Myopia is classified by degree. Refractive errors with myopia degree greater than 600 degrees (children> 400 degrees) are called high myopia. Because this type of myopia often has pathological changes in the eye, high myopia is equated with pathological myopia or degenerative myopia. The cause of high myopia is not yet known. Pathological myopia occurs due to a greater genetic relationship. The acquired environment plays an important role in the onset of myopia. Recommended reading: high myopia? Exercise caution!

1 Pathophysiology

Eye axis lengthening is the pathological anatomy basis of myopia. The main lesion is the back of the eyeball, which is pear-shaped or egg-shaped.

(1) Cornea The posterior elastic layer of the cornea in highly myopic eyes may rupture.

(2) Sclera Thinning of the sclera in myopia is one of the characteristics of pathological changes. The longitudinal fibers become thinner, and the transverse fibers separate or disappear. This is related to the abnormal scleral collagen.

(3) The ciliary body is mainly manifested as atrophy, which can be confined to circular fibers.

(4) Vitreous body Due to denaturation and liquefaction, the normal network structure is destroyed, and gray fibers and vacuoles increase. Adhesion can occur around.

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(5) Choroid The main changes are the progressive atrophy and thinning of the choroid, including degeneration, melanocyte destruction and the appearance of new blood vessels. The elastic layer is cracked, showing paint cracks

(6) Optic disc As the eyeball stretches backward, the choroid around the optic disc is pulled away from the optic disc. Bruch's membrane also ends here, and the sclera is exposed in the absence of the outer layer of the retina and the pigmented epithelium, thereby forming a white arc-shaped spot.

(7) The retina is mainly manifested as degenerative changes. Including atrophy and degeneration. The normal hexagonal arrangement of retinal pigment epithelial cells is replaced by an irregular cell layer. There are many pigments outside the cell. Pigment proliferates and accumulates at the cracked Bruch membrane. A ring-shaped Fuchs spot can be formed in the macula. The loss of the elastic layer causes the retina and choroid to fuse together, and finally scars and pigments appear. Choroidal neovascularization can pass through the rupture of Bruch's membrane and grow under the retina to form a subomental neovascular membrane. Rupture of new blood vessels causes macular hemorrhage. The vitreous can be attached to and traction on the shrinking retina. Can cause retinal tears and detachment.