Retinal Laser Therapy: Mechanisms of Interaction and Tissue Response

Since its introduction nearly 40 years ago, laser photocoagulation remains the standard of care for many ocular disorders. Despite widespread use of lasers in retinal therapy it remains largely unknown how its benefits and deleterious side effects relate to parameters of laser treatment and subsequent retinal healing. Arrhenius model of retinal coagulation predicts the lateral extent and severity of tissue damageThus strategies to reduce untoward effects of laser therapy while maintaining clinical benefit are highly desirable.

We developed a new method of retinal photocoagulation using Pattern Scanning Laser (PASCAL). In this approach patterns of pulses are applied during the eye fixation time (under half a second) with pulse durations in the range of 10-30 ms. In addition to much faster and less painful delivery of the laser treatment, PASCAL enabled the computer-guided sub-visible treatments and sparked renewed interest in research of photocoagulation.

We study dynamics of retinal photocoagulation and vaporization of pigmented tissue with millisecond and microsecond pulses. Our computational model of retinal hyperthermia helps optimizing the laser treatment parameters for sub-damaging, sub-visible, and minimally-traumatic retinal therapy.Selective destruction of RPE cells along the lines of laser scanning.

 

We work on selective ablation of specific retinal layers, including Retinal Pigmented Epithelium (RPE) and photoreceptors. For selective ablation of RPE we use rapidly scanning continuous laser providing microsecond exposures. Heat confinment in melanosomes during such short pulses can result in explosive vaporization of melanosomes, leading to mechanical destruction of RPE cells without damage to surrounding tissues. We study healing response of RPE to selective laser therapy, and develop therapeutic applications of this approach.

We also study cellular response to hyperthermia below the threshold of tissue damage, and applications of the sub-lethal hyperthermia to treatment of various retinal diseases. In particular, we explore the cellular markers of the thermal stress such as the heat-shock proteins, and long-term changes in the tissue associated with non-damaging hyperthermia.