1, cornea

The transparent part in front of the outer layer of the eyeball wall. It is round, accounting for one-sixth of the outer layer area, and is about 1 mm thick. It is mainly composed of connective tissue without blood vessels, with a slightly protruding front end and bending like a sphere.

Function: It has refractive function, and the joint between cornea and sclera is called limbus corneae. Blood vessels at the limbus of cornea and aqueous humor in eyeball provide corneal nutrition. The curvature of each radial line of normal cornea is the same, so the refractive index is the same. If the curvature is uneven, it will cause refractive abnormality, which is called astigmatism.

2. aqueous humor

Aqueous humor is a transparent and clear liquid, which is filled in the front room and the back room. It is produced by ciliary process. Plasma is the mother liquid that forms aqueous humor. The electrolyte and other components contained in aqueous humor are basically the same as those in blood, but the concentration is quite different.

Function: There is also water and electrolyte exchange between aqueous humor and iris capillaries. When the intense beam passes through the anterior chamber, it is not reflected, but seems to pass through a completely transparent "space" and form a refraction channel.

Step 3: lens

The lens is located in front of the vitreous body and connected with the ciliary body through the suspensory ligament of the lens, which is lenticular and elastic. The lens is a biconvex transparent tissue, which is fixed by suspensory ligament and suspended behind the iris and in front of the vitreous body.

Function: The lens is an important part of the refractive system of the eyeball, and it is also the only refractive stroma with adjustment ability. The lens also provides a focusing function at different distances, which is called adjustment and is called a part of the refractive device.

4. Vitreous body

Vitreous body is a colorless and transparent colloid, located behind the lens, filled between the lens and retina, and filled in the cavity behind the lens.

Function: Vitreous body, lens, aqueous humor and cornea together form the refractive stroma of the eye, and support the retina and the eye wall, so that the retina adheres to the choroid.

5. Students

The pupil is a small round hole in the center of the iris of the eye, which is the passage for light to enter the eye. The contraction of the sphincter of pupil on iris can make the pupil shrink, and the contraction of dilators can make the pupil dilate. The opening and narrowing of the pupil controls the amount of light entering the pupil.

Function: In order to ensure clear imaging on retina, the change of pupil size and lens curvature plays an important role. The pupil's reflection of light and accommodation reflection are the physiological basis to realize refractive imaging function.

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