Palanker Lab: BioMedical Physics

Dynamics of Retinal Photocoagulation

Since its introduction nearly 40 years ago, laser photocoagulation remains the standard of care for long-term therapy of several retinopathies. Pan-retinal photocoagulation (PRP), for example, is highly effective to reverse angiogenesis, and focal laser therapy is effective for treating macular edema. Unfortunately, multiple adverse effects often follow these treatments, including decreased peripheral, color, and night vision and retinal scars that can enlarge postoperatively and cause choroidal neo-vascularization, sub-retinal fibrosis and additional visual field loss.

Despite widespread use of lasers in retinal therapy, a systematic clinico-pathological analysis of laser-induced retinal lesions and their evolution over time is largely lacking. Moreover, it remains largely unknown how the benefits of PRP or its many deleterious side effects relate to parameters of laser treatment and subsequent retinal healing. Thus strategies to reduce untoward effects of PRP 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 multiple pulses are applied during the eye fixation time (under half a second) using a scanning laser with pulse durations in the range of 10-30 ms. In addition to much faster and less painful delivery of the PRP treatment, PASCAL enabled the sub-visible treatments and sparked renewed interest in research of retinal photocoagulation. This technology has been licensed to OptiMedica Corp.

We recently discovered that dynamics of retinal healing of highly confined laser lesions is very different from that of conventional retinal burns. For these lighter lesions, not only can the inner retina be spared, but photoreceptor migration into damaged areas restore photoreceptor continuity over time, as opposed to formation of permanent scars in the conventional visible lesions. This way retinal scotomas and scarring can be avoided, thereby ameliorating many side effects of PRP, and allowing for re-treatment.

Histology of the rabbit retina 1 day and 4 months after very mild photocoagulation. Yellow bar indicates the damage area in the photoreceptors layer. Complete restoration of retinal continuity at 4 months can be observed.

We study dynamics of retinal photocoagulation and adverse events, such as vaporization and rupture in millisecond and microsecond ranges of pulse duration. We developed a computational model of retinal photocoagulation and rupture that helps optimizing the laser treatment parameters for enhancement of the safe therapeutic range of the short-pulse retinal photocoagulation.

We develop a minimally-traumatic approach to retinal laser therapy utilizing the effect of retinal plasticity. We also work on minimally-traumatic approach to laser therapy of glaucoma, and on computer-guided ocular laser therapies.

Publications