Vision refers to the ability of retina to distinguish images. Vision is judged by the ability of retina to distinguish images. However, when the refractive medium of the eye (such as cornea, lens, vitreous body, etc.). ) become turbid or have refractive errors (including myopia, hyperopia, astigmatism, etc.). ).
Even if the retina function is good, the vision of the eyes will still decline. Opacity of refractive medium can be treated by surgery, and ametropia needs to be corrected by lens.
Strictly speaking, the standard of normal vision also includes central vision, peripheral vision and stereoscopic vision.
Extended data:
Three main points of normal vision:
1, contrast sensitivity
The ability to distinguish different levels of "gray scale" is contrast sensitivity. Contrast sensitivity = 1 divided by contrast threshold. When the contrast threshold is low, the contrast sensitivity is high and the visual function is good. Contrast sensitivity decreases, which is very common in cataract people. Although the visual acuity of some cataract patients is 0.7, 0.8 or even 1.0, they always feel blurred and have obstacles in front of them, which is because the contrast sensitivity has decreased.
2, color vision
Color vision refers to the ability of human eyes to distinguish colors, which is a basic and important part of visual function. Various eye diseases, such as cataract, macular degeneration, refractive stroma, retinal cells, optic nerve, visual center, etc. , can cause color blindness, color weakness and other color vision disorders, of which color weakness is the most common. To cure color vision disorder, the premise is to cure eye diseases first.
3. eyesight
Visual field refers to the spatial range that people can see when they look at the object in front with their heads and eyeballs fixed. Retinitis pigmentosa, advanced glaucoma, retrobulbar optic neuritis (peripheral type), periretinal choroiditis, pathological myopia, optic disc edema, optic disc defect and other eye diseases will all lead to visual field defects, so we must pay positive attention to them.
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