Age is the most common cause of macular hole. With age, the vitreous begins to shrink and pull away from the retina. Usually the vitreous pulls away with no problems. But sometimes the vitreous can stick to the retina. This causes the macula to stretch and a hole to form.
Sometimes a macular hole can form when the macula swells from other eye disease. Or it can be caused by an eye injury.
A macular hole is usually treated with surgery ( vitrectomy ) wherein the vitreous that is pulling on the retina is removed followed by injection of gas bubble. The gas bubble usually goes away on its own after a few days.