Dr. Harry Zwick Profile

Dr. Harry Zwick

Research Psychologist; Professor

SPIE Involvement:

Author

Publications (56)

Proceedings Article | 5 March 2007 Paper

Acute threshold damage, minimal spot, Q-switched exposure effects on focal contrast sensitivity

H. Zwick, D. Lund, B. Stuck, D. Robbins

Proceedings Volume 6426, 642624 (2007) https://doi.org/10.1117/12.712237

KEYWORDS: Contrast sensitivity, Spatial frequencies, Visualization, Q switching, Laser damage threshold, Q switched lasers, Retina, Pulsed laser operation, Diffraction, Laser induced damage

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In previous investigations of minimal spot, q-switched laser visible (532 nm) on-line pulsed laser exposure, non-human primate (NHPs) required up to 13 times the retinal damage threshold for the emergence of permanent visual acuity dysfunction. In the present experiment, a Landolt ring contrast sensitivity task, employing 4 NHPs trained on a Landolt ring contrast sensitivity task, was employed to determine the effect of threshold retinal damage (532 nm, 3 microjoules, 20 Hz, PRF) on the slope of the NHP Landolt ring contrast sensitivity function measured under repeated threshold exposure conditions. All four animals initially showed uniform deficits in contrast sensitivity requiring about 6 to 16 min post exposure for complete recovery. Over several months of repeated exposures made in 3 NHPs, a steepening of the contrast sensitivity slopes appeared, manifested by an inability to measure sensitivity for the finest Landolt ring spatial frequencies and an associated enhancement in the mid and lower spatial frequencies. In one animal that had undergone a longer period of repeated threshold laser exposure, the slope of its contrast sensitivity function shifted to a uniform deficit relative to pre exposure with an inability to provide sensitivity measurements above 20 Hz/deg, demonstrating an abrupt loss in the ability to measure the higher spatial frequencies associated with maximal optimal visual acuity. Ophthalmic retinal observations demonstrated the presence of punctate lesions induced by minimal spot foveal exposure. These data support measurements of high contrast acuity undergoing repeated q-switched exposure at damaging levels. While the acuity in such exposure situations eventually undergoes a permanent deficits, measurements of the entire contrast sensitivity function, in which acuity function maybe obtained at and above 60 Hz/deg, may reveal enhanced lower spatial frequency sensitivity as well as permanent a permanent deficits in higher spatial frequencies.

Proceedings Article | 5 March 2007 Paper

NHP spectral sensitivity metric derived from acute laser exposure effects on pursuit motor tracking task

H. Zwick, P. Edsall, K. Jenkins, R. Cunningham, B. Stuck

Proceedings Volume 6426, 64262A (2007) https://doi.org/10.1117/12.712227

KEYWORDS: Visualization, Cones, Eye, Optical tracking, Laser induced damage, Retina, Visible radiation, Laser sources, Interference filters, Absorbance

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Proceedings Article | 5 March 2007 Paper

In vivo visualizing the dynamics of bone marrow stem cells in mouse retina and choroidal-retinal circulation

Heuy-Ching Wang, Harry Zwick, Peter Edsall, Rachel Cheramie, David Lund, Bruce Stuck

Proceedings Volume 6426, 642621 (2007) https://doi.org/10.1117/12.711487

KEYWORDS: Stem cells, Bone, Injuries, Retina, Scanning laser ophthalmoscopy, In vivo imaging, Visualization, Neuroprotection, Tissues, Flow cytometry

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Proceedings Article | 5 March 2007 Paper

Development of an advanced Aidman Vision Screener (AVS) for selective assessment of outer and inner laser induced retinal injury

Michael Boye, Harry Zwick, Bruce Stuck, Peter Edsall, Andre Akers

Proceedings Volume 6426, 64262B (2007) https://doi.org/10.1117/12.712240

KEYWORDS: Visualization, Colorimetry, Cones, Eye, Retina, Injuries, Color vision, Weapons, Contrast sensitivity, Diagnostics

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Proceedings Article | 12 September 2006 Paper

Utilization of the Crawford transformation in evaluation of the spectral efficiency of solid state light sources

H. Zwick, P. Edsall, J. Ness, L. Hare, B. Stuck

Proceedings Volume 6337, 63370N (2006) https://doi.org/10.1117/12.679154

KEYWORDS: Light emitting diodes, Light sources, Visible radiation, Solid state electronics, Rods, Night vision, Light, Speckle, Cones, Solid state physics

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Proceedings Article | 18 April 2005 Paper

Multifocal electroretinogram (MFERG) evaluation of laser-induced retinal injury with both indirect and direct registration of the MFERG stimulus pattern with the retinal landmarks

Harry Zwick, Bruce Stuck, Andre Akers, Peter Edsall, Cheryl DiCarlo, David Lund

Proceedings Volume 5688, (2005) https://doi.org/10.1117/12.598198

KEYWORDS: Neodymium, Injuries, Retina, Laser induced damage, Eye, Pathology, Macula, Optical coherence tomography, Fiber lasers, Cones

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Proceedings Article | 18 April 2005 Paper

In vivo characterization of photoreceptor and vascular blood cell response to laser-induced trauma in the small eye model

Harry Zwick, Bruce Stuck, Peter Edsall, Henry Hacker, F. Wood, Rachael Cheramie, William Elliott

Proceedings Volume 5688, (2005) https://doi.org/10.1117/12.598203

KEYWORDS: Blood, Reflectivity, In vivo imaging, Eye models, Confocal microscopy, Argon ion lasers, Retina, Injuries, Eye, Laser induced damage

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Proceedings Article | 18 April 2005 Paper

Choroidal abnormalities and masquerade syndromes confounding the diagnosis of laser-induced eye injuries

Henry Hacker, Harry Zwick, Jeremiah Brown, Bruce Stuck

Proceedings Volume 5688, (2005) https://doi.org/10.1117/12.598548

KEYWORDS: Injuries, Eye, Visualization, Angiography, Contrast sensitivity, Optical coherence tomography, Laser energy, Pathology, Indocyanine green, Retina

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Proceedings Article | 18 April 2005 Paper

Effect of Light Emitting Diode (LED) therapy on the survival of photoreceptors following Argon laser injury

Cheryl DiCarlo, Jeremiah Brown, Henry Hacker, Steven Schuschereba, Rachael Cheramie, James Sankovich, Harry Zwick, David Lund, Bruce Stuck

Proceedings Volume 5688, (2005) https://doi.org/10.1117/12.593670

KEYWORDS: Light emitting diodes, Laser therapeutics, Light-emitting diode therapy, Injuries, Tissues, Argon ion lasers, Eye, Retina, Digital photography, Photography

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Proceedings Article | 13 July 2004 Paper

Use of the multifocal electroretinogram (mfERG) for assessing the response of 670 nm light emitting diodes (LED) photoillumination in an animal model with laser retinal injuries

Cheryl DiCarlo, Jeremiah Brown, Andres Grado, James Sankovich, Harry Zwick, David Lund, Bruce Stuck

Proceedings Volume 5312, (2004) https://doi.org/10.1117/12.528351

KEYWORDS: Light emitting diodes, Eye, Injuries, Laser therapeutics, Animal model studies, Argon ion lasers, Medical research, Retina, Visualization, Semiconductor lasers

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Proceedings Article | 1 July 2004 Paper

N-acetylcysteine and acute retinal laser lesions in the colubrid snake eye

William Elliott, Heike Rentmeister-Bryant, Norman Barsalou, Jeremy Beer, Harry Zwick

Proceedings Volume 5319, (2004) https://doi.org/10.1117/12.530362

KEYWORDS: Injuries, Eye, Scanning laser ophthalmoscopy, Eye models, Laser development, Retina, Cones, In vivo imaging, Animal model studies, Diode pumped solid state lasers

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Proceedings Article | 20 June 2003 Paper

Human color vision deficits induced by accidental laser exposure and potential for long-term recovery

Harry Zwick, Brian Lund, Jeremiah Brown, Bruce Stuck, J. Loveday

Proceedings Volume 4953, (2003) https://doi.org/10.1117/12.488645

KEYWORDS: Cones, Visualization, Color vision, Roentgenium, Retina, Injuries, Colorimetry, Fermium, Frequency modulation, Vitreous

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Purpose: To evaluate long term deficits in human color discrimination induced by accidental laser macular damage and assess potential for recovery of color vision deficits. Methods: Nine laser accident cases (Q-switched Neodymium) presenting initially with confined or vitreous macular hemorrhage were evaluated with the Farnsworth-Munsell 100 Hue test within 2 days to 3 months post exposure. Both total as well as partial errors in the blue/yellow (B/Y) and red/green (R/G) regions were assessed. Independent assessment of axis orientation and complexity were obtained via a Fourier series expansion of error scores. Comparisons of both total and partial B/Y and R/G errors were made with age matched normal subjects, idiopathic and juvenile onset macular holes. Confocal Scanning Laser Ophthalmoscopy and Optical Coherence Tomography characterized the presence of retinal traction, intraretinal scar, macular thickness and macular hole formation. Results: Comparison of exposed and non-exposed age matched individuals were significant (P<.001) for both total and partial errors. In four cases where macular injury ranged from mild scar to macular hole, color discrimination errors achieved normal levels in 1 to 12 months post exposure. A mild tritan axis, dominant B/Y ("blue/yellow") errors, and retinal traction were observed in a macular hole case. At 12 months post exposure, traction about the hole disappeared, and total and partial errors were normal. Where damage involved a greater degree of scarring, retinal traction and multiple injury sites, long term recovery of total and partial error recovery was retarded with complex axis makeup. Single exposures in the paramacula produced tritan axes, while multiple exposures within and external to the macula increased total and partial R/G ("red/green") error scores. Total errors increased when paramacular hole enlargement induced macular traction. Such hole formation produced significant increases in total errors, complex axis formation and increased amplitude in higher Fourier error expansion components. Conclusion: Color discrimination losses reflect the distribution of different cone systems in and about the macula and their selective loss. When secondary damage is minimal, color discrimination deficits recover within 12 months post exposure. When macular scarring and retinal traction are severe, recovery is significantly retarded. Laser induced macular holes may affect color discrimination less when retinal scar and traction are small but may become equivalent with that of idiopathic and juvenile species when scar and traction are severe.

Proceedings Article | 20 June 2003 Paper

Multifocal electroretinography: a functional laser injury metric

Cheryl DiCarlo, Harry Zwick, Heike Rentmeister-Bryant, James Sankovich, Araceli Brown, Andres Grado, Ronald Dicks, Andre Akers, Bruce Stuck

Proceedings Volume 4953, (2003) https://doi.org/10.1117/12.488647

KEYWORDS: Eye, Retina, Injuries, Visualization, Imaging systems, Macula, Electrodes, Cameras, Medical research, Pathology

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Proceedings Article | 20 June 2003 Paper

Laser-induced macular holes demonstrate impaired choroidal perfusion

Jeremiah Brown, Ronald Allen, Harry Zwick, Steven Schuschereba, David Lund, Bruce Stuck

Proceedings Volume 4953, (2003) https://doi.org/10.1117/12.488644

KEYWORDS: Angiography, Injuries, Nd:YAG lasers, Indocyanine green, Visualization, Luminescence, Q switched lasers, Vitreous, Retina, Tissues

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Proceedings Article | 20 June 2003 Paper

Foveal photoreceptor explanation of short-term visual acuity recovery associated with laser-induced foveal damage

Amir Langus, Harry Zwick, Bruce Stuck, Michael Belkin

Proceedings Volume 4953, (2003) https://doi.org/10.1117/12.476889

KEYWORDS: Visualization, Cones, Visual process modeling, Eye, Laser damage threshold, Q switching, Q switched lasers, Laser induced damage, Brain, Tissues

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Proceedings Article | 27 June 2002 Paper

Modeling of laser-induced threshold damage in the peripheral retina

Garrett Polhamus, Robert Thomas, Rebecca Hall, Joseph Zuclich, Harry Zwick, Leon McLin

Proceedings Volume 4617, (2002) https://doi.org/10.1117/12.472540

KEYWORDS: Retina, Injuries, Laser damage threshold, Absorption, Eye models, Macula, Reflectivity, Laser safety, Thermal modeling, Image quality

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SPIE Journal Paper | 1 July 2001

Efficiently tracking a moving object in two-dimensional image space

Steven Barrett, Cameron Wright, Harry Zwick, Michael Wilcox, Benjamin Rockwell, Espen Naess

JEI, Vol. 10, Issue 03, (July 2001) https://doi.org/10.1117/12.10.1117/1.1380202

KEYWORDS: Detection and tracking algorithms, Retina, Algorithm development, Video, Eye, Head, Laser coagulation, Cameras, Scanning laser ophthalmoscopy, Electrical engineering

Proceedings Article | 17 May 2001 Paper

Clinical features of laser-induced macular holes as imaged by optical coherence tomography (OCT)

Jeremiah Brown, Harry Zwick, Steven Schuschereba, Bruce Stuck

Proceedings Volume 4246, (2001) https://doi.org/10.1117/12.426719

KEYWORDS: Optical coherence tomography, Injuries, Visualization, Eye, Retina, Tissues, Radon, Macula, Photography, Laser applications

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Proceedings Article | 17 May 2001 Paper

Automated PRL measurements using a confocal laser ophthalmoscope

Steven Barrett, Harry Zwick

Proceedings Volume 4246, (2001) https://doi.org/10.1117/12.426721

KEYWORDS: Eye, Retina, Visualization, Video, Scanning laser ophthalmoscopy, Detection and tracking algorithms, Confocal microscopy, Image resolution, Optical tracking, Laser safety

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Proceedings Article | 17 May 2001 Paper

Effect of source intensity on the variability of eye movements during deliberate fixation

Brian Lund, Harry Zwick, David Lund, Bruce Stuck, James Ness

Proceedings Volume 4246, (2001) https://doi.org/10.1117/12.426716

KEYWORDS: Eye, Retina, Cornea, Helium neon lasers, Light sources, Safety, Optical filters, Data acquisition, Medical research, Head

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Proceedings Article | 17 May 2001 Paper

Ocular dynamics and visual tracking performance after Q-switched laser exposure

Harry Zwick, Bruce Stuck, David Lund, Maqsood Nawim

Proceedings Volume 4246, (2001) https://doi.org/10.1117/12.426724

KEYWORDS: Visualization, Q switched lasers, Optical tracking, Q switching, Laser damage threshold, Retina, Helium neon lasers, Brain, Surveillance, Visual system

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In previous investigations of q-switched laser retinal exposure in awake task oriented non-human primates (NHPs), the threshold for retinal damage occurred well below that of the threshold for permanent visual function loss. Visual function measures used in these studies involved measures of visual acuity and contrast sensitivity. In the present study, we examine the same relationship for q-switched laser exposure using a visual performance task, where task dependency involves more parafoveal than foveal retina. NHPs were trained on a visual pursuit motor tracking performance task that required maintaining a small HeNe laser spot (0.3 degrees) centered in a slowly moving (0.5deg/sec) annulus. When NHPs reliably produced visual target tracking efficiencies > 80%, single q-switched laser exposures (7 nsec) were made coaxially with the line of sight of the moving target. An infrared camera imaged the pupil during exposure to obtain the pupillary response to the laser flash. Retinal images were obtained with a scanning laser ophthalmoscope 3 days post exposure under ketamine and nembutol anesthesia. Q-switched visible laser exposures at twice the damage threshold produced small (about 50?m) retinal lesions temporal to the fovea; deficits in NHP visual pursuit tracking were transient, demonstrating full recovery to baseline within a single tracking session. Post exposure analysis of the pupillary response demonstrated that the exposure flash entered the pupil, followed by 90 msec refractory period and than a 12 % pupillary contraction within 1.5 sec from the onset of laser exposure. At 6 times the morphological threshold damage level for 532 nm q-switched exposure, longer term losses in NHP pursuit tracking performance were observed. In summary, q-switched laser exposure appears to have a higher threshold for permanent visual performance loss than the corresponding threshold to produce retinal threshold injury. Mechanisms of neural plasticity within the retina and at higher visual brain centers may mediate the stability of visual function and performance metrics. Long term repeated exposure to the retina, however, may eventually dampen the ability of higher visual brain centers to detect declining retinal neural output from cumulative retinal damage. Individuals chronically exposed to such laser sources should have more frequent ophthalmic retinal surveillance.

SPIE Journal Paper | 1 July 2000 Open Access

On the use of schematic eye models to estimate retinal image quality

Guo Li, Harry Zwick, Bruce Stuck, David Lund

JBO, Vol. 5, Issue 03, (July 2000) https://doi.org/10.1117/12.10.1117/1.430001

KEYWORDS: Eye, Modulation transfer functions, Eye models, Image resolution, Point spread functions, Diffraction, Scanning laser ophthalmoscopy, Refraction, Geometrical optics, Vitreous

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Proceedings Article | 18 June 1999 Paper

Laser-induced acute and long-term alterations to visual fuction

David Robbins, Harry Zwick

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350600

KEYWORDS: Visualization, Eye, Q switching, Retina, Q switched lasers, Laser damage threshold, Pathology, Ophthalmoscopy, Laser sources, Laser induced damage

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Proceedings Article | 18 June 1999 Paper

In-vivo imaging of photoreceptor structure and laser injury pathophysiology in the snake eye

Harry Zwick, Rowe Elliot, Guo Li, Andre Akers, Peter Edsall, Bruce Stuck

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350599

KEYWORDS: Reflectivity, Retina, Eye, In vivo imaging, Confocal microscopy, Injuries, Visualization, Image processing, Receptors, Blood

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Proceedings Article | 18 June 1999 Paper

On- and off-axis confocal double-pass measurements of the point spread function in the human eye

Guo Li, Harry Zwick, Jerri Tribble, James Ness, David Lund, Michael Reddix

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350596

KEYWORDS: Point spread functions, Eye, Confocal microscopy, Optical filters, Light emitting diodes, Medical research, Beam splitters, Signal to noise ratio, Retina, Cornea

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Proceedings Article | 18 June 1999 Paper

Laser accident and incident register (LAIR)

Stephen Hoxie, James Ness, Harry Zwick, Bruce Stuck

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350603

KEYWORDS: Laser safety, Databases, Standards development, Injuries, Eye, Laser systems engineering, Internet, Medical research, Visualization, Analytical research

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Proceedings Article | 18 June 1999 Paper

Eye movements during fixation: implications to long-term viewing of small optical sources

James Ness, Harry Zwick, David Lund, Bruce Stuck, David Sliney

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350595

KEYWORDS: Eye, Head, Retina, Laser safety, Standards development, Light emitting diodes, Visualization, Safety, Laser sources, Statistical analysis

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Proceedings Article | 18 June 1999 Paper

Longitudinal evaluation of selected human laser eye accident cases

Harry Zwick, Bruce Stuck, David Scales, Jeremiah Brown, James Ness

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350601

KEYWORDS: Visualization, Eye, Contrast sensitivity, Optical coherence tomography, Injuries, Spatial frequencies, Retina, Target detection, Color vision, Brain

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Proceedings Article | 18 June 1999 Paper

Imaging of the choroid with the scanning slit laser ophthalmoscope (SSLO)

Greg Heacock, Harry Zwick, John Marshall, Bruce Stuck, Helen Cook

Proceedings Volume 3591, (1999) https://doi.org/10.1117/12.350610

KEYWORDS: Objectives, Eye, Scanning laser ophthalmoscopy, Video, Head, Photography, Cameras, Mirrors, Optic nerve, Confocal microscopy

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Proceedings Article | 13 May 1998 Paper

Accidental bilateral Q-switched neodymium laser exposure: treatment and recovery of visual function

Harry Zwick, Bruce Stuck, Weldon Dunlap, David Scales, David Lund, James Ness

Proceedings Volume 3254, (1998) https://doi.org/10.1117/12.308151

KEYWORDS: Visualization, Contrast sensitivity, Injuries, Eye, Optical coherence tomography, Retina, Q switched lasers, Spatial frequencies, Angiography, Neodymium lasers

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Proceedings Article | 2 May 1997 Paper

Macular pigmentary alterations after repeated viewing of argon laser trabeculoplasty

David Scales, Harry Zwick, David Lund, Michael Belkin, J. Loveday

Proceedings Volume 2974, (1997) https://doi.org/10.1117/12.275251

KEYWORDS: Contrast sensitivity, Visualization, Argon ion lasers, Spatial frequencies, Colorimetry, Eye, Fiber lasers, Scanning laser ophthalmoscopy, Cones, Nerve

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Proceedings Article | 2 May 1997 Paper

In-vivo confocal scanning laser ophthalmoscopic characterization of retinal pathology in a small-eye-animal model

Harry Zwick, Rowe Elliot, Steven Schuschereba, David Lund, Bruce Stuck

Proceedings Volume 2974, (1997) https://doi.org/10.1117/12.275253

KEYWORDS: Reflectivity, Blood, Eye, Injuries, Retina, Confocal microscopy, In vivo imaging, Q switching, Argon ion lasers, Argon

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Proceedings Article | 2 May 1997 Paper

Optimization of neural retinal visual motor strategies in recovery of visual acuity following acute laser-induced macula injury

Harry Zwick, James Ness, J. Loveday, Jerome Molchany, Bruce Stuck

Proceedings Volume 2974, (1997) https://doi.org/10.1117/12.275230

KEYWORDS: Visualization, Spatial frequencies, Contrast sensitivity, Macula, Retina, Injuries, Receptors, Laser induced damage, Colorimetry, Target recognition

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Proceedings Article | 2 May 1997 Paper

Database structure for the Laser Accident and Incident Registry (LAIR)

James Ness, Stephen Hoxie, Harry Zwick, Bruce Stuck, David Lund, Elmar Schmeisser

Proceedings Volume 2974, (1997) https://doi.org/10.1117/12.275237

KEYWORDS: Injuries, Eye, Databases, Visualization, Laser safety, Reliability, Laser development, Contrast sensitivity, Scanning laser ophthalmoscopes, Statistical analysis

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Proceedings Article | 2 May 1997 Paper

Visual acuity changes in rhesus following low-level Q-switched exposures

David Robbins, Harry Zwick, Bradley Bearden, Brenda Evans, Bruce Stuck

Proceedings Volume 2974, (1997) https://doi.org/10.1117/12.275231

KEYWORDS: Visualization, Q switching, Retina, Laser irradiation, Eye, Q switched lasers, Camera shutters, Laser damage threshold, Head

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