What is a refractive error?
A refractive error is a type of vision problem that makes it hard to see clearly. Specifically, it means the shape of your eye keeps light from focusing correctly on your retina which causes distortions in your vision. Refractive errors include nearsightedness, farsightedness and astigmatisms.
Someone with myopia or nearsightedness can see objects close by clearly but will struggle to see objects at a distance. Distant objects may appear blurry or fuzzy.
On the other hand, someone with hyperopia or farsightedness has no trouble seeing objects that are far away. However, objects close at hand will appear blurry or unfocused. This is often referred to as “mild hyperopia”. In more advanced cases of hyperopia, vision can be blurry at all distances.
Presbyopia (loss of near vision with age)
After age 40, the lens of the eyes becomes less flexible which makes it more difficult for the eye to focus and change focus fluidly. Presbyopia is perfectly normal and just another part of the aging process. Even people who already have myopia, hyperopia or astigmatism can get presbyopia.
Astigmatism occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea has a smooth and equal curvature which allows light to enter the cornea evenly. Someone with astigmatism may have vision that appears wavy or distorted, much like a funhouse mirror. Usually, astigmatism causes blurred vision at all distances.