Abstract: when the curvature of cornea and lens is too large or the eyeball is too long, and the light finally focuses in front of the retina, it is myopia. At this time, it’s OK for you to see near, but you can’t see far. A concave lens needs to be used for correction so that the light can be normally focused on the retina. Concave lens is generally represented by a minus sign (-). For example, myopia is 200 degrees, which is written as -2.00d.
what is the accurate concept of myopia, hyperopia, astigmatism and presbyopia?
Although many patients come to optometry every year and have seen the doctor and can say some terms, they don’t know what’s going on and what’s going on. Perhaps in the eyes of ophthalmologists, these concepts are too simple and common. How can you not understand them. But I find that many people really don’t understand. Today let’s distinguish what these nouns are.
through this picture, it is not difficult to find that the eyes are actually quite like a camera. When light enters the eye from the outside, it passes through two zoom lenses – the cornea and the lens, in which the lens plays a major regulatory role. The light then passes through the vitreous and finally focuses on the retina. The path of light should be transparent, that is, the refractive medium in the mouth of ophthalmologists should be transparent, so as to ensure clear imaging. Then these images are converted into signals, which are transmitted to the brain through nerves, and then through complex processing, we can see things clearly.
when the curvature of the cornea and lens is too large or the eyeball is too long, and the light finally focuses in front of the retina, it is myopia. At this time, it’s OK for you to see near, but you can’t see far. A concave lens needs to be used for correction so that the light can be normally focused on the retina. Concave lenses are generally represented by a minus sign (-). For example, myopia of 200 degrees is written as -2.00d.
After understanding myopia, it’s not difficult for us to look at hyperopia again. Hyperopia is when the curvature of the cornea and lens is too small or the eyeball is too short, and the light finally focuses on the back of the retina. When the degree of hyperopia is small, it can generally be compensated by adjustment; However, if you are far sighted, you will not see clearly from far to near, which can easily lead to symptoms such as eye acid and headache. A convex lens is needed to correct so that the light can focus on the retina normally. Convex lens is generally represented by a positive sign (+). For example, hyperopia at 300 degrees will be written as + 3.00d.
so what is astigmatism? In short, it is because the eye shape is not so perfect and regular. When light refracts through the eye, it is not a focus. It is usually corrected by cylindrical mirror.
Myopia, hyperopia and astigmatism mentioned above belong to ametropia.
presbyopia, that is, presbyopia. Many people think that Lao Hua just can’t see clearly near and is easy to confuse with hyperopia. We began to mention that light entering the eye is mainly achieved through the regulation of the lens. With the increase of age, the regulation ability of the lens decreases, resulting in unclear vision. It usually appears after the age of 40. With the increase of age, the degree of reading glasses is also increasing.
let’s take a look at what vision really means.
1. Naked eye vision can be understood literally. Seeing with naked eyes is the vision without the help of any glasses.
2. The best corrected vision is the vision when the optometrist uses the lens to help you adjust to your best state. When the best corrected visual acuity is lower than the average level of the corresponding age, or one eye is 2 lines or more worse than the other eye, it is amblyopia and needs to be treated in time.
3. Life vision is easy to understand. For example, some people may need to wear 800 degree glasses to correct their best vision to 1.0, but due to dizziness and other discomfort, they wear 700 degree glasses to correct to 0.8, which is 0.8 after wearing glasses.
children have myopia for several years. What should we do?
China is a high incidence area of myopia. At present, the prevalence of myopia among primary school students has reached 40%, and shows a trend of younger age. Faced with myopia at the age of 6 or 7, and the degree is still growing every year, many parents are particularly worried. So how can we prevent the deepening of myopia?
increase outdoor activities
outdoor activities are generally recognized as factors related to myopia. Increasing the time of outdoor activities can delay the development of myopia. At least 1-2 hours of outdoor activities per day can be guaranteed, and the time can be accumulated.
reduce close work
whether close work is related to myopia is still uncertain, but now myopia is so high, especially in some parts of Southeast Asia, the prevalence rate is as high as 80%, which is still closely related to long-time learning. In recent years, with the popularity of electronic products, close work is not limited to reading and homework, but also includes watching mobile phones and other video terminals. It is recommended to reduce the time of close work as much as possible and rest for 5 minutes after half an hour of eye use.
too dark or too bright light is not conducive to visual health. It is appropriate to feel comfortable brightness with your eyes. If you write with your right hand, please put the desk lamp in front of you to avoid the shadow of your hand blocking your line of sight.
correct eye posture
when doing homework or reading, sitting posture is very important. Try to keep the distance between eyes and books no less than 30cm. Avoid reading with your head tilted. Different distances between your eyes and the book may lead to different degrees of your eyes and anisometropia.
eat less sweets
excessive sweets will reduce the calcium content in the blood, and the decrease of blood calcium concentration may increase the ocular axis. For every 1mm increase in the ocular axis, the degree of myopia will deepen by about 300 degrees.
reduce peripheral hyperopia defocus
many studies have shown that peripheral hyperopia defocus will promote the development of myopia. Therefore, the use of some products to reduce peripheral hyperopia defocus, such as ring focus or defocus specially designed lenses, may slow the development of myopia than wearing universal lenses.