Determining laser dosimetry for consistent retinal photocoagulation

Laser photocoagulation is used extensively by ophthalmologists to treat retinal disorders such as diabetic retinopathy, macular degeneration, and retinal tears. Currently, the procedure is performed manually and suffers from several drawbacks that a computer-assisted system could help alleviate. These drawbacks include the tedious nature of the procedure for both the patient and the physician and also the extreme criticality of the task. A system is under development that will rapidly and safely place multiple therapeutic lesions at desired locations on the retina in a matter of seconds. This system provides real-time, motion-stabilized lesion placement for typical clinical irradiation times on the order of 100 ms. Considerable work has been accomplished on stabilizing the irradiating laser on the retinal surface. Various tracking systems have been designed, prototypes implemented, and tested in vivo on laboratory animals [1]. Our efforts have most recently concentrated on developing a system to monitor lesion growth in real time and turn off the laser when the desired lesion parameters have been achieved. This subsystem employs dynamic lesion reflectance as an indirect measure of lesion depth. Our goal has been to establish a correlation between the measurable lesion reflectance parameter with the actual lesion depth. Once this correlation is established, these parameters will be used to generate a control signal for the irradiation time of the laser. The goal is to optimize the therapeutic effect, without over- or under-exposing the tissue. The result is consistent lesion formation over any part of the non-homogeneous retinal tissue.