This is a fluid build-up in the part of the eye that is responsible for central vision. Diabetic macular oedema affects up to 10 percent of all patients with diabetes.
It is caused when high blood sugar eventually causes damage in blood vessels of the retina and a decrease in the supply of oxygen and nutrients. When the retina experiences low oxygen levels it releases vascular endothelial growth factor (VEGF) and other substances that cause the retinal blood vessels to become leaky and stimulates the growth of new blood vessels. The leakage of fluid into the macular causes it to become thickened and results in vision loss. Many patients have laser treatment to try and correct it, however many patients find that they still suffer persistent oedema. A pilot study has monitored diabetic patients breathing supplemental oxygen through a nasal cannula and found that it helped to reduce fluid build-up and swelling and in some cases improved their visual acuity fairly dramatically.
Patients were given 4 litres per minute of oxygen via a nasal cannula and asked to use it continuously for three months day and night. After the three months it was found that there was an average 50% decreases in the excess thickness of the macular, the excess thickness of the fovea (responsible for sharpness of vision) and in the macular volume. Also a third had improved visual acuity with the ability to read two lines higher on an eye chart. In addition it was noted that when the supplemental oxygen therapy was discontinued the subject’s vision slowly worsened.
However in those where their eyes had returned to within the normal range whilst on supplemental oxygen, their eyesight did not worsen but remained within the normal ranges once the supplemental oxygen was stopped. It appears that supplemental oxygen reduces the production of VEGF, which reduces the amount of leaking in retinal vessels and therefore lessens the severity of macular oedema. Researchers believe that this could be used in conjunction with eye laser treatment to improve oxygenation to the retina to provide long-term eye stability. The oxygen treatment could reduce the thickness of the retina prior to laser treatment in order to make the laser treatment more effective and long-lasting, for when supplemental oxygen is ceased. There are also oral drugs being developed that block receptors for VEGF and could be used in conjunction with supplemental oxygen to help improve results.
References: http://www.hopkinsmedicine.org and http://iovs.arvojournals.org