Dirk Theisen-Kunde

Structural Changes of the Retina after Conventional Laser Photocoagulation and Selective Retina Treatment (SRT) in Spectral Domain OCT

Background: Spectral domain optical coherence tomography (SD-OCT) in patients can deliver retinal cross-sectional images with high resolution. This may allow the evaluation of the extent of damage to the retinal pigment epithelium (RPE) and the neurosensory retina after laser treatment. This article aims to investigate the value of SD-OCT in comparing laser lesions produced by conventional laser photocoagulation and selective retina treatment (SRT). Material and Methods: In a retrospective study, conventional retinal laser (CRL) lesions and SRT laser lesions were evaluated with SD-OCT. One hundred seventy-five CRL lesions were investigated in 10 patients with diabetic maculopathy at timepoints between 1 hr and 4 years after treatment. Ninety-one SRT lesions were examined in 9 patients with central serous retinopathy, geographic atrophy, and diabetic maculopathy at timepoints between 1 hr and 2 years. CRL lesions were applied with an ophthalmoscopically slightly grayish-white appearance (Nd:YAG laser at 532-nm wavelength; power 100–200 mW; retinal spot diameter 100 μm; pulse duration 100 ms). SRT lesions were applied with a Nd:YLF (527 nm; pulse duration 200 ns [30 pulses at 100 Hz]; energy 100–200 μJ/pulse; retinal spot diameter 200 μm) and were visible only angiographically. Results: All CRL lesions were characterized by high reflectivity in OCT images throughout the full thickness of the neurosensory tissue 1 hr after irradiation, suggesting complete neurosensory coagulation. Strong contraction through the full thickness of the neurosensory layers was observed within 7 days after treatment. In contrast, the neural retina appeared unaffected after SRT. For both lesion types, the RPE layer appeared to be regular or thinner immediately after treatment, whereas within a period of 4 weeks, a RPE thickening indicating RPE proliferation was observable. One year and later after treatment, CRL lesions were characterized by RPE atrophy combined with significant damage of the neurosensory tissue. SRT lesions aged one year and older revealed unaffected neurosensory structures and an intact RPE layer. Conclusion: Spectral domain OCT can be used clinically to follow the development of laser-induced lesions over time. Postoperative RPE proliferation was observed in both CRL and SRT laser lesions. RPE atrophy appeared subsequently only in CRL lesions, whereas the neurosensory retina appeared unaffected following SRT. These results suggest the selective effect of SRT in humans without causing adverse effects to the neurosensory retina.

Percutaneous aortic valve replacement: Endovascular resection of human aortic valves in situ

OBJECTIVE Transluminal in vitro resection of severely calcified human aortic valves has already been successfully carried out by our group. The aim of this study was to analyze endovascular laser-assisted resection of human aortic valves in situ in 10 human cadavers. MATERIAL AND METHODS After anterolateral minithoracotomy, the aortic valve isolation chamber system was inserted into the descending aorta and pushed forward transluminally into the aortic position to generate a separate operation space between the subvalvular and the proximal ascending aortic area. After deployment and sealing of the chamber, stable function with a continuous chamber lavage of 1.58 L/min saline solution was established (8/10 cases). The endoscopically guided laser fiber was delivered via the right carotid artery. After fixation of a leaflet by a forceps catheter, the native leaflets were resected each by a thulium:YAG laser with 20-W power rating. Macropathology and micropathology of surrounding anatomic structures were analyzed. RESULTS The duration of transluminal positioning and deployment of the aortic valve isolation chamber took 7.3 +/- 5.8 minutes. Fluoroscopy confirmed sealed chambers. The resection was completed in all leaflets and took, on average, 6.0 +/- 3.5 minutes per leaflet. The aortic wall was moderately injured in 4 of 10 cases and the aortic annulus in two cases with one aortic wall perforation. The surrounding tissue, the coronary ostia, the mitral valve, and the left ventricular outflow tract remained unaffected. CONCLUSION This study demonstrates the feasibility of endovascular resection of human aortic valves in situ. This is a subsequent step toward complete percutaneous replacement (resection and implantation) of human aortic valves.

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

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

Comparison of threshold irradiances and online dosimetry for selective retina treatment (SRT) in patients treated with 200 nanoseconds and 1.7 microseconds laser pulses

Selective retina therapy (SRT) solely affecting the RPE while sparing of the photoreceptors is usually performed with a train of repetitive laser pulses of 1.7 microseconds in duration. It was our purpose to evaluate the principle feasibility of SRT with shorter 200 nanoseconds laser pulses in patients.

Selective Retina Therapy in Acute and Chronic-Recurrent Central Serous Chorioretinopathy.

Purpose: Selective retina therapy (SRT), the confined laser heating and destruction of retinal pigment epithelial cells, has been shown to treat acute types of central serous chorioretinopathy (CSC) successfully without damaging the photoreceptors and thus avoiding laser-induced scotoma. However, a benefit of laser treatment for chronic forms of CSC is questionable. In this study, the efficacy of SRT by means of the previously used 1.7-µs and shorter 300-ns pulse duration was evaluated for both types of CSC, also considering re-treatment for nonresponders. Material and Methods: In a two-center trial, 26 patients were treated with SRT for acute (n = 10) and chronic-recurrent CSC (n = 16). All patients presented with subretinal fluid (SRF) in OCT and leakage in fluorescein angiography (FA). SRT was performed using a prototype SRT laser system (frequency-doubled Q-switched Nd:YLF-laser, wavelength 527 nm) with adjustable pulse duration. The following irradiation settings were used: a train of 30 laser pulses with a repetition rate of 100 Hz and pulse durations of 300 ns and 1.7 µs, pulse energy 120-200 µJ, retinal spot size 200 µm. Because SRT lesions are invisible, FA was always performed 1 h after treatment to demonstrate laser outcome (5-8 single spots in the area of leakage). In cases where energy was too low, as indicated by missing FA leakage, energy was adjusted and the patient re-treated immediately. Observation intervals were after 4 weeks and 3 months. In case of nonimprovement of the disease after 3 months, re-treatment was considered. Results: Of 10 patients with active CSC that presents focal leakage in FA, 5 had completely resolved fluid after 4 weeks and all 10 after 3 months. Mean visual acuity increased from 76.6 ETDRS letters to 85.0 ETDRS letters 3 months after SRT. Chronic-recurrent CSC was characterized by less severe SRF at baseline in OCT and weaker leakage in FA than in acute types. Visual acuity changed from baseline 71.6 to 72.8 ETDRS letters after 3 months. At this time, SRF was absent in 3 out of 16 patients (19%), FA leakage had come to a complete stop in 6 out of 16 patients (38%). In 6 of the remaining chronic CSC patients, repeated SRT with higher pulse energy was considered because of persistent leakage activity. After the re-treatment, SRF resolved completely in 5 patients (83.3%) after only 25 days. Conclusion: SRT showed promising results in treating acute CSC, but was less effective in chronic cases. Interestingly, re-treatment resulted in enhanced fluid resolution and dry conditions after a considerably shorter time in most patients. Therefore, SRT including re-treatment if necessary might be a valuable CSC treatment alternative even in chronic-recurrent cases.

Resection of Calcified Aortic Heart Leaflets In Vitro by Q‐Switched 2 µm Microsecond Laser Radiation

Transcatheter aortic valve implantation (TAVI) can result in paravalvular leakage and stent deformation in the presence of severe calcification. This study was undertaken to determine the efficacy of laser‐assisted resection of calcific aortic valve leaflets as a method to minimize the effects of calcium on perivalvular leakage during TAVI.

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

Abstract 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 &mgr;J. 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 &mgr;m at baseline to 236.0 ± 57.9 &mgr;m 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.

Temperature dependence of water absorption for wavelengths at 1920 nm and 1940 nm

In this study the absorption coefficient of water at different temperatures was investigated for wavelengths at 1920 nm and 1940 nm respectively. The laser radiation was transmitted via a quartz fibre (O 600 µm core) into a thermal isolated and heated water filled cuvette. At different temperatures the transmittance of water was measured for both wavelengths. According to Beer-Lambert’s law the absorption coefficient α was calculated.

Retinal sensitivity after selective retina therapy (SRT) on patients with central serous chorioretinopathy.

PurposeTo assess retinal sensitivity after selective retina therapy (SRT) in patients with central serous chorioretinopathy (CSCR).MethodsSeventeen eyes of 17 patients with CSCR lasting longer than 3 months were treated with SRT (wavelength 527 nm Nd: YLF laser, 50–150 μJ/pulse, spot diameter 200 μm). Measurement of best-corrected visual acuity (BCVA), optical coherence tomography, fluorescence angiography, and microperimetry (MAIA™) were conducted before, and 1 and 3 months after treatment. Microperimetry was performed in the central 10° of the macula, and at the test spots applied near the vascular arcade for energy titration. In addition to the treatment effect, all test irradiation spots were thoroughly analyzed with regard to their sensitivity changes.ResultsThe mean logMAR BCVA had improved from 0.06 to 0.02 after 1 month (p = 0.11) and to 0.03 after 3 months (p = 0.003). Eleven out of 17 eyes (64.7%) showed complete resolution of subretinal fluid after 3 months. Retinal sensitivity in the central 10° increased after 1 month (median: 25.9 dB) and 3 months (26.6 dB) as compared with that before treatment (23.0 dB) (p < 0.001). Analysis of the test spots revealed a slight decrease in retinal sensitivity after 1 month (ΔdB = −0.5 ± 2.1, p = 0.006), while there was no significant difference from baseline after 3 months (ΔdB = −0.3 ± 2.2, p = 0.09). No correlation was found between laser energy and the change in focal retinal sensitivity.ConclusionsResults suggest that SRT is a safe and effective treatment for persistent CSCR and does not leave permanent scotoma regardless of irradiation energy in the therapeutic range.

Automatic irradiation control by an optical feedback technique for selective retina treatment (SRT) in a rabbit model

Selective Retina Therapy (SRT) targets the Retinal Pigment Epithelium (RPE) without effecting neighboring layers as the photoreceptors or the choroid. SRT related RPE defects are ophthalmoscopically invisible. Owing to this invisibility and the variation of the threshold radiant exposure for RPE damage the treating physician does not know whether the treatment was successful or not. Thus measurement techniques enabling a correct dosing are a demanded element in SRT devices. The acquired signal can be used for monitoring or automatic irradiation control. Existing monitoring techniques are based on the detection of micro-bubbles. These bubbles are the origin of RPE cell damage for pulse durations in the ns and μs time regime 5μs. The detection can be performed by optical or acoustical approaches. Monitoring based on an acoustical approach has already been used to study the beneficial effects of SRT on diabetic macula edema and central serous retinopathy. We have developed a first real time feedback technique able to detect micro-bubble induced characteristics in the backscattered laser light fast enough to cease the laser irradiation within a burst. Therefore the laser energy within a burst of at most 30 pulses is increased linearly with every pulse. The laser irradiation is ceased as soon as micro-bubbles are detected. With this automatic approach it was possible to observe invisible lesions, an intact photoreceptor layer and a reconstruction of the RPE within one week.