REFINING DME MANAGEMENT

David Pelayes MD

Although retinal laser photocoagulation has been the gold standard for treatment of diabetic macular oedema (DME), the paradigm may change in the future because of developments in laser therapy and imaging technology, according to David Pelayes MD.

At WOC 2016 in Guadalajara, Mexico, Dr Pelayes spoke about refined approaches to laser management of DME using a subumbral approach and swept-source optical coherence tomography (SS-OCT) imaging and angiography.

“Using these new modalities and anti-VEGF therapy, we will be exploring new questions about the treatment of DME that may lead us in the future to change our criteria for DME evaluation and treatment selection,” said Dr Pelayes, Full Professor of Ophthalmology, Buenos Aires University, Argentina, and Full Professor of Ophthalmology, Maimonides University.

Discussing subumbral laser treatment, Dr Pelayes explained that it is performed using a 577nm yellow multi-spot laser with proprietary software (PASCAL Streamline 577™ laser system with Endpoint Management, Topcon). He explained that, compared with 532nm green light, 577nm yellow light is a more efficient wavelength for DME treatment because it is subject to less scatter by ocular structures and penetrates better to pigmented and vascular retinal structures. These features enable lower power and shorter pulse duration laser settings.

YELLOW WAVELENGTH

In addition, the yellow wavelength is particularly attractive when treating near the macula or foveal regions, because it penetrates to and is absorbed by the retinal pigment epithelium (RPE) with less diffusion to the choriocapillaris.

“Higher efficiency gives the surgeon finer control and the ability to fine-tune laser parameters, and it also improves patient comfort. With this laser we can produce the burn in the area we want to treat. Still, more evidence about its efficacy is needed,” he told delegates.

Compared with standard laser photocoagulation, the subumbral treatment approach creates a minor photothermal injury with lesions in Bruch’s membrane and RPE. Although the lesions are not visible, evidence of the limited tissue damage is available from multimodal imaging and histology studies of rabbit eyes. It has also been demonstrated by post-treatment imaging of human eyes using autofluorescence, OCT, and fluorescein angiography.

Endpoint Management is a titration protocol for performing subumbral laser therapy that uses tissue modelling and advanced algorithms to ensure treatment precision while controlling laser power and exposure duration.

First, treatment is titrated outside of the macula to produce a barely visible endpoint (100 per cent level). This “landmark” is placed at the corners of the grid pattern, and the power for spots inside the grid is set at a lower level to create the subvisible burns.

David Pelayes: davidpelayes@gmail.com