Steven F. Barrett

Computer-aided retinal photocoagulation system

Researchers at the University of Texas at Austins Biomedical Engineering Laser Laboratory and the U. S. Air Force Academy’s Department of Electrical Engineering are developing a computer-assisted prototype retinal photocoagulation system. The project goal is to rapidly and precisely automatically place laser lesions in the retina for the treatment of disorders such as diabetic retinopathy and retinal tears while dynamically controlling the extent of the lesion. Separate prototype subsystems have been developed to control lesion parameters (diameter or depth) using lesion reflectance feedback and lesion placement using retinal vessels as tracking landmarks. Successful subsystem testing results in vivo on pigmented rabbits using an argon continuous wave laser are presented. A prototype integrated system design to simultaneously control lesion parameters and placement at clinically significant speeds is provided.

Hybrid approach to retinal tracking and laser aiming for photocoagulation

The initial experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control are described. The results demonstrate tracking rates that exceed the equivalent of 60 deg per second in the eye, with automatic creation of lesion patterns and robust loss of lock detection. Robotically assisted laser surgery to treat conditions such as diabetic retinopathy and retinal tears can soon be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components.

Hybrid tracking and control system for computer-aided retinal surgery

We describe initial experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control. Initial results demonstrate tracking rates which exceed the equivalent of 50 degrees per second in the eye, with automatic lesion pattern creation and robust loss of lock detection. Robotically assisted laser surgery to treat conditions such as diabetic retinopathy, macular degeneration, and retinal tears can now be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components.

Automated retinal robotic laser system instrumentation

Researchers at the University of Texas at Austins Biomedical Engineering Laser Laboratory investigating the medical applications of lasers have worked toward the development of a retinal robotic laser system. The ultimate goal of this ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Researchers at the USAF Academys Department of Electrical Engineering have also become involved with this research due to similar interests. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Work is ongoing to build a prototype system to simultaneously control lesion depth and placement. The instrumentation aspects of the prototype subsystems were presented at SPIE Conference 1877 in January 1993. Since then our efforts have concentrated on combining the lesion depth control subsystem and the lesion placement subsystem into a single prototype capable of simultaneously controlling both parameters. We have designed this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. An initial CALOSOS prototype design is provided. We have also investigated methods to improve system response time. The use of high speed non-standard frame rate CCD cameras and high speed local bus frame grabbers hosted on personal computers are being investigated. A review of system testing in vivo to date is provided in SPIE Conference proceedings 2374-49 (Novel Applications of Lasers and Pulsed Power, Dual-Use Applications of Lasers: Medical session).

Hybrid retinal tracking and coagulation system

Laser photocoagulation is used extensively by ophthalmologists to treat retinal disorders such as diabetic retinopathy and retinal breaks and tears. Currently, the procedure is performed manually and suffers from several drawbacks: it often requires many clinical visits, it is very tedious for both patient and physician, the laser pointing accuracy and safety margin are limited by a combination of the physicians manual dexterity and the patients ability to hold their eye still, and there is a wide variability in retinal tissue absorption parameters. A computer-assisted hybrid system is under development that will rapidly and safely place multiple therapeutic lesions at desired locations on the retina in a matter of seconds. In the past, one of the main obstacles to such a system has been the ability to track the retina and compensate for any movement with sufficient speed during photocoagulation. Two different tracking modalities (digital image-based tracking and analog confocal tracking) were designed and tested in vivo on pigmented rabbits. These two systems are being seamlessly combined into a hybrid system which provides real-time, motion stabilized lesion placement for typical irradiation times (100 ms). This paper will detail the operation of the hybrid system and efforts toward controlling the depth of coagulation on the retinal surface.

Hybrid retinal photocoagulation system

We describe initial in vivo experimental results of a new hybrid digital and analog design for retinal tracking and laser beam control. An overview of the design is given. The results show in vivo tracking rates which exceed the equivalent of 38 degrees per second in the eye, with automated lesion pattern creation. Robotically-assisted laser surgery to treat conditions such as diabetic retinopathy and retinal breaks may soon be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components based on this design.

Automated placement of retinal laser lesions in vivo

Researchers at the University of Texas at Austins Biomedical Engineering Laser Laboratory investigating the medical applications of lasers have worked toward the development of a retinal robotic laser system. The overall goal of the ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Researchers at the USAF Academys Department of Electrical Engineering and the Optical Radiation Division of Armstrong Laboratory have also become involved with this research due to similar related interests. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Work is ongoing to build a prototype system to simultaneously control lesion depth and placement. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies. Specifically, the system is being adapted for use with an ultra-short pulse laser system at Armstrong Laboratory and Frank J. Seiler Research Laboratory to study the effects of ultra-short laser pulses on the human retina. The instrumentation aspects of the prototype subsystems were presented at SPIE Conference 1877 in January 1993. Since then our efforts have concentrated on combining the lesion depth control subsystem and the lesion placement subsystem into a single prototype capable of simultaneously controlling both parameters. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. We have also investigated methods to improve system response time. Use of high speed nonstandard frame rate CCD cameras and high speed frame grabbers hosted on personal computers featuring the 32 bit, 33 MHz PCI bus have been investigated. Design details of an initial CALOSOS prototype design is provided in SPIE Conference proceedings 2396B-32 (Biomedical Optics Conference, Clinical Laser Delivery and Robotics Session). This paper will review in vivo testing to date and detail planned system upgrades.