Experiences with PASCAL sub-threshold laser treatments for DME
Fortunately, advances in laser therapy have yielded refinements in pulse duration, lesion intensity and several other parameters, improving overall quality of treatment. A recent application furthering physician control over these factors is the Endpoint Management software available for the PASCAL Photocoagulator (Topcon Medical Laser Systems, Santa Clara, California, USA).
Development of treatment protocols
The goal of focal laser treatment for DME should be to combine safety with efficacy. In this case, that means a resolution of - or, at least, a significant reduction of - macular oedema. Hopefully, this will facilitate improved or preserved vision. The idea that visible lesions are not necessary for effective treatment has been reinforced by the recent success of micropulse lasers.3 However, one distinct disadvantage of micropulse is its difficulty and complexity in setting laser dosimetry. A key advantage of Endpoint Management is its Landmark feature, which delivers laser application at the visible, titrated dose.
The goal of sub-threshold laser treatment is to achieve the best results with reduced energy, thereby reducing unintended effects from thermal reaction. Endpoint Management first titrates to a comfortable visible endpoint and then uses algorithms to modulate power and duration, enabling control over treatment endpoints.
I then apply my laser treatment pattern, typically using 2x2 and arc grid patterns. I can add a grid with uniform intensity or vary the grid so that landmarks use a higher amount of energy than central points. In this instance, endpoints would deliver a reduced amount of energy as set by the endpoint percentage. These points would use just enough energy to stimulate the retina into pumping out accumulated fluid, but not enough to cause visible whitening of the RPE and actual thermal burn. Here, greater physician control yields a more precise - and potentially efficacious - treatment.