Einleitung: Phoniater sind in die Frühdiagnose von Stimmlippenkarzinomen und anderen Kehlkopfkarz... more Einleitung: Phoniater sind in die Frühdiagnose von Stimmlippenkarzinomen und anderen Kehlkopfkarzinomen eingebunden. Diese stützt sich bisher auf weißlichtlaryngoskopische und stroboskopische Befunde. Auf der DGPP-Tagung 2003 berichteten wir über eine visuelle Kontrastverstärkung durch Nutzung der natürlichen Autofluoreszenz des Stimmlippenepithels, die bei invasiver Infiltration typischerweise reduziert ist. Die Farbverschiebung konnte durch ein charakteristisches Grün-Rot-Verhältnis quantifiziert werden (QAF). Methode: Diese Methode haben wir seit 2003 an einem größeren Kollektiv angewendet (57 Patienten mit benignen und 26 mit malignen Larynxneubildungen). Die Korrelationen der Quotienten mit den histologischen Merkmalen wurden nach Spearman auf Signifikanz geprüft und die Sensitivitäten und Spezifitäten mit ROC-Kurven bestimmt. Ergebnisse: Die Korrelation des Grün-Rot-Quotienten mit dem Merkmal der Malignität betrug 0,325 (p=0,003), bei einem Quotienten von 1,43 war die Sensitiv...
10. Kongreß der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, 1997
Hintergrund Zweck der vorliegenden Studie sollte sein, die prinzipielle Eignung eines Infrarotlas... more Hintergrund Zweck der vorliegenden Studie sollte sein, die prinzipielle Eignung eines Infrarotlasers zur Emulsifikation auch harter Linsenkerne zu uberprufen.
Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopi... more Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopia and hyperopic astigmatism by means of collagen coagulation in the peripheral cornea. The purpose of our study was to optimize the ratio between the volume of damaged corneal stroma and the refractive effect so as to minimize potential side effects such as endothelial damage or induction of glare phenomena. We therefore performed histological and morphometrical examinations of enucleated pig eyes to determine the relationship between the coagulated stromal volume and the refractive change after LTK using a pulsed Cr:Tm:Ho:YAG laser (wavelength 2.12 microns) on enucleated pig eyes. The refractive change was documented with a Littman ophthalmometer. Morphometrical analysis was performed using polarized light microscopy of sirius red-stained specimens. This special stain separated the thermally changed stroma into a dark nonbirefringent center and a birefringent peripheral zone. The volume of both zones was positively correlated with the refractive change induced. The volume was in turn influenced by the choice of laser parameters. From the ratio of the volume to the refractive change it was found that pulse energies above 30 mJ let to an enlargement of the coagulation volume without increasing the refractive change effectively. The use of high pulse energies did not improve the effect of LTK but only increased the risk of unwanted side effects. However, an increase in the laser repetition rate at a constant pulse number per spot led to refractive changes with minimal coagulation volume. The highest relative refractive change was achieved with a dark central zone and a birefringent zone, each having a volume of about 50-80 x 10(-3) mm3.
Information on the extent and degree of the thermal effect produced is of great importance for co... more Information on the extent and degree of the thermal effect produced is of great importance for control of the laser dosage in laser thermokeratoplasty (LTK) and for postoperative follow-up. We investigated on acute LTK effects which information images obtained by optical low coherence tomography (OCT) offer compared to those obtained by polarization microscopy. Porcine eyes were irradiated through a 400 microns quartz fiber using light from a laser diode emitting up to 300 mW at a wavelength of 1.86 microns. Thermal lesions of varying strength were scanned using an experimental OCT device with about 25 microns lateral and 20 microns axial resolution. Histologic evaluation of the scanned areas was done by polarization microscopy after Sirlus-Red staining, and similar lesions were also analyzed by TEM. Both methods differentiated three damage zones a transition zone, a zone of moderate coagulation, and a central zone of strong coagulation. In the transition zone, increased birefringence was seen in polarization microscopy, which correlated with increased light scattering seen in the OCT images. In the moderately coagulated zone, a decrease in birefringence was associated with an even stronger increase of the OCT signal. In the central zone, a loss of the fibrillar tissue structure was observed, which led to a complete loss of birefringence and a strong reduction of the OCT signal. Although OCT does not provide the detailed information on thermal changes of tissue seen by the histologic method, it offers information on the extent and degree of tissue changes without preparation artifacts and provides a non-invasive method of immediate and follow-up control of LTK lesions. A quantitative analysis of changes in corneal thickness and curvature is much simpler than by a slit lamp. Time-resolved measurements of corneal light scattering may be used for on-line control of the laser-light dosage during LTK.
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1999
Pulsed holmium lasers are currently used to correct hyperopia by means of laser thermokeratoplast... more Pulsed holmium lasers are currently used to correct hyperopia by means of laser thermokeratoplasty (LTK). Series of microsecond laser pulses are applied with a high repetition rate to induce shrinkage of corneal collagen fibers. The pulsed energy application results in intrastromal temperature peaks of up to 200 degrees C. A continuously emitting laser diode can--as we demonstrated recently in an invivo study on minipigs--be used for LTK and may be of advantage because the temperature rise is more steady. The aim of this study was to examine the safety, amount, and stability of hyperopic correction of diode LTK on blind human eyes. We used a laserdiode that was set to continuously emit light at lambda = 1.854 microns/mu a = 1.04 mm-1 (group I, n = 4) or 1.87 microns/mu a = 1.92 mm-1 (group II, n = 4). Radiation energy was 100 to 150 mW for 10 s per coagulation. Eight coagulations on a single ring (group I) and 16 coagulations on a double ring (group II) diameter were applied in the ...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
Information on the extent and degree of the thermal effect produced is of great importance for co... more Information on the extent and degree of the thermal effect produced is of great importance for control of the laser dosage in laser thermokeratoplasty (LTK) and for postoperative follow-up. We investigated on acute LTK effects which information images obtained by optical low coherence tomography (OCT) offer compared to those obtained by polarization microscopy. Porcine eyes were irradiated through a 400 microns quartz fiber using light from a laser diode emitting up to 300 mW at a wavelength of 1.86 microns. Thermal lesions of varying strength were scanned using an experimental OCT device with about 25 microns lateral and 20 microns axial resolution. Histologic evaluation of the scanned areas was done by polarization microscopy after Sirlus-Red staining, and similar lesions were also analyzed by TEM. Both methods differentiated three damage zones a transition zone, a zone of moderate coagulation, and a central zone of strong coagulation. In the transition zone, increased birefringen...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
The method of optical coherence tomography (OCT) was investigated regarding its suitability and l... more The method of optical coherence tomography (OCT) was investigated regarding its suitability and limits for measuring the cornea and the anterior segment of the eye. Furthermore, the stromal expansion of thermally induced lesions in the cornea directly after irradiation was determined within the scope of the laser thermokeratoplasty (LTK). With the experimental scanning OCT system, x-z sections of the anterior eye segment were made with an optical resolution of about 20 microns axially and 25 microns laterally. Freshly enucleated, tonicized porcine eyes were used as model eyes. Thermal lesions were applied with a continuously emitting laser diode (lambda = 1.86 microns) and various radiation parameters. Before and after coagulation, the cornea was viewed from limbus to limbus in a central OCT scan and the individual coagulation source was measured. Global and local changes of the thickness of the cornea as well as the distance between cornea and lens were measured with high precision...
The energy of the erbium: YAG laser (2.940-nm wave-length) can be used for minimally traumatic ph... more The energy of the erbium: YAG laser (2.940-nm wave-length) can be used for minimally traumatic photoablation due to its high absorption at the tissue water and its consequently low penetration depth. Laser sclerostomy ab externo, an application of this principle, has undergone advanced clinical investigation. Another potential application is photofragmentation of the lens for cataract extraction. A laboratory model Er: YAG laser (flashlamp-pumped. 200-microseconds pulse length, 5-Hz repetition frequency) was coupled to a short low-OH quartz fiber (400 microns in diameter). The laser energy was applied by direct contact of the fiber tip to human lenses with very dense cataract. The lenses rested in a small cuvette filled with an aqueous-humor-analogous fluid. The fragmentablation rate was evaluated in relation to the number of pulses and the pulse energy. A laser-triggered flash-photography unit was engaged to visualize the ablation dynamics. We found tissue-ablation rates to range f...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1996
Refraction of the cornea head been generally measured with ophthalmometers or computer disk kerat... more Refraction of the cornea head been generally measured with ophthalmometers or computer disk keratometers. We therefore used a confocal laser scanning system for measurement of the corneal topography. Enucleated tonicized pig eyes were measured before and after laser thermokeratoplasty (LTK). The topographical data were used to determine refraction and refractive change; the data were stored digitally. The single images and their differences were displayed on a PC. Unlike conventional ophthalmometry, confocal laser scanning can demonstrate the topographical shape, showing the overall topography of the cornea and local corneal effects, e.g., coagulation, mechanical lesions or high-energy laser effects. Topographical laser scanning has proven to be a generally useful method of determining refraction and surface alterations in corneal refractive surgery.
Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopi... more Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopia and hyperopic astigmatism by means of collagen coagulation in the peripheral cornea. The purpose of our study was to optimize the ratio between the volume of damaged corneal stroma and the refractive effect so as to minimize potential side effects such as endothelial damage or induction of glare phenomena. We therefore performed histological and morphometrical examinations of enucleated pig eyes to determine the relationship between the coagulated stromal volume and the refractive change after LTK using a pulsed Cr:Tm:Ho:YAG laser (wavelength 2.12 microns) on enucleated pig eyes. The refractive change was documented with a Littman ophthalmometer. Morphometrical analysis was performed using polarized light microscopy of sirius red-stained specimens. This special stain separated the thermally changed stroma into a dark nonbirefringent center and a birefringent peripheral zone. The volume...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
It is difficult to measure the topography of the cornea with high resolution and visualize it on ... more It is difficult to measure the topography of the cornea with high resolution and visualize it on a map displaying refraction. This is demonstrated by the ongoing improvement and further development of different methods and by the fact that users of these techniques are not always satisfied. Five different ring projectors were compared. Spherical and aspherical ball standards were used to measure the standard deviation of the refraction of the system. A patient group of eight people with healthy eyes was used to compare the measurement accuracy and operational errors. Some patients were also measured after cataract surgery. The lateral and axial range of the devices was determined. The measurement accuracy for ball standards for the five devices was below 1/8 D. For the in vivo case in the control group it was below 1/4 D for four devices. Furthermore, the reproducibility of the results, the accuracy of angle determination and the influence of mechanical and optical design will be di...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1999
Laser thermokeratoplasty (LTK) can be applied for correction of hyperopia and astigmatism by mean... more Laser thermokeratoplasty (LTK) can be applied for correction of hyperopia and astigmatism by means of concentrically placed coagulations. Because of the temperature rise during coagulation, damage of the endothelial cells directly below the irradiated areas is possible. In this study, we examined the extent of the thermally denatured zones for different laser parameters and the threshold of thermal endothelial damage as a function of of temperature and duration of elevated temperatures. The threshold for thermal damage of endothelial cells was determined in isotonic NaCl solution for temperature exposures of 10 s and 1 min in a water bath. To determine the damage zones, corneas were irradiated under standardized conditions with a continuously emitting infrared (cw-IR) laser diode at various wave-lengths and different power values and were stained after preparation with trypan blue and alizarine red. The extensions of the damage zones were compared with calculated isotherms. Fifty pe...
Einleitung: Phoniater sind in die Frühdiagnose von Stimmlippenkarzinomen und anderen Kehlkopfkarz... more Einleitung: Phoniater sind in die Frühdiagnose von Stimmlippenkarzinomen und anderen Kehlkopfkarzinomen eingebunden. Diese stützt sich bisher auf weißlichtlaryngoskopische und stroboskopische Befunde. Auf der DGPP-Tagung 2003 berichteten wir über eine visuelle Kontrastverstärkung durch Nutzung der natürlichen Autofluoreszenz des Stimmlippenepithels, die bei invasiver Infiltration typischerweise reduziert ist. Die Farbverschiebung konnte durch ein charakteristisches Grün-Rot-Verhältnis quantifiziert werden (QAF). Methode: Diese Methode haben wir seit 2003 an einem größeren Kollektiv angewendet (57 Patienten mit benignen und 26 mit malignen Larynxneubildungen). Die Korrelationen der Quotienten mit den histologischen Merkmalen wurden nach Spearman auf Signifikanz geprüft und die Sensitivitäten und Spezifitäten mit ROC-Kurven bestimmt. Ergebnisse: Die Korrelation des Grün-Rot-Quotienten mit dem Merkmal der Malignität betrug 0,325 (p=0,003), bei einem Quotienten von 1,43 war die Sensitiv...
10. Kongreß der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, 1997
Hintergrund Zweck der vorliegenden Studie sollte sein, die prinzipielle Eignung eines Infrarotlas... more Hintergrund Zweck der vorliegenden Studie sollte sein, die prinzipielle Eignung eines Infrarotlasers zur Emulsifikation auch harter Linsenkerne zu uberprufen.
Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopi... more Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopia and hyperopic astigmatism by means of collagen coagulation in the peripheral cornea. The purpose of our study was to optimize the ratio between the volume of damaged corneal stroma and the refractive effect so as to minimize potential side effects such as endothelial damage or induction of glare phenomena. We therefore performed histological and morphometrical examinations of enucleated pig eyes to determine the relationship between the coagulated stromal volume and the refractive change after LTK using a pulsed Cr:Tm:Ho:YAG laser (wavelength 2.12 microns) on enucleated pig eyes. The refractive change was documented with a Littman ophthalmometer. Morphometrical analysis was performed using polarized light microscopy of sirius red-stained specimens. This special stain separated the thermally changed stroma into a dark nonbirefringent center and a birefringent peripheral zone. The volume of both zones was positively correlated with the refractive change induced. The volume was in turn influenced by the choice of laser parameters. From the ratio of the volume to the refractive change it was found that pulse energies above 30 mJ let to an enlargement of the coagulation volume without increasing the refractive change effectively. The use of high pulse energies did not improve the effect of LTK but only increased the risk of unwanted side effects. However, an increase in the laser repetition rate at a constant pulse number per spot led to refractive changes with minimal coagulation volume. The highest relative refractive change was achieved with a dark central zone and a birefringent zone, each having a volume of about 50-80 x 10(-3) mm3.
Information on the extent and degree of the thermal effect produced is of great importance for co... more Information on the extent and degree of the thermal effect produced is of great importance for control of the laser dosage in laser thermokeratoplasty (LTK) and for postoperative follow-up. We investigated on acute LTK effects which information images obtained by optical low coherence tomography (OCT) offer compared to those obtained by polarization microscopy. Porcine eyes were irradiated through a 400 microns quartz fiber using light from a laser diode emitting up to 300 mW at a wavelength of 1.86 microns. Thermal lesions of varying strength were scanned using an experimental OCT device with about 25 microns lateral and 20 microns axial resolution. Histologic evaluation of the scanned areas was done by polarization microscopy after Sirlus-Red staining, and similar lesions were also analyzed by TEM. Both methods differentiated three damage zones a transition zone, a zone of moderate coagulation, and a central zone of strong coagulation. In the transition zone, increased birefringence was seen in polarization microscopy, which correlated with increased light scattering seen in the OCT images. In the moderately coagulated zone, a decrease in birefringence was associated with an even stronger increase of the OCT signal. In the central zone, a loss of the fibrillar tissue structure was observed, which led to a complete loss of birefringence and a strong reduction of the OCT signal. Although OCT does not provide the detailed information on thermal changes of tissue seen by the histologic method, it offers information on the extent and degree of tissue changes without preparation artifacts and provides a non-invasive method of immediate and follow-up control of LTK lesions. A quantitative analysis of changes in corneal thickness and curvature is much simpler than by a slit lamp. Time-resolved measurements of corneal light scattering may be used for on-line control of the laser-light dosage during LTK.
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1999
Pulsed holmium lasers are currently used to correct hyperopia by means of laser thermokeratoplast... more Pulsed holmium lasers are currently used to correct hyperopia by means of laser thermokeratoplasty (LTK). Series of microsecond laser pulses are applied with a high repetition rate to induce shrinkage of corneal collagen fibers. The pulsed energy application results in intrastromal temperature peaks of up to 200 degrees C. A continuously emitting laser diode can--as we demonstrated recently in an invivo study on minipigs--be used for LTK and may be of advantage because the temperature rise is more steady. The aim of this study was to examine the safety, amount, and stability of hyperopic correction of diode LTK on blind human eyes. We used a laserdiode that was set to continuously emit light at lambda = 1.854 microns/mu a = 1.04 mm-1 (group I, n = 4) or 1.87 microns/mu a = 1.92 mm-1 (group II, n = 4). Radiation energy was 100 to 150 mW for 10 s per coagulation. Eight coagulations on a single ring (group I) and 16 coagulations on a double ring (group II) diameter were applied in the ...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
Information on the extent and degree of the thermal effect produced is of great importance for co... more Information on the extent and degree of the thermal effect produced is of great importance for control of the laser dosage in laser thermokeratoplasty (LTK) and for postoperative follow-up. We investigated on acute LTK effects which information images obtained by optical low coherence tomography (OCT) offer compared to those obtained by polarization microscopy. Porcine eyes were irradiated through a 400 microns quartz fiber using light from a laser diode emitting up to 300 mW at a wavelength of 1.86 microns. Thermal lesions of varying strength were scanned using an experimental OCT device with about 25 microns lateral and 20 microns axial resolution. Histologic evaluation of the scanned areas was done by polarization microscopy after Sirlus-Red staining, and similar lesions were also analyzed by TEM. Both methods differentiated three damage zones a transition zone, a zone of moderate coagulation, and a central zone of strong coagulation. In the transition zone, increased birefringen...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
The method of optical coherence tomography (OCT) was investigated regarding its suitability and l... more The method of optical coherence tomography (OCT) was investigated regarding its suitability and limits for measuring the cornea and the anterior segment of the eye. Furthermore, the stromal expansion of thermally induced lesions in the cornea directly after irradiation was determined within the scope of the laser thermokeratoplasty (LTK). With the experimental scanning OCT system, x-z sections of the anterior eye segment were made with an optical resolution of about 20 microns axially and 25 microns laterally. Freshly enucleated, tonicized porcine eyes were used as model eyes. Thermal lesions were applied with a continuously emitting laser diode (lambda = 1.86 microns) and various radiation parameters. Before and after coagulation, the cornea was viewed from limbus to limbus in a central OCT scan and the individual coagulation source was measured. Global and local changes of the thickness of the cornea as well as the distance between cornea and lens were measured with high precision...
The energy of the erbium: YAG laser (2.940-nm wave-length) can be used for minimally traumatic ph... more The energy of the erbium: YAG laser (2.940-nm wave-length) can be used for minimally traumatic photoablation due to its high absorption at the tissue water and its consequently low penetration depth. Laser sclerostomy ab externo, an application of this principle, has undergone advanced clinical investigation. Another potential application is photofragmentation of the lens for cataract extraction. A laboratory model Er: YAG laser (flashlamp-pumped. 200-microseconds pulse length, 5-Hz repetition frequency) was coupled to a short low-OH quartz fiber (400 microns in diameter). The laser energy was applied by direct contact of the fiber tip to human lenses with very dense cataract. The lenses rested in a small cuvette filled with an aqueous-humor-analogous fluid. The fragmentablation rate was evaluated in relation to the number of pulses and the pulse energy. A laser-triggered flash-photography unit was engaged to visualize the ablation dynamics. We found tissue-ablation rates to range f...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1996
Refraction of the cornea head been generally measured with ophthalmometers or computer disk kerat... more Refraction of the cornea head been generally measured with ophthalmometers or computer disk keratometers. We therefore used a confocal laser scanning system for measurement of the corneal topography. Enucleated tonicized pig eyes were measured before and after laser thermokeratoplasty (LTK). The topographical data were used to determine refraction and refractive change; the data were stored digitally. The single images and their differences were displayed on a PC. Unlike conventional ophthalmometry, confocal laser scanning can demonstrate the topographical shape, showing the overall topography of the cornea and local corneal effects, e.g., coagulation, mechanical lesions or high-energy laser effects. Topographical laser scanning has proven to be a generally useful method of determining refraction and surface alterations in corneal refractive surgery.
Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopi... more Laser thermal keratoplasty (LTK) is currently under clinical trial for the correction of hyperopia and hyperopic astigmatism by means of collagen coagulation in the peripheral cornea. The purpose of our study was to optimize the ratio between the volume of damaged corneal stroma and the refractive effect so as to minimize potential side effects such as endothelial damage or induction of glare phenomena. We therefore performed histological and morphometrical examinations of enucleated pig eyes to determine the relationship between the coagulated stromal volume and the refractive change after LTK using a pulsed Cr:Tm:Ho:YAG laser (wavelength 2.12 microns) on enucleated pig eyes. The refractive change was documented with a Littman ophthalmometer. Morphometrical analysis was performed using polarized light microscopy of sirius red-stained specimens. This special stain separated the thermally changed stroma into a dark nonbirefringent center and a birefringent peripheral zone. The volume...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1997
It is difficult to measure the topography of the cornea with high resolution and visualize it on ... more It is difficult to measure the topography of the cornea with high resolution and visualize it on a map displaying refraction. This is demonstrated by the ongoing improvement and further development of different methods and by the fact that users of these techniques are not always satisfied. Five different ring projectors were compared. Spherical and aspherical ball standards were used to measure the standard deviation of the refraction of the system. A patient group of eight people with healthy eyes was used to compare the measurement accuracy and operational errors. Some patients were also measured after cataract surgery. The lateral and axial range of the devices was determined. The measurement accuracy for ball standards for the five devices was below 1/8 D. For the in vivo case in the control group it was below 1/4 D for four devices. Furthermore, the reproducibility of the results, the accuracy of angle determination and the influence of mechanical and optical design will be di...
Der Ophthalmologe : Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 1999
Laser thermokeratoplasty (LTK) can be applied for correction of hyperopia and astigmatism by mean... more Laser thermokeratoplasty (LTK) can be applied for correction of hyperopia and astigmatism by means of concentrically placed coagulations. Because of the temperature rise during coagulation, damage of the endothelial cells directly below the irradiated areas is possible. In this study, we examined the extent of the thermally denatured zones for different laser parameters and the threshold of thermal endothelial damage as a function of of temperature and duration of elevated temperatures. The threshold for thermal damage of endothelial cells was determined in isotonic NaCl solution for temperature exposures of 10 s and 1 min in a water bath. To determine the damage zones, corneas were irradiated under standardized conditions with a continuously emitting infrared (cw-IR) laser diode at various wave-lengths and different power values and were stained after preparation with trypan blue and alizarine red. The extensions of the damage zones were compared with calculated isotherms. Fifty pe...
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