Vision is divided into central vision and peripheral vision, and the examination of central vision is divided into far vision and near vision. Because the examination of distance vision is relatively simple and convenient, it is of certain significance as one of the monitoring indexes of adolescent vision health. The state stipulates that primary and secondary school students should have their distance vision tested twice every semester, but the dynamic monitoring of distance vision is rough and general, and the monitoring of vision health can't just stay in distance vision, such as the primary school students with distance vision 1.0. Although their eyesight is within the normal range, their refractive status is not the same, which may be hyperopia, emmetropia or early myopia. It is necessary to check the refractive state of the eyes and analyze it in combination with the age of the child. If the child is 7 years old, he has little hyperopia reserve, or he is already facing the eye, and his vision is normal on the surface. In fact, the child is not far from myopia. According to scientific research data, 7-year-old children are emmetropia, and the probability of myopia within six months is 0. The probability of myopia in one year is about 80%, and it is not comprehensive to evaluate children's visual health only by their visual acuity 1.0 without secondary and tertiary tests. Parents think that children's eyesight is normal, and it is even more wrong to ignore and give up early prevention of myopia, so experts have repeatedly pointed out that "it is too late to prevent myopia until children's eyesight drops!" . Of course, primary and secondary school students' hyperopia is lower than 1.0, so they need to be tested at the second and third levels, because the decline of hyperopia is only a phenomenon. What is the refractive state of the eyes? Are you nearsighted? What kind of myopia is it? Any other eye diseases? How to intervene? Is there any way to fix it? Should I wear glasses? Wait, it's difficult to determine the test results of farsightedness alone.
The purpose and significance of secondary (refractive state) detection
The refractive system of the eye mainly includes cornea, aqueous humor, lens and vitreous body. The refractive system is equivalent to a set of compound lenses. The parallel light from the outside is refracted by the refraction system and focused on the retina. Distant objects form a clear, inverted and reduced real image on the retina. This physiological function of the eye is called eye refraction. Most people's eyes are not ideal eyes. After being refracted by the refractive system of the eye, the parallel rays cannot be focused on the retina accurately, but are focused on the front or back of the retina, or they cannot form a focus at all. Only the focus line. Refractive defects in human eyes are very common. It's not that there is anything wrong with eyes at a certain distance, just because the refractive state is different. The refractive state is constantly changing and has certain regularity in a person's life, and the refractive change of the eyes is the fastest in adolescence. Therefore, people will show different refractive defects at different stages of life, and their nature and degree vary from person to person. Ophthalmic optics is to study these problems. In ophthalmic optics, we call the process of detecting the refractive state of someone's eyes "optometry". Precision optical instruments and skilled professional technology are the basis to ensure the accuracy of refractive state detection (optometry).
The refractive state of eyes can be divided into dynamic and static. The so-called static state refers to the state that the lens is not adjustable, and the so-called dynamic state refers to the state that the lens is adjustable. Teenagers' eyes are very regulated, so it is difficult to show a static state. Therefore, we emphasize that/kloc-under 0/5 years old, pupils are dilated and foggy, and static refractive examination should be done in a relaxed state. The dynamic refractive examination can be completed by Wuhan visual defense physical examination team, and the static refractive examination can only be carried out in Wuhan visual defense "detection, rehabilitation and correction base" because it involves mydriasis drugs and imaging equipment. The base can also complete both dynamic and static refractive examinations at one time.
The purpose and significance of three-level (fine vision) test
Fine optometry (Grade III) is the essence of vision health monitoring, which is very important for the prevention and rehabilitation of low vision and is the basis of optical correction prescription. The fine optometry detection carried out by Wuhan Institute of Vision Prevention mainly includes: early warning detection of juvenile myopia; Binocular visual function detection; Screening of non-refractive eye diseases.
First, the detection and early warning of juvenile myopia
The development of children and adolescents' eye refraction is monophasic and has certain regularity, and its refractive dynamics changes along the direction of hyperopia → emmetropia → myopia, and the whole process is irreversible.
The result of refractive detection is only the refractive state of the eyeball, but the biological detection of refractive elements of the eye is more accurate and objective than refractive detection. During the development of adolescent eyeball, there are five main refractive factors that determine the refractive state of the eye, namely, axial length (al), anterior chamber depth (ACD), LENS thickness (Lens), vitreous cavity length (UITR), corneal curvature radius and corneal diopter (CR/ K value). The changes of biological values of these five refractive elements are closely related to the visual environment, especially al and AL/CR. Are the five refractive factors matched during children's growth and development? It determines whether his eyes are positive, hyperopia, myopia or astigmatism.
The latest research found that hyperopia defocus caused by overuse of eyes at close range and accommodation lag during eyeball development, that is, the accommodation response of eyes lags behind the accommodation demand at close range, and the focus always falls behind the retina at close range. In this state, the structure of the eye will adapt to the nearby environment, and the retina will stretch backward to "find" the focus, causing abnormal growth of the axial (al), and axial myopia will occur. According to this theory, the prevention and rehabilitation methods of axial myopia should be taken before the abnormal growth of axial length, such as using optical methods to compensate the accommodation of short-distance eyes, pulling the focus behind the retina to the retina, or using physical methods to exercise and adjust muscle strength. The principle is to control the abnormal growth of axial length (al), which can be said to control myopia!
If a vision health file is established from the age of 3, and the values of vision, refractive state and refractive factors of all ages are recorded, and scientific analysis is carried out, and scientific detection and early warning are carried out according to the law of eyeball development, many students with myopia (hyperopia decline) can be kept out of the door of myopia, and at the same time, it can be judged whether children under 1-2 years old will have myopia. How to delay the onset age of myopia? How to control the rapid development of myopia? Making a correct early warning, we can take practical intervention measures to achieve the purpose of preventing micro-duration, treating fake and preventing truth and controlling aggravation.
Third, the investigation of non-refractive eye diseases
1, purpose and significance:
Eye diseases in childhood are very harmful to vision development. It is very important to find and diagnose non-refractive eye diseases that affect vision as soon as possible. Many eye diseases will cause lifelong disability if they are not found and treated in time.
Why do you want to do A ultrasound and B ultrasound?
A-mode ultrasound is mainly used to measure the axial length. Adolescent axial length (al) is the most sensitive data among refractive factors, and excessive axial length is a high-risk indicator for myopia warning. B-ultrasound is mainly used to explore the position and nature of vitreous and retinopathy. High myopia can lead to vitreous opacity, retinal detachment, posterior scleral staphyloma and other complications. B-ultrasound is helpful to further clarify the degree of these organic ocular lesions.
Why should we check the corneal curvature?
Corneal curvature radius (CR) can be detected by corneal curvature instrument. CR value is also one of the refractive factors of eyes, and AL/CR is an important early warning index of myopia. Through the examination of corneal curvature instrument, we can understand the corneal astigmatism and provide reference for optometry. Measuring the curvature of the anterior surface of the cornea with a corneal curvature instrument can provide a basis for selecting the appropriate basal arc of the contact lens.
Why do you want to check the fundus and take pictures?
Myopia, especially high myopia, is often complicated with fundus diseases, mainly including retinal choroidal atrophy, macular hemorrhage, retinal detachment and so on. Some of them will cause irreversible visual damage. Patients with high myopia need mydriasis to examine the fundus carefully. While determining whether the above lesions exist, it is more important to find the degenerative lesions of the retina and carry out preventive laser photocoagulation to reduce complications. Fundus photography can objectively print out the color image of fundus, and keep it for data preservation and comparison in the next examination. Difficult fundus signs can be used as the basis for consultation.
Why do you want to measure intraocular pressure?
Myopia is a risk factor for glaucoma. Most myopia patients have gradually become accustomed to poor vision, but they lack vigilance and sensitivity to vision decline, and the gradual damage of glaucoma to vision and vision is often ignored. Therefore, if conditions permit, routine intraocular pressure examination for such patients has two purposes, one is to exclude primary glaucoma, and the other is to exclude mydriasis. Non-contact tonometer is widely used in ophthalmology clinic.
Why do you want to do a visual field test?
Vision detection is also called peripheral vision detection. We usually use an eye chart to check the central vision. Many eye diseases first appear in the visual field, such as retinitis pigmentosa, and even very serious. Central vision can still be in the normal range, so visual field detection is the basic method to diagnose retinal and optic nerve eye diseases such as glaucoma.