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

Long-Term Multimodal Imaging Analysis of Selective Retina Therapy Laser Lesions

This study evaluates the long-term effects of selective retina therapy (SRT) on the retinal pigment epithelium (RPE) and neuroretina in patients with central serous chorioretinopathy. SRT was performed on 36 patients using a Nd:YLF-Laser at 527 nm (R:GEN®, Lutronic, Goyang-Si, Republic of Korea). A total of 994 titration spots were examined using up to three years’ multimodal imaging. Leakage in fluorescein angiography (FA) was observed after SRT in 523 lesions and resolved after one month. SRT lesions were not visible clinically, but appeared as brightly reflective areas in infrared and multicolor images. Normal morphology was observed in optical coherence tomography (OCT) immediately after SRT. After one month, thickening of the RPE and interdigitation zone changes were seen and disappeared after 539 ± 308 days. No RPE atrophies occurred during the observation period. Decreased fundus autofluorescence (FAF) was mostly observed directly after SRT followed by increased FAF at one month, which faded over time. A significant decrease in the number of visible lesions in the FA and FAF was observed within the three-year follow-up. OCT findings are consistent with animal studies showing SRT-related defect closure by hypertrophy and migration of neighboring cells without RPE atrophy or photoreceptor damage. This suggests that SRT is a safe treatment option for macular diseases and does not lead to retinal atrophy.

Algorithms for optoacoustically controlled selective retina therapy (SRT)

OBJECTIVES

Selective Retina Therapy (SRT) uses microbubble formation (MBF) to target retinal pigment epithelium (RPE) cells selectively while sparing the neural retina and the choroid. Intra- and inter-individual variations of RPE pigmentation makes frequent radiant exposure adaption necessary. Since selective RPE cell disintegration is ophthalmoscopically non-visible, MBF detection techniques are useful to control adequate radiant exposures. It was the purpose of this study to evaluate optoacoustically based MBF detection algorithms.

METHODS

Fifteen patients suffering from central serous chorioretinopathy and diabetic macula edema were treated with a SRT laser using a wavelength of 527 nm, a pulse duration of 1.7 µs and a pulse energy ramp (15 pulses, 100 Hz repetition rate). An ultrasonic transducer for MBF detection was embedded in a contact lens. RPE damage was verified with fluorescence angiography.

RESULTS

An algorithm to detect MBF as an indicator for RPE cell damage was evaluated. Overall, 4646 irradiations were used for algorithm optimization and testing. The tested algorithms were superior to a baseline model. A sensitivity/specificity pair of 0.96/1 was achieved. The few false algorithmic decisions were caused by unevaluable signals.

CONCLUSIONS

The algorithm can be used for guidance or automatization of microbubble related treatments like SRT or selective laser trabeculoplasty (SLT).

Factors Predicting Response to Selective Retina Therapy in Patients with Chronic Central Serous Chorioretinopathy

This retrospective study aimed to assess the safety and efficacy of selective retina therapy (SRT) with real-time feedback-controlled dosimetry (RFD) for chronic central serous chorioretinopathy (CSC) and to evaluate factors predictive of treatment response. We included 137 eyes of 135 patients with chronic CSC. SRT was performed to cover each of the leakage areas on fundus fluorescein angiography. Changes in mean best-corrected visual acuity (BCVA), central macular thickness (CMT), and subretinal fluid (SRF) height were evaluated at baseline and at 3 and 6 months after treatment. Complete SRF resolution was observed in 52.6% (72/137 eyes) and 90.5% (124/137 eyes) at 3 and 6 months, respectively. Mean BCVA (logMAR) significantly improved from 0.41 ± 0.31 at baseline to 0.33 ± 0.31 at month 6 (p < 0.001). Mean CMT significantly decreased from 347.67 ± 97.38 μm at baseline to 173.42 ± 30.95 μm at month 6 (p < 0.001). Mean SRF height significantly decreased from 187.85 ± 97.56 µm at baseline to 8.60 ± 31.29 µm after 6 months (p < 0.001). Baseline SRF height was a significant predictive factor for retreatment requirement (p = 0.008). In conclusion, SRT showed favorable anatomical outcomes in patients with chronic CSC. A higher baseline SRF height was a risk factor for retreatment.

The Effect of Selective Retina Therapy for Bevacizumab-Resistant Chronic Central Serous Chorioretinopathy

PURPOSE

The aim of this study was to evaluate the efficacy of selective retina therapy (SRT), used in conjunction with real-time feedback dosimetry (RFD), in the treatment of bevacizumab-resistant chronic central serous chorioretinopathy (CSC).

PATIENTS AND METHODS

In this retrospective cohort study, 22 eyes of 22 patients with bevacizumab-resistant chronic CSC, showing focal or diffuse foveal leakages on fundus fluorescein angiography (FFA), were included. After evaluation of the test spots at temporal arcades, SRT (wavelength, 527 nm; pulse repetition rate, 100 Hz; ramping over maximal 15 micropulses; and spot diameter, 200 μm) using RFD was applied to the leakage sites observed on FFA. Changes in the mean best-corrected visual acuity (BCVA), central macular thickness (CMT), and subretinal fluid (SRF) height were evaluated at baseline and at 1, 3, 6, 9, and 12 months following treatment.

RESULTS

SRF completely resolved in 81.8% (18/22 eyes) cases at 12 months post-treatment. The mean BCVA (logarithm of the minimum angle of resolution [logMAR]) improved from 0.49 ± 0.29 at baseline to 0.43 ± 0.36 at 12 months (p = 0.067). The mean BCVA gain was 0.06 logMAR, equivalent to 3 ETDRS letters. The CMT significantly decreased from 323 ± 85.6 μm at baseline to 221.5 ± 60.4 μm at 12 months (p < 0.001). The mean SRF height also significantly decreased from 174.6 ± 86.4 μm at baseline to 35.1 ± 75.4 μm at 12 months (p < 0.001).

CONCLUSION

SRT showed favorable visual and anatomical outcomes in patients with bevacizumab-resistant chronic CSC.

Investigations on Retinal Pigment Epithelial Damage at Laser Irradiation in the Lower Microsecond Time Regime

Purpose

New lasers with a continuous wave power exceeding 15 W are currently investigated for retinal therapies, promising highly localized effects at and close to the Retinal Pigment Epithelium (RPE). The goal of this work is to evaluate mechanisms and thresholds for RPE cell damage by means of pulse durations up to 50 µs.

Methods

A diode laser with a wavelength of 514 nm, a power of 15 W, and adjustable pulse durations between 2 µs and 50 µs was used. Porcine RPE-choroidal explants (ex vivo) and chinchilla bastard rabbits (in vivo) were irradiated to determine threshold radiant exposures for RPE damage H¯Cell by calcein vitality staining and fluorescence angiography, respectively. Thresholds for microbubble formation (MBF) H¯MBF were evaluated by time-resolved optoacoustics. Exemplary histologies support the findings.

Results

H¯MBF is significantly higher than H¯Cell at pulse durations ≥ 5 µs (P < 0.05) ex vivo, while at 2 µs, no statistically significant difference was found. The ratios between H¯MBF and H¯Cell increase with pulse duration from 1.07 to 1.48 ex vivo and 1.1 to 1.6 in vivo, for 5.2 and 50 µs.

Conclusions

Cellular damage with and without MBF related disintegration are both present and very likely to play a role for pulse durations ≥ 5 µs. With the lower µs pulses, selective RPE disruption might be possible, while higher values allow achieving spatially limited thermal effects without MBF. However, both modi require a very accurate real-time dosing control in order to avoid extended retinal disintegration in this power range.

The Effect of Selective Retina Therapy with Automatic Real-Time Feedback-Controlled Dosimetry for Chronic Central Serous Chorioretinopathy: A Randomized, Open-Label, Controlled Clinical Trial

This prospective randomized controlled trial evaluated the safety and efficacy of real-time feedback-controlled dosimetry (RFD)-guided selective retina therapy (SRT) in chronic central serous chorioretinopathy (CSC). Forty-four participants with chronic CSC were included and randomly assigned to the control group or SRT group. The SRT laser system with RFD-guidance was applied to cover the entire leakage area. If SRF remained at the 6-week follow-up visit, re-treatment and rescue SRT was performed for the SRT group and crossover group, respectively. The rate of complete resolution of subretinal fluid (SRF), mean SRF height, and mean retinal sensitivity were compared between the two groups at 6-weeks post-treatment. The complete SRF resolution rate in all SRT-treated eyes was evaluated at 12-weeks post-treatment. The rate of complete SRF resolution was significantly higher in the SRT group (63.6%) than in the control group (23.8%) at 6-weeks post-treatment (p = 0.020). The mean SRF height at 6 weeks after SRT was significantly lower in the SRT group (p = 0.041). Overall, SRT-treated eyes showed complete SRF resolution in 70.3% of eyes at 12-weeks post-treatment. RFD-guided SRT was safe and effective to remove SRF in chronic CSC patients during the 3-month follow-up period.

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

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

Retinal pigment epithelial responses based on the irradiation density of selective retina therapy

PURPOSE

We evaluated the response of the retinal pigment epithelium (RPE) to high-density (HD) or low-density (LD)-selective retina therapy (SRT) with real-time feedback-controlled dosimetry (RFD) in rabbits.

METHODS

Sixteen eyes of 8 Chinchilla Bastard rabbits underwent SRT with RFD (527-nm wavelength, 1.7-μs pulse duration), using automatically titrated pulse energy, by using optoacoustic dosimetry or real-time reflectometry. Fifty-six 25-μJ SRT, including LD-SRT (1-spot or 2-spot-spacing) and HD-SRT (4-spot, 7-spot, or 9-spot-no-spacing), were applied per eye. Color fundus photography and fundus fluorescein angiography (FFA) were used to confirm SRT spots 1-h post-SRT. Light microscopy and scanning electron microscopy (SEM) were performed at 2-h, 3-day, 7-day, and 1-month post-treatment.

RESULTS

We tested 896 spots irradiated by SRT with RFD and confirmed that SRT lesions were adequate, based on invisibility on fundoscopy and visibility on FFA. On SEM, at 2-h post-SRT, flattened RPE cells were observed in the center of the SRT lesion. While normal RPE cells were clearly observed between LD-SRT lesions, healthy RPE cells were rare in HD-SRT lesions at 2-h post-treatment. At 7-day post-SRT, SEM revealed completely restored LD-SRT lesions with small or large RPE cells with microvilli, whereas HD-SRT lesions were covered with RPE cells without microvilli. At 1-month post-SRT, SEM revealed restored RPE cells with microvilli in HD-SRT lesions. On light microscopy, both HD- and LD-SRT lesions were completely restored with adjacent RPE cells and spared photoreceptors at 1-month post-treatment.

CONCLUSIONS

Although both HD- and LD-SRT lesions had recovered at 1-month post-SRT, LD-SRT lesions healed faster than HD-SRT lesions.

One-Year Functional and Anatomical Outcomes After Selective Retina Therapy With Real-Time Feedback-Controlled Dosimetry in Patients With Intermediate Age-Related Macular Degeneration: A Pilot Study

BACKGROUND AND OBJECTIVES

This pilot study sought to evaluate changes in macular function and drusen volume (DV) after selective retina therapy (SRT) in patients with intermediate age-related macular degeneration (iAMD).

STUDY DESIGN/MATERIALS AND METHODS

Twenty participants with bilateral iAMD were included in this prospective interventional case series study. After titrating pulse energy by real-time feedback-controlled dosimetry, SRT with a wavelength of 527 nm was applied around the macula of one eye of each patient. Changes in best-corrected visual acuity (BCVA), DV within the central 5-mm ring (C5), and retinal sensitivity (RS) of the SRT-treated eyes (treated eyes) and untreated fellow eyes (untreated eyes) were evaluated at baseline and then at 3, 6, 9, and 12 months after treatment using linear mixed models.

RESULTS

The mean BCVA did not change significantly between baseline and 12 months in both treated and untreated eyes (P = 0.06, P = 0.24, respectively), whereas the BCVA increase rate was faster for treated than for untreated eyes at the 12-month visit (-0.072 logMAR; 95% confidence interval [CI], -0.085 to -0.059 logMAR; P = 0.006). The mean cube root transformation of DV (cube root DV) within C5 in the untreated eyes increased significantly from 0.278 ± 0.115 at baseline to 0.295 ± 0.132 mm (P = 0.027) at 12 months, whereas the cube root DV change in treated eyes was not significant (P = 0.553). The rate of increase in the cube root DV was lower in treated than in untreated eyes at the 12-month visit (-0.016 mm; 95% CI, -0.018 to -0.011 mm; P = 0.015). The mean RS was increased from 22.49 ± 2.40 dB to 24.09 ± 2.19 dB (P < 0.001) in the treated eyes, whereas the change of mean RS in the untreated eyes was not significant at the 12-month visit (P = 0.18). The treated eyes had a higher rate of increase in RS than untreated eyes at the 12-month visit (1.012 dB; 95% CI, 0.776-1.251 dB; P = 0.037). The RS change was significantly associated with the interaction between SRT treatment and time (P = 0.028), whereas it was not associated with cube root DV change (P = 0.106). No SRT-related adverse effects were observed in all participants during the 1-year follow-up.

CONCLUSION

Since SRT improved the mean RS and reduced the rate of change in drusen load in the treated eyes, as compared to the untreated eyes, SRT might slow the progression of iAMD. However, further large randomized clinical trials are necessary to confirm the efficacy of SRT for iAMD. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Potential of sub-microsecond laser pulse shaping for controlling microcavitation in selective retinal therapies

Pilot results showing the potential of sub-microsecond laser pulse shaping to optimize thermomechanical confinement in laser-tissue interactions involving microcavitation are presented. Model samples based on aqueous suspensions of retinal melanosomes and eumelanin particles were irradiated at 532 nm with nanosecond laser pulses and picosecond laser pulse trains having differing shapes and durations. The cavitation threshold radiant exposure and the bubble lifetime above the threshold were measured using a pump-probe setup and sub-nanosecond time-resolved imaging. Both quantities were found to strongly depend on the pulse format. These results suggest that sub-microsecond laser pulse shaping could be exploited to optimize precision and control in numerous applications of laser-directed microcavitation, including selective retinal laser treatments.

Towards Automatically Controlled Dosing for Selective Laser Trabeculoplasty

Purpose

Selective laser trabeculoplasty (SLT) is a treatment option for open-angle glaucoma; however, it lacks an instant evidence for successful irradiation. So far ophthalmologists use the visible appearance of permanent champagnelike bubbles (macro bubbles) as an indicator for appropriate pulse energy. We hypothesize that micro bubbles, which start energetically far below the appearance of macro bubbles, already trigger the therapeutic benefit. Here we present two methods to capture the onset of these micro bubbles.

Methods

The trabecular meshwork of freshly enucleated porcine eye globes was irradiated with a series of 15 pulses with a pulse duration of 1.7 μs and with increasing energy at a repetition rate of 100 Hz per each spot of 200 μm in diameter. An optical and an optoacoustic method have been developed and appropriate algorithms investigated towards the real-time detection of the onset of micro bubbles.

Results

Both observation methods are capable of detecting micro bubble nucleation. Threshold radiant exposures were found at 310 ± 137 mJ/cm². By combination of both methods a sensitivity and specificity of 0.96 was reached.

Conclusions

In case that the therapeutically demanded pressure reduction is already achieved with these micro bubbles, which needs to be proven clinically, then the methods presented here can be used in an automatic feedback loop controlling the laser irradiation. This will unburden the clinicians from any dosing during SLT.

Translational Relevance

Automatic real-time pulse energy dosing based on the formation of micro bubbles in SLT significantly improves and facilitates the treatment for the physician.

Retinal Laser Therapy Preserves Photoreceptors in a Rodent Model of MERTK-Related Retinitis Pigmentosa

Purpose

We investigated the effects of various retinal laser therapies on preservation of the photoreceptors in an animal model of Mer tyrosine kinase receptor (MERTK)-related retinitis pigmentosa (RP). These modalities included photocoagulation with various pattern densities, selective RPE therapy (SRT), and nondamaging retinal therapy (NRT).

Methods

Laser treatments were performed on right eyes of RCS rats, using one of three laser modalities. For photocoagulation, six pattern densities (spot spacings of 0.5, 1, 1.5, 3, 4, and 5 spot diameters) were delivered in 19-day-old animals, prior to the onset of photoreceptor degeneration, to determine the optimal treatment density for the best preservation of photoreceptors. The left eye was used as control. Rats were monitored for 6 months after treatment using electroretinography, optical coherence tomography, and histology.

Results

Photocoagulation resulted in long-term preservation of photoreceptors, manifested morphologically and functionally, with the extent of the benefit dependent on the laser pattern density. Eyes treated with a 1.5 spot size spacing showed the best morphologic and functional preservation during the 6-month follow-up. SRT-treated eyes exhibited short-term morphologic preservation, but no functional benefit. NRT-treated eyes did not show any observable preservation benefit from the treatment.

Conclusions

In a rodent model of MERTK-related RP, pattern photocoagulation of about 15% of the photoreceptors (1.5 spot diameter spacing) provides long-term preservation of photoreceptors in the treatment area.

Translational Relevance

Availability of retinal lasers in ophthalmic practice enables rapid translation of our study to clinical testing and may help preserve the sight in patients with photoreceptor degeneration.

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

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

Comparison of pre-retinal oxygen pressure changes after selective retina therapy versus conventional photocoagulation in the rabbit eye

PURPOSE

To evaluate oxygen consumption by photoreceptors, we estimated changes in pre-retinal oxygen pressure (PO₂) after selective retina therapy (SRT) compared with conventional photocoagulation (PC) in rabbits.

METHODS

One eye of each of 10 Chinchilla Bastard rabbits received both 144 laser SRT spots and 144 laser PC spots. Color fundus photography, optical coherence tomography (OCT), and fluorescein angiography were used to evaluate the lesions after treatment. Fiber-optic sensors (optodes) were used to determine the pre-retinal PO₂ levels of untreated, SRT-treated, and PC-treated areas of laser-damaged eyes 7 days after treatment. The pre-retinal PO₂ was measured in the other five eyes (controls). The same procedures were applied to these remaining five eyes 4 weeks after treatment. Light microscopy (LM) was used to evaluate histological changes 7 days and 4 weeks after treatment.

RESULTS

We found no significant difference in the mean pre-retinal PO₂ values among untreated, SRT-treated, and control eyes 7 days after treatment. However, the mean pre-retinal PO₂ value in PC-treated regions (24.3 ± 4.9 mmHg; mean ± SD) was higher than those in untreated regions (17.0 ± 1.8 mmHg; P = 0.019), SRT-treated regions (16.7 ± 2.6 mmHg; P = 0.015), and controls (16.9 ± 2.4 mmHg; P = 0.018). Similarly, the mean pre-retinal PO₂ of only PC-treated regions (25.2 ± 4.7 mmHg) was higher than those of the untreated regions (16.3 ± 2.5 mmHg; P = 0.006), SRT-treated regions (17.7 ± 3.1 mmHg; P = 0.023), and controls (16.4 ± 2.4 mmHg; P = 0.007) 4 weeks after treatment. OCT and LM revealed selective retinal pigment epithelium damage with the sparing of photoreceptors in SRT lesions.

CONCLUSIONS

SRT treatment did not induce changes in the oxygen consumption of photoreceptors, or the pre-retinal PO₂.

Motion-invariant SRT treatment detection from direct M-scan OCT imaging

PURPOSE

Selective retina therapy (SRT) is a laser treatment targeting specific posterior retinal layers. It is focused on inducing damage to the retinal pigment epithelium (RPE), while sparing other retinal tissue compared to traditional photocoagulation. However, the targeted RPE layer is invisible with most imaging modalities and induced SRT lesions cannot be monitored. In this work, imaging scans acquired from an experimental setup that couples the SRT laser beam with an optical coherence tomography (OCT) beam are analyzed in order to evaluate the treatment as they occur.

METHODS

We isolated a small part of the time-resolved scan corresponding to the end of the treatment, for which we have microscopic evidence of the SRT outcome. We then use a convolutional neural network to correspond each scan to the treatment result. We explore which aspects of the scan convey more valuable information for a robust therapy evaluation. By only using this adequately small part, we can achieve an online estimation, while being resilient to eye movement.

RESULTS

The available dataset consists of time- resolved OCT scans of 98 ex vivo porcine eyes, treated with different energy levels. The proposed method yields high performance in the task of predicting whether the applied energy was adequate for SRT treatment, by focusing on the immediate OCT signal acquired during treatment time.

CONCLUSIONS

We propose a strategy toward online noninvasive SRT treatment assessment, able to provide a satisfying evaluation of a treatment status, that therefore could be used for the planning of the treatment continuation.

Selective Retina Therapy with Real-Time Feedback-Controlled Dosimetry for Treating Acute Idiopathic Central Serous Chorioretinopathy in Korean Patients

PURPOSE

To evaluate short-term treatment outcomes following selective retina therapy (SRT) with real-time feedback-controlled dosimetry in Korean patients with acute idiopathic central serous chorioretinopathy (CSC).

METHODS

Sixteen eyes (16 patients) with acute idiopathic CSC (symptom duration < 3 months) were included in this retrospective study. All patients underwent a single session of SRT with real-time feedback-controlled dosimetry. Best-corrected visual acuity (BCVA) and central foveal thickness (CFT) before and 3 months after treatment were examined and compared.

RESULTS

The logarithm of minimal angle of resolution BCVA was significantly better 3 months after treatment (0.16 ± 0.18) than at the time of diagnosis (0.27 ± 0.18, P = 0.002). Additionally, subretinal fluid had resolved in all 16 eyes 3 months after treatment and CFT was significantly lower 3 months after treatment (215.6 ± 17.9 μm) than at baseline (441.4 ± 124.8 μm, P < 0.001). No notable SRT-related complications were observed during the study period.

CONCLUSION

The results of the present study suggest that SRT is a useful therapeutic option for patients with acute idiopathic CSC. Further studies are required to better understand the long-term efficacy of this treatment. This trial is registered with clinical trial registration number NCT03339856.

Comparison of the neuroinflammatory responses to selective retina therapy and continuous-wave laser photocoagulation in mouse eyes

PURPOSE

This study investigated microglia and inflammatory cell responses after selective retina therapy (SRT) with microsecond-pulsed laser in comparison to continuous-wave laser photocoagulation (cwPC).

METHODS

Healthy C57BL/6 J mice were treated with either a train of short pulses (SRT; 527-nm, Q-switched, 1.7-μs pulse) or a conventional thermal continuous-wave (532-nm, 100-ms pulse duration) laser. The mice were sacrificed and their eyes were enucleated 1, 3, 7, and 14 days after both laser treatments. Pattern of cell death on retinal section was evaluated by TUNEL assay, and the distribution of activated inflammatory cells and glial cells were observed under immunohistochemistry. Consecutive changes for the expression of cytokines such as IL-1β, TNF-α, and TGF-β were also examined using immunohistochemistry, and compared among each period after quantification by Western blotting.

RESULTS

The numbers of TUNEL-positive cells in the retinal pigment epithelium (RPE) layer did not differ in SRT and cwPC lesions, but TUNEL-positive cells in neural retinas were significantly less on SRT. Vague glial cell activation was observed in SRT-treated lesions. The population of inflammatory cells was also significantly decreased after SRT, and the cells were located in the RPE layer and subretinal space. Proinflammatory cytokines, including IL-1β and TNF-α, showed significantly lower levels after SRT; conversely, the level of TGF-β was similar to the cwPC-treated lesion.

CONCLUSIONS

SRT resulted in selective RPE damage without collateral thermal injury to the neural retina, and apparently produced negligible glial activation. In addition, SRT showed a markedly less inflammatory response than cwPC, which may have important therapeutic implications for several macular diseases.

Advances in Retinal Laser Therapy

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

Automatic assessment of time-resolved OCT images for selective retina therapy

Purpose

In recent years, selective retina laser treatment (SRT), a sub-threshold therapy method, avoids widespread damage to all retinal layers by targeting only a few. While these methods facilitate faster healing, their lack of visual feedback during treatment represents a considerable shortcoming as induced lesions remain invisible with conventional imaging and make clinical use challenging. To overcome this, we present a new strategy to provide location-specific and contact-free automatic feedback of SRT laser applications.

Methods

We leverage time-resolved optical coherence tomography (OCT) to provide informative feedback to clinicians on outcomes of location-specific treatment. By coupling an OCT system to SRT treatment laser, we visualize structural changes in the retinal layers as they occur via time-resolved depth images. We then propose a novel strategy for automatic assessment of such time-resolved OCT images. To achieve this, we introduce novel image features for this task that when combined with standard machine learning classifiers yield excellent treatment outcome classification capabilities.

Results

Our approach was evaluated on both ex vivo porcine eyes and human patients in a clinical setting, yielding performances above 95 % accuracy for predicting patient treatment outcomes. In addition, we show that accurate outcomes for human patients can be estimated even when our method is trained using only ex vivo porcine data.

Conclusion

The proposed technique presents a much needed strategy toward noninvasive, safe, reliable, and repeatable SRT applications. These results are encouraging for the broader use of new treatment options for neovascularization-based retinal pathologies.

New Diagnostic and Therapeutic Approaches for Preventing the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is a severe sight-threatening complication of diabetes mellitus. Retinal laser photocoagulation, antivascular endothelial growth factors, steroid therapy, and pars plana vitrectomy are now used extensively to treat advanced stages of diabetic retinopathy. Currently, diagnostic devices like ultrawide field fundus fluorescein angiography and the improvement of optical coherence tomography have provided quicker and more precise diagnosis of early diabetic retinopathy. Thus, treatment protocols have been modified accordingly. Various types of lasers, including the subthreshold micropulse laser and RPE-targeting laser, and selective targeted photocoagulation may be future alternatives to conventional retinal photocoagulation, with fewer complications. The new developed intravitreal medications and implants have provided more therapeutic options, with promising results.

Selective Retina Therapy in Patients With Chronic Central Serous Chorioretinopathy: A Pilot Study

We evaluated visual outcomes, changes of maximum macular thickness (MMT) and subretinal fluid (SRF), and safety in patients with chronic central serous chorioretinopathy (CSC) after treatment with selective retina therapy (SRT). Retrospective cohort study of patients with chronic CSC presenting to a university-based hospital from January 2014 through January 2015 was conducted. A total of 12 eyes of 12 patients with chronic CSC lasting for at least 3 months was recruited. The follow-up period ranged from 3 to 12 months. Following evaluation of test spots at temporal arcades, SRT (Q-switched neodymium-doped yttrium lithium fluoride [Nd:YLF] laser; wavelength, 527 nm, pulse duration, 1.7 microsececond) was applied to the surrounding areas of leakage observed on fluorescein angiogram and/or pigment epithelial detachment (PED). Changes in best-correct visual acuity (BCVA), MMT, and SRF and macular sensitivity (MS) by microperimetry (MP) were evaluated. Eyes received treatment in a mean of 3.83 spots at the pulse energy of 65 to 90 μJ. Mean BCVA (logMAR) improved from 0.23 ± 0.12 at baseline to 0.14 ± 0.13 at 3 months. MMT decreased from 341.4 ± 85.5 μm at baseline to 236.0 ± 57.9 μm at 3 months. SRF completely resolved in 75% (9 eyes) at 3 months. Large PEDs (2 eyes) were flattened at 3 months. Retreatment was performed in 4 eyes. MP showed no evidence of scotoma around SRT-treated lesions. SRT treatment targeting the surrounding area of leakage point showed favorable visual and structural outcomes in chronic CSC patients without the risk of scotoma.

A Comparative Study of Retinal Function in Rabbits after Panretinal Selective Retina Therapy versus Conventional Panretinal Photocoagulation

Purpose. This study evaluates functional changes in electroretinographic findings after selective retina therapy (SRT) compared to panretinal photocoagulation (PRP) in rabbits. Methods. The right eyes of 12 Chinchilla rabbits received 200 laser treatment spots. The right eyes of six rabbits received SRT (SRT group), whereas the other six animals were treated using PRP on the right eye (PRP group). The eyes were investigated using full-field ERG 1 hour and 3 weeks after treatment. Histologic exam to assess the tissue response of lasers was performed on 3 weeks. Results. No significant changes in the mean ROD or CR b-wave amplitudes of the SRT lesions were evident, compared to baseline, 1 h after laser treatment (p = 0.372 and 0.278, resp.). In addition, the OPs and 30 Hz flickers of the SRT lesions were not significantly altered (p = 0.17 and 0.243, resp.). At 3 weeks, similar results were found. Comparing the two groups, the ROD b-wave amplitude was reduced in the PRP and SRT groups to 60.04 ± 4.2% and 92.32 ± 6.43% of baseline (p < 0.001). Histologically, there was no visible photoreceptor alterations on week 3. Conclusions. SRT in rabbit eyes induced less functional loss than PRP in both rod-mediated retinal function and cone-mediated retinal function. In addition, SRT irradiated eyes had no functional loss compared to its control.

Laser-based strategies to treat diabetic macular edema: history and new promising therapies

Diabetic macular edema (DME) is the main cause of visual impairment in diabetic patients. The management of DME is complex and often various treatment approaches are needed. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal pharmacologic therapies (e.g., corticosteroids and anti-VEGF drugs), laser photocoagulation still remains the current standard in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME and describe the developments in laser systems. And we will also discuss the new laser techniques and review the latest results including benefits of combined therapy. In this paper, we briefly summarize the major laser therapeutics for the treatment of diabetic macular edema and allude to some future promising laser therapies.