Diabetes can affect the eyes, and the nervous system...
It can affect the eyes by damaging the blood vessals in them. It can also damage your nervous system by when you have too much glucose circulating in the blood, and so it can damage any of the nerves in your body. This can lead to numbness, tingling and pain, especially in the feet and legs. If you develop cuts or sores you may not feel them, and they may heal very slowly. You may lose sensation in these areas, and if the damage is severe enough, amputations may be necessary.
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Hope this helps!