There are many diseases which are caused by malnutrition like
.. weakened eyesight..
scurvy is caused due to deficiency of calcium.it's symptom is that your tooth will not remain in good condition..
....rickets is caused by deficiency of vitamin D. it's symptom is that your bones will become weak and will become irregular than its original shape.
.... weakened eyesight is caused by deficiency of vitamin A and its symptoms is that you will not be able to see things at a distance from you..
and you will not be able to see anything clearly even when its close. you will see the image or object blurred.