Most cases of blurry vision are caused by a form of refractive error. Just like when you’re photographing something and you can’t bring it into focus, the eye also struggles until it’s brought into focus by the ideal lens.
This is because the retina at the back of the eye acts as a canvas for light to focus on and it doesn’t always focus as it should. There are generally three different categories of refractive error we correct for. Myopia, hyperopia and astigmatism.
Myopia (short-sightedness) is a condition in which light focuses just short of the retina, and results in things being blurrier in the distance than it is close up.
Hyperopia (long-sightedness) is a condition in which light focuses too far behind the retina meaning that things are blurrier up close than they are in the distance. Some small amounts of hyperopia can be compensated for using the eye’s internal focusing system, but this may cause eye strain over prolonged periods.
Astigmatism is a condition in which light focuses at multiple different planes and can result in distortion of images, streaking of lights, or glare. Some astigmatism may also lead to eye strain as the focusing system attempts to adjust between multiple focal points.
All these kinds of refractive errors may be corrected with personalised spectacles or contact lenses to allow people to continue their lives with clear and comfortable vision.