1, the eyeball is equivalent to a camera. The lens and cornea work together as convex lenses. The retina at the back of the eyeball is equivalent to a light curtain. Objects are imaged on the retina through the lens. It is an inverted and reduced real image.

2, myopia, like in front of the retina. You can wear a concave lens to correct it. Because it has the property of diverging light. Move the clear image back slightly and form it accurately on the retina.

3. Hyperopia (also called presbyopia) is just like behind the retina. You can wear a convex lens to correct it, as shown in Figure 4. Because it has the property of converging light. Move the clear image forward slightly and form it accurately on the retina.

Eye introduction

The eye can change the focal length of the lens by adjusting the curvature (refraction) of the lens, so as to obtain an inverted and reduced real image. The farthest point that the eyes can see is called the adjustment far point, and the far point that the eyes can see is extremely far; The closest point that the eye can see is called the accommodation near point, and the accommodation range is called between two points. The near point of normal eyes is about 10 cm away from the eyes.

The human eye is approximately spherical and located in the orbit. The average diameter of normal adults is 24mm, the average vertical diameter is 23 mm, and the front end protrudes from the orbit 12- 14mm, which is protected by eyelids. The eyeball includes the wall of the eyeball, the inner cavity of the eye, contents, nerves, blood vessels and other tissues.