@article{Vogel2002,
   author = {Vogel, Alfred . and Schweiger, P. and Frieser, A. and Asiyo, M. and Birngruber, R.},
   title = {Intraocular Nd: YAG Laser Surgery: Light-Tissue Interaction, Damage Range, and Reduction of Collateral Effects},
   journal = {IEEE J Quant Electr},
   volume = {26},
   pages = {2241-2260},
   year = { 2002},
   type = {Journal Article}
}

@article{Vogel1997,
   author = {Vogel, A. and Gunther, T. and Asiyo-Vogel, M. and Birngruber, R.},
   title = {Investigations on the origin of refractive effects in intrastromal refractive surgery with the picosecond laser},
   journal = {Ophthalmologe},
   volume = {94},
   number = {7},
   pages = {467-474},
   note = {Yp140
Times Cited:2
Cited References Count:21},
   abstract = {Background: Picosecond laser intrastromal photorefractive keratectomy (ISPRK) aims at achieving a flattening of the central cornea by plasma-mediated tissue evaporation without affecting the anterior or posterior corneal layers. We investigated the laser-induced tissue effects to establish a functional relationship between laser parameters and tissue removal and to assess their influence on the healing process and long-term refractive changes.
Materials and methods: A modified ISL 2001 System with a cone angle of 30 degrees was used for in vitro investigations of the laser effects in water and porcine cornea. Photographic methods were used to determine the plasma volume and the thickness of the laser-generated intrastromal bubble layer as a function of the pulse energy and the number and separation in which the pulses were applied (216 eyes). Histological evaluation was done by polarization microscopy (9 eyes).
Results: Polarization microscopy revealed only minor signs of thermal tissue damage. The maximum amount of tissue that can be evaporated without damaging the outer corneal layers corresponds to a layer about 10 mu m thick. With a 6-mm optical zone, this tissue removal yields an immediate refractive effect of only 0.85 dpt. Stronger long-term refractive changes observed in animal experiments and clinical studies must thus be due to the healing response of the cornea. The healing response may be induced by mechanical distortion due to intrastromal bubble formation affecting about one third of the corneal thickness.
Conclusion: Since the refractive effects are apparently strongly influenced by corneal healing, they are poorly predictable and can probably not be used for clinical purposes.},
   keywords = {refractive surgery
intrastromal photorefractive keratectomy
picosecond laser
photodisruption
cavitation
photorefractive keratectomy
intraocular photodisruption
corneal tissue
pulses},
   ISSN = {0941-293X},
   DOI = {DOI 10.1007/s003470050141},
   url = {<Go to ISI>://WOS:000071246700001},
   year = {1997},
   type = {Journal Article}
}

@article{Asiyo-Vogel1997,
   author = {Asiyo-Vogel, M and Koop, N and Brinkmann, R and Engelhardt, R and Eggers, R and Birngruber, R and Vogel, A},
   title = {Darstellung von LTK-Läsionen durch optische Kurzkohärenztomographie (OCT) und Polarisationsmikroskopie nach Sirius-Rot-Färbung},
   journal = {Ophthalmologe},
   volume = {94},
   pages = {487-491},
   year = {1997}
}

@article{Brinkmann1997,
   author = {Brinkmann, R. and Koop, N. and Kampmeier, J. and Bruhns, A. and AsiyoVogel, M. and Engelhardt, R. and Birngruber, R.},
   title = {Corneal collagen denaturation in laser thermokeratoplasty (LTK)},
   journal = {Investigative Ophthalmology & Visual Science},
   volume = {38},
   number = {4},
   pages = {2514-2514},
   note = {1
Wn186
Times Cited:0
Cited References Count:0},
   ISSN = {0146-0404},
   url = {<Go to ISI>://WOS:A1997WN18602506},
   year = {1997},
   type = {Journal Article}
}

@article{Asiyo-Vogel,
   author = {Asiyo-Vogel, M. and Brinkmann, R and Notbohm, H. and Eggers, R. and Lubatschowski, H. and Laqua, H. and Vogel, A.},
   title = {Histologic analysis of thermal effects of laserthermokeratoplasty and corneal ablation using Sirius-Red polarization microscopy},
   journal = {J Cataract Refr Surg},
   volume = {23},
   pages = {515-526},
   year = {1997}
}

@article{Vogel1997,
   author = {Vogel, A. and Günther, T. and Asiyo-Vogel, M. and Birngruber, R.},
   title = {Factors determining the refractive effects of intrastromal photorefractive keratectomy with the picosecond laser},
   journal = {J Cataract Refract Surg},
   volume = {23},
   number = {9},
   pages = {1301-1310},
   abstract = {To determine the relationship between laser parameters and tissue removal with picosecond laser intrastromal photorefractive keratectomy (ISPRK) and to assess the effect of the parameters on the healing process and the long-term refractive changes.},
   keywords = {Animals
Corneal Stroma
Follow-Up Studies
Lasers, Excimer
Microscopy, Polarization
Photorefractive Keratectomy
Refraction, Ocular
Refractive Errors
Swine
Wound Healing
pathology
physiopathology
surgery
adverse effects
methods
physiology
etiology},
   year = {1997}
}

@article{Asiyo-Vogel1997,
   author = {Asiyo-Vogel, M. N. and Koop, N. and Brinkmann, R. and Engelhardt, R. and Eggers, R. and Birngruber, R. and Vogel, A.},
   title = {Evaluation of LTK lesions by optical low coherence tomography (OCT) and polarization microscopy after Sirius-Red staining},
   journal = {Ophthalmologe},
   volume = {94},
   number = {7},
   pages = {487-491},
   note = {Yp140
Times Cited:5
Cited References Count:21},
   abstract = {Background: 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.
Methods: Porcine eyes were irradiated through a 400 mu m quartz fiber using light from a laser diode emitting up to 300 mW at a wavelength of 1.86 mu m. Thermal lesions of varying strength were scanned using an experimental OCT device with about 25 mu m lateral and 20 mu m axial resolution. Histologic evaluation of the scanned areas was done by polarization microscopy after Sirius-Red staining, and similar lesions were also analyzed by TEM.
Results: 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 DCT images,ln 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.
Conclusions: 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.},
   keywords = {refractive surgery
laser thermokeratoplasty
collagen denaturation
collagen shrinkage
optical low coherence tomography
polarization microscopy
sirius-red staining
tissue
collagen
eye},
   ISSN = {0941-293X},
   DOI = {DOI 10.1007/s003470050144},
   url = {<Go to ISI>://WOS:000071246700004},
   year = {1997},
   type = {Journal Article}
}

@inproceedings{Brinkmann1996-7,
   author = {Brinkmann, Ralf and Kampmeier, Juergen and Grotehusmann, Ulf and Vogel, Alfred and Koop, Norbert and Asiyo-Vogel, Mary and Birngruber, Reginald},
   title = {Corneal collagen denaturation in laser thermokeratoplasty},
   volume = {2681},
   pages = {56-63},
   note = {10.1117/12.239611},
   abstract = {In laserthermokeratoplasty (LTK) thermal denaturation and shrinkage of corneal collagen is used to correct hyperopia and astigmatism. In order to optimize dosimetry, the temperature at which maximal shrinkage of collagen fibrils occurs is of major interest. Since the exposure time in clinical LTK-treatment is limited to a few seconds, the kinetics of collagen denaturation as a rate process has to be considered, thus the time of exposure is of critical importance for threshold and shrinkage temperatures. We investigated the time-temperature correlation for corneal collagen denaturation within different time domains by turbidimetry of scattered HeNe laser probe light using a temperature controlled water bath and pulsed IR laser irradiation. In the temperature range of 60 degree(s)C to 95 degree(s)C we found an exponential relation between the denaturation time and temperature. For the typical LTK-treatment time of 2 s, a temperature of 95 degree(s)C is needed to induce thermal damage. Use of pulsed Holmium laser radiation gave significant scattering of HeNe laser probe light at calculated temperatures of around 100 degree(s)DC. Rate parameters according to the formalism of Arrhenius were fitted to these results. Force measurements showed the simultaneous onset of light scattering and collagen shrinkage.},
   url = {http://dx.doi.org/10.1117/12.239611},
   type = {Conference Proceedings},
Year ={  1996}
}

@article{Vogel,
   author = {Vogel, A. and Capon, M. R. and Asiyo-Vogel, M. and Birngruber, R.},
   title = {Intraocular photodisruption with picosecond and nanosecond laser pulses: tissue effects in cornea, lens, and retina},
   journal = {Invest Ophthalmol Vis Sci},
   volume = {35},
   number = {7},
   pages = {3032-44},
   note = {0146-0404 (Print)
Journal Article
Research Support, Non-U.S. Gov't},
   abstract = {PURPOSE. Nd:YAG laser photodisruption with nanosecond (ns) pulses in the millijoule range is an established tool for intraocular surgery. This study investigates tissue effects in cornea, lens, and retina to assess whether picosecond (ps) pulses with energies in the microjoule range can increase the surgical precision, reduce collateral damage, and allow applications requiring more localized tissue effects than can be achieved with ns pulses. METHODS. Both ps and ns Nd:YAG laser effects on Descemet's membrane, in the corneal stroma, in the lens, and at the retina were investigated in vitro in bovine and sheep eyes and in cataractous human lens nuclei. For each tissue, the optical breakdown threshold was determined. The morphology of the tissue effects and the damage range of the laser pulses were examined by light and scanning electron microscopy. The cavitation bubble dynamics during the formation of corneal intrastromal laser effects were documented by time-resolved photography. RESULTS. The optical breakdown threshold for ps pulses in clear cornea, lens, and vitreous is, on average, 12 times lower than that for ns pulses. In cataractous lens nuclei, it is lower by a factor of 7. Using ps pulses, Descemet's membrane could be dissected with fewer disruptive side effects than with ns pulses, whereby the damage range decreased by a factor of 3. The range for retinal damage was only 0.5 mm when 200 microJ ps pulses were focused into the vitreous. Picosecond pulses could be used for corneal intrastromal tissue evaporation without damaging the corneal epithelium or endothelium, when the pulses were applied in the anterior part of the stroma. The range for endothelial damage was 150 microns at 80 microJ pulse energy. Intrastromal corneal refractive surgery is compromised by the laser-induced cavitation effects. Tissue displacement during bubble expansion is more pronounced than tissue evaporation, and irregular bubble formation creates difficulties in producing predictable refractive changes. CONCLUSIONS. The use of ps pulses improves the precision of intraocular Nd:YAG laser surgery and diminishes unwanted disruptive side effects, thereby widening the field of potential applications. Promising fields for further studies are intrastromal corneal refractive surgery, cataract fragmentation, membrane cutting, and vitreolysis close to the retina.},
   keywords = {Animals
Cattle
Cornea/injuries/surgery/*ultrastructure
Laser Surgery/adverse effects/instrumentation/*methods
Lens, Crystalline/injuries/surgery/*ultrastructure
Microscopy, Electron, Scanning
Retina/injuries/surgery/*ultrastructure
Sheep},
   year = {1994}
}

@article{Vogel1994,
   author = {Vogel, A. and Asiyovogel, M. and Birngruber, R.},
   title = {Investigations on Intrastromal Refractive Surgery with Picosecond Nd-Yag Laser-Pulses},
   journal = {Investigative Ophthalmology & Visual Science},
   volume = {35},
   number = {4},
   pages = {2155-2155},
   note = {Mz585
Times Cited:0
Cited References Count:0},
   ISSN = {0146-0404},
   url = {<Go to ISI>://WOS:A1994MZ58504161},
   year = {1994},
   type = {Journal Article}
}

@article{Hettlich1994,
   author = {Hettlich, H. J. and Lucke, K. and Asiyo-Vogel, M. N. and Schulte, M. and Vogel, Alfred},
   title = {Lens refilling and endocapsular polymerization of an injectable intraocular lens: in vitro and in vivo study of potential risks and benefits},
   journal = {J Cataract Refract Surg},
   volume = {20},
   number = {2},
   pages = {115-23},
   note = {Using Smart Source Parsing
Mar},
   abstract = {Endocapsular cataract removal and injection of a liquid artificial lens has several advantages, including restitution of accommodation, small corneoscleral incision, a more physiological position of the intraocular lens, and a reduced rate of secondary opacification. Our technique consists of bimanual phacofragmentation followed by injection of a fluid monomeric material that can be polymerized inside the capsular bag by short light exposure. Our study assessed the potential risks of the technique (e.g., heat damage to ocular tissue, light damage to the retina) and investigated the technique in vivo. We performed in vitro experiments on porcine cadaver eyes and an in vivo study on 15 rabbits. After a clinical follow-up of at least 12 weeks, the eyes were investigated histopathologically. During the polymerization process, the highest temperature measured at the posterior lens capsule was 45.1 degrees Celsius for a few seconds. The measured irradiance (0.065 watts per cm2) and the risk of photochemical damage to the retina during 20 seconds of polymerization were comparable to that caused by 1.5 minutes of standard coaxial illumination with the operating microscope. In vivo there were no serious inflammatory reactions except in four cases in which there had been intraoperative problems. The rate of secondary opacification appeared less than in conventional intraocular lens implantation in rabbits, especially when the capsule refilled completely. Retinal damage could not be detected histopathologically. In conclusion, refilling techniques may be successful once appropriate refilling materials become available.},
   ISSN = {0886-3350 (Print)
0886-3350 (Linking)},
   year = {1994},
   type = {Journal Article}
}

@book{Vogel,
   author = {VOGEL, A. and ASIYO-VOGEL, M. and BIRNGRUBER, R.},
   title = {Untersuchungen zur intrastromalen refraktiven Hornhautchirurgie mit Picosekunden-Nd: YAG-Laser-Pulsen},
   publisher = {Springer},
   address = {Berlin, ALLEMAGNE},
   volume = {91},
   keywords = {Surgery
Chirurgie
Cornea
Corn&#233
e
YAG laser
Laser YAG
Neodymium
N&#233
odyme
Stroma
Laser produced plasma
Plasma produit par laser
Cavitation bubble
Bulle cavitation
Eye
Oeil
Sheep
Mouton
Animal
In vitro
Artiodactyla
Ungulata
Mammalia
Vertebrata},
   year = {1994}
}

@article{Vogel1994,
   author = {Vogel, Alfred and Asiyo-Vogel, M. and Birngruber, R.},
   title = {[Intrastromal refractive corneal surgery with pico-second Nd:YAG laser pulses]},
   journal = {Ophthalmologe},
   volume = {91},
   number = {5},
   pages = {655-62},
   note = {0941-293X (Print)
English Abstract
Journal Article
Research Support, Non-U.S. Gov't},
   abstract = {Intrastromal laser surgery with picosecond pulses aims to achieve refractive changes of the cornea without damaging the epithelium, Bowman's membrane, or the endothelium. For that, a tissue layer with well-defined thickness has to be evaporated by creating laser plasmas within the corneal stroma. We investigated the plasma formation and the plasma-induced shock wave emission and bubble generation (cavitation) in the cornea, as well as the tissue effects and the range for endothelial damage. The laser light source used was an Nd:YAG laser emitting pulses with a duration of 30 ps at a repetition rate of 10 Hz. Intrastromal plasma formation and cavitation were investigated in sheep eyes in vitro by means of time-resolved macro-photography with 20 ns exposure time. Photographs were taken at various delay times (3 microseconds-2 min) after the release of the Nd:YAG laser pulse. The morphology of the laser effects and the incidence of endothelial damage was investigated by light-microscopic inspection of histological cross sections of the irradiated corneas. The minimal plasma size at energies close to the breakdown threshold was about 40 microns. Using a laser effects could be created without causing microscopically detectable damage to the epithelium, endothelium, or Bowman's membrane. To avoid damage, the distance between endothelium and laser focus had to be larger than 150 microns. Shock wave-induced tissue damage was not observed, although the maximum shock wave pressure was up to 13 kbar. The laser-generated intrastromal cavities are at least 10 times larger than the plasma volume.(ABSTRACT TRUNCATED AT 250 WORDS)},
   keywords = {Animals
Corneal Stroma/pathology/*surgery
Endothelium, Corneal/pathology
Epithelium/pathology
Equipment Design
Laser Surgery/*instrumentation
*Refraction, Ocular
Sheep
Surface Properties},
   url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=7812100},
   year = {1994},
   type = {Journal Article}
}

@inproceedings{Vogel1993,
   author = {Vogel, Alfred and Busch, Stefan and Asiyo-Vogel, Mary},
   title = {Time-resolved measurements of shock-wave emission and cavitation-bubble generation in intraocular laser surgery with ps- and ns-pulses and related tissue effects},
   volume = {1877},
   pages = {312-322},
   note = {10.1117/12.147544},
   abstract = {Intraocular microsurgery relies on plasma generation with subsequent shock wave emission and cavitation bubble formation. To assess the potentials of photodisruption with picosecond pulses in comparison to the clinical techniques presently used, the shock wave characteristics and the bubble expension after optical breakdown with picosecond and nanosecond laser pulses were investigated by time resolved photography and acoustic measurements. Nd:YAG laser pulses with a wavelength of 1064 nm and a duration of 30 ps and 6 ns were focused into a water-filled glass cuvette. Their breakdown thresholds were 15 (mu) J and 200 (mu) J, respectively. Frequency doubled light from the same laser pulses was optically delayed between 2 ns and 136 ns and used as illumination source for photography. Since the individual events were well reproducible, the shock wave position and bubble wall position could be determined as a function of time. From the slope of these r(t) curves, the shock wave and bubble wall velocities were determined. The shock wave pressure p(r) was calculated from the shock velocity using the `jump conditions' of the shock front and the equation of state of water. The collateral effects of intraocular microsurgery can thus be considerably reduced by using ps-pulses, and with series of ps-pulses a `laser scalpel' may be realized which offers new applications of photodisruption.},
   url = {http://dx.doi.org/10.1117/12.147544},
   type = {Conference Proceedings},
year = { 1993}
}

@article{Vogel1990,
   author = {Vogel, A. and Schweiger, P. and Frieser, A. and Asiyo, M. and Birngruber, R.},
   title = {Intraocular Nd:YAG Laser Surgery: Damage Mechanism, Damage Range and Reduction of Collateral Effects.},
   journal = {IEEE J Quant Electr},
   volume = {26},
   number = {12 Special Issue on Lasers in Biology and Medicine},
   pages = {2240-2260},
   year = {1990}
}

@article{Vogel1990,
   author = {Vogel, Alfred and Schweiger, P. and Frieser, A. and Asiyo, M. and Birngruber, R.},
   title = {Mechanism of action, scope of the damage and reduction of side effects in intraocular Nd:YAG laser surgery},
   journal = {Fortschr Ophthalmol},
   volume = {87},
   number = {6},
   pages = {675-87},
   note = {0723-8045 (Print)
English Abstract
Journal Article},
   abstract = {The damage mechanisms of intraocular Nd:YAG laser surgery and their respective damage ranges were investigated in vitro using bovine cornea specimens as a model tissue. The main damage mechanisms are plasma formation and expansion, emission of acoustic transients, and cavitation with jet formation. When a sequence of laser pulses is applied, the interaction of the acoustic transients with gas bubbles remaining from preceding laser exposures is also important. To distinguish the effects caused by the different physical mechanisms, laser pulses were aimed directly onto the corneal endothelium, and parallel to the cornea at various distances. Simultaneously, the cavitation bubble size was determined. The surface morphology and sections of the same lesions were studied by light and electron microscopy. The primary surgical mechanism is tissue evaporation by the laser plasma, whereas the collateral damage from single laser pulses is mainly caused by the cavitation and jet formation. The damage range after a 4-mJ laser pulse is 0.8 mm which is slightly larger than the corresponding cavitation bubble radius. The damage range of the acoustic transients produced by a 4-mJ laser pulse is several millimeters, when they can interact with small gas bubbles attached to the corneal endothelium. The damage range of the acoustic transients alone is smaller than that of cavitation as far as damage detected by light and scanning electron microscopy is concerned. However, on a subcellular level the acoustic transients may possibly cause damage up to a much larger distance. The damage range observed varies with the cube root of the laser pulse energy. A reduction of collateral effects therefore requires the use of small pulse energies. For energies of less than 1 mJ, the pulse duration has to be reduced to ensure plasma production. It is proposed to use low-energy picosecond pulses with moderate repetition rate instead of single nanosecond pulses to reduce collateral damage effects.},
   keywords = {Animals
Cattle
Endothelium, Corneal/*injuries/pathology
Laser Surgery/*adverse effects/instrumentation
Microscopy, Electron, Scanning},
   url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=2086418},
   year = {1990},
   type = {Journal Article}
}

@article{Vogel1990,
   author = {Vogel, A. and Schweiger, P. and Frieser, A. and Asiyo, M. and Birngruber, R.},
   title = {Wirkungsmechanismen, Schadensreichweite und Reduzierung von Nebenwirkungen bei der intraokularen Nd:YAG-Laserchirurgie},
   journal = {Fortschritte der Ophthalmologie},
   volume = {87},
   number = {6},
   pages = {675-687},
   keywords = {Oeil pathologie
Animal
Prévention
Physiopathologie
Complication
In vitro
Cornée
Oeil
Néodyme
Laser YAG
Laser
Chirurgie},
   year = {1990}
}