Laser continues to play an important role in diabetic macular edema amid an increasing reliance on anti-VEGF drugs.
Reviewed by Elias Reichel, MD
Laser remains a critical component in the treatment of diabetic macular edema (DME) amid an increasing number of new devices designed to deliver subthreshold laser. “Laser still plays a very important role in the treatment of diabetic macular edema despite our reliance on anti-vascular endothelial drugs,” said Elias Reichel, MD, professor of ophthalmology and vice chairman, Tufts University School of Medicine, Boston.
The Diabetic Retinopathy Clinical Research Network (DRCR.net) Protocol I study supports that statement, with patients treated with deferred laser therapy, defined as application between 24 weeks, fared the best. Over the course of two years, Dr. Reichel pointed out, there was a benefit in those patients compared with those treated promptly with laser and accompanied by anti-VEGF or steroid therapy and sham treatment. As an additive therapy, laser is helpful even in DRCR.net Protocol T compared to primary VEGF therapy.
Subthreshold laser is defined as that which shows no signs of damage to the clinical examiner, Dr. Reichel explained, and demonstrated what constitutes subthreshold laser therapy. In a patient with 20/50 visual acuity (VA), fluorescein angiography (FA) showed diffuse leakage through the macula, and optical coherence tomography (OCT) showed the cystic change. The patient was treated with micropulse laser in the left eye with the setting of 400 mW, 200 μm spot size, for 200 ms; 343 spots were applied, which is seven applications on a 7 x 7 grid.
An important factor in this treatment was the 5% duty cycle, which has been able to perform subthreshold laser treatment safely even with application to the fovea, he emphasized. Four months after laser treatment, the VA was 20/30. No changes resulting from the treatment or pigmentary changes were visible on fluorescein angiography. The foveal appearance on OCT was more normal than before treatment with some small central cysts visible.
All of the basic science research has supported subthreshold laser; however, the clinical efficacy is supported only by limited case series, which provided data on Micropulse and Endpoint Management (Topcon Medical Systems, Inc.), he commented. The usefulness of laser demonstrated in the DRCR.net concerned conventional laser photocoagulation only.
“It is important to understand that micropulse therapy can be applied to the fovea in patients with DME, but Endpoint Management and microbubble disruption avoids the fovea,” he said.
Elias Reichel, MD
E: [email protected]
Dr. Reichel is a consultant to Lutronics, a member of the speakers’ bureau for IRIDEX, and received a research grant from Lumenis.