 hr, 1 week and 4 weeks after photocoagulation. We analysed 100 μm lesions (in humans) and 133 μm lesions (in rabbits) of 200 ms exposures at powers titrated from the histological threshold up to intense damage. Lesions were matched according to morphological criteria.

RESULTS

Dome-shaped layer alterations, retinal infiltration by round, pigmented cells, outer nuclear layer interruption, and eventually full thickness retinal coagulation are detectable in histology and OCT. Horizontal damage extensions are found 1½ times larger in OCT. More intense irradiation was necessary to induce comparable layer affection in rabbit OCT as in histology. Restoration of the inner retinal layers is only shown in the OCT images. Comparable primary lesions caused more pronounced OCT changes in patients than in rabbits during healing.

CONCLUSIONS

Optical coherence tomographic images indicate different tissue changes than histologic images. After photocoagulation, they show wider horizontal damage diameters, but underestimate axial damage particularly during healing. Conclusions on retinal restoration should not be drawn from OCT findings alone. Retinal recovery after comparable initial lesions appears to be more complete in rabbit than in patient OCTs.

Subthreshold diode laser micropulse photocoagulation for the treatment of diabetic macular edema

Diabetic macular edema (DME) is a sight-threatening complication of diabetic retinopathy, the leading cause of visual loss in the working-age population in the industrialized and emerging world. The standard of care for DME is focal/grid laser photocoagulation, which is proven effective in reducing the risk of vision loss, but inherently destructive and associated with tissue damage and collateral effects. Subthreshold diode laser micropulse photocoagulation is a nondestructive tissue-sparing laser procedure, which, in randomized controlled trials for the treatment of DME, has been found equally effective as conventional photocoagulation. Functional and anatomical outcomes from four independent randomized controlled trials provide level one evidence that vision stabilization/improvement and edema resolution/reduction can be elicited with less or no retinal damage, and with fewer or no complications. This review describes the principles of subthreshold diode laser micropulse photocoagulation, its treatment modalities and clinical outcomes in the context of standard laser treatments and of emerging nonlaser therapies for DME.

Therapeutic window of retinal photocoagulation with green (532-nm) and yellow (577-nm) lasers

BACKGROUND AND OBJECTIVE

The 577-nm (yellow) laser provides an alternative to the 532-nm (green) laser in retinal photocoagulation, with potential benefits in macular treatment and through ocular opacities. To assess relative risk of thermomechanical rupture of Bruch's membrane with yellow laser in photocoagulation, the therapeutic window, the ratio of threshold powers for mild coagulation and rupture, was measured.

MATERIALS AND METHODS

Retinal coagulation and rupture thresholds, visualized ophthalmoscopically, were measured with 577- and 532-nm lasers using 10- to 100-ms pulses in 34 rabbit eyes. Lesions at 1 and 7 days were assessed histologically.

RESULTS

Coagulation threshold with yellow laser was 26% lower than with green laser. The therapeutic window increased linearly with log-duration for both wavelengths with a difference in parallel-slope intercept of 0.36 ± 0.20, corresponding to 8% to 15% wider therapeutic window for yellow wavelength.

CONCLUSION

The therapeutic window of retinal photocoagulation in rabbits at 577 nm is slightly wider than at 532 nm, whereas histologically the lesions are similar.

Micropulsed diode laser therapy: evolution and clinical applications

Many clinical trials have demonstrated the clinical efficacy of laser photocoagulation in the treatment of retinal vascular diseases, including diabetic retinopathy. There is, however, collateral iatrogenic retinal damage and functional loss after conventional laser treatment. Such side effects may occur even when the treatment is appropriately performed because of morphological damage caused by the visible endpoint, typically a whitening burn. The development of the diode laser with micropulsed emission has allowed subthreshold therapy without a visible burn endpoint. This greatly reduces the risk of structural and functional retinal damage, while retaining the therapeutic efficacy of conventional laser treatment. Studies using subthreshold micropulse laser protocols have reported successful outcomes for diabetic macular edema, central serous chorioretinopathy, macular edema secondary to retinal vein occlusion, and primary open angle glaucoma. The report includes the rationale and basic principles underlying micropulse diode laser therapy, together with a review of its current clinical applications.

High-resolution imaging of the human retina in vivo after scatter photocoagulation treatment using a semiautomated laser system

PURPOSE

To image the ultrastructural morphology of retinal laser effects and their healing response in vivo using spectral domain optical coherence tomography (SD-OCT).

DESIGN

Prospective, interventional study.

PARTICIPANTS

Ten patients undergoing panretinal photocoagulation for proliferative diabetic retinopathy.

METHODS

Panretinal photocoagulation (PRP) was performed using a semiautomated patterned scanning laser system providing a raster of effects with homogenous intensity. Retinal morphology and localization of effects owing to laser-tissue interaction were imaged at 1 day, 1 week, and at monthly intervals for 6 months. The characteristic, specific structural changes during the healing process were followed over time using an SD-OCT device (Spectralis OCT) allowing for high-resolution raster scanning of the entire lesion pattern with identification of identical retinal sites (tracking modality).

MAIN OUTCOME MEASURES

Retinal morphology and localization of effects of photocoagulation on SD-OCT images.

RESULTS

At day 1 after PRP, the photocoagulation effects were sharply delineated from the surrounding unaffected retina and all spots seemed to be identical in size and location. The area of tissue destruction was confined to the outer retinal layers, extending from the outer nuclear layer (ONL) to the retinal pigment epithelium (RPE). At 1 week, images showed a progressive loss of the affected outer retinal layers, namely, the ONL and the outer plexiform layer. Concomitant distortion of the inner nuclear and plexiform layers generated a pattern of "archways" between adjacent laser spots. The photoreceptor layers (PRL) seemed to be eliminated in the photocoagulated area, particularly at the borders of each lesion. The lesion center contained a condensed RPE and PRL segment. The ONL recovered partially, but the PRL inner and outer segments remained absent. During the long-term follow-up, RPE cells migrated to the center of the lesion, forming a hyperplastic scar.

CONCLUSIONS

The characteristic morphology of retinal photocoagulation effects in vivo and over time was identified for the first time in human eyes using SD-OCT. The OCT imaging demonstrated a well-defined reproducible area of destruction confined to the outer retinal layers. Healing proceeded as the condensation of the RPE and PRL in the lesion center.

Large-spot subthreshold infrared laser to treat diabetic macular edema

PURPOSE

To evaluate the efficacy of a large-spot subthreshold infrared laser protocol to treat diabetic maculopathy.

METHODS

In a prospective, fellow eye, controlled case series, all patients had clinically significant diabetic macular edema (DME) treated with a single application of subthreshold infrared (810 nm) laser. If bilateral disease was present, the fellow eye was treated with conventional macular laser. The study was to include 20 patients. Visual acuity and central macular thickness (CMT) measured by optical coherence tomography (OCT) were assessed in the study and fellow eyes at baseline and 6 months, and any changes were compared.

RESULTS

The 11th patient developed a choroidal infarct with subsequent profound loss of vision immediately after treatment. The study was terminated prematurely at this point. For the remaining 10 patients, there was a trend toward improvement in visual acuity in the study eye compared with the fellow eye at the 6-month follow-up (median change: +1.5 letters for study eye vs -6.5 letters for fellow eye; P = 0.08). There was also significant improvement in OCT-measured CMT in the study eye (mean decrease, 117 microm) compared with deterioration in OCT-measured CMT in the fellow eye (mean increase, 24 microm; P = 0.02).

CONCLUSION

This subthreshold infrared laser protocol led to improvement in OCT-measured CMT and stabilization of vision in most subjects. The current protocol is however unpredictable and should not be used in the treatment of DME without further modification.

Modulation of Ku70/80, Clusterin/ApoJ Isoforms and Bax Expression in Indocyanine-Green-Mediated Photo-Oxidative Cell Damage

PURPOSE

In order to characterize the biological effects and molecular mechanism underlying indocyanine-green (ICG)-mediated photo-oxidative cell damage, human cultured retinal pigmented epithelium (RPE) cells preloaded with ICG were exposed to 810-nm laser irradiation. Cell viability and death induction were examined, as well as the modulation of proteins involved in cell death and DNA repair.

METHODS

ARPE-19 cells preloaded with 100 microM ICG were irradiated using continuous and micropulsed 810-nm laser for the dye photoactivation, and cell viability and apoptosis were evaluated. The expression and subcellular localization of Bax, Ku70, Ku80 and clusterin/ApoJ were analyzed by immunocytochemistry and Western blot.

RESULTS

ICG photoactivation induced apoptosis in RPE cells. The micropulsed laser irradiation induced a higher percentage of cell killing as compared to continuous wave. Cell killing was inhibited by sodium azide, suggesting the involvement of reactive oxygen species in the laser-induced cell damage. Bax was strongly induced after 4 and up to 24 h of treatment. The nuclear proapoptotic isoform of clusterin/ApoJ was selectively upregulated after 24 h of treatment. The DNA repair machinery was upregulated after 4 and up to 24 h.

CONCLUSION

These data elucidate some molecular mechanisms involved in cell death induced by ICG photosensitization. The increase and relocalization of Bax into the mitochondria and the upregulation and translocation of the proapoptotic isoform of clusterin/ApoJ in the nucleus demonstrated the involvement of these proteins in the photo-oxidative cell death pathway. These data point out new molecular targets and suggest potential applications in the therapy of the retinal diseases that could benefit by selective RPE treatment.

Combination therapy for the treatment of ocular neovascularization

The growth of inappropriately regulated, leaky blood vessels is a prominent component of several debilitating eye diseases, such as age-related macular degeneration (AMD), proliferative diabetic retinopathy (PDR), and retinopathy of prematurity (ROP). New pharmacological therapies that target vascular endothelial growth factor-A (VEGF-A) have significantly enhanced the treatment of AMD by limiting the progression of the disease, and in some cases, by improving vision. Although anti-VEGF therapy will undoubtedly prove valuable in the treatment of other neovascular diseases of the eye, improvements with this type of therapy are still required. At present, anti-VEGF therapy requires intravitreal injection and a relatively frequent dosing regimen (4-6 weeks). Furthermore, in experimental models of neovascularization, anti-VEGF treatment becomes less effective at blocking vessel growth and at regressing vessels as the neovascularization develops over time. As such, the use of anti-VEGF therapy in late-stage AMD may be limited. An important strategy for improved treatment of neovascular diseases of the eye could be combination therapy. Combination therapy of anti-VEGF drugs with established treatments, such as photodynamic therapy with verteporfin (PDT-V), or with newly-developed drugs targeting specific kinases, presents opportunities for increased efficacy and improved therapeutic outcome. In this review, we evaluate the opportunities for combination therapy for the treatment of neovascular diseases of the eye.