Provider factors also influence the barrier to screening which is a lack of awareness of the screening guidelines, skills or having the right tools to perform eye exams which can affect the diagnosis and treatment. A cross-sectional study showed that when physicians treating black patients had more difficulty providing proper subspecialty care and diagnostic imaging for the patients. There is evidence to support interventions to improve attendance for diabetic retinopathy screening. These might be specifically targeted at diabetic retinopathy screening, or could be general strategies to improve diabetes care. There are three major treatments for diabetic retinopathy, which are very effective in reducing vision loss from this disease. In fact, even people with advanced retinopathy have a 95 percent chance of keeping their vision when they get treatment before the retina is severely damaged. These three treatments are laser surgery, injection of corticosteroids or anti-VEGF agents into the eye, and vitrectomy. Although these treatments are very successful (in slowing or stopping further vision loss), they do not cure diabetic retinopathy. Caution should be exercised in treatment with laser surgery since it causes a loss of retinal tissue. It is often more prudent to inject triamcinolone or anti-VEGF drugs. In some patients it results in a marked increase of vision, especially if there is an edema of the macula. Although commonly used in some parts of the world, it is unclear whether herbal medicine (for example, Ruscus extract and Radix Notoginseng extract) are of benefit to people with diabetic retinopathy. Avoiding tobacco use and correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy. Obstructive sleep apnea (OSA) has been associated with a higher incidence of diabetic eye disease due to blood desaturation caused by intermittent upper airway obstructions. Treatment for OSA can help reduce the risk of diabetic complications. The best way of preventing the onset and delaying the progression of diabetic retinopathy is to monitor it vigilantly and achieve optimal glycemic control. Since 2008 there have been other therapies (e.g. kinase inhibitors and anti-VEGF) drugs available. Laser photocoagulation can be used in two scenarios for the treatment of diabetic retinopathy. It can be used to treat macular edema by creating a Modified Grid at the posterior pole and it can be used for panretinal coagulation for controlling neovascularization. It is widely used for early stages of proliferative retinopathy. There are different types of lasers but there is limited evidence available on their benefits and harms to treat proliferative diabetic retinopathy.