Dr. Hanna J. Hoffman Profile

Dr. Hanna J. Hoffman

Manager/Adv. Research & Development at Electro Optics Organization Inc

SPIE Involvement:

Author

Proceedings Article | 21 February 2007 Paper

Photodarkening measurements in large mode area fibers

Joona Koponen, Mikko Söderlund, Hanna Hoffman, Dahv Kliner, Jeffrey Koplow

Proceedings Volume 6453, 64531E (2007) https://doi.org/10.1117/12.712545

KEYWORDS: Optical fibers, Ytterbium, Cladding, Glasses, Continuous wave operation, Fiber lasers, Fiber amplifiers, Absorption, Optical amplifiers, Ions

Read Abstract +

SPIE Journal Paper | 1 October 1999 Open Access

Minimizing thermal damage in corneal ablation with short pulse mid-infrared lasers

Hanna Hoffman, William Telfair

JBO, Vol. 4, Issue 04, (October 1999) https://doi.org/10.1117/12.10.1117/1.429958

KEYWORDS: Tissues, Mid-IR, Laser ablation, Absorption, Laser tissue interaction, Pulsed laser operation, Excimer lasers, Natural surfaces, Cornea, Thermal effects

DOWNLOAD PAPER

Proceedings Article | 18 June 1999 Paper

Scanning mid-IR laser apparatus with eye tracking for refractive surgery

William Telfair, Paul Yoder, Carsten Bekker, Hanna Hoffman, Eric Jensen

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350567

KEYWORDS: Eye, Laser vision correction, Laser ablation, Sensors, Mirrors, Surgery, Cornea, Laser therapeutics, Laser systems engineering, Mid-IR

Read Abstract +

Proceedings Article | 14 June 1999 Paper

Corneal ablation with short-pulse mid-IR laser radiation

Hanna Hoffman, William Telfair, Henry Plaessmann

Proceedings Volume 3601, (1999) https://doi.org/10.1117/12.350028

KEYWORDS: Laser ablation, Tissues, Laser tissue interaction, Absorption, Mid-IR, Pulsed laser operation, Cornea, Excimer lasers, Natural surfaces, Excimers

Read Abstract +

Proceedings Article | 1 June 1998 Paper

Evaluation of corneal ablation by an optical parametric oscillator (OPO) at 2.94 um and an Er:YAG laser and comparison to ablation by a 193-nm excimer laser

William Telfair, Hanna Hoffman, Robert Nordquist, Richard Eiferman

Proceedings Volume 3246, (1998) https://doi.org/10.1117/12.309421

KEYWORDS: Laser ablation, Optical parametric oscillators, Excimer lasers, Er:YAG lasers, Excimers, Laser vision correction, Eye, Cornea, LASIK, Tissues

Read Abstract +

Purpose: This study first evaluated the corneal ablation characteristics of (1) an Nd:YAG pumped OPO (Optical Parametric Oscillator) at 2.94 microns and (2) a short pulse Er:YAG laser. Secondly, it compared the histopathology and surface quality of these ablations with (3) a 193 nm excimer laser. Finally, the healing characteristics over 4 months of cat eyes treated with the OPO were evaluated. Methods: Custom designed Nd:YAG/OPO and Er:YAG lasers were integrated with a new scanning delivery system to perform PRK myopic correction procedures. After initial ablation studies to determine ablation thresholds and rates, human cadaver eyes and in-vivo cat eyes were treated with (1) a 6.0 mm Dia, 30 micron deep PTK ablation and (2) a 6.0 mm Dia, -5.0 Diopter PRK ablation. Cadaver eyes were also treated with a 5.0 mm Dia, -5.0 Diopter LASIK ablation. Finally, cats were treated with the OPO in a 4 month healing study. Results: Ablation thresholds below 100 mJ/cm² and ablation rates comparable to the excimer were demonstrated for both infrared systems. Light Microscopy (LM) showed no thermal damage for low fluence treatments, but noticeable thermal damage at higher fluences. SEM and TEM revealed morphologically similar surfaces for low fluence OPO and excimer samples with a smooth base and no evidence of collagen shrinkage. The Er:YAG and higher fluence OPO treated samples revealed more damage along with visible collagen coagulation and shrinkage in some cases. Healing was remarkably unremarkable. All eyes had a mild healing response with no stromal haze and showed topographic flattening. LM demonstrated nothing except a moderate increase in keratocyte activity in the upper third of the stroma. TEM confirmed this along with irregular basement membranes. Conclusions: A non- thermal ablation process called photospallation is demonstrated for the first time using short pulse infrared lasers yielding damage zones comparable to the excimer and healing which is also comparable to the excimer. Such Infrared sources are, therefore, potentially attractive competitors to the excimer to perform PRK and LASIK.