I'm sorry to hear about your sister's situation. Diabetes normally affects two places first; the eyes and the kidneys. These effects are almost exclusively linked to the blood sugar levels. As the blood sugar remains high, the cells that surround the blood vessels in the retina (the back of the eye) become defective. This allows the blood vessels to bleed and leak. Furthermore, new blood vessels begin to grow due to poor oxygenation of the retina. These new blood vessels are fragile and also tend to easily bleed. Once the bleeding occurs, the body can react in a number of ways:
1. the blood can be reabsorbed without any consequences.
2. the blood can remain there, requiring surgery for removal. This surgery does not prevent future episodes of bleeding.
3. the blood can begin to harden and shrink causing traction on the retina and ultimately a retinal detachment. Retinal detachments often cause permanent reduction in the vision.
If her situation resembles the first two possibilities I have presented, laser treatment and surgery can be effective treatment along with very strict blood sugar control. The blood sugar control is crucial to prevent a continuation of the problem.
If she has reached the third possibility then the treatment options do not offer much in way of improving vision. Rather, the treatment options are geared towards preserving the vision that still remains.
I recommend very strict sugar control in order to prevent a worsening of the condition. You may want to consider a visit to the closest or best known academic institution in your area. There are clinical studies being performed in these institutions that may offer the latest treatments and give her the best chance to stabilize the condition and possibly offer some improvements in vision.
I know this is a difficult situation. If there are no options that can improve vision to a level where she can function independently, a low-vision specialist should be consulted to help her manage with the vision that she curretly has. Low-vision specialist devote their careers towards helping patients with this type of situation.
Good Luck as you attempt to find the best treatment for your sister...