First of all, to say " eyesight " simply said that people see the ability to see things, the vision is good or bad to see the distance of things to judge; good, there are 1.5, 2, poor 0.1.
Many factors affect vision, ocular inflammation can cause vision loss (trachoma, conjunctivitis, etc.); trauma can also cause vision loss; decreased lens opacity, vitreous body opacity, retinal lesions and other diseases can also cause vision; but most of young students with decreased visual acuity close eye fatigue.
" " myopia; generally refers to the eye diopter, the most direct refractive change is the reaction in the bending degree of lens, vision closer, the greater curvature of the lens, in the regulation is more laborious, reaction in self feels is equivalent to the lens eye fatigue; a convex lens is to adjust the degree of bending it according to their own needs, to change the focus distance to see the visual object.
Simply put, myopia refers to the corneal diopter, vision refers to the ability of the retina imaging, the same degree can have different vision, similarly, the same vision can also have different degrees.
Although the same person in the same period, the higher the degree of vision is worse, but there is no absolute relationship between vision and myopia, more disproportionate. Myopia, some myopia degree 300 degrees, measuring visual acuity 0.2, and some myopia is only 400 degrees, measurement vision is 0.2. So, it's just an inspection standard.
Uncorrected visual acuity and refractive power are two indicators that are often used to measure visual acuity, both of which are related but not positively related. Long wearing glasses glasses people mainly through the view of things, rather than their own eyes, eye regulation function and visual function degradation, even if the diopter little eyes vision is poor; and is often people who wear glasses because their eye adjustment function and visual function is good, even higher degrees of glasses the eyes, vision is relatively good.
So, we can often see in the life of this situation: 200 people who have been wearing myopia, his naked eye vision is not as good as 400 glasses of nearsighted people do not often wear.