Intraocular pressure is the pressure inside the eyeball, referred to as intraocular pressure. It is the balanced pressure exerted by the contents of the eye on the wall of the eyeball. The intraocular pressure of normal people is stable within a certain range to maintain the normal shape of the eyeball and maintain good refractive status at each refractive media interface. The normal intraocular pressure range is 10mmHg ~ 21mmHg (1.33kPa ~ 2.80kPa).
The contents of the eye include aqueous humor, lens, and vitreous body. Among them, aqueous humor has the greatest impact on intraocular pressure. The total amount of aqueous humor is 0.13mL ~ 0.3mL. Its main component is water. In addition, there are proteins, electrolytes, ascorbic acid, lactic acid, glucose, lipids, enzymes, etc. The pH value is 7.3 ~ 7.5. Aqueous humor is produced by the ciliary process in the ciliary body, then enters the posterior chamber, flows into the anterior chamber through the pupil, and then drains out of the eyeball through some pipes through the angle of the anterior chamber. Under normal circumstances, the production and excretion of aqueous humor maintain a dynamic balance, that is, within a certain period of time, the amounts of aqueous humor produced and discharged are equal. If the drainage channel of aqueous humor is blocked, or the amount of aqueous humor produced increases for some reason, it can lead to accumulation of aqueous humor and increase intraocular pressure. If the amount of aqueous humor produced is too small and the accumulation of aqueous humor cannot reach a certain amount, the intraocular pressure will be too low. Basic introduction Chinese name: intraocular pressure Foreign name: Intraocular pressure Concept: pressure inside the eyeball Normal range: (10~21) mmHg (1.33~2.80)kPa Peak time: highest in the morning and lowest at night or late at night. Main influencing factors: Aqueous humor detection method: digital intraocular pressure method and tonometer measurement method Function: The main basis for detecting glaucoma is intraocular pressure value, precautions, digital intraocular pressure method, tonometer measurement method, functions, influencing factors ,Measurement method advantages and disadvantages, glaucoma diagnosis, various tonometers, intraocular pressure value intraocular pressure From a clinical perspective, the definition of normal intraocular pressure should be the intraocular pressure range that does not cause damage to the optic nerve. Because the tolerance of the optic nerve to intraocular pressure varies greatly among individuals, normal intraocular pressure cannot be defined by a precise value. The average intraocular pressure of normal people is 15.8mmHg (1mmHg≈0.133kPa), and the standard deviation is 2.6mmHg. From a statistical perspective, normal intraocular pressure is defined as 10~21mmHg (mean ± 2 × standard deviation). However, in fact, the intraocular pressure of normal people is not normally distributed. Therefore, intraocular pressure >21mmHg cannot be mechanically considered as a pathological value. Clinically, although the intraocular pressure of some patients has exceeded the upper limit of statistical normality, no damage to the optic nerve or visual field occurs during long-term follow-up, which is called ocular hypertension; some patients have intraocular pressure within the normal range but develop typical symptoms. Glaucoma optic nerve atrophy and visual field defects are called normal tension glaucoma (NTG). It can be seen that not all high intraocular pressure is glaucoma, and normal intraocular pressure cannot rule out glaucoma. In the author's many years of medical career, I have encountered glaucoma patients who responded after asking for intraocular pressure: "Oh! The intraocular pressure is seventeen, one more than last time, too high." In fact, this kind of anxiety about the intraocular pressure difference of one to two millimeters of mercury is unnecessary. Intraocular pressure and other physiological indicators of the body, like body temperature, heartbeat, blood pressure, etc., are fluid, as long as it is still within the acceptable range of the patient's optic nerve. In many normal people, intraocular pressure is highest in the morning and lowest in the evening or late at night. But some people's intraocular pressure peaks in the afternoon or evening. Generally speaking, the intraocular pressure of a normal person fluctuates between three and six millimeters of mercury throughout the day, while the intraocular pressure of patients with glaucoma may fluctuate within a larger range than this. Body posture also affects intraocular pressure. When a normal person changes from a sitting position to a lying position, the intraocular pressure may rise by 6 mmHg. If you adopt an inverted posture, the intraocular pressure may increase by more than ten millimeters of mercury. Therefore, if glaucoma patients do yoga exercises, we will advise them to avoid inversions as much as possible. In addition, drinking a large amount of fluid (such as five hundred C.C.) in a short period of time can increase intraocular pressure. Some medicines can also cause the side effect of increasing intraocular pressure, the most noteworthy of which are medicines containing steroids. Whether it is administered orally, applied to the skin, nasal spray or eye drops, as long as it contains steroids, there is a chance that this side effect will occur.
Precautions: Humans have known for a long time that glaucoma and high intraocular pressure are closely related. Because this correlation has been overemphasized for a long time, many people believe that high intraocular pressure means suffering from glaucoma, while normal intraocular pressure means immunity to glaucoma. This concept is too crude according to today's medical standards. Many patients with intraocular pressure higher than the so-called "normal range" may not develop optic neuropathy throughout their lives; conversely, some patients with intraocular pressure within the normal range may still have optic nerve damage due to other risk factors for glaucoma. Destroyed bit by bit. Therefore, whether when diagnosing or treating glaucoma, doctors do not only care about one factor: intraocular pressure, but make conclusions after multiple assessments. Although intraocular pressure is not the only causative factor, it is important to understand that patients with higher intraocular pressure are more likely to develop glaucoma. Intraocular pressure However, high intraocular pressure does not mean glaucoma. It is just that people with high intraocular pressure have a higher chance of causing damage to the optic nerve and progressing to glaucoma than people with normal intraocular pressure. As far as intraocular pressure is concerned, there is no absolutely safe intraocular pressure limit. Some people maintain intraocular pressure within the so-called normal range, but continue to have changes in their optic nerves. Some people have high intraocular pressure, but their optic nerves have always been normal. Therefore, high intraocular pressure is only one of the factors causing glaucoma. It is also extremely important and the only one that can be measured and controlled. The digital intraocular pressure measurement method is to make the patient's eyes look downward naturally. The examiner lightly touches the eyeball with the tips of two index fingers from above the upper edge of the tarsal plate. The remaining fingers are placed on the patient's forehead for support, and the tips of the two index fingers alternate. Press lightly and estimate the level of eyeball pressure based on the undulating sensation that reaches your fingertips. Generally, normal is Tn, high intraocular pressure is T+1, 2, and 3, and low intraocular pressure is T-1, 2, and 3. Intraocular Pressure Tonometer Measurement Method Tonometer measurement methods are divided into two types: indentation type and applanation type. The Schiotz indentation tonometer is commonly used in clinical practice. It uses a weight of a certain weight to indent the central part of the cornea to measure intraocular pressure. The electric tonometer is made according to Schiotz standard tonometer specifications. It is connected to the automatic galvanometer recording system and can be used for intraocular pressure tracing. The applanation tonometer uses a certain weight to flatten the cornea and measure the intraocular pressure based on the flattened cornea area, or uses a variable weight to flatten a certain cornea and measure the intraocular pressure based on the required weight. Intraocular pressure is directly proportional to the applied external force and inversely proportional to the area of ??the cornea that is flattened. Applanation tonometers include Makakob, Goldmann, Mackay Marg (all contact type) and non-contact tonometer (NCT). The Goldmann tonometer uses a plastic measuring head to flatten a circular area with a central diameter of 3.06 mm in the cornea, and the intraocular pressure is determined based on the force used; while the NCT uses air pressure pulses to impact the cornea, and determines the intraocular pressure based on the corneal deformation and time. Correspondence to determine intraocular pressure. Tonometry is a method of measuring the aqueous fluid flow coefficient (C value) and aqueous humor production rate (F value) of a living eye. When the eyeball is exposed or pressure is exerted on the eyeball, the discharge of aqueous humor in the normal eye can be accelerated and the intraocular pressure will decrease. However, the intraocular pressure measured by glaucoma rarely decreases or does not decrease at all. To check for glaucoma, you also need to make a daily intraocular pressure curve to understand the intraocular pressure fluctuations within a day. The method is to measure intraocular pressure every 4 hours within 24 hours. The approximate times are 5, 7, 10, 14, 18 and 22 o'clock. Function: The main function of intraocular pressure is to maintain the shape of the eyeball and maintain normal physiological functions. Therefore, it must be kept within a constant range, neither high nor low. Just like a balloon, the intraocular pressure is the air inside. With the support of the air, pressure is exerted on the wall of the ball, so that the balloon can inflate. If there is less air, the ball will deflate. If there is too much air, it may burst at any time. possible. Normal intraocular pressure is 10mmHg~21mmHg (1.33kPa~2.80kPa), the pressure difference between the two eyes is <4mmHg~5mmHg (0.53kPa~0.67kPa), and the difference between day and night fluctuations is <5mmHg (0.67kPa). If the intraocular pressure exceeds the normal range, it is generally considered Already suffering from glaucoma.. Intraocular Pressure Intraocular pressure is an important basis for diagnosing glaucoma, but it is not the only factor. The level of intraocular pressure cannot be used to mechanically determine whether there is glaucoma. Clinically, there is a kind of glaucoma that can lead to blindness, but the intraocular pressure is still within the normal range, which is called "low-tension glaucoma". This is because the basic intraocular pressure itself is low, even within the fluctuation range of normal intraocular pressure, it is enough. causing damage to his eyes. There is also a form of high intraocular pressure, but without any clinical manifestations of glaucoma and intraocular pressure damage. We call this "ocular hypertension" and only 10% of these people develop glaucoma.
Therefore, intraocular pressure is an important and indispensable basis for the diagnosis of glaucoma, but it is not the only basis. Influencing factors include lens opacity, etc. The most important damage is optic nerve atrophy. The human eyeball is equivalent to a light bulb, and the optic nerve is like a wire. If the optic nerve cells die one by one, the corresponding visual field will be damaged, and in severe cases, blindness will occur. Intraocular pressure There are many factors that affect intraocular pressure. The normal intraocular pressure fluctuation for a normal person during the day is 2-3mmHg. The intraocular pressure is generally the highest in the morning and may be lower in the afternoon. There is an examination called 24-hour dynamic intraocular pressure measurement. The intraocular pressure should be measured 6 times a day, preferably every 4 hours. The Chinese Academy of Ophthalmology has set 6 time points. If the intraocular pressure fluctuates within 5mmHg within a day, It is normal. If it is greater than or equal to 8mmHg, it is considered to be a pathological intraocular pressure fluctuation. Factors that affect intraocular pressure include ***. When lying down, intraocular pressure will be 2-3mmHg higher than when standing. Pressure on the eyeball and blinking forcefully will temporarily increase intraocular pressure, so you must cooperate well when measuring intraocular pressure. Intraocular pressure drops during anesthesia. Whether it is local anesthesia or general anesthesia, intraocular pressure will be affected. The older you get, the lower the intraocular pressure is. If the intraocular pressure is still 20mmHg at the age of 80, in fact, the intraocular pressure at the age of 80 is 17 or 18mmHg. Intraocular pressure is higher in winter and lower in summer. Food and toxins such as caffeine and smoking can increase intraocular pressure. Drink a lot of water. If you drink 500 ml of water at once, the water in the blood vessels will be diluted. At this time, the water in the blood vessels may seep into the eyes. Therefore, it is recommended that patients with glaucoma not drink a large amount of water at once. In addition, hormonal drugs can increase intraocular pressure in 26% of normal people when used locally for 4-6 weeks. Advantages and Disadvantages of the Measurement Method: You can use the gaze light directly above, or you can look at your finger raised 20cm to 40cm away from your eyes. The doctor gently places the base of the tonometer on the cornea, and adjusts the weight according to the indication of the pointer and the acting weight. , the intraocular pressure value of the eye can be found from the comparison table. The general record is: weight weight/pointer reading = intraocular pressure value (1 unit is mmHg or Kpa, 1kp=7.5mmHg). Another method for intraocular pressure is to sit in front of the slit lamp after applying topical anesthetic eye drops. When the examiner touches the cornea with the manometer head, the intraocular pressure value can be read directly on the scale. There are also non-contact or tonometers. There is no need to drop anesthetic eye drops before the examination. The airflow from the instrument impacts the cornea, and the intraocular pressure value can be displayed on the fluorescent screen and printed on paper. This method does not require any equipment and directly contacts the cornea. The operation is very simple and safe, and there is no possibility of damage. Moreover, because it does not touch the eyeball, it will not cause cross-infection. During the epidemic period of pink eye, there will be no infection due to intraocular pressure measurement. On pinkeye, this is the most prominent advantage of the tonometer, but it is expensive. When measuring intraocular pressure, the eyes need to work closely together. Keep your eyes fixedly looking straight ahead or at the light. Don't be nervous or afraid. Don't move your eyes randomly to avoid accidents that may cause corneal abrasions. Loosen collar buttons and ties and keep breathing calmly. For those who use topical anesthetic eye drops, if the corneal sensation has not fully recovered within one hour after the examination, do not rub your eyes with your hands to prevent accidental corneal abrasion. In most normal people, intraocular pressure is higher in the early morning and lower in the evening and night. There is a regular fluctuation range within a day, and the difference is within 5mmHg. Therefore, it is best to measure the intraocular pressure at the same time every time, so that Only then can there be better comparability. Glaucoma Diagnosis Currently, glaucoma is the second most irreversible blinding eye disease in the world. According to statistics, there are more than 67 million primary glaucoma patients in the world. There are currently at least 5 million glaucoma patients in my country, of which 790,000 are both blind. Blind. The prevalence of glaucoma is 0.21%-1.64%, and the prevalence of this eye disease increases with age. The survey shows that the prevalence rate of people over 40 years old is significantly higher than that of young people, at 1.4%. At least two out of every 100 people over 50 years old suffer from glaucoma. The number of people blinded by glaucoma accounts for 5.3% to 21% of all blind people. areas are even as high as 30%. In recent years, China has achieved remarkable results in controlling cataracts. Many first-level hospitals in townships can perform cataract surgery. This has made the problem of blindness caused by glaucoma more and more prominent. In some areas, glaucoma has replaced cataracts and become the number one killer of blindness. trend. What needs to be pointed out in particular is that in China, the popularity of knowledge about glaucoma prevention and treatment is far less than that in developed countries. As a result, a considerable number of chronic glaucoma patients gradually lose most or even all of their vision without realizing it and regret it for the rest of their lives.
Intraocular Pressure Glaucoma is an eye disease caused by damage to retinal nerve fibers and visual field defects caused by pathological high intraocular pressure (rarely under normal intraocular pressure). Europeans and Americans mostly have open-angle type, while in my country, closed-angle type is the main type. The anterior and posterior chambers of the eyeball are filled with a clear fluid, aqueous humor. Aqueous humor is produced in the posterior chamber, enters the anterior chamber through the pupil, and then exits the eye through the external drainage channel. Under normal circumstances, the production and discharge of aqueous humor are in a state of dynamic balance to maintain intraocular pressure. However, although this fluid is still produced normally in patients with glaucoma, its drainage is blocked. If too much aqueous humor accumulates in the eye, it will cause an increase in intraocular pressure. Over time, the increased pressure can compress the optic nerve, eventually leading to blindness. Normal people's intraocular pressure is in the range of 10 to 21mmHg. However, some people's intraocular pressure is higher than the normal value but does not cause damage to the optic nerve and visual field. This is called ocular hypertension and cannot be diagnosed as glaucoma. Others have damage to the optic nerve and visual field. Defect, but the intraocular pressure is within normal values, it is called normal tension glaucoma or low tension glaucoma. Therefore, high intraocular pressure does not necessarily mean glaucoma, and normal intraocular pressure does not rule out glaucoma. Various tonometers Non-contact tonometer (barometric tonometer) Fully automatic non-contact tonometer, with the characteristics of joystick-free, fully automatic focusing, three-dimensional automatic eye tracking, quiet operation, fully automatic air jet When used for pressure measurement, a gentle air wave will be produced, and the pressure value of the air wave hitting your cornea and then reflected back can be used to determine the level of your intraocular pressure. The patient only needs to rely on the forehead rest of the instrument to focus on the fixation target. Using the patented joystick-free autofocus system, the operator only needs to press a button to activate the intraocular pressure (IOP) measurement program. The forehead rest slides left and right, and the upgraded software inside can automatically identify the left and right eyes. Advantages: Convenient, fast, safe and hygienic, and can be used repeatedly. Disadvantages: The measurement data is inaccurate for some patients, such as patients with thick corneas. Contact tonometer (applanation tonometer) Contact tonometer has certain clinical accuracy. Its principle is to directly contact the patient's eyeball through the pressure needle, and accurately determine the patient's intraocular pressure value through the depth of the cornea after applying pressure. . Each time the tonometer is used, the tonometer should be placed on the examination table for measurement. The pointer must be at the "0" position before it can be used. If it is not at the "0" position, the pointer position must be adjusted so that the pointer reaches the "0" position. The pressure needle should be disinfected with alcohol before use to avoid infection of the patient during use. Advantages Accurate measurement, clinical accuracy, and the most accurate measurement method currently available. Disadvantages: Improper use can easily cause infection. Patients must use anesthesia when using it, which has certain side effects on the body. There are many types of portable tonometers. They are generally used in small clinics and have low accuracy, but they are suitable for portability. Generally, this type of tonometer is not recommended as the basis for diagnosis if conditions permit.