July 29 (Reuters) - Regeneron Pharmaceuticals Inc said the U.S. Food and Drug Administration has approved the expanded use of its eye drug Eylea for the treatment of diabetic macular edema.

The condition causes swelling of an oval spot within the retina in the eyes of patients with diabetes, and can lead to severe vision loss or blindness.

Eylea is already approved in the United States to treat wet age-related macular edema - the leading cause of blindness in the elderly, and for treatment of macular edema following central retinal vein occlusion.

The injectable drug has been steadily grabbing market share from Roche AG's Lucentis since its launch in late 2011.

(Reporting by Shailesh Kuber; Editing by Bernard Orr)