Protective effect of a laser-induced sub-lethal temperature rise on RPE cells from oxidative stress

Short-term dietary teprenone improved thermal tolerance and mitigated liver damage caused by heat stress in juvenile largemouth bass (Micropterus salmoides)

Heat stress seriously threatens fish survival and health, demanding immediate attention. Teprenone is a gastric mucosal protective agent that can induce heat shock protein expression. This research investigated the effects of teprenone on largemouth bass (Micropterus salmoides) subjected to heat stress. Juvenile fish were assigned to different groups: group C (control group, 0 mg teprenone/kg diet), T0, T200, T400, and T800 (0, 200, 400, and 800 mg teprenone/kg diet, respectively), which were fed for 3 days, followed by a day without the diet. All groups except group C were subjected to acute heat stress (from 24 °C to 35 °C at 1 °C per hour and then maintained at 35 °C for 3 h). The results were as follows: The critical thermal maxima were significantly higher in the T200, T400, and T800 groups compared with the T0 group (P < 0.05). Heat stress caused severe damage to the tissue morphology of the liver, while teprenone significantly reduced this injury (P < 0.05). Serum cortisol concentration decreased gradually as teprenone concentration increased, and the lowest concentration was observed in the T800 group (P < 0.05). Compared with the T0 group, the serum activities of aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase were significantly lower in the T200, T400, and T800 groups (P < 0.05). The liver activities of catalase, total superoxide dismutase, and peroxidase were significantly higher in the T200 group than in the T0 group (P < 0.05). Transcript levels of the heat shock proteins (hsp90, hsp70, hspa5, and hsf1) and caspase family (caspase3 and caspase9) in the liver of the T200 group were significantly higher than those of the T0 group (P < 0.05). Western blot results showed that HSP70 and HSPA5 in the liver were significantly upregulated in the T200 group compared with the T0 group (P < 0.05). In summary, dietary teprenone improved thermal tolerance, alleviated heat stress damage in the liver, enhanced antioxidant capacity, and upregulated heat shock proteins in juvenile largemouth bass. This study offers theoretical support for applying teprenone in aquaculture to reduce financial losses caused by abiotic factors.

Temperature Increase and Damage Extent at Retinal Pigment Epithelium Compared between Continuous Wave and Micropulse Laser Application

Continuous wave (CW) and microsecond pulse (MP) laser irradiations were compared regarding cell damage and laser-induced temperature rise at retinal pigment epithelium (RPE). The RPE of porcine RPE-choroid-sclera explants was irradiated with a 577 nm laser in CW or MP mode (5% or 15% duty cycle (DC)) for 20 ms or 200 ms at an average laser power of 20−90 mW. Cell viability was investigated with calcein-AM staining. Optoacoustic (OA) technique was employed for temperature measurement during irradiation. For 200 ms irradiation, the dead cell area (DCA) increased linearly (≈1600 µm2/mW) up to the average power of 40 mW for all modes without significant difference. From 50 mW, the increase of DCA of MP-5% significantly dropped to 610 µm2/mW (p < 0.05), likely due to the detected microbubble formation. OA temperature measurement showed a monotonic temperature increase in CW mode and a stepwise increase in MP mode, but no significant difference in the average temperature increase at the same average power, consistent with the temperature modeling. In conclusion, there is no difference in the average temperature rise between CW and MP modes at the same average power regardless of DC. At lower DC, however, more caution is required regarding mechanical damage due to microbubble formation.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Diabetic Retinopathy: An Overview of Treatments

Diabetic retinopathy (DR), substantially impacts the quality of life of diabetic patients, it remains, in developed countries, the leading cause of vision loss in working-age adults (20-65 years). Currently, about 90 million diabetics suffer from DR. DR is a silent complication that in its early stages is asymptomatic. However, over time, chronic hyperglycemia can lead to sensitive retinal damage, leading to fluid accumulation and retinal haemorrhage (HM), resulting in cloudy or blurred vision. It can, therefore, lead to severe visual impairment or even blindness if left untreated. It can be classified into nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR is featured with intraretinal microvasculature changes and can be further divided into mild, moderate, and severe stages that may associate with diabetic macular oedema (DME). PDR involves the formation and growth of new blood vessels (retinal neovascularisation) under low oxygen conditions. Early identification and treatment are key priorities for reducing the morbidity of diabetic eye disease. In the early stages of DR, a tight control of glycemia, blood pressure, plasma lipids, and regular monitoring can help prevent its progression to more advanced stages. In advanced stages, the main treatments of DR include intraocular injections of anti-vascular endothelial growth factor (VEGF) antibodies, laser treatments, and vitrectomy. The aim of this review is to provide a comprehensive overview of the published literature pertaining to the latest progress in the treatment of DR.

Influence of Retinal Microsecond Pulse Laser Treatment in Central Serous Chorioretinopathy: A Short-Term Optical Coherence Tomography Angiography Study

Background: Central serous chorioretinopathy (CSC) is a common macular condition characterized by detachment of the neuroretina and is a frequent cause of central vision loss in adults. Among the various therapeutic strategies, subthreshold microsecond pulsed laser (SML) treatment has become a useful option. Despite the suggested involvement of choroidal circulatory disturbances in CSC, the effects of this treatment on macular microperfusion have not been fully evaluated yet. Herein, we report the impact of SML on retinal and choroidal microvascular flow using non-invasive optical coherence tomography (OCT) angiography (OCTA). Methods: In this study, CSC patients with persistent subretinal fluid (SRF) with or without secondary choroidal neovascularization (CNV) were included (referred to as the pachychoroid neovasculopathy (PNV) group and the CSC group, respectively). SML was conducted using a yellow (577 nm) laser with a duty cycle of 10%, spot size of 200 µm and duration of 200 ms. Best corrected visual acuity (BCVA) as well as OCT and OCTA images were evaluated at baseline and 4 weeks after SML. OCTA parameters of interest included full retinal perfusion (FRP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP), and Haller’s layer perfusion (HLP), which were evaluated longitudinally and compared to unaffected fellow eyes. Results: 27 affected eyes and 17 fellow eyes from 27 patients were included. Before treatment, central retinal thickness (CRT) and subfoveal choroidal thickness (SFCT) of affected eyes were significantly larger than in fellow eyes. Four weeks after SML, CRT decreased significantly, whereas perfusion parameters did not change. In subgroup analyses, the CSC group showed a significant decrease in SFCT, whereas the PNV group did not despite the decrease in CRT. Conclusion: Our results suggest that the SML may affect the SFCT of the CSC, but not the PNV patients at least within four weeks following treatment. This effect seems to be independent of the change in choroidal perfusion measured with OCTA.

Slowed Progression of Age-Related Geographic Atrophy Following Subthreshold Laser

Purpose

To determine the effect of panmacular low-intensity/high-density subthreshold diode micropulse laser (SDM) on age-related geographic atrophy (ARGA) progression.

Methods

The retinal images of all eyes with ARGA in a previously reported database, consisting of all eyes with dry age-related macular degeneration (AMD) active in a vitreoretinal practice electronic medical record (EMR), were identified and analyzed to determine the velocity of radial linear ARGA progression during observation and after panmacular SDM.

Results

Sixty-seven eyes of 49 patients with ARGA, mean age of 86 years were identified as having follow-up both before and after initiation of SDM treatment. All were included in the study. These eyes were followed a mean 910 days (2.5 years) prior to SDM treatment and a mean 805 days (2.2 years) after. Measurement masked to treatment vs observation found the radius of ARGA lesions progressed 1 to 540 µm per year (mean 137µm, SD 107) prior to treatment (controls); and −44 to 303 µm per year (mean 73µm, SD 59) after initiation of periodic panmacular SDM laser. Thus, the velocity of radial linear progression decreased 47% per year following panmacular SDM (p<0.0001). There were no adverse treatment effects.

Conclusion

In cohort of eyes with high-risk dry AMD, panmacular SDM slowed linear radial ARGA progression velocity 47% per year (p<0.0001) without adverse treatment effects. Validated, these findings would constitute an important advance in the prevention of age-related visual loss and a benchmark for future therapies.

Subthreshold Diode Micropulse Laser (SDM) for Persistent Macular Thickening and Limited Visual Acuity After Epiretinal Membrane Peeling

Purpose

To examine the effect of low-intensity/high-density subthreshold diode micropulse laser (SDM) on visual acuity (VA) and macular thickness in eyes with limited visual recovery and persistent macular thickening after epiretinal membrane peeling.

Methods

A retrospective review of medical records identified all patients undergoing SDM after membrane peeling in a clinical vitreoretinal subspecialty practice. Exclusion criteria included other obfuscating ocular disease or loss to follow-up after SDM treatment.

Results

All 19 eyes of 18 patients identified were included for study. After membrane peeling, VA improved from an avg. Snellen 20/240 [logMAR 1.08] to 20/72 [0.56] (p=0.0004). Attributed to persistent macular thickening following membrane peeling, overall VAs then gradually declined to an avg. of 20/91 [0.66] by 4−109 months (avg. 41) post vitrectomy, at which point panmacular SDM was performed. An avg. 15 months post SDM, both VA (to avg. 20/68 [0.53]) and maximum macular thickness improved (p=0.007 and p=0.008, respectively). There were no adverse treatment effects.

Conclusion

Low-intensity/high-density subthreshold (sublethal) diode micropulse laser (SDM) may reduce macular thickening and improve visual in eyes with persistent macular thickening after membrane peeling even years after vitrectomy.

Management of cystoid macular edema secondary to retinitis pigmentosa via subliminal micropulse yellow laser

To investigate the effects of subliminal micropulse yellow laser application on the central macular thickness and best-corrected visual acuity in cystoid macular edema secondary to retinitis pigmentosa patients. This prospective open-label clinical trial, conducted between January 2018 and October 2019, included 32 eyes of 29 patients who had cystoid macular edema secondary to retinitis pigmentosa. Patients were treated by subliminal micropulse yellow laser for one session. Central macular thickness and best-corrected visual acuity changes were investigated just before the treatment and 1 year later after the one session of the treatment. The mean central macular thickness was 651.3 μm before the treatment and 247.7 μm at 12 months after the treatment. The decrease in mean central macular thickness was statistically significant (p = 0.01). Median best-corrected visual acuity was 66.8 ETDRS letters before the treatment and 70.0 letters at 12 months after the treatment. The increase in best-corrected visual acuity was not statistically significant (p = 0.18). Eighty-six percent of the patients stated that the quality of central vision increased and that color vision, contrast sensitivity, and distortion improved. We did not encounter any serious adverse events related to the application of subliminal micropulse yellow laser. The subliminal micropulse yellow laser seems to be a therapeutic, effective, and safe option for the treatment of non-inflammatory and resistant cystoid macular edema secondary to retinitis pigmentosa patients. ClinicalTrials.gov ID: NCT04234438, January 17, 2020.

Induction of Heat Shock Protein 70 in Mouse RPE as an In Vivo Model of Transpupillary Thermal Stimulation

The induction of heat shock response in the macula has been proposed as a useful therapeutic strategy for retinal neurodegenerative diseases by promoting proteostasis and enhancing protective chaperone mechanisms. We applied transpupillary 1064 nm long-duration laser heating to the mouse (C57Bl/6J) fundus to examine the heat shock response in vivo. The intensity and spatial distribution of heat shock protein (HSP) 70 expression along with the concomitant probability for damage were measured 24 h after laser irradiation in the mouse retinal pigment epithelium (RPE) as a function of laser power. Our results show that the range of heating powers for producing heat shock response while avoiding damage in the mouse RPE is narrow. At powers of 64 and 70 mW, HSP70 immunostaining indicates 90 and 100% probability for clearly elevated HSP expression while the corresponding probability for damage is 20 and 33%, respectively. Tunel staining identified the apoptotic regions, and the estimated 50% damaging threshold probability for the heating (ED50) was ~72 mW. The staining with Bestrophin1 (BEST1) demonstrated RPE cell atrophy with the most intense powers. Consequently, fundus heating with a long-duration laser provides an approachable method to develop heat shock-based therapies for the RPE of retinal disease model mice.

The Evolving Treatment of Diabetic Retinopathy

Purpose

To review the current therapeutic options for the management of diabetic retinopathy (DR) and diabetic macular edema (DME) and examine the evidence for integration of laser and pharmacotherapy.

Methods

A review of the PubMed database was performed using the search terms diabetic retinopathy, diabetic macular edema, neovascularization, laser photocoagulation, intravitreal injection, vascular endothelial growth factor (VEGF), vitrectomy, pars plana vitreous surgery, antiangiogenic therapy. With additional cross-referencing, this yielded 835 publications of which 301 were selected based on content and relevance.

Results

Many recent studies have evaluated the pharmacological, laser and surgical therapeutic strategies for the treatment and prevention of DR and DME. Several newer diagnostic systems such as optical coherence tomography (OCT), microperimetry, and multifocal electroretinography (mfERG) are also assisting in further refinements in the staging and classification of DR and DME. Pharmacological therapies for both DR and DME include both systemic and ocular agents. Systemic agents that promote intensive glycemic control, control of dyslipidemia and antagonists of the renin-angiotensin system demonstrate beneficial effects for both DR and DME. Ocular therapies include anti-VEGF agents, corticosteroids and nonsteroidal anti-inflammatory drugs. Laser therapy, both as panretinal and focal or grid applications continue to be employed in management of DR and DME. Refinements in laser devices have yielded more tissue-sparing (subthreshold) modes in which many of the benefits of conventional continuous wave (CW) lasers can be obtained without the adverse side effects. Recent attempts to lessen the burden of anti-VEGF injections by integrating laser therapy have met with mixed results. Increasingly, vitreoretinal surgical techniques are employed for less advanced stages of DR and DME. The development and use of smaller gauge instrumentation and advanced anesthesia agents have been associated with a trend toward earlier surgical intervention for diabetic retinopathy. Several novel drug delivery strategies are currently being examined with the goal of decreasing the therapeutic burden of monthly intravitreal injections. These fall into one of the five categories: non-biodegradable polymeric drug delivery systems, biodegradable polymeric drug delivery systems, nanoparticle-based drug delivery systems, ocular injection devices and with sustained release refillable devices. At present, there remains no one single strategy for the management of the particular stages of DR and DME as there are many options that have not been rigorously tested through large, randomized, controlled clinical trials.

Conclusion

Pharmacotherapy, both ocular and systemic, will be the primary mode of intervention in the management of DR and DME in many cases when cost and treatment burden are less constrained. Conventional laser therapy has become a secondary intervention in these instances, but remains a first-line option when cost and treatment burden are more constrained. Results with subthreshold laser appear promising but will require more rigorous study to establish its role as adjunctive therapy. Evidence to support an optimal integration of the various treatment options is lacking. Central to the widespread adoption of any therapeutic regimen for DR and DME is substantiation of safety, efficacy, and cost-effectiveness by a body of sound clinical trials.

Leucinostatin acts as a co-inducer for heat shock protein 70 in cultured canine retinal pigment epithelial cells

Dysregulation of retinal pigment epithelium (RPE) cells is the main cause of a variety of ocular diseases. Potentially heat shock proteins, by preventing molecular and cellular damage and modulating inflammatory disease, may exert a protective role in eye disease. In particular, the inducible form of heat shock protein 70 (Hsp70) is widely upregulated in inflamed tissues, and in vivo upregulation of Hsp70 expression by HSP co-inducing compounds has been shown to be a potential therapeutic strategy for inflammatory diseases. In order to gain further understanding of the potential protective effects of Hsp70 in RPE cells, we developed a method for isolation and culture of canine RPE cells. Identity of RPE cells was confirmed by detection of its specific marker, RPE65, in qPCR, flow cytometry, and immunocytochemistry analysis. The ability of RPE cells to express Hsp70 upon experimental induction of cell stress, by arsenite, was analyzed by flow cytometry. Finally, in search of a potential Hsp70 co-inducer, we investigated whether the compound leucinostatin could enhance Hsp70 expression in stressed RPE cells. Canine RPE cells were isolated and cultured successfully. Purity of cells that strongly expressed RPE65 was over 90%. Arsenite-induced stress led to a time- and dose-dependent increase in Hsp70 expression in canine RPE cells in vitro. In addition, leucinostatin, which enhanced heat shock factor-1-induced transcription from the heat shock promoter in DNAJB1-luc-O23 reporter cell line, also enhanced Hsp70 expression in arsenite-stressed RPE cells, in a dose-dependent fashion. These findings demonstrate that leucinostatin can boost Hsp70 expression in canine RPE cells, most likely by activating heat shock factor-1, suggesting that leucinostatin might be applied as a new co-inducer for Hsp70 expression.

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.

Low incidence of choroidal neovascularization following subthreshold diode micropulse laser (SDM) in high-risk AMD

Purpose

To determine the incidence of new choroidal neovascularization (CNV) in eyes with dry age-related macular degeneration (AMD) following subthreshold diode micropulse laser (SDM).

Method

In an observational retrospective cohort study, the records of all patients active in the electronic medical records database were reviewed to identify eyes with dry AMD treated with SDM. Identified eyes were classified by simplified AREDS categories, and analyzed for the primary endpoint of new CNV after treatment.

Results

The EMR revealed SDM was offered to 373/392 (95%) patients with dry AMD and elected by 363/373 (97%) between 2008–2017. Follow up was available for 354/363 patients (547 eyes, 98%) (range 6–108 mos., avg. 22). CNV risk factors included age (median 84 years, 67% > 80); reticular pseudodrusen (214 eyes, 39%); AREDS category (78% category 3 and 4); and fellow eye CNV (128 eyes, 23%). New CNV developed in 9/547 eyes (1.6%, annualized rate 0.87%). Visual acuity was unchanged. There were no adverse treatment effects.

Summary

In a review of a large group of eyes with exceptionally high-risk AMD, SDM was followed by a very low incidence of new CNV. If confirmed by further study, SDM would offer a new and highly effective treatment to reduce the risk of vision loss from AMD.

Thermal Stimulation of the Retina Reduces Bruch's Membrane Thickness in Age Related Macular Degeneration Mouse Models

Purpose

To investigate the effect of thermal stimulation of the retina (TS-R) on Bruch's membrane (BrM) thickness in age-related macular degeneration (AMD) mouse models as a novel concept for the prophylaxis and treatment of dry AMD.

Methods

Two knockout AMD mouse models, B6.129P2-Apoe^tm1Unc/J (ApoE−/−) and B6.129X1-Nfe2I2^tm1Ywk/J (NRF2−/−), were chosen. One randomized eye of each mouse in four different groups (two of different age, two of different genotype) of five mice was treated by TS-R (532 nm, 10-ms duration, 50-μm spot size), the fellow eye served as control. Laser power was titrated to barely visible laser burns, then reduced by 70% to guarantee for thermal elevation without damage to the neuroretina, then applied uniformly to the murine retina. Fundus, optical coherence tomography (OCT), and fluorescein angiography (FLA) images were obtained at the day of treatment and 1 month after treatment. Eyes were enucleated thereafter to analyze BrM thickness by transmission electron microscopy (TEM) in a standardized blinded manner.

Results

Fundus images revealed that all ApoE−/− and NRF2−/− mice had AMD associated retinal alterations. BrM thickness was increased in untreated controls of both mouse models. Subvisible TS-R laser spots were not detectable by fundus imaging, OCT, or FLA 2 hours or 1 month after laser treatment. TEM revealed a significant reduction of BrM thickness in laser-treated eyes of all four groups compared to their fellow control eyes.

Conclusions

TS-R reduces BrM thickness in AMD mouse models ApoE−/− and NRF2−/− without damage to the neuroretina. It may become a prophylactic or even therapeutic treatment option for dry AMD.

Translational Relevance

TS-R may become a prophylactic or even therapeutic treatment option for dry AMD.

Expression of heat shock protein 70 and cell death kinetics after different thermal impacts on cultured retinal pigment epithelial cells

Recent technologies are broadening the possibility to treat the retinal pigment epithelium (RPE) with different thermal impacts, from sublethal to lethal ranges. Thus temperature-dependent subcellular molecular responses need to be elucidated in more detail. In this study, RPE cell viability and expression of heat shock protein 70 (Hsp70) were investigated after thermal irradiation with different temperature increase using an in-vitro model. Primary porcine RPE cell cultures were irradiated with different laser power of a thulium laser (λ = 1940 nm, beam-diameter 30 mm) for 10 s, such that the maximal temperatures at the center of the culture dish (T_max) reach 40, 44, 47, 51 or 59 °C after 10-s irradiation. The temperature distribution across the culture dish shows a Gaussian decay from central position to the periphery of the dish. At 3, 24 and 48 h after irradiation cell viability was assessed with fluorescence microscopy using cell viability-indicating fluorescence dyes, followed by the determination of the threshold temperature for apoptotic change and death of RPE cells. Intracellular localization and amount of Hsp70 were investigated with immunofluorescence and western blotting, respectively. The threshold temperature (at the 10th second of irradiation: T_10s) for cellular apoptosis and complete cell death showed a decrease over time after irradiation, suggesting a long-term process of thermally induced cell death. For complete cell death the threshold T_10s was 52.1 ± 0.6 °C, 50.1 ± 1.4 °C, and 50.1 ± 0.8 °C, for 3, 24 and 48 h, respectively, whereas for the apoptotic changes 48.6 ± 1.8 °C, 47.2 ± 1.3 °C, and 46.7 ± 0.9 °C, respectively. Quantitative analysis of Hsp70 with western blotting showed a significant increase in intracellular Hsp70 at lethal irradiation with T_max ≥ 51 °C, up to 19.6 ± 2.3 fold after 48 h at 59 °C, whereas sub-lethal irradiations with T_max ≤ 44 °C led to a slight tendency of time-dependent increases (up to 1.8 ± 1.1 fold) over 48 h. Immunostainings for Hsp70 showed a circle- or ring-pattern of the Hsp70 staining during 3-48 h after irradiation, and the range of the 1st and 3rd quartiles of T_10s for heat-induced Hsp70 expression over this time period was between 44.8 °C and 48.2 °C. A very strong staining of Hsp70 was observed at the border to the damaged zone, where many cells show the strong staining in the whole cytoplasmic space, while some cells in the nucleus, or some cells show the signs of cell migration and proliferation. Moreover, among the cells showing high intensity of Hsp70 staining, there are small round cells like apoptotic cells. Results suggest that RPE cell death after thermal irradiation may take time, and mostly undergoes through apoptosis, unless cells are immediately killed. Thermal irradiation-induced Hsp70 expression is not only temperature-dependent, but also depends largely on the existence of neighboring cell death, suggesting the crucial role of Hsp70 in apoptosis and wound healing processes of RPE cells. The increase of Hsp70 over 24-48 h indicates its long-term roles in cell responses both after sublethal and lethal thermal laser irradiations.

Improved retinal and visual function following panmacular subthreshold diode micropulse laser for retinitis pigmentosa

Objectives

To examine the effect of subthreshold diode micropulse laser (SDM) on pattern electroretinography (PERG) and visual function in retinitis pigmentosa (RP).

Methods

The records of all patients (pts) undergoing SDM in a vitreoretinal subspecialty practice were reviewed. Inclusion criteria included the presence of RP evaluated before and after SDM by PERG. As a secondary outcome measure, the results of automated omnifield resolution perimetry (ORP) were also reviewed.

Results

All eyes undergoing SDM for RP were eligible study, including 26 eyes of 15 pts; seven male and eight female, aged 16–69 (avg. 47) years. Retinal function by PERG improved by all indices, with significant improvements in the 24° field signal latency measures; the MagD(µV)/ Mag(µV) ratio (P < 0.0001) and the MagD(µV) amplitude (P = 0.0003). ORP significantly improved by all indices (p = 0.02–0.002). Average best-corrected chart visual acuities improved from 0.6 to 0.4 logMAR units (p = 0.02). There were no adverse treatment effects.

Conclusions

SDM significantly improved chart visual acuity, mesopic logMAR visual acuity perimetry, and retinal function by PERG in RP without adverse treatment effects. Treatment responses indicate a significant capacity for rescue of dysfunctional retina. These results suggest that early and periodic treatment with SDM might slow disease progression and reduce long-term vision loss.

Oxidant-Antioxidant Balance in the Aqueous Humor of Patients with Retinal Vein Occlusion

PURPOSE

To analyze oxidative stress parameters in the aqueous humor with retinal vein occlusion.

MATERIALS AND METHODS

A total of 56 patients who underwent cataract surgery were enrolled in this study. The eyes with retinal vein occlusion were included in the study group. Aqueous humor was sampled from all patients and analyzed by an automated measurement method. Total oxidant status (TOS), total antioxidant status (TAS), and oxidative stres index (OSI) were calculated.

RESULTS

OSI was significantly higher in the study group (p = 0.04). TAS was significantly lower (p = 0.01) and OSI was significantly higher (p = 0.01) in cases with both central retinal vein occlusion and macular edema. Previous laser photocoalugation to the retina and the duration of disease had no significant effect on the levels of oxidative stress parameters.

CONCLUSION

OSI was found higher in patients with retinal vein occlusion. This increase is more significant in patients with macular edema and central retinal vein occlusion; in which TAS was also found to decrease.

Power-controlled temperature guided retinal laser therapy

Laser photocoagulation has been a treatment method for retinal diseases for decades. Recently, studies have demonstrated therapeutic benefits for subvisible effects. A treatment mode based on an automatic feedback algorithm to reliably generate subvisible and visible irradiations within a constant irradiation time is introduced. The method uses a site-individual adaptation of the laser power by monitoring the retinal temperature rise during the treatment using optoacoustics. This provides feedback to adjust the therapy laser power during the irradiation. The technique was demonstrated on rabbits in vivo using a 532-nm continuous wave Nd:YAG laser. The temperature measurement was performed with 523-nm Q-switched Nd:YLF laser pulses with 75-ns pulse duration at 1-kHz repetition rate. The beam diameter on the fundus was 200  μm for both lasers, respectively. The aim temperatures ranged from 50°C to 75°C in 11 eyes of 7 rabbits. The results showed ophthalmoscopically invisible effects below 55°C with therapy laser powers over a wide range. The standard deviation for the measured temperatures ranged from 2.1°C for an aim temperature of 50°C to 4.7°C for 75°C. The ED50 temperature value for ophthalmoscopically visible lesions in rabbits was determined as 65.3°C. The introduced method can be used for retinal irradiations with adjustable temperature elevations.

Continuous-wave Thulium Laser for Heating Cultured Cells to Investigate Cellular Thermal Effects

An original method to heat cultured cells using a 1.94 µm continuous-wave thulium laser for biological assessment is introduced here. Thulium laser radiation is strongly absorbed by water, and the cells at the bottom of the culture dish are heated through thermal diffusion. A laser fiber with a diameter of 365 µm is set about 12 cm above the culture dish, without any optics, such that the laser beam diameter is almost equivalent to the inner diameter of the culture dish (30 mm). By keeping a consistent amount of culture medium in each experiment, it is possible to irradiate the cells with a highly reproducible temperature increase. To calibrate the temperature increase and its distribution in one cell culture dish for each power setting, the temperature was measured during 10 s of irradiation at different positions and at the cellular level. The temperature distribution was represented using a mathematical graphics software program, and its pattern across the culture dish was in Gaussian form. After laser irradiation, different biological experiments could be performed to assess temperature-dependent cell responses. In this manuscript, viability staining (i.e., distinguishing live, apoptotic, and dead cells) is introduced to help determine the threshold temperatures for cell apoptosis and death after different points in time. The advantages of this method are the preciseness of the temperature and the time of heating, as well as its high efficiency in heating cells in a whole cell culture dish. Furthermore, it allows for study with a wide variety of temperatures and time durations, which can be well-controlled by a computerized operating system.

Water-filtered infrared A reduces chlamydial infectivity in vitro without causing ex vivo eye damage in pig and mouse models

Repeated ocular infections with Chlamydia trachomatis trigger the development of trachoma, the most common cause of infectious blindness worldwide. Water-filtered infrared A (wIRA) has shown positive effects on cultured cells and human skin. Our aim was to evaluate the potential of wIRA as a possible non-chemical treatment for trachoma patients. We both modeled ocular chlamydial infections using C. trachomatis B to infect human conjunctival epithelial cells (HCjE) and studied the effects of wIRA on non-infected ocular structures with two ex vivo eye models. We focused on the temperature development during wIRA irradiation in cell culture and perfused pig eyes to exclude potentially harmful side effects. Furthermore, cell viability of HCjE and cytotoxicity in mouse retina explants was analyzed. We demonstrated a significant wIRA-dependent reduction of chlamydial infectivity in HCjE cells. Moreover, we observed that wIRA treatment of HCjE prior to infection was sufficient to inhibit chlamydial infectivity and that visible light enhances the effect of wIRA. Irradiation did not reduce cell viability and there was no indication of retinal damage post treatment. Additionally, temperatures during wIRA exposure did not markedly exceed physiological eye temperatures, suggesting that hyperthermia-related lesions are unlikely. For clinical applications, further exploration of wIRA as a non-chemical treatment device in an experimental animal model is essential.

A Revised Hemodynamic Theory of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) afflicts one out of every 40 individuals worldwide, causing irreversible central blindness in millions. The transformation of various tissue layers within the macula in the retina has led to competing conceptual models of the molecular pathways, cell types, and tissues responsible for the onset and progression of AMD. A model that has persisted for over 6 decades is the hemodynamic, or vascular theory of AMD progression, which states that vascular dysfunction of the choroid underlies AMD pathogenesis. Here, we re-evaluate this hypothesis in light of recent advances on molecular, anatomic, and hemodynamic changes underlying choroidal dysfunction in AMD. We propose an updated, detailed model of hemodynamic dysfunction as a mechanism of AMD development and progression.

LASER RESENSITIZATION OF MEDICALLY UNRESPONSIVE NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: Efficacy and Implications

PURPOSE

Drug tolerance is the most common cause of treatment failure in neovascular age-related macular degeneration. "Low-intensity/high-density" subthreshold diode micropulse laser (SDM) has been reported effective for a number of retinal disorders without adverse effects. It has been proposed that SDM normalizes retinal pigment epithelial function. On this basis, it has been postulated that SDM treatment might restore responsiveness to anti-vascular endothelial growth factor drugs in drug-tolerant eyes.

METHODS

Subthreshold diode micropulse laser treatment was performed in consecutive eyes unresponsive to all anti-vascular endothelial growth factor drugs, including at least three consecutive ineffective aflibercept injections. Monthly aflibercept was resumed 1 month after SDM treatment.

RESULTS

Thirteen eyes of 12 patients, aged 73 to 97 years (average, 84 years), receiving 16 to 67 (average, 34) anti-vascular endothelial growth factor injections before SDM treatment were included and followed for 3 months to 7 months (average, 5 months) after SDM treatment. After SDM treatment and resumption of aflibercept, 92% (12 of 13) of eyes improved, with complete resolution of macular exudation in 69% (9 of 13). Visual acuity remained unchanged. Central and maximum macular thicknesses significantly improved.

CONCLUSION

Subthreshold diode micropulse laser treatment restored drug response in drug-tolerant eyes with neovascular age-related macular degeneration. Based on these findings, a theory of SDM action is proposed, suggesting a wider role for SDM as retinal reparative/protective therapy.