My aunt has a visual impairment. She has vision loss to a degree that cannot be fixed by glasses.
Wow that sounds serious. I have glasses but my vision is not that bad.
I wear glasses as well. It's unfortunate because she has a hard time doing normal things like driving and reading.
That's aweful. Doe she have someone to help her?
She has my uncle, thank goodness. Hers is caused by cataracts, which is the most common cause of visual impairments. 
Are there any other causes of visual impairments?
Many. The other more common causes are refractive errors and glaucoma.
I've heard of glaucoma but what are refractive errors?
Refractive error
Refractive error, also known as refraction error, is a problem with focusing light accurately onto the retina due to the shape of the eye. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.
Near-
Visual impairment
Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term blindness is used for complete or nearly complete vision loss. Visual impairment may cause people difficulties with normal