Transpupillary thermotherapy (TTT) with short duration laser exposures induce heat shock protein (HSP) hyperexpression on choroidoretinal layers

Our experience of combined treatment of chronic central serous chorioretinopathy using laser exposure of different wavelengths

Central serous chorioretinopathy is a disease that occurs in young people and causes a significant decrease in visual functions. In some cases, the pathological process acquires a chronic course, the treatment of which remains an urgent problem. Unfortunately, the available methods of conservative treatment of this problem do not have proven effectiveness, and laser treatment methods do not always lead to rapid and persistent remission and do not guarantee the absence of relapses of the disease.

The aim of this study. To evaluate the effectiveness of the treatment of this pathology using a combined treatment method: a combination of transpupillary thermotherapy of the optic nerve disc with micropulse laser exposure to the retinal neuroepithelial detachment zone in the treatment of patients with chronic central serous chorioretinopathy.

Patients with chronic central serous chorioretinopathy were divided into two groups: patients who were treated with simultaneous application of laser exposure in micropulse mode (wavelength – 577 nm) with a single session of transpupillary thermotherapy on the optic nerve disc area (wavelength – 810 nm); and patients whose treatment consisted in laser exposure in micropulse mode (wavelength – 577 nm). In patients of the combined laser treatment group, there was an improvement in visual acuity after a month and a half from the start of therapy in 84 % of cases, whereas in patients who received only micropulse laser exposure it happened in 57 % of cases. A noticeable improvement in the linear blood flow rate in the posterior short ciliary arteries according to the ultrasound triplex examination of the eye vessels was also observed in the combined treatment group: the blood flow rate increased by 36 %, in the other group the blood flow rate did not significantly change. Also, in the combination therapy group, only 1 relapse of the disease was detected within 24 months, while in the second group, relapses were observed in 8.7 % of cases. Subjectively, patients from the combined treatment group noted a faster disappearance of complaints of visual discomfort.

FUNCTIONAL AND STRUCTURAL EFFECTS OF NONDAMAGING RETINAL LASER THERAPY FOR MACULAR TELANGIECTASIA TYPE 2: A Randomized Sham-Controlled Clinical Trial

PURPOSE

Macular telangiectasia (MacTel) Type 2 is a progressing neurovascular disease of the macula, currently lacking effective treatment. This study assessed the effect of nondamaging retinal laser therapy (NRT) compared with sham.

METHODS

Twelve MacTel patients were enrolled in this double-masked, controlled, randomized clinical trial. For the nine patients with both eyes eligible, one eye was randomized to NRT or sham and the other received alternate treatment. For three patients with only one eye eligible, that eye was randomly assigned either NRT or sham. Ellipsoid zone disruption, best-corrected visual acuity, and macular automated perimetry at 12 months served as structural and functional measures.

RESULTS

Eleven eyes were randomized to sham and 10 to NRT. Baseline best-corrected visual acuity was 66 letters (20/50) for sham and 72 letters (20/40) for NRT (P = 0.245). Ellipsoid zone disruption area was 298 µm2 in sham and 368 µm2 in NRT (P = 0.391). At 12 months, ellipsoid zone disruption increased by 24% in sham and decreased by 34% in NRT (P < 0.001). Best-corrected visual acuity measures remained stable during follow-up compared with baseline. At 1 year, the mean macular sensitivity was 28 dB in the NRT group, compared with 26 dB in sham.

CONCLUSION

Nondamaging retinal laser therapy was safe and well tolerated in patients with MacTel and resulted in structural and functional improvements, which could represent a protective effect of laser-induced hyperthermia. Longer follow-up and larger number of patients should help corroborate these effects.

Efficient high-power continuous-wave lasers at green-lime-yellow wavelengths by using a Nd:YVO4 self-Raman crystal

Efficient high-power continuous-wave Nd:YVO₄ visible lasers at versatile wavelengths of 532 (green), 559 (lime), and 588 nm (yellow) are demonstrated to be achieved by using the identical cavity mirrors and gain medium. A dichroic coating is deposited on one end surface of the gain medium to gather the backward green-yellow emission. The green, lime, and yellow outputs are individually optimized by using different phase-matched lithium triborate (LBO) crystals for second harmonic generation (SHG) of the fundamental field, sum frequency generation (SFG) of the fundamental and the stimulated Raman fields, and SHG of the stimulated Raman field, respectively. At a pump power of 31.6 W, the output powers at 532, 559, and 588 nm can be up to 6.8, 5.4, and 3.1 W. The high efficient and compact Nd:YVO₄ lasers at green-lime-yellow wavelengths can be potentially beneficial to future applications in retinal photocoagulation.

Retinal pigment epithelium in the pathogenesis of age-related macular degeneration and photobiomodulation as a potential therapy?

The retinal pigment epithelium (RPE) comprises a monolayer of cells located between the neuroretina and the choriocapillaries. The RPE serves several important functions in the eye: formation of the blood-retinal barrier, protection of the retina from oxidative stress, nutrient delivery and waste disposal, ionic homeostasis, phagocytosis of photoreceptor outer segments, synthesis and release of growth factors, reisomerization of all-trans-retinal during the visual cycle, and establishment of ocular immune privilege. Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. Dysfunction of the RPE has been associated with the pathogenesis of AMD in relation to increased oxidative stress, mitochondrial destabilization and complement dysregulation. Photobiomodulation or near infrared light therapy which refers to non-invasive irradiation of tissue with light in the far-red to near-infrared light spectrum (630-1000 nm), is an intervention that specifically targets key mechanisms of RPE dysfunction that are implicated in AMD pathogenesis. The current evidence for the efficacy of photobiomodulation in AMD is poor but its safety profile and proposed mechanisms of action motivate further research as a novel therapy for AMD.

[Intravitreal ranibizumab injection for the treatment of idiopathic choroidal neovascularisation in young patients]

PURPOSE

To evaluate the safety and efficacy of intravitreal injection of ranibizumab 0.5mg in the treatment of idiopathic choroidal neovascularisation in young patients, which is the second most common cause of macular CNV in patients under 50 years of age.

PATIENTS AND METHODS

This single-center, prospective, interventional, uncontrolled, nonrandomized clinical case series study included 13 eyes of 13 consecutive young patients with idiopathic macular choroidal neovascularisation treated with monthly intravitreal injections of 0.5mg ranibizumab. Prior to treatment, measurement of best-corrected visual acuity (BCVA), fundus examination, fluorescein angiography (FA) and macular optical coherence tomography (OCT) were performed. Measurement of visual acuity, fundus exam and OCT were repeated each month. A repeated monthly injection was performed in the event of persistence or recurrence of neovascular activity.

RESULTS

Ten women and three men, mean age 34±7.88 years at time of diagnosis, were included in the study. Mean best-corrected visual acuity improved dramatically throughout the study, going from 0.74 LogMar at enrolment to 0.45 LogMar at 13 months (P<10(-6)). On average, two intravitreal injections of ranibizumab (0.5 mg) were required during this year. Mean follow-up was 13±7.6 months.

DISCUSSION

Management of idiopathic CNV in young patients is difficult, due to frequent recurrences despite treatment. Argon laser photocoagulation, photodynamic therapy, and subretinal surgery offer limited results in terms of visual recovery and recurrence.

CONCLUSION

Intravitreal ranibizumab injection appears to be safe and effective for treatment of idiopathic macular CNV in young patients. A longer-term prospective trial is required to corroborate these results.

Large-spot subthreshold transpupillary thermotherapy for chronic serous macular detachment

Purpose:

To report the effect of subthreshold transpupillary thermotherapy (TTT) in treating serous detachment of the neurosensory retina secondary to chronic central serous chorioretinopathy (CCSC).

Methods:

Seven eyes from five patients with CCSC, persistent serous detachment of the neurosensory retina and a clinical course of between 12 and 60 months were treated. All eyes received large-spot TTT guided by indocyanine green angiography (ICGA). Subthreshold TTT was performed using an 810 nm diode laser with a spot size of 3.0 mm (power was set at 350 mW). Treatment was applied for 60 seconds to the areas of choroidal hyperfluorescence on ICGA.

Results:

The mean number of TTT sessions was 1.4 ± 0.5. All eyes were followed up for at least 6 months (mean 9.6 ± 3.2 standard deviation; range 6–12 months). The mean logarithm of the minimum angle of resolution best-corrected visual acuity was significantly better compared with baseline. All TTT-treated eyes had stable or improved vision (P < 0.001). Mean optical coherence tomography (OCT) central foveal thickness was significantly lower in all patients (P < 0.001) compared with pretreatment OCT, with a reduction in subretinal fluid and resolution of serous detachment associated with anatomical fovea restoration. No patient had any treatment-related side effects.

Conclusion:

Modified subthreshold TTT appears to have a beneficial effect in treating patients with CCSC and persistent neurosensory detachment. The encouraging results and lack of visually significant complications suggest that further investigation is warranted.

Theoretic, experimental, clinical bases of the water oscillator hypothesis in near-infrared photobiomodulation

The objective of this review is to propose and document a role for the water oscillator in near-infrared (NIR) photobiomodulation. Greater understanding of the role of the water oscillator may add to a more-coherent description of central effects of NIR light on redox centers and key transmembrane enzymes such as cytochrome c oxidase (CcO). In addition, water provides a complementary pathway for absorption and transportation of NIR energy in photobiomodulation. Because of its unexpected potential, we propose terming it the "water oscillator paradox." Photobiologic mechanisms involved in the treatment of complex diseases are discussed in light of the present state of the art.

Laser-induced hyperthermia for treatment of granulation tissue growth in rats

OBJECTIVE

We aimed to develop a new technique for treatment of granulation tissue (GT) growth using local hyperthermia.

METHODS

A temperature-controlled diode laser system was developed for induction of mild hyperthermia in real time. GT was generated by harvesting the skin over the gluteal fascia in rats. Histopathological analysis was used to estimate the effect of hyperthermia on the tissue.

RESULTS

In untreated rats, GT was detected within 3 days and reached maximal thickness after 12 days. Hyperthermia at 43 degrees C and above significantly decreased GT thickness (n = 8 per group). Hyperthermia at 48 degrees C for 3 minutes was the most efficient parameter for treatment of GT (51% reduction), with minimal (5%) muscle necrosis.

CONCLUSIONS

Hyperthermia can significantly inhibit GT growth, with minimal damage to surrounding structures. Our findings suggest a possible role for hyperthermia as a therapeutic model against GT. Further research and long-term studies are needed to explore the utility of laser-induced hyperthermia for inhibition of GT growth.

TRANSPUPILLARY THERMOTHERAPY

PURPOSE

To correlate changes in primate fundus after transpupillary thermotherapy (TTT) at two wavelengths.

METHODS

Twelve primate eyes were treated with TTT using a wavelength of 635 nm (n=7) or 810 nm (n=5). Laser parameters were as follows: 635 nm (spot size, 1 mm; duration, 30-8 seconds; and fluence [power over time], 20-91.4 J/cm) and 810 nm (spot size, 2 mm; duration, 60 seconds; and fluence, 96-436 J/cm). Fundus photography, fluorescein and indocyanine green angiography, and enucleation were performed at time 0 or 2 weeks after TTT for histologic analysis.

RESULTS

Threshold for fundus lesions (91.4 J/cm at 635 nm and 191 J/cm at 810 nm), acute and chronic retinal damage shown by histologic analysis (79.2 J/cm at 635 nm and 96 J/cm at 810 nm), and choroidal vessel occlusion (50 J/cm at 635 nm and 96 J/cm at 810 nm) were lower at 635 nm. Disorganization of the retina and retinal pigment epithelium was seen for both wavelengths at time 0 and 2 weeks after TTT. Occlusion of the choriocapillaris and choroidal stromal vessels was noted only in specimens obtained 2 weeks after TTT.

CONCLUSIONS

TTT resulted in acute and delayed damage to the neurosensory retina that persisted at 2 weeks. The 635-nm wavelength demonstrated a lower threshold fluence for visible fundus lesions, retinal damage, and choroidal vascular occlusion than the 810-nm laser.

Photo-infrared pulsed bio-modulation (PIPBM): a novel mechanism for the enhancement of physiologically reparative responses

OBJECTIVE

The present manuscript describes the non-invasive, long-range, energy transport of a singular infrared pulsed laser device (IPLD) and the upstream components of the original action mechanism, designated photo-infrared pulsed bio-modulation (PIPBM).

BACKGROUND DATA

Major strides have been taken in recent years towards scientifically acceptable clinical applications of low-energy lasers. Nevertheless, challenges still abound. For instance, the range of potential target tissues for laser therapy in medicine has been, until now, limited by the optical penetration of the beam or to sites accessible by fiberoptics. In addition, much needs to be learned about the action mechanisms of pulsed lasers, which can induce unique biological effects.

METHODS

We present a review of the IPLD laser technology and the PIPBM mechanism.

RESULTS

The studies reviewed suggest that the PIPBM enhances physiologically reparative processes in a non-toxic and selective manner through the activation and modulation of chaotic dynamics in water. These, in turn, lead not only to local, but also long-distance (systemic) effects.

CONCLUSIONS

Though additional studies are necessary to fully explore the biological effects of the PIPBM induced by the IPLD, this mechanism may have multiple potential applications in medicine that are the subject of active current and future investigations.

Transpupillary thermotherapy for occult subfoveal choroidal neovascularization: a 1-year, prospective randomized pilot study

PURPOSE

To evaluate the 1-year effect of transpupillary thermotherapy (TTT) on occult choroidal neovascularization membranes (CNV).

METHODS

In this prospective, randomized, controlled pilot study of 28 patients with occult or minimally classic (< 10%) neovascularization membranes with a diameter less than 4500 microm, 19 patients were treated with TTT, while nine received sham treatment. Outcome measures were membrane diameter, visual acuity and reading ability.

RESULTS

The median age of patients randomized to TTT was 78 years (range 24 years); that of patients randomized to sham was 79 years (range 9 years). There was no difference regarding membrane diameter at baseline between the two groups; the median membrane diameters were 3400 microm (range 2400 microm) in the TTT group and 3200 microm (range 2300 microm) in the sham group (p = 0.639). Visual acuity (VA) was similar, with a median of 0.2 (minimum-maximum 0.08-0.5) in the TTT group and a median of 0.16 (min-max 0.10-0.32) in the sham group. A total of 21 patients were followed for 1 year, 13 in the TTT group (2.7 treatments/patient) and eight in the sham group. Membrane diameter increased in both groups, by a median of 350 microm (range 1600 microm) in the TTT group and 800 microm (range 1700 microm) in the sham group (p = 0.414), respectively, and there was a loss in VA of > or = 15 letters in 5/13 patients (38%) in the TTT group compared with 2/8 patients (25%) in the sham group (p = 0.266). Reading ability deteriorated equally over time in both groups. Seven patients were lost to follow-up due to reluctance to continue in the study (n = 4) or development of a classical component > 50% (n = 3) requiring photodynamic therapy (PDT).

CONCLUSION

The results from this randomized, prospective pilot study of TTT for occult CNV did not indicate that TTT has a beneficial effect on visual outcome 1 year after treatment compared with the visual outcome that results from the natural course of the disease. The small study size limits statistical power and results from large control studies are needed.

Subthreshold diode micropulse photocoagulation for the treatment of clinically significant diabetic macular oedema

AIM

To report the visual and clinical outcomes of a pilot study of subthreshold diode micropulse (SDM) laser photocoagulation for clinically significant diabetic macular oedema (CSMO).

METHODS

The results of infrared (810 nm) SDM laser photocoagulation for CSMO were retrospectively reviewed in 95 eyes of 69 consecutive patients with mild to moderate non-proliferative diabetic retinopathy. The same laser parameters were used for each patient. Only the number of laser applications varied between patients, depending on their macular findings. Primary outcome measures were Snellen visual acuity, fluorescein angiographic leakage, and CSMO status.

RESULTS

Visual acuity was stable or improved in 85% of treated eyes, with a mean follow up of 12.2 months (range 3-29 months). CSMO decreased in 96% and resolved in 79% of treated eyes. No adverse laser events occurred. No laser lesions were detectable ophthalmoscopically or angiographically after treatment, consistent with calculations based on ANSI Z136.1 laser safety standards suggestive of only histologically detectable tissue effects at the laser exposure levels. No laser scarring was observed during the follow up period.

CONCLUSION

Subthreshold diode micropulse laser photocoagulation minimises chorioretinal damage in the management of CSMO and demonstrates a beneficial effect on visual acuity and CSMO resolution. Prospective studies are needed to fully evaluate this technique.