Diabetes does not have any clear symptoms. For that reason, when patients are diagnosed with diabetes, there are some who do not heed medical advice. This ia a tragedy for those diagnosed with this disease, because if you do not take care about a high blood sugar level, sooner or later you will have an eye problem as a secondary disease.
This indisposition centers around the retina, which is at the bottom of the eyes, causing retinopathy. This secondary disease does not show any noticeable symptoms in its early stage, so we cannot easily detect it until our eyes are checked with ophthalmic treatment.

When it is in its early stage, it can be cured with both internal and ophthalmic treatment. But when retinopathy becomes worse, present medical science has no cure for it.

When retinopathy advances to a later stage, bleeding occurs in the eyes(retinal bleeding), in the end you lose your eyesight.
In Japan the main reason for losing one's eyesight is diabetic retinopathy.

Beside retinopathy, cataract sometimes can occur, if you do not care about your blood sugar level. This is a disease where the lens, which is comparatively closer to the surface of the eyes than the retina, becomes unclean.

So, if you are diagnosed with diabetes, even if you do not feel any symptoms concerning your eyes, you should be examined at ophthalmology at least once a year to prevent these serious secondary disease. The most effective way to do this is by keeping your blood sugar level stable.