A new clinical trial carried out by researchers in Belfast has shown that a type of laser treatment offers the best option to people affected by diabetic macular oedema (DMO).

DMO is the most common sight-threatening complication of diabetes, affecting over 27 million adults worldwide. It occurs when blood vessels in the retina at the back of the eye leak, causing fluid build-up at the macula, which provides central vision. The leakage occurs when high blood glucose levels damage blood vessels.

There are currently several treatment options offered to people with the condition, including two types of laser treatment and eye injections.

This research from Queen’s University has shown that a type of laser treatment is both non-invasive and cost effective.

The researchers explained that the severity of DMO is most often determined by measuring the thickness of the macula, which in turn determines the treatment offered. Patients with more severe DMO (with thickness of 400 microns or more) are treated with injections into the eye with drugs known as anti-VEGFs.

Patients with mild DMO (with thickness of less than 400 microns) can be treated with macular laser, which can be standard threshold laser or subthreshold micropulse laser. The former produces a burn or scar on the retina. The latter, which is a more recent technology, works without leaving a burn or scar, or any type of visible change or mark, on the retina.

The clinical trial found that subthreshold micropulse laser was effective in maintaining a patient’s vision. Furthermore, it required significantly less visits to the clinic and is much more cost effective than treatment via eye injections. Currently, eye injections cost almost 10 times more than laser treatments.

According to the study’s lead author and clinical professor of ophthalmology at Queen’s University, Prof Noemi Lois, the absence of a scar or burn following subthreshold micropulse laser “led to some healthcare professionals to doubt its effectiveness compared to the standard threshold laser”.

“However, our research addressed this by demonstrating that subthreshold micropulse laser is as good as standard threshold laser for helping people’s vision, reducing macula thickness, allowing people to meet driving standards and maintaining their quality of life, both in general terms and for vision in particular,” she explained.

The researchers compared both types of available laser treatment through a large randomised clinical trial, known as DIAMONDS (DIAbetic Macular Oedema aNd Diode Subthreshold micropulse laser SML). They recruited 266 patients across 16 NHS hospitals around the UK, with half receiving standard threshold laser and the other half receiving subthreshold micropulse laser. At the end of the two-year trial, DIAMONDS found both laser treatments to offer equivalent benefits, with similar costs associated.

Prof Lois noted that some ophthalmologists advise patients with milder forms of DMO to have injections of anti-VEGFs, rather than laser, despite laser being less invasive, requiring less visits to the clinic and costing significantly less.

“Until we published these findings, there was no robust evidence comparing these types of laser treatments. A lack of information led some healthcare professionals to favour standard laser over subthreshold micropulse laser. We now have robust evidence to show that both laser treatments are not only effective in clearing the fluid from the retina and maintaining vision for at least two years, but both are also cost effective.”

“Armed with this knowledge, it’s likely that patients will opt for micropulse subthreshold laser, which doesn’t burn the retina and is comparable to standard laser. Whilst we didn’t directly compare laser treatments to treatment via eye injections of anti-VEGFs, hopefully we have shown that laser is an effective treatment, while remaining much less invasive to the patient and much less costly,” Prof Lois said.

This study is published in the journal Ophthalmology and can be viewed here.