[Reflection measurement during retinal laser coagulation in patients. Development of an automatically controlled dosimeter]. / Reflexionsmessung während Netzhautlaserkoagulationen bei Patienten. Entwicklung einer automatisch gesteuerten Dosiseinrichtung.

PURPOSE: Retinal laser coagulation has limited reproducibility, because every laser exposition is unpredictably affected by pigmentation and media opacities. This can lead to complications. A feedback-controlled dosimeter would make retinal laser treatment a safer, more reproducible and faster procedure. METHOD: A reflectometer was developed that allows monitoring of the reflection of laser light during standard photocoagulation. Hundreds of coagulations in rabbit eyes and about 12,000 coagulations in patients undergoing routine laser treatment were recorded. RESULTS: The results of the first reflectance measurements in humans are presented along with extensive animal studies. A typical reflectance history was found for different lesion intensities. The degree of retinal whitening correlates with reflectance characteristics. These characteristics allow an early prediction of lesion intensity. Motion during laser exposure affects each coagulation in a fashion similar to spot size and exposure time. CONCLUSION: Reflectometry is the currently most effective means of monitoring lesion development. An automatic dosimeter for retinal photocoagulation seems feasible.

Dynamic reflectometer for control of laser photocoagulation on the retina.

In retinal laser photocoagulation, constant exposure parameters do not result in identical lesions. This lack of reproducibility increases the rate of complications from over- or undertreatment and inhibits determination of the optimal treatment endpoints for different retinal disorders. To this end, a feedback-controlled photocoagulator could make retinal photocoagulation a safer, more reproducible, and faster procedure. A dynamic confocal reflectometer was integrated into a slit lamp laser delivery system. Real-time reflectance changes on the retinas of pigmented rabbits were obtained by monitoring the increasing back-scattered light of the coagulating beam during argon laser photocoagulation. Reproducible temporal reflectance patterns were measured that correlated with ophthalmoscopically assessed lesion intensity independent of the exposure parameters, the transparency of the optical media, and the focusing conditions. As a step toward the development of a feedback-controlled photocoagulator, the confocal reflectometer has been proven in animal trials closely resembling clinical practice.