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Kim H.D.,Soonchunhyang University | Han J.W.,Soonchunhyang University | Ohn Y.-H.,Soonchunhyang University | Brinkmann R.,Medical Laser Center Lubeck GmbH | Park T.K.,Soonchunhyang University
Investigative Ophthalmology and Visual Science | Year: 2015

PURPOSE. To evaluate the changes of retinal function with multifocal electroretinogram (mfERG), and estimate the association between functional and structural changes after selective retina therapy (SRT) with microsecond-pulsed laser in comparison to continuous wave laser photocoagulation (cwPC).METHODS. Selective retina therapy and cwPC were applied with 10 × 10 shots and 1/2 lesionwidth on the retina in the right and left eyes of 20 healthy Chinchilla Bastard rabbits, respectively. Optical coherence tomography (OCT), fundus fluorescein angiography (FFA), and mfERG were performed before, and on days 1, 7, and 30 after both laser treatments. The mean ratios of amplitudes and implicit times of N1 and P1 from eight hexagons covering lasertreated retinal lesions/total retina were measured. Histology was obtained after killing three rabbits at each time period to observe the anatomic changes after both laser treatments.RESULTS. The mean ratios of amplitudes of N1 and P1 in SRT lesions did not change significantly for 30 days after laser treatment. Only subtle reductions of the mean ratios of N1 and P1 amplitudes on day 1, thereafter the amplitudes showed the trend to recover toward baseline values. Histology and OCT revealed temporary and reversible morphologic changes after SRT, which restored to normal within 1 month. However, the mean ratios of N1 amplitudes on days 7 and 30 (P = 0.010, P < 0.001, respectively), and P1 amplitudes on days 7 and 30 (P < 0.001, P < 0.001, respectively) declined significantly in cwPC lesions compared with baseline. Disorganization and atrophic changes were identified on histology and OCT after cwPC.CONCLUSIONS. The results suggest that SRT preserved retinal function as well as anatomical structure after treatment. © 2015 The Association for Research in Vision and Ophthalmology, Inc. Source

Lu T.,Wuhan University | Lu T.,Medical Laser Center Lubeck GmbH | Xiao Q.,Huazhong University of Science and Technology
Applied Physics B: Lasers and Optics | Year: 2012

In order to investigate the influence of water environment on fiber-guided holmium laser ablation of hard tissues, high-speed photography is performed to accurately record the dynamic evolutions of vaporization bubbles and ablation plumes, and optical coherence microscopy is also used to measure the crater morphology. Experimental results indicate that under the same condition, the ablation performances in air and in water for a single long-pulse laser are comparable when the used fibers are in perpendicular contact with the tissues. But for multiple-pulses ablation, the ablation performances such as ablation efficiency and surface morphology in water become better than those in air because of more and more significant vaporization effect for bigger ablation craters. Optical coherence microscopy is an effective tool for the morphological measurement of craters. ©Springer-Verlag 2012. Source

Park Y.G.,Catholic University of Korea | Kang S.,Catholic University of Korea | Brinkmann R.,Medical Laser Center Lubeck GmbH | Roh Y.-J.,Catholic University of Korea
Journal of Ophthalmology | Year: 2015

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. © 2015 Young Gun Park et al. Source

Muller H.H.,University of Lubeck | Muller H.H.,Medical Laser Center Lubeck GmbH | Ptaszynski L.,Medical Laser Center Lubeck GmbH | Schlott K.,University of Lubeck | And 9 more authors.
Biomedical Optics Express | Year: 2012

Visualizing retinal photocoagulation by real-time OCT measurements may considerably improve the understanding of thermally induced tissue changes and might enable a better reproducibility of the ocular laser treatment. High speed Doppler OCT with 860 frames per second imaged tissue changes in the fundus of enucleated porcine eyes during laser irradiation. Tissue motion, measured by Doppler OCT with nanometer resolution, was correlated with the temperature increase, which was measured non-invasively by optoacoustics. In enucleated eyes, the increase of the OCT signal near the retinal pigment epithelium (RPE) corresponded well to the macroscopically visible whitening of the tissue. At low irradiance, Doppler OCT revealed additionally a reversible thermal expansion of the retina. At higher irradiance additional movement due to irreversible tissue changes was observed. Measurements of the tissue expansion were also possible in vivo in a rabbit with submicrometer resolution when global tissue motion was compensated. Doppler OCT may be used for spatially resolved measurements of retinal temperature increases and thermally induced tissue changes. It can play an important role in understanding the mechanisms of photocoagulation and, eventually, lead to new strategies for retinal laser treatments. © 2012 Optical Society of America. Source

Koinzer S.,University of Kiel | Saeger M.,University of Kiel | Hesse C.,University of Kiel | Portz L.,University of Kiel | And 5 more authors.
Acta Ophthalmologica | Year: 2013

Purpose: To examine spectral domain optical coherence tomographic (OCT) and histological images from comparable retinal photocoagulation lesions in rabbits, and to correlate these images with comparable OCT images from patients. Methods: 508 rabbit lesions were examined by HE-stained paraffin histology. 1019 rabbit lesions versus 236 patient lesions were examined by OCT, all at the time-points 1 hr, 1 week and 4 weeks after photocoagulation. We analysed 100 μm lesions (in humans) and 133 μm lesions (in rabbits) of 200 ms exposures at powers titrated from the histological threshold up to intense damage. Lesions were matched according to morphological criteria. Results: Dome-shaped layer alterations, retinal infiltration by round, pigmented cells, outer nuclear layer interruption, and eventually full thickness retinal coagulation are detectable in histology and OCT. Horizontal damage extensions are found 1 times larger in OCT. More intense irradiation was necessary to induce comparable layer affection in rabbit OCT as in histology. Restoration of the inner retinal layers is only shown in the OCT images. Comparable primary lesions caused more pronounced OCT changes in patients than in rabbits during healing. Conclusions: Optical coherence tomographic images indicate different tissue changes than histologic images. After photocoagulation, they show wider horizontal damage diameters, but underestimate axial damage particularly during healing. Conclusions on retinal restoration should not be drawn from OCT findings alone. Retinal recovery after comparable initial lesions appears to be more complete in rabbit than in patient OCTs. © 2013 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd. Source

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