Your optometrist can explain the specifics of your vision in more detail, as there are a number of conditions that may require the use of spectacles. In brief, nearsightedness typically results in blurred distance vision, while farsightedness often causes headaches, strain, or blurring when reading or using a computer. Astigmatism causes distortion at all distances, leading to blurring and strain. Around the age of forty, essentially everyone develops presbyopia, a focusing deficiency that blurs near vision, often after a lifetime of otherwise excellent sight. All these conditions, or a combination thereof, may necessitate the wearing of glasses.