How to distinguish myopia from ametropia

Abstract: the refractive state of the eye depends on the refractive power of the ocular flexion system and the length of the ocular axis. As far as myopia is concerned, low myopia is mainly related to corneal refractive power, while medium, high and ultra-high myopia are closely related to ocular axis length., The collimated light more than 5m away, without adjustment, clearly focuses on the fovea of the macula of the retina through the refraction of the refractive system of the eye, which is the emmetropia. In other words, the refractive system of the eye, including cornea, aqueous humor, lens and vitreous body, is a concentric coaxial group of refractive qualities, and its focus is adapted to the position of the retina. In other words, the total refractive power of the eye is normal, and the axial length of the eye is normal, which is emmetropia., Relationship between myopia and ametropia: if the parallel light at a distance of more than 5m can not clearly focus on the fovea of the macula of the retina through the refraction of the refractive system of the eye without adjustment, and the refractive power of the refractive system of the eye is inconsistent with the axial length of the eye, it is abnormal refraction or ametropia., According to the relationship between focus and retinal position, ametropia can be divided into myopia and hyperopia. Myopia is divided into low myopia of 300 degrees or below, moderate myopia of more than 300 degrees to 600 degrees, and ultra-high myopia of 600 degrees to 900 degrees. If the focus cannot be focused into one point at the focal point, but the form is a light cone composed of two focal lines, this is astigmatism., It can be seen that the refractive state of the eye depends on the refractive power of the ocular flexion system and the length of the ocular axis. As far as myopia is concerned, low myopia is mainly related to corneal refractive power, while medium, high and ultra-high myopia are closely related to ocular axis length., It must be pointed out that few normal people have emmetropia with a diopter of 0. Therefore, those with normal vision and minor ametropia are also included in the scope of emmetropia. It is proposed that the standard of emmetropia is 0.00d ~ + 0.75D or -0.25d ~ + 0.50D. In the normal population, the prevalence of ametropia is about 36%, and high and ultra-high myopia account for about 0.5%., The collimated light 5m away from

clearly focuses on the fovea of the macula of the retina through the refraction of the refractive system of the eye without adjustment. In other words, the refractive system of the eye, including cornea, aqueous humor, lens and vitreous body, is a concentric coaxial group of refractive qualities, and its focus is adapted to the position of the retina. In other words, the total refractive power of the eye is normal, and the axial length of the eye is normal. The two are adapted. This is emmetropia.

the relationship between myopia and ametropia:

if the parallel light more than 5m away passes through the refraction of the refractive system of the eye without adjustment, it can not clearly focus on the fovea of the macula of the retina. The refractive power of the refractive system of the eye is not suitable for the axial length of the eye, that is, abnormal refraction or ametropia.

according to the relationship between focus and retinal position, ametropia can be divided into myopia and hyperopia. Myopia is divided into low myopia of 300 degrees or below, moderate myopia of more than 300 degrees to 600 degrees, and ultra-high myopia of 600 degrees to 900 degrees. If the focus cannot be focused into a point at the focus, but in the form of a light cone composed of two focal lines, this is astigmatism.

it can be seen that the refractive state of the eye depends on two elements: the refractive power of the refractive system and the axial length of the eye. As far as myopia is concerned, low myopia is mainly related to corneal refractive power, while medium, high and ultra-high myopia are closely related to ocular axis length.

it must be pointed out that in the normal population, there are few emmetropia eyes with diopter exactly 0. Therefore, those with normal vision and minor ametropia are also included in the scope of emmetropia. It is proposed that the standard of emmetropia is 0.00d ~ + 0.75D or -0.25d ~ + 0.50D. In the normal population, the prevalence of ametropia is about 36%, and high and ultra-high myopia account for about 0.5%.