<title>Automated placement of retinal laser lesions in vivo</title>

Abstract

Researchers at the University of Texas at Austin's 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 Academy's 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.