Tissue effects of subclinical diode laser treatment of the retina

Safety and efficacy of subthreshold micropulse yellow laser for persistent subretinal fluid after scleral bucking a randomized clinical trial

Persistent subretinal fluid (PSF) after scleral bucking of rhegmatogenous retinal detachment may delay recovery and affect the final visual quality, but with no effective treatment. This study firstly investigated the safety and efficacy of 577 nm yellow subthreshold micropulse laser (SML) on PSF after scleral bucking surgery. This double-masked randomized clinical trial was conducted from December 2020 to October 2022 at Chongqing Aier Eye Hospital. Participants with PSF last for 1 month after scleral bucking surgery with break closed and retina reattachment were recruitment. These participants were treated by 577 nm yellow SML or sham treatment. Funduscopy, optical coherence tomography (OCT) volume change, best corrected vision acuity (BCVA) and visual field test were evaluated for six mouths follow-up. A total of 24 participants were randomized into SML group or Sham group equally. Compared with Sham group, the OCT volume within 6 mm of macular fovea was significantly less in SML group 6 months after therapy (P = 0.048). There were no statistically significant differences of OCT volume at 1, 2 and 3 months from baseline between groups. BCVA of ETDRS letters had no statistically significant difference. Pattern Standard Deviation amelioration (P = 0.039) had statistically significance in SML group compared with Sham group. There were no complications in the 2 groups. These preliminary findings suggest that 577 nm yellow SML therapy could accelerate PSF absorption after scleral bucking surgery.Trial registration: Chinese Clinical Trial Registry No. ChiCTR2000037838, 02/09/2020, https://www.chictr.org.cn/showproj.html?proj=51885 .

Micropulse diode laser therapy in refractory glaucoma

Purpose

Description of safety and efficacy of micropulse Transscleral cyclophotocoagulation as a treatment option for refractory glaucoma.

Methods

This is a prospective study including 39 eyes of 31 patients followed for refractory glaucoma, who benefited from transscleral cyclophotocoagulation using a microplused laser. The main indication for the procedure was increased ocular pressure refractory to quadritherapy in various types of glaucoma. The patients were treated using iridex Cyclo G6 laser with a Micropulse P3 infrared probe with a wavelength of 810 ​nm. The parameters for the procedure were a duration of 90 ​s per hemisphere with a power of 2000 mW and an energy of 180 ​J. Both the upper and lower hemispheres were treated in the same procedure, sparing the 3 o'clock and 9 o'clock meridians, and all the patients benefited from a single treatment session. The following parameters were evaluated: ocular pain and overall tolerance; visual acuity; and the evolution of IOP postoperatively up to 9 months.

Results

The glaucoma subtypes treated are as follows: primary open-angle glaucoma (n ​= ​05), chronic angle-closure glaucoma (n ​= ​13), neovascular glaucoma (n ​= ​07), aphakic glaucoma (n ​= ​06), malignant glaucoma (n ​= ​04), post-traumatic angle recession (n ​= ​02), and inflammatory glaucoma (n ​= ​02). The mean pre-operative intraocular pressure was 42.3 ​± ​5.2 ​mmHg and the mean post-operative intraocular pressure at 9 months was 16.9 ​± ​1.9 ​mmHg. The reduction in IOP was 49.9%. The average number of intraocular pressure-lowering medications used prior to surgery was four, and the average number of medications used at the 9-month post-operative visit was 2.0 ​± ​1.2 (70.3% of patients were on dual therapy). The overall success rate was 60.5%.

Conclusions

Micropulse transscleral cyclophotocoagulation appears to be a safe and efficient treatment for refractory glaucoma. Its indications should therefore be broadened and proposed early in various situations.

Activation of Wnt/β-Catenin Signaling Involves 660 nm Laser Radiation on Epithelium and Modulates Lipid Metabolism

Research has proven that light treatment, specifically red light radiation, can provide more clinical benefits to human health. Our investigation was firstly conducted to characterize the tissue morphology of mouse breast post 660 nm laser radiation with low power and long-term exposure. RNA sequencing results revealed that light exposure with a higher intervention dosage could cause a number of differentially expressed genes compared with a low intervention dosage. Gene ontology analysis, protein-protein interaction network analysis, and gene set enrichment analysis results suggested that 660 nm light exposure can activate more transcription-related pathways in HC11 breast epithelial cells, and these pathways may involve modulating critical gene expression. To consider the critical role of the Wnt/T-catenin pathway in light-induced modulation, we hypothesized that this pathway might play a major role in response to 660 nm light exposure. To validate our hypothesis, we conducted qRT-PCR, immunofluorescence staining, and Western blot assays, and relative results corroborated that laser radiation could promote expression levels of β-catenin and relative phosphorylation. Significant changes in metabolites and pathway analysis revealed that 660 nm laser could affect nucleotide metabolism by regulating purine metabolism. These findings suggest that the Wnt/β-catenin pathway may be the major sensor for 660 nm laser radiation, and it may be helpful to rescue drawbacks or side effects of 660 nm light exposure through relative interventional agents.

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.

Micropulse trans-scleral laser therapy outcomes for uncontrolled glaucoma: a prospective 18-month study

OBJECTIVE

To evaluate the efficacy and safety of micropulse trans-scleral laser therapy (mTLT) in glaucomatous patients.

DESIGN

Prospective, interventional study in a university hospital setting.

PARTICIPANTS

Fifty-two eyes of 52 adult patients with uncontrolled glaucoma despite maximal tolerated medical treatment, and/or poor candidates for filtering surgery.

METHODS

Participants received a 360-degree mTLT diode laser treatment (2000mW, 31.33% duty cycle), with duration adjusted to iris pigmentation and glaucoma severity (160-320 seconds). They were followed for 18 months to assess intraocular pressure (IOP), number of medications, corrected distance visual acuity (CDVA), glaucoma progression based on Humphrey Sita 24-2 perimetry and Cirrus high-definition optical coherence tomography, and complications. The primary outcome measure was the absolute success at 18 months. Absolute success was defined as an IOP 6-21 mm Hg and at least 25% IOP reduction, with equal or less number of IOP medications. Qualified success allowed for an increased number of IOP medications. Failure was defined as an inability to meet the criteria for success or the need for incisional glaucoma surgery.

RESULTS

Treatment absolute success was 61.5% at 12 months and 59.6% at 18 months. Mean IOP was reduced by 35.6% at 18 months (23.6 ± 6.5 mm Hg at baseline; 15.2 ± 4.1 mm Hg at 18 months, p < 0.001). mTLT did not significantly reduce the number of topical glaucoma medications (p = 0.075); however, 15 eyes (29%) had systemic oral glaucoma treatment at baseline and 10 eyes (20%) at 18 months. Eight patients (15%) experienced vision loss of ≥2 lines after the procedure. Three patients (6%) regained their preoperative CDVA by 1 month, and 3 patients (6%) by 3 months, while 2 patients (4%) sustained persistent visual loss. No ocular complications were noted in 84.6%. Incisional surgery was required in 25% of eyes owing to inadequately controlled glaucoma despite mTLT.

CONCLUSIONS

mTLT is a good therapeutic option for moderate IOP reduction, while being safe and predictable. This improved safety profile makes mTLT a treatment to be considered earlier in the management of glaucoma.

Crossover to Photodynamic Therapy or Micropulse Laser After Failure of Primary Treatment of Chronic Central Serous Chorioretinopathy: The REPLACE Trial

PURPOSE

To assess whether chronic central serous chorioretinopathy (cCSC) patients without a complete resolution of subretinal fluid (SRF) after either half-dose photodynamic therapy (PDT) or high-density subthreshold micropulse laser (HSML) treatment may benefit from crossover treatment.

DESIGN

Multicenter prospective interventional case series.

METHODS

cCSC patients with persistent SRF at the final visit of the PLACE trial were included. Patients received crossover treatment with either half-dose PDT or HSML.

RESULTS

Thirty-two patients received PDT and 10 patients received HSML. At the first evaluation visit (6-8 weeks after treatment), 81% of patients in the PDT group had complete resolution of SRF, while none of the HSML-treated patients had complete resolution of SRF. At final visit (1 year after baseline), 78% (P = .030) and 67% (P = .109) of the patients, respectively, had a complete resolution of SRF. The mean retinal sensitivity in the PDT group increased from 21.7 dB (standard error [SE]: 0.9) to 23.4 dB (SE: 0.8) at evaluation visit 1 (P = .003), to 24.7dB (SE: 0.8) at final visit (P < .001), while there were no significant changes in the HSML group (23.7 dB [SE: 1.6] at baseline, 23.8 dB [SE: 1.4] at evaluation 1, and 23.3 dB [SE: 1.4] at final visit). The mean visual acuity and mean visual quality-of-life questionnaire score did not change significantly in both groups.

CONCLUSIONS

Crossover to half-dose PDT after previous unsuccessful HSML treatment for cCSC may lead to improved anatomic and functional endpoints, while crossover to HSML after half-dose PDT does not seem to significantly affect these endpoints.

The effect of various media and probe angles on the power output of the Cyclo G6 Glaucoma Laser System

To evaluate the effect of various media and Iridex MicroPulse P3 (MP3) probe angles on the power output from the Cyclo G6 Glaucoma Laser (G6) System. A laser power meter was used to measure the power output (milliwatts, mW) of the Cyclo G6 System. Each of the ten trials consisted of measurements in six different media: no substrate, balanced salt solution (BSS), artificial tears (AT), tetracaine eye drop, lubricating ointment, and lidocaine gel. The output of the MP3 probe was measured at an angle of 90° and 45°, submerged in the respective media. The output was also measured with the probe held at 90° but above the medium. The mean power outputs with the probe being held at 90° to the sensor with no substrate, BSS, AT, tetracaine eye drop, lubricating ointment, and lidocaine gel were 358 ± 16.8 mW, 612 ± 14.2 mW, 613 ± 13.3 mW, 612 ± 14.0 mW, 620 ± 9.9 mW, and 610 ± 12.2 mW, respectively. These values were statistically higher than noncontact and 45° probe angles for each medium. The values between any two media (excluding no substrate) at a 90° probe angle with full contact were not statistically significant. The highest output of the G6 System was obtained with a 90° probe angle, with full contact and any of the coupling media.

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.

Central serous chorioretinopathy: Towards an evidence-based treatment guideline

Central serous chorioretinopathy (CSC) is a common cause of central vision loss, primarily affecting men 20-60 years of age. To date, no consensus has been reached regarding the classification of CSC, and a wide variety of interventions have been proposed, reflecting the controversy associated with treating this disease. The recent publication of appropriately powered randomised controlled trials such as the PLACE trial, as well as large retrospective, non-randomised treatment studies regarding the treatment of CSC suggest the feasibility of a more evidence-based approach when considering treatment options. The aim of this review is to provide a comprehensive overview of the current rationale and evidence with respect to the variety of interventions available for treating CSC, including pharmacology, laser treatment, and photodynamic therapy. In addition, we describe the complexity of CSC, the challenges associated with treating CSC, and currently ongoing studies. Many treatment strategies such as photodynamic therapy using verteporfin, oral mineralocorticoid antagonists, and micropulse laser treatment have been reported as being effective. Currently, however, the available evidence suggests that half-dose (or half-fluence) photodynamic therapy should be the treatment of choice in chronic CSC, whereas observation may be the preferred approach in acute CSC. Nevertheless, exceptions can be considered based upon patient-specific characteristics.

Benefits of SubCyclo Laser Therapy Guided by High-frequency Ultrasound Biomicroscopy in Patients With Refractory Glaucoma

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of subliminal cyclophotocoagulation using a 25% duty cycle diode laser (Supra 810, SubCyclo, Quantel Medical).

METHODS

This was a pilot study of patients who underwent a SubCyclo photocoagulation procedure with a 25% duty cycle, between April 2016 and April 2017 at the Glaucoma Institute of Saint Joseph Hospital of Paris. All patients presented with an evolving moderate to severe glaucoma that were resistant to previous surgical treatments or with a contraindication for filtration surgery. Laser settings were programmed as follows: power 2000 mW, "on" time 0.63 ms, "off" time 1.9 ms, and 25% duty cycle per 100 seconds to each eye.

RESULTS

A total of 44 eyes of 34 patients were treated with subliminal cyclophotocoagulation, with a mean follow-up time of 12 months. Surgical success was defined as IOP ranging 6 to 21 mm Hg or a 20% IOP reduction at the last 12 months follow-up visit. The mean age of patients was 63.83±16.2 years. The mean preoperative IOP was 32.8±11.8 mm Hg which then decreased postoperatively to 24.02±7.03 mm Hg after 1 day, 18.34±8.31 mm Hg after 1 week, 18.26±8.53 mm Hg after 1 month, 20.5±8.53 mm Hg after 3 months, 18.9±9.2 mm Hg after 6 months and 18.8±9.3 mm Hg after 12 months. Our preliminary study using Subcyclo transscleral cyclophotocoagulation with a 25% duty cycle showed a 37% IOP reduction from the baseline after 3 months with a single laser session and a 45% reduction at the last 12 months follow-up, after more than one laser session. The mean number of ocular antihypertensive medications used was 3.4±1.7 before treatment which decreased to 3.0±1.6 after treatment. No significant complications or anatomic modifications were found after subliminal cyclophotocoagulation.

CONCLUSIONS

Subliminal cyclophotocoagulation with a 25% duty cycle is a safe and effective procedure for reducing IOP in cases of refractory glaucoma and seems to be safer than conventional transscleral cyclophotocoagulation.

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.

Application of subthreshold laser therapy in retinal diseases: a review

Introduction

Laser photocoagulation has been a valuable tool in the ophthalmologist's armamentarium for decades. Conventional laser photocoagulation relies on visible retinal burns as a treatment endpoint, which is thought to result in photocoagulative necrosis of retinal tissue. Recent studies have suggested that using subthreshold (ST) laser, which does not cause detectable damage to the retina may also have therapeutic effects in a variety of retinal diseases. Areas covered: We review the proposed biological mechanisms mediating the therapeutic effects of subthreshold laser on the retina, followed by the evidence for ST laser efficacy in retinal diseases such as diabetic macular edema, central serous chorioretinopathy, age-related macular degeneration, and retinal vein occlusion.

Expert Commentary

Multiple clinical studies demonstrate that subthreshold laser does not cause structural damage to the retina based on multimodal imaging. Evidence suggests that there is a therapeutic effect on decreasing diabetic macular edema and subretinal fluid in chronic central serous retinopathy; however, the effect may be relatively modest and is not as efficacious as first line treatments for these diseases. Given the repeatability and lack of damage to the retina by this treatment, subthreshold laser deserves further study to determine its place in the retina specialist's armamentarium.

Subthreshold Continuous Wave Autofluorescence-controlled Laser Treatment of Chronic Central Serous Chorioretinopathy

Purpose

To investigate the therapeutic effect of clinically invisible subthreshold continuous wave autofluorescence-controlled laser treatment on visual acuity and macular status of patients with chronic central serous chorioretinopathy (CSCR).

Methods

In this prospective case series, patients with clinical and fluorescein angiographic (FA) findings of CSCR and chronic visual loss (>6 months) were included. Complete ocular examination, FA, and optical coherence tomography (OCT) tests were performed. Each eye was subjected to a direct laser treatment of leakage points by 532 nm continuous wave low energy laser pulses, which were kept invisible by reducing the power to 70% of the threshold test spot. Considering the lack of visible effect on the retinal pigment epithelium (RPE), the laser effect was monitored by pre- and post -treatment infrared and autofluorescence images.

Results

A total of 20 patients were included in this study, of whom 12 patients (9 male and 3 female patients) with an average age of 38 years had complete follow-up (Average: 3.5 months). The mean preoperative visual acuity was 20/80, which improved to 20/40 at the final visit. The mean preoperative central macular thickness (CMT) was 330 μm and the average final CMT in the last OCT test was 188 μm (P = 0.001).

Conclusion

Subthreshold continuous wave autofluorescence-controlled laser treatment may be a good treatment for chronic CSCR to avoid the risks of retinal damage by clinically suprathreshold laser therapy.

Functional and morphological outcome in patients with chronic central serous chorioretinopathy treated by subthreshold micropulse laser

Background

Chronic central serous chorioretinopathy is a serious therapeutic problem as it may lead to significant visual impairment. The aim of this retrospective study is to evaluate functional and morphological effects, as well as factors influencing visual outcome in patients treated by subthreshold micropulse laser.

Methods

Fifty-one eyes with chronic central serous chorioretinopathy lasting longer than 4 months (18 months on average) underwent up to two sessions of subtreshold micropulse laser treatment. Change in best corrected visual acuity, central retinal thickness, central retinal volume, average central retinal thickness and maximum subretinal fluid height were measured. Relation between the effects of the treatment and the initial retinal morphological and functional parameters was then analyzed.

Results

The total resorption of subretinal fluid was achieved in 36 cases (70.6%). There was, however, only a minor improvement in best corrected visual acuity of approximately one line on the Snellen chart. No correlation was observed between the effects of the treatment and the duration of the symptoms, retinal morphology and initial visual acuity. Younger patients responded better to the therapy.

Conclusion

Subthreshold micropulse laser treatment in chronic serous chorioretinopathy provides good morphological results, however significant improvement of visual acuity is not to be expected.

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.

Tissue response of selective retina therapy by means of a feedback-controlled energy ramping mode

BACKGROUND

The purpose of the study was to evaluate the safety and selectivity of the retinal pigment epithelium lesions by using automatic energy ramping and dosimetry technique for selective retina therapy and to investigate the healing response.

METHODS

Ten eyes of Chinchilla Bastard rabbits were treated with an automatic dosage controlled selective retina therapy laser (frequency doubled Q-switched Nd:YLF, wavelength: 527 nm, pulse duration: 1.7 μs, repetition rate: 100 Hz, pulse energy: linear increasing from pulse to pulse up to shut down - maximal 110 μJ, max. number of pulses in a burst: 30, retinal spot diameter: 133 μm). After treatment, fundus photography, optical coherence tomography and fluorescein angiography were performed at three time points from 1 h to 3 weeks. Histological analysis was performed.

RESULTS

A total of 381 selective retina therapy laser spots were tested (range 13-104 μJ).Typical fundus photographs obtained at 1 h after irradiation showed that 379 out of 381 lesions produced by selective retina therapy were not visible ophthalmoscopically and the lesions could be detected by angiography only. Optical coherence tomography images revealed that the structure of photoreceptors was preserved, but a disrupted retinal pigment epithelium layer was observed as was expected. By 3 weeks, histology showed selective retinal pigment epithelium damage without any effect on the inner retina and focal proliferation of the retinal pigment epithelium layer.

CONCLUSIONS

Automatically controlled selective retina therapy is a significant improvement in this innovative treatment. It could be demonstrated that the non-contact, reflectometric technique with a controlled pulse energy ramp is safe and selective.

Recruitment of stem cells into the injured retina after laser injury

Retinal degeneration is a devastating complication of diabetes and other disorders. Stem cell therapy for retinal degeneration has shown encouraging results but functional regeneration has not been yet achieved. Our study was undertaken to evaluate the localization of stem cells delivered to the retina by intravenous versus intravitreal infusion, because stem cell localization is a key factor in ultimate in vivo function. We used lineage-negative bone marrow-derived stem cells in a model wherein retina of mice was induced by precise and reproducible laser injury. Lin(-ve) bone marrow cells (BMCs) were labeled with a tracking dye and their homing capacity was analyzed at time points after infusion. We found that Lin(-ve) BMCs get incorporated into laser-injured retina when transplanted through either the intravitreal or intravenous route. The intravenous route resulted in optimal localization of donor cells at the site of injury. These cells incorporated into injured retina in a dose-dependent manner. The data presented in this study reflect the importance of dose and route for stem cell-based treatment designed to result in retinal regeneration.

Long-term therapeutic efficacy of the subthreshold micropulse diode laser photocoagulation for diabetic macular edema

PURPOSE

To investigate the long-term efficacy of subthreshold micropulse diode laser photocoagulation (SMDLP) on diabetic macular edema (DME).

METHODS

The effects of SMDLP (810 nm) were studied on 56 eyes of 44 patients with DME. Optical coherence tomography-determined foveal thickness and best-corrected visual acuity (BCVA) were evaluated at 1, 3, 6, and 12 months after the SMDLP.

RESULTS

The mean foveal thickness was 504 μm before the SMDLP, and it was significantly reduced to 439 μm at 1 month (P = 0.001), 409 μm at 3 months (P < 0.0001), 358 μm at 6 months (P < 0.0001), and 320 μm at 12 months (P < 0.0001). The mean BCVA at baseline was 0.47 logarithm of the minimal angle of resolution (logMAR) units, and it was not changed significantly at all of the postoperative examinations. Among the 56 eyes, 10 (17.8%) had an improvement of BCVA of >0.2 logMAR units, 36 (64.2%) remained the same, and 10 eyes (17.8%) had a reduction of >0.2 logMAR units at 12 months postoperatively.

CONCLUSION

Our results indicate that SMDLP has a beneficial effect on DME. However, prospective studies are needed to evaluate this technique in more detail.

Long-term SD-OCT/SLO imaging of neuroretina and retinal pigment epithelium after subthreshold infrared laser treatment of drusen

PURPOSE

The purpose of this study was to determine the long-term effect of subthreshold diode laser treatment for drusen in patients with nonexudative age-related macular degeneration with spectral domain optical coherence tomography combined with simultaneous scanning laser ophthalmoscope.

METHODS

Eight eyes of four consecutive age-related macular degeneration patients with bilateral drusen previously treated with subthreshold diode laser were imaged with spectral domain optical coherence tomography/scanning laser ophthalmoscope. Abnormalities in the outer retinal layers' reflectivity as seen with spectral domain optical coherence tomography/scanning laser ophthalmoscope were retrospectively analyzed and compared with color fundus pictures, and autofluorescence images were acquired immediately before and after the laser treatment.

RESULTS

A focal discrete disruption in the reflectivity of the outer retinal layers was noted in 29% of the laser lesions. The junction in between the inner and outer segment of the photoreceptor was more frequently affected, with associated focal damage of the outer nuclear layer. Defects of the retinal pigment epithelium were occasionally detected. These changes did not correspond to threshold burns on color fundus photography but corresponded to focal areas of increased autofluorescence in the majority of the cases.

CONCLUSION

Subthreshold diode laser treatment causes long-term disruption of the retinal photoreceptor layer as analyzed by spectral domain optical coherence tomography/scanning laser ophthalmoscope. The concept that subthreshold laser treatment can achieve a selected retinal pigment epithelium effect without damage to rods and cones may be flawed.

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.

[Central serous chorioretinopathy (CSC)]

In the acute stage central serous chorioretinopathy (CSC) is characterized by serous retinal detachment. Monofocal or multifocal structural changes of the pigment epithelium layer are common. Unilateral blurred vision is the major clinical symptom. The pathogenesis is unclear but corticosteroids and stress may trigger the disease. Normal vision often returns spontaneously within a few months. Therapeutic options are at a low evidence level. Carbonic anhydrase, mild laser photocoagulation, selective retinal therapy, photodynamic therapy and the intravitreal injection of bevacizumab have been reported. The authors suggest a treatment strategy on the basis of the available data.

Micropulse transscleral diode laser cyclophotocoagulation in the treatment of refractory glaucoma

BACKGROUND

Transscleral diode laser cyclophotocoagulation (TSCPC) is an established method of treatment for refractory glaucoma, but is associated with significant complications. This study evaluates the efficacy and safety of a new form of TSCPC using micropulse diode laser and trans-pars plana treatment with a novel contact probe.

METHODS

Prospective interventional case series of 40 eyes of 38 consecutive patients with refractory glaucoma treated with micropulse TSCPC with a novel probe. Outcomes measured were success, hypotony and response rates.

RESULTS

The mean age of patients was 63.2 +/- 16.0 years. The mean follow-up period was 16.3 +/- 4.5 months. The mean intraocular pressure (IOP) before micropulse TSCPC was 39.3 +/- 12.6 mmHg. Mean IOP decreased to 31.1 +/- 13.4 mmHg at 1 day, 28.0 +/- 12.0 mmHg at 1 week, 27.4 +/- 12.7 mmHg at 1 month, 27.1 +/- 13.6 mmHg at 3 months, 25.8 +/- 14.5 mmHg at 6 months, 26.6 +/- 14.7 mmHg at 12 months and 26.2 +/- 14.3 mmHg at 18 months (P < 0.001 at all time points). No patient had hypotony or loss of best-corrected visual acuity. The overall success rate after a mean of 1.3 treatment sessions was 72.7%.

CONCLUSION

Micropulse TSCPC is a safe and effective method of lowering IOP in cases of refractory glaucoma and is comparable with conventional TSCPC.

Development and recovery of laser-induced retinal lesion in rats

PURPOSE

Laser-induced retinal lesions undergo primary and secondary degeneration followed by a partial reduction of the lesion size. To evaluate treatment effects, detailed data regarding the changes of the lesion over time are essential. The purpose of the study is to describe the histologic changes in an argon laser-induced retinal lesion over a period of 60 days.

METHODS

Argon laser lesions were produced in retinas of pigmented rats. The lesions were examined by light microscopy 1 hour and 1, 2, 3, 20, and 60 days after the exposure.

RESULTS

The diameter of the lesion increased 24 hours after photocoagulation and then decreased by day 20. Most pyknotic nuclei seen in the outer nuclear layer 1 hour after lasering disappeared 3 days later. Remodeling began 3 days after lasering. By day 60, partial filling in of the empty area with sliding of adjacent nuclei was observed. Recovery was also seen in the other retinal layers.

CONCLUSION

The course of a laser-induced retinal lesion is gradual: the photoreceptors are damaged first and the damage then spreads to other layers and to the adjacent retina. By day 3, the damage spreading stops, and adjacent cells begin to fill in and remodel the area of the lesion.

Reduction of fluence to decrease pain during panretinal photocoagulation in diabetic patients

BACKGROUND AND OBJECTIVE

To assess the effect of laser fluence reduction to reduce pain during panretinal photocoagulation.

PATIENTS AND METHODS

Twenty-five patients (50 eyes) with diabetic retinopathy who had indication for panretinal photocoagulation were included in this prospective, interventional, and comparative study. The right eyes were treated using low fluence parameters (LFP), whereas the left eyes were treated with standard fluence parameters (SFP). At the end of each session, the patient was asked to rate pain from 0 (no pain) to 10 (maximum pain) for each eye (NRS-11 scale). Fluence per burn and total fluence were determined for each eye. Statistical analysis was performed using the Mann-Whitney U test and the Pearson correlation coefficient.

RESULTS

Pain perception (P < .01) and fluence per burn (P < .01) were significantly less using LFP compared with SFP. Pain was proportional to fluence per burn (R(2) = 0.4), but not to number of burns (R(2) = -0.2).

CONCLUSION

The use of LFP seems to be a good option to diminish the pain during panretinal photocoagulation.

Dynamics of retinal photocoagulation and rupture

In laser retinal photocoagulation, short (<20 ms) pulses have been found to reduce thermal damage to the inner retina, decrease treatment time, and minimize pain. However, the safe therapeutic window (defined as the ratio of power for producing a rupture to that of mild coagulation) decreases with shorter exposures. To quantify the extent of retinal heating and maximize the therapeutic window, a computational model of millisecond retinal photocoagulation and rupture was developed. Optical attenuation of 532-nm laser light in ocular tissues was measured, including retinal pigment epithelial (RPE) pigmentation and cell-size variability. Threshold powers for vaporization and RPE damage were measured with pulse durations ranging from 1 to 200 ms. A finite element model of retinal heating inferred that vaporization (rupture) takes place at 180-190 degrees C. RPE damage was accurately described by the Arrhenius model with activation energy of 340 kJ/mol. Computed photocoagulation lesion width increased logarithmically with pulse duration, in agreement with histological findings. The model will allow for the optimization of beam parameters to increase the width of the therapeutic window for short exposures.

Retina remodeling following diode laser

BACKGROUND

The purpose of this study was to characterize the sequential development of focal and surround retinal injury and repair following transscleral diode laser to rat retina.

METHODS

Transscleral laser photocoagulation of the retina was induced with a diode laser (DioPexy Probe, 810 nm, 200 mW, 2 seconds) in adult Long-Evans rats. The right eye of rats with survival times of 0 days (n = 4), 5 days (n = 6), 2 weeks (n = 4), 6 weeks (n = 6), and 12 weeks (n = 4) was studied. Using serial sections, detailed pathological changes in laser-treated and surrounding retinal and choroidal areas were compared with the control fellow eye.

RESULTS

Photocoagulation damage was limited to the retina, sparing Bruch's membrane, with minimal choroidal involvement in almost all cases (23/24 eyes). Following damage to the neural retina, the sequence of major remodeling processes was consistent and included inflammatory response, reparative changes, and formation of glial-vascular scar with neovascularization.

INTERPRETATION

This new laser model caused reproducible injury, inflammation, and scarring confined to the retina, and may be a tool to help test the effects of candidate neuroprotective/regenerative agents on retinal degeneration to prevent vision loss.

Diode laser-induced mitosis in the rabbit retinal pigment epithelium

BACKGROUND AND OBJECTIVE

The induction of retinal pigment epithelium (RPE) proliferation without damaging the inner layers of the retina might be helpful in patients with RPE atrophic changes and degeneration. This study aimed to induce mitosis in the RPE of the rabbit after subthreshold photocoagulation with the diode laser.

MATERIALS AND METHODS

Twenty-five male Dutch rabbits received retinal photocoagulation using an 810-nm diode laser with different power settings and exposure times. The eyes were processed for light microscopy, electron transmission microscopy, and immunohistochemistry.

RESULTS

Neither morphological alterations nor mitotic activity was found after 5-mJ energies. Retinal layers were not affected and RPE hyperplasia appeared in the treated areas associated with mitotic activity when 10 mJ was used. Mitosis induction and retinal damage appeared with 20, 50, and 100 mJ and were associated with ophthalmoscopic damage.

CONCLUSIONS

The use of subthreshold 810-nm diode laser treatment may induce mitosis in the RPE without causing damage to the neighboring layers.

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.

Chorioretinal scar growth after 810-nanometer laser treatment for retinoblastoma

PURPOSE

To determine the extent of expansion of laser scars after single treatment with transpupillary thermotherapy (TTT) for retinoblastoma.

DESIGN

We retrospectively reviewed medical records and RetCam (Massie Industries, Dublin, CA) digital fundus photographs of patients with retinoblastoma who received TTT by use of an 810-nm diode laser with large-spot indirect ophthalmoscope. Digital images were measured by use of RetCam software beginning immediately after treatment. Lesions were measured in both linear size and area by 2 observers. In addition, optic disc diameters were also measured for each image.

PARTICIPANTS

We identified 9 patients with hereditary retinoblastoma who were treated from 1997 to 2000.

MAIN OUTCOME MEASURES

Linear and area expansion of laser scars as a function of time.

RESULTS

Fourteen tumors in 10 eyes were treated successfully with 1 session of TTT. Follow-up for all eyes was at least 16 months. Scars of 12 of the 14 lesions increased beyond their original borders (mean starting linear diameter, 2.02 mm; range 1.46-2.59 mm; mean increase, 0.72 mm [36%]) over time, most within 6 months to 1 year after treatment.

CONCLUSIONS

Scars from TTT for retinoblastoma may increase in size after treatment. This expansion must be considered when applying TTT to tumors near vital macular structures, such as the fovea and optic nerve.

Predictors of drusen reduction after subthreshold infrared (810 nm) diode laser macular grid photocoagulation for nonexudative age-related macular degeneration

PURPOSE

To determine the predictors of drusen reduction in eyes with nonexudative age-related macular degeneration (ARMD) treated with subthreshold infrared (810 nm) diode laser macular grid photocoagulation. Additionally, to determine the relationship of laser-induced drusen reduction and best-corrected visual acuity (BCVA) 18 months after laser treatment.

DESIGN

Randomized controlled clinical trial.

METHODS

Fifty patients (100 eyes) with bilateral nonexudative ARMD were enrolled at two centers. One eye of each patient was randomized to the observation; the other eye was treated with 48 subthreshold (invisible end point) applications of infrared (810 nm) diode laser in a macular grid pattern. The eyes that received subthreshold laser treatment were compared with the eyes that received no treatment. The baseline fundus characteristics (number, size, and distribution of drusen, as well as focal hyperpigmentation) from two macula areas (central 1500 micro diameter, pericentral 1500 micro ring area) on stereo color photographs, the number of laser-induced lesions, and the area of laser induced retinal pigment epithelial (RPE) lesions on fluorescein angiography 3 months after treatment were studied as predictors of major drusen reduction (> or = 50% drusen reduction from baseline) 18 months after laser treatment. BCVA at baseline and 18 months later was compared in observation eyes and in laser-treated eyes.

RESULTS

Eighteen months after randomization, 24 (48%) of 50 eyes treated with subthreshold laser had major drusen reduction compared with three (6%) of 50 observation eyes (P =.00001). At 3 months post-treatment in laser-treated eyes with major drusen reduction, the mean number of laser-induced lesions on fluorescein angiography was 30.7 and the mean area of RPE change was 0.81 mm(2) compared with 14.8 laser-induced lesions and 0.35 mm(2) area of RPE change in eyes without major drusen reduction (P =.0001 and P =.0003, respectively). At baseline, fundus characteristics were not significantly different between observation eyes and laser-treated eyes or between the major drusen reduction group and the nonmajor drusen reduction group. At 18 months after treatment, BCVA was not significantly different in laser-treated eyes and in observation eyes.

CONCLUSIONS

Subthreshold infrared (810 nm) diode laser macular grid photocoagulation in eyes with nonexudative ARMD significantly reduced drusen 18 months after laser treatment. Both the number of subthreshold laser lesions and the area of RPE changes visible on fluorescein angiography 3 months after treatment appeared to be predictors for major drusen reduction 18 months after treatment. However, it remains to be determined whether laser-induced drusen reduction is beneficial for visual acuity or reduces the incidence of choroidal neovascularization (CNV) in eyes with nonexudative ARMD.

Yellow dye laser thermotherapy of choroidal neovascularisation in age related macular degeneration

AIM

A pilot study of the feasibility of using dye laser thermotherapy (LTT) at a subcoagulation temperature to occlude newly formed vessels in patients with age related macular degeneration (AMD).

METHODS

Choroidal neovascularisation (CNV) in 24 eyes with exudative AMD was treated with a continuous wave yellow laser at 578 nm. Parameters were an exposure time of 2 or 5 seconds, a spot size of 750 or 1000 microm, and a laser power of 100-200 mW. The clinical end point was a greyish discoloration at the treatment site. The effect of thermotherapy was documented by ophthalmoscopic and fluorescein angiographic examination. The follow up after LTT was 4-16 months, mean 5 months.

RESULTS

LTT resulted in total occlusion of newly formed vessels in 15 eyes (62.5%). Neovascular outgrowth within 6 weeks and recurrences 2-4 months after LTT were observed, each in three eyes. In six of the nine eyes with occlusion of CNV without recurrence the choriocapillaris remained perfused; in two eyes only the large choroidal vessels remained perfused. In six eyes pigmentary changes were the only ophthalmoscopic and fluorescein angiographic signs of treatment. The effect of LTT is rather unpredictable.

CONCLUSION

CNV in AMD can effectively be treated by yellow dye laser thermotherapy with preservation of choroidal perfusion. The technique requires dosimetric adaptation.

Decreasing retinal photocoagulation damage: principles and techniques

Conventional suprathreshold retinal photocoagulation is a destructive procedure, but chorioretinal damage can be decreased by changing laser parameters and clinical endpoints. Laser effects can be localized by decreasing laser wavelength, spot size, and exposure duration, as well as by adopting threshold or subthreshold treatment protocols. Problems with short-pulse treatment regimens can be circumvented by the use of repetitively pulsed laser photocoagulators. Preliminary clinical results with reduced-damage photocoagulation methods are promising and await confirmation in larger, controlled clinical trials.

Therapeutic benefits of infrared (810-nm) diode laser macular grid photocoagulation in prophylactic treatment of nonexudative age-related macular degeneration: two-year results of a randomized pilot study

OBJECTIVE

This pilot study collected preliminary information on the effectiveness and safety of infrared (810-nm) diode laser macular grid photocoagulation in patients with nonexudative age-related macular degeneration (AMD). Results from this pilot study were used in designing a larger, multicenter, randomized clinical trial.

DESIGN

A multicenter, randomized, controlled, clinical trial.

PARTICIPANTS

A total of 229 eyes of 152 patients with AMD were enrolled in the pilot study. Seventy-five patients with 1 eye eligible (75 eyes) were enrolled in the unilateral arm of the study; 77 patients with both eyes eligible (154 eyes) were enrolled in the bilateral arm of the study. In the unilateral study arm, 32 eyes were randomized to the observation group, 27 eyes were treated with visible endpoint burns, and 16 eyes were treated with invisible endpoint (subthreshold) lesions. In the bilateral study arm, 77 eyes were in the observation group, 36 eyes were treated with visible burns, and 41 eyes were treated with subthreshold (invisible) lesions.

INTERVENTION

Eyes were treated with infrared (810-nm) diode laser macular grid photocoagulation using either visible burns or subthreshold (invisible) lesions and compared to eyes receiving no treatment.

MAIN OUTCOME MEASURES

Reduction of drusen, change in visual acuity, and rate of choroidal neovascularization (CNV) membrane formation.

RESULTS

At 12 months after treatment, 62% of eyes treated with visible burns had a clinically significant reduction in drusen, whereas this proportion (65%) was reached in 18 months for eyes treated with subthreshold lesions. At 24 months' follow-up, treated eyes had a significant reduction in drusen compared to observation eyes (P < 0.0001). Visual acuity was significantly improved in treated eyes at 12, 18, and 24 months compared to observation eyes (P < 0.001). Choroidal neovascularization formation was similar in treated and observation eyes through 24 months' follow-up. Complications included CNV associated with six eyes treated with visible burns and a juxtafoveal laser scar in one eye treated with visible burns.

CONCLUSIONS

Infrared (810-nm) diode laser macular grid photocoagulation in patients with nonexudative AMD significantly reduces drusen levels (P < 0.0001) and significantly improves visual acuity (P < 0.001) when either visible endpoint burns or subthreshold endpoint lesions are used. Complications were fewer using subthreshold endpoint lesions. A larger, multicenter, prospective clinical trial with longer follow-up is needed to determine the efficacy of treatment in reducing the rate of CNV formation. Data from this clinical pilot study have been used to design the Prophylactic Treatment of AMD Trial (PTAMD), a multicenter, randomized, prospective clinical trial currently in progress comparing subthreshold (invisible) treatment to observation in eyes with nonexudative AMD.