Unconscious danger of losing visual field for a long time: invisible blindness.
What it is?
Chronic Glaucoma is a disease of the optic nerve (neuropathy), characterized by progressive loss of vision, which has characteristic signs (narrowing and loss of the peripheral visual field), and these signs are reflected in the physical changes in the appearance of the optic nerve.
Known causes of this disease?
Despite the fact that this disease is considered to be multifactorial, and can be triggered by various factors, one of its most well-known causes and, currently curable, is increased intraocular pressure, ocular hypertension.
What are the symptoms?
Chronic glaucoma at the onset of the disease has no significant symptoms. As the disease progresses, the visual field defects become more pronounced and slowly increase until the disease begins to affect central vision, which is considered the end of the pathology. In addition to the loss of the peripheral and lateral visual field, when glaucoma advances in its development, the patient experiences difficulties in adapting to light or darkness. This happens when the patient drastically changes the form of lighting from a dark place to a light one, or vice versa. With such dramatic changes in lighting, the patient with glaucoma feels blinded for a few seconds.
Are there people who are at greater risk than others?
The risk of glaucoma increases with age, despite this it is very important to check the intraocular pressure in patients of any age, these measurements of intraocular pressure are especially important, starting at the age of 45 years.
Glaucoma is a disease with a high hereditary coefficient, since there are many cases of hereditary distribution of the disease. It is very important to identify or exclude the presence of glaucoma in those direct relatives of patients who have already been diagnosed. In many cases, we recommend genetic studies that accurately determine the risk of illness of the family or its descendants.
Glaucoma is a particularly aggressive disease in people of dark race, thus, the controls for this ethnic group of people should be more complete.
How is it treated?
Treatment of chronic glaucoma is initially therapeutic and aimed at reducing intraocular pressure (IOP). Eye drops can control IOP, keeping it at appropriate levels for many years, but if the pressure is not properly controlled, or eye drops lead to local or systemic side effects, we have laser or surgical techniques that can be used to support IOP at a safe level for each patient.
Is it possible to prevent the occurrence of the disease?
Prevention of glaucoma is achieved by identifying risk factors that, through the control of intraocular pressure, will prevent the development of the disease. Therefore, it is extremely important to identify the population that suffers from ocular hypertension (increased intraocular pressure), otherwise, if this population is not identified and left with high IOP, all of these people will develop glaucoma in the future. These patients should be closely monitored and, depending on each case, should follow an individually developed method of prophylactic treatment.
Is this a very serious disease?
Chronic glaucoma is the leading cause of irreversible blindness throughout the world. Detection, control and appropriate treatment of the disease slow down and, in most cases, prevent the progression of the disease leading to blindness.
If I suffer from glaucoma. Is it bad that I read a lot? Because after reading or after working with a computer, I feel very tired and my eyes are stinging.
Of course, no, this is not bad. In general, the eyes do not wear out because they work, but rather the opposite. The only thing you need to be in certain adequate working conditions. This means that when we read or sit at a computer, we must maintain correct posture and warn our eyes from drying out, because when we focus on the same distance for a long time, our eyes blink less often, which causes faster evaporation tears. Obviously, patients with glaucoma should not forget to read or perform any type of activity requiring the work of the visual apparatus.
I suffer from glaucoma. How will I feel the loss of vision if glaucoma progresses?
Initial glaucoma does not give any symptoms, but we need to know that as the disease progresses, the field of view will narrow, which is very difficult to detect with self-analysis. The cerebral cortex has certain compensation mechanisms that fill the gaps (scotomas) of the visual field with information from nearby areas. This “filling” mechanism does not allow the patient to notice the black areas of visual field loss, deceiving perception. When the scotoma or hole in the field of view becomes too large, the compensation mechanism cannot fill these zones. Only then does the patient realize that he has lost his field of vision and perceives this loss as a sharp deterioration, despite the fact that this disease was slow and progressive.
How can I suspect that I have lost sight?
Loss of visual field is detected and calculated using computer perimetry. It is important to carry out this study at least 1 – 2 times a year, although the frequency of its implementation depends on the stage of the disease and on the accuracy with which the patient performs this test. If the disease progresses, it is necessary to implement a multitude of visual field tests in order to quickly detect the problem, and before solving this problem becomes unnecessary. If the disease progresses slowly, the frequency of visual field tests decreases. For this reason, with each visit to the clinic, the ophthalmologist decides how often and how much tests need to be done to better control each patient.
Whenever I am measured for intraocular pressure, my results are different, even if the measurements are carried out on the same day. Which dimension should I believe?
Intraocular pressure (IOP) changes naturally during the day and on different days. For this reason, the ophthalmologist will often ask you to implement a “pressure chart”, which consists of measuring pressure every 3-4 hours for one day. This technique gives us the opportunity to assess changes in the IOP of the patient. This is very important, as recent studies have shown that not only the pressure itself, but also its fluctuations can be harmful to the optic nerve. The ideal treatment for glaucoma does not involve simply reducing IOP, and also trying to reduce its fluctuations during the day.
What is Pachymetry for in glaucoma research?
With regard to glaucoma, it is known that a large thickness of the cornea gives hyperoplasty of IOP, while thin corneas give low parameters. With the help of certain algorithms that mean corneal thickness values, glaucoma specialists are able to recalculate these parameters of intraocular pressure, thus determining more accurate IOP values. Thereby, we avoid the possibility of not revealing a manifestly high pressure in people with thick corneas, which give normal IOP values; or the possibility of making a false diagnosis of glaucoma for people with thin corneas who give false high IOP readings.
WATERED MOISTURE (OR INTRATIGLASE LIQUID) – aqueous humor (humor aqualis), which is contained in the perivasal, perineural crevices, perichoroidal and retrolental space, but its main depot are the anterior and posterior chambers of the eye (camerae bulbi anterior and posterior). It contains about 99% of water and a very small proportion of proteins, among which albumin, glucose and its decomposition products, vitamins B1 and B2, C, hyaluronic acid, proteolytic enzymes, traces of oxygen, sodium, potassium dominate in childhood and adulthood. , calcium, magnesium, zinc, copper, phosphorus, chlorine, etc. The amount of aqueous humor in early childhood does not exceed 0.2 cm3, and in adults it reaches 0.45 cm3.
The aqueous humor is transparent, its specific gravity is 1.0036, and the refractive index is 1.33, which is almost the same as that of the cornea, and therefore, the aqueous humor practically does not refract light rays that penetrate the eye. It provides the vital functions of the avascular formations of the eyeball (lens, vitreous body and partially of the cornea).
The outflow of aqueous humor from the eye with products of interstitial intermediary metabolism is continuously carried out in special ways: iridescent corneal angle (angulus iridocornealis), perivascular and perineural spaces. The main anterior outflow main is the iridescent corneal angle with the venous sinus system of the sclera (sinus venosus sclerae, Schlemm’s canal) and an abundant lymphatic system of tissue gaps and perivascular iris spaces, from which the aqueous humor enters the anterior ciliary and, in part, also into the vorticotic veins (see whirlpools). The posterior route of the outflow is the perivascular and perineural crevices of the ciliary body, the choroid and the optic nerve itself, then the perihorioidal space – the system of vorticose veins.
The composition and amount of aqueous humor affect not only the life support of the avascular tissues of the eye, but also the stability of the level of intraocular pressure. The slightest fluctuations, for example, in the content of acetylcholine cause a noticeable increase or decrease in intraocular pressure, and the delay in the outflow of aqueous humor or its more intense “production” contributes to a significant increase in pressure inside the eye. The main component of the aqueous humor is water; It is filtered from the chambers of the eye mainly through the corneal cornea, so it is necessary to know the topography of these areas.
The relationship between the level of secretion of intraocular fluid and the difference in chemical composition between the moisture of the anterior chamber of the eye and serum.
In accordance with the existing concept, the production of intraocular fluid (VGZH) is the result of a combination of ultrafiltration and active secretion of fluid. In accordance with the laws of hydrodynamics, passive ultrafiltration occurs as a result of the difference between the hydrostatic pressure created by the blood in the capillaries of the ciliary processes and the fluid pressure in the back chamber of the eye. This can provide only the production of the baseline amount of the VGZH until the intraocular pressure (IOP) reaches the pressure level in the capillaries of the ciliary body (8–12 mm Hg). Further production of VGZH is already against the gradient of hydrostatic pressure due to active secretion, which is an energy-intensive process. The more IOP exceeds the pressure in the capillaries of the ciliary body, the more work is needed to transfer water from the bloodstream to the posterior chamber of the eye, and the more energy-intensive the process of IGL secretion is.
When studying the blood flow of the eye using Doppler ultrasound and flowmetry, it was found that as the IOP increases from the HAH, there is an increase in compression of the intrabulbar vessels and inhibition of intrabulbar (including ciliary) blood flow, which should inevitably lead to inhibition of active secretion of the HRH. Nevertheless, practice shows that IOP in glaucoma can increase to numbers that are many times greater than the capillary pressure.
When trying to explain hypersecretion of HDV against the background of the already existing high IOP only with the help of ultrafiltration and normal active secretion of fluid, a number of serious questions arise that do not fit into the existing model, in accordance with which the rise of IOP more than 30–40 mm Hg. seems unlikely. In addition, it is impossible not to take into account the existence of oncotic pressure, which also prevents the movement of fluid from the capillaries of the ciliary body into the eyeball.
Since the active secretion is based on the processes associated with osmotic mechanisms, the study of the chemical composition of blood serum (IC) and moisture of the anterior chamber (MIC) of the eye and a comparative study of these parameters will expand our understanding of the secretion mechanisms.
Find the relationship between the level of IHV secretion and the difference in chemical composition between MIC and SC with normal and decompensated IOP.
Material and methods
The patients were divided into 2 groups. The 1st group included 33 patients (33 eyes) with primary open-angle glaucoma (POAG) and decompensated IOP (Ro ≥ 21 mmHg), while using maximum local antihypertensive therapy (a combination of prostaglandins, carbonic anhydrase inhibitors and selective beta-blockers ). In the 2nd group – 33 patients (33 eyes) with a cataract with normal IOP (Ro≤20 mm Hg) without the use of antihypertensive drops, which were taken as the conventional norm.
The sampling of the MIC was carried out in the 1st group – in the process of penetrating antiglaucoma surgery, in the 2nd – with cataract phacoemulsification. The blood for the study was taken from the cubital vein, centrifuged for 6 minutes at a speed of 1500 rpm. The supernatant part of the centrifuge (SC) and the MIC of the eye were examined on an Oxford X-Max50 energy dispersive spectrometer (EMF) (Oxford, UK) integrated into a Zeiss EVO LS10 (Zeiss, Germany) low-vacuum (70Pa) scanning electron microscope (SEM) at accelerating voltage of 20 kV and current on the sample 470 pA.
The obtained indicators of the absolute values of the concentrations of chemical elements in samples of these biological samples are fully presented in our article.
Among the elements included in the studied biological fluids, our attention was attracted by Na, K, and N, since they are present in chemical compounds with high osmotic activity, which can affect the transmembrane movement of the fluid and can affect the level of IHV secretion. Cl was not included in the study for the reason that the concentration of this chemical element was taken by us as a constant to obtain the absolute initial concentrations of the remaining chemical elements in the initial solution.
It was found that with normal IOP, the concentration ratio (in mmol/l) of Na in the MIC/SC is 1.512/1.300, and the concentration ratio K is 0.108/0.032, respectively. In the eyes with POAG with decompensated IOP, the ratio of Na concentrations in the MIC/SC is 1.488/1.306, and the ratio of K concentrations is 0.124/0.034, respectively.
It was found that the concentration of Na and K, regardless of the degree of compensation of IOP, in the MIC was significantly and consistently higher than in the SC. Excess concentrations of the above elements in the MIC is an indirect confirmation of the fact that Na and K are actively involved in the process of normal secretion of IGF. The equivalence of the concentration of Na and K in the MIC, regardless of the level of IOP, indicates that these elements do not participate in the pathological hypersecretion of moisture and in the increase in IOP.
In order to clarify the possible effect of nitrogen-containing osmotically active substances on hydrodynamic processes and on the course of pathological secretion in decompensated IOP, a comparative study was conducted of N concentrations in eye VPK specimens with both normal IOP and IOP decompensated with hypotensive drops. We did not attach much importance to the difference in N concentration between the MIC and SC. This is due to the fact that the concentration of nitrogen-containing compounds in the SC is a multifactor characteristic and depends on many reasons: on the liver, kidneys, previous physical exertion, severity of muscle mass, sex, and also on the amount of protein food eaten on the eve, etc. caused a difference in concentrations (in mmol/l) N in the MIC with different levels of IOP compensation. In our studies, the concentration of N in normal IOP was 1,123, and in decompensated IOP, 1.388.
This allowed us to assume that N is part of the osmotically active substances involved in the pathological hypersecretion of IGL and in the enhancement of IOP.
Considering that the concentration in the MIC of such nitrogen-containing substances, such as proteins, is normally minimal, it can be assumed that the N detected in the study is urea nitrogen, a substance with high osmotic activity. This is consistent with the results of a previously conducted study that revealed an excess of urea concentration in liquid media of the vitreal cavity in the eyes with refractory forms of glaucoma with sharply decompensated IOP (Po≥35 mm Hg).
1. Revealed a stable excess of the concentrations of Na and K in the MIC of the eyes compared with the content of these elements in the SC, regardless of the level of IOP.
This indicates the active participation of these elements in the process of the normal secretion of the Hepatitis C and their lack of interest in the pathological secretion of the Hepatitis C and in the decompensation of IOP.
2. The detected elevated N concentrations in the MIC of the eye with POAG with decompensated IOP compared to eyes with normal IOP suggested that nitrogen-containing osmotically active substances may be involved in the pathological hypertension of IGD and in the mechanism of IOP elevation. Such a nitrogen-containing substance may be urea, which has a high osmotic activity.