Photobiomodulation May Benefit Some Diabetic Macular Edema Patients

By Lorraine L. Janeczko

April 25, 2014

NEW YORK (Reuters Health) - Patients with non-center-involving diabetic macular edema (NCDME) may benefit from photobiomodulation, a new case series suggests.

Two 80-second photobiomodulation (PBM) treatments a day significantly reduced macular thickening in all four treated eyes, the authors reported online March 28 in the British Journal of Ophthalmology.

PBM may help inhibit macular edema and is non-invasive and cost-effective, they wrote.

"In fact, the patients administered the treatments themselves at home. The treatment device itself is lightweight, portable, and battery-powered," lead author Dr. Johnny Tang of the University of Kansas Medical Center in Prairie Village and the Louis Stokes Cleveland VA Medical Center in Ohio, told Reuters Health.

Senior author Dr. Timothy S. Kern of the Louis Stokes Cleveland VA Medical Center and Case Western Reserve University School of Medicine in Cleveland, added, "This treatment offers the hope of a totally non-invasive therapy that patients can deliver themselves."

But both doctors cautioned that this is a preliminary study that needs a larger clinical trial.

"This is a very small study and it needs to be done in a bigger way to really see how useful it's going to be in what kind of patients. If this is a successful and useful therapy, it has the potential of being delivered anywhere no matter what medical care people have access to," Dr. Kern said.

The researchers conducted a non-randomized, consecutive case series, treating four patients with PBM for 160 seconds per day.

They enrolled patients who had NCDME - retinal edema from diabetic retinopathy within 3,000 microns of the macular center but not involving the center, determined by clinical exam and spectral domain ocular coherence tomography (SD-OCT) - and a central SD-OCT subfield of 225 microns or less.

They excluded patients who received systemic or topical anti-inflammatory agents, intravitreal steroid injections, antivascular endothelial growth factor/trap or focal laser within three months, patients with vision <20/40, and those unable to undergo treatment.

All patients were male, aged 42 through 71 years. During the study, their treatment for systemic diseases did not change and their average hemoglobin A1c percentage, 7.1, remained stable.

Patients with two eligible eyes were randomly selected for which eye was treated, with the fellow eyes acting as controls. They were treated for at least two months and had the option to continue for up to nine months; three patients continued beyond two months.

The patients treated themselves twice daily using the devices (Warp 10, Quantum Devices, Barneveld, WI/QBMI Photomedicine, Dodgeville, Wisconsin), which emitted light at 670 nm and produced a dose of 25 Joules/cm2 at 1 inch.

They were instructed to hold the device an inch from the closed treatment eye. After 80 seconds, the device automatically turned off and a delay timer prevented it from turning back on for several minutes.

The authors found that, in treated eyes, the regions corresponding to thickened areas on SD-OCT decreased by a mean of 20.0%, while the untreated eyes showed a mean change of 3.0%, indicating a worsening effect.

Neither the patients nor the researchers noted any adverse effects attributable to therapy.

"The treatment for non-center-involving diabetic macular edema is observation. We picked this subset of patients as a surrogate patient population for individuals who have center-involving diabetic macular edema. The current treatment involves invasive laser surgery, injections of anti-vascular endothelial growth-factor medications into the eyeball, involving a lot of morbidity and expense," said Dr. Tang.

Dr. Colin A. McCannel of the Jules Stein Eye Institute and the David Geffen School of Medicine at UCLA in Los Angeles, California, expressed caution regarding the results.

"It is hard to draw any conclusions when four patients have a mild to minimal benefit. Usually I look for dramatic results for studies with a very small number. As such, it is hard to predict the impact, but if the technology proves to work in a randomized trial, it may address an unmet need of the poorly studied NCDME," he told Reuters Health by email.

"However, the paper indicates in the methods that a t-test was used for data analysis, and the results are referred to as 'significant,' implying statistical significance. But, unfortunately, no p-values are presented," he added.

"Also, the outcome measure of retinal thickness was done in a very unconventional way, analyzing the color of the printout and using the color change as the changes assessed for the study outcome (but these values are not reported). All in all, this report is not done to any level of scientific rigor," said Dr. McCannel.

Responding by email, Dr. Kern wrote, "We agree that the p value somehow got omitted from the printed copy. We apologize for this oversight, but the results of the light-induced reduction in thickening were statistically significant (p<0.05). Due to space limitations, we were not able to include raw data that would have provided useful information to interested readers. This work is presented only as a small series of case reports using a potentially interesting approach to therapy. The study must be repeated with a much larger group of patients to achieve the necessary scientific rigor."

That light alone may have a therapeutic effect is not intuitive, Dr. McCannel said, adding, "I hope that the authors may be right, as simple light treatment might be a wonderfully safe treatment for macular edema," he said.

As to the therapeutic value of light, Dr. Kern said, "Using light has been shown to be very valuable in retinal degeneration, in wound healing. So we may have opportunities in multiple diseases and clinical modalities."

The authors and Dr. McCannel stated that they have no related conflicts of interest.


Br J Ophthalmol 2014.


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