Prevention depends on the cause. Early detection and treatment of glaucoma can often prevent vision loss. Control of diabetes can help prevent vision changes caused by diabetic retinopathy. Frequent hand washing and not touching the eyes with the hands helps prevent conjunctivitis. Many cases of vision changes cannot be prevented.
Long-term effects depend on the cause. Presbyopia causes a permanent loss of vision in near objects. But reading glasses or bifocals are the only treatment needed and there are no other long- term effects. A brain tumor can cause death. Glaucoma, macular degeneration, and diabetes can all result in permanent blindness or vision changes.
Vision changes themselves pose no risks to others unless the person engages in dangerous activities such as driving. If the cause of the vision change is an eye infection, such as conjunctivitis or keratitis, the infection may be catching in some cases.