There are many conditions that can contribute to partial vision loss. So, it is really  difficult to tell you what causes it for your eyes according to the information you provided. For example, disbetes, glaucoma, retinal detachment and stroke can contribute to partial vision loss. Besides, other eye problems such as nearsightedness, pink eyes, eye injury  astigmatism and low blood pressure can also cause the  partial blindness in one eye. So, if you want to cure it, you shall consult an eye doctor and find out the causes so as to cure your eyes.