Causes and risk factors for the development of glaucoma

If we summarize the causative factors of the development of glaucoma, we can make the following picture: dysfunction of the hypothalamus leads to endocrine and metabolic disorders, which in turn cause local disturbances. Hereditary glaucoma is associated with dysfunction of the hypothalamus, endocrine and metabolic disorders. Hereditary factors cause anatomical predisposition, disturbances of hydrostatics and hydrodynamics, which causes an increase in intraocular pressure.

Theories of glaucoma development

The first period (late XIX - early XX centuries) - the theory of retention, i.e., delayed outflow of intraocular fluid from the eye. The increase in intraocular pressure was due to the development of goniosinia, the pigmentation of the anterior chamber angle. Information was obtained in the study of enucleated eyes (blind with absolute glaucoma). Other factors (nervous, vascular, endocrine) were ignored. But it turned out that the pigmentation of goniosynexia does not always lead to glaucoma.

The second period (1920-1950-ies.) - Neurohumoral, characterized by the study of various aspects of life of patients with glaucoma, ie, the state of the nervous and endocrine systems. Ignored local, mechanical and vascular factors.

The third period (from the 1950s) is a synthetic approach that takes into account the general and local mechanisms of increasing intraocular pressure, based on new data: the role of heredity in the transmission of glaucoma, the phenomenon of steroid glaucoma, the direct causes of increased intraocular pressure (histological, histochemical, tonographic and etc.), the pathogenesis of glaucoma atrophy of the optic nerve.

1. Heredity. A genetic predisposition to primary glaucoma exists (at least two genes are found that contribute to the development of this disease). It was established that the only gene responsible for the development of glaucoma is not. There are several genes that, if they have pathological changes, lead to the disease. The disease, in addition, manifests itself only with other external factors affecting the body, or if mutations are present in several genes at the same time. In cases where the incidence of glaucoma in the family is often enough, heredity should be considered as an important risk factor. It is also important that family members, when living together, are exposed to the same environmental factors. And this parade with a genetic predisposition plays an important role in the development of glaucoma. "Steroid test" - increasing intraocular pressure on the introduction of steroids - complements the genetic predisposition. Predisposition to glaucoma is transmitted by a dominant type. There are no glaucoma in isomeric tribes, in Normandy, Sweden, Denmark, glaucoma occurs in 2-3% of the inhabitants.
2. Neurogenic theory - a violation of the interaction of inhibitory processes of the cortex and subcortex, the balance of excitability of the sympathetic and parasympathetic systems.
3. Violation of the hemodynamics of the eye - the anterior and posterior segments, With age, the pulse blood pressure decreases, the peripheral volume of the circulating blood decreases, which leads to a decrease in the volume of blood flowing along the uveal tract, the anterior section to the eye. This causes dystrophic phenomena in the trabeculae, ciliary body, which leads to a change in intraocular pressure and a decrease in visual function.

SN Fedorov, developing the hemodynamic theory, suggested that glaucoma is an ischemic eye disease and has three stages, such as:

1. ischemia of the anterior part of the eye;
2. increased intraocular pressure;
3. ischemia of the optic nerve with increasing intraocular pressure.

NV Volkov suggested the correlation of intracranial, intraocular and arterial pressure as the leading factor in the genesis of glaucoma. The normal ratio of intraocular and intracranial pressure is disrupted. This ratio is normal; if there is an increase of 3: 1, then this leads to the development of glaucomatous optic nerve atrophy.

The pathogenesis of primary glaucoma according to AP Nesterov

1. Age-related dystrophic and functional disorders in the anatomically predisposed eye.
2. Hydrostatic shifts - a change in the normal ratio of intraocular pressure in various closed and semi-closed systems of the eye (1 / 4-1 / 3 of the intraocular fluid flowing along the back way).
3. Functional block of the drainage system of the eye.
4. Disturbance of the hydrodynamics of the eye.
5. Increased intraocular pressure, secondary vascular degenerative changes in the anterior and posterior segments of the eye.
6. Organic block of the drainage system of the eye with atrophy of the optic nerve and loss of visual functions.

Secondary changes in the eye lead to an increase in intraocular pressure, which in turn causes secondary changes.

Patients with diabetes mellitus are three times more likely to have glaucoma. In 35% of patients with glaucoma, there is a violation of protein metabolism and hypercholesterolemia.

Dystrophic changes. Degeneration of connective tissue leads to fragmented disintegration of connective tissue substances in vessels, trabeculae. Endothelial dystrophy leads to its proliferation and sclerosis trabeculae, resulting in obliteration of the collectors. Decay of collagen fibers leads to the fact that trabeculae lose tonus and are pressed into the zone of the helmet canal, the coefficient of ease of outflow of fluid C decreases almost 2-fold, then the outflow almost ceases, the secretion is again broken.

In the initial stages of glaucoma, the coefficient C decreases to 0.13, in the developed stage of glaucoma - to 0.07, in the terminal stage - to 0.04 and less.

Blocks of the hydrostatic and hydrodynamic system according to AP Nesterov and their causes

1. Superficial scleral block. Reason: compression and infection of episcleral venous vessels.
2. Block of graduates of the helmet canal. Reason: the inner walls of the helmet rope cover the mouth of the collector channels.
3. Blockade of the helmet canal. Reason: the inner wall of the helmet drop is displaced and blocks its lumen, the collapse of the helmet channel occurs.
4. Block trabecular network. Reason: compression of trabecular gaps, departure of exfoliative pigments of blood. Inflammatory and dystrophic changes,
5. Block the angle of the front chamber. The reason: the displacement of the corneal root anteriorly, the development of goniosynexia in congenital glaucoma - defects in embryonic development.
6. Lens unit. Cause: lens shift toward the anterior chamber, the ciliary body touches the lens, directing into the vitreous cavity.
7. Rear visreal unit. Cause: the intraocular fluid accumulates in the vitreous body, and it moves away anteriorly.
8. The pupil block is relative and absolute. Reason: tight fit and increment of the cornea to the anterior capsule of the hrustatik - pupil occlusion.

Risk factors for the development of glaucoma

Age, especially with primary glaucoma, plays an important role. The age group most often include patients older than 40 years. With age, increased intraocular pressure is noted even in healthy eyes, as the aging process occurs in the trabecular network. During this period, the production of watery moisture also decreases, so the intraocular pressure moderately increases. Intraocular pressure in most patients with glaucoma begins to increase between 40 and 50 years, sometimes in a later period.

Paul. Women are more likely to suffer from closed-angle glaucoma, and men - with pigment glaucoma. In women, glaucoma with normal pressure is more often determined, although the optic nerve disk is more sensitive to intraocular pressure.

Race affiliation. Patients of African descent often have higher intraocular pressure. Elevated intraocular pressure is observed at an earlier age. Pigmentary glaucoma is most common in people with fair skin. Closed-angle glaucoma is characteristic of Asia, in Japanese glaucoma often with normal pressure. The development of pseudoexfoliation glaucoma is most affected by Caucasians living in the Nordic countries.

Heredity. The fact of hereditary predisposition to glaucoma is known for a long time. However, this does not mean that a child whose parents are suffering from glaucoma will necessarily develop this disease. Glaucoma can appear spontaneously and without a family predisposition to this disease. Congenital, juvenile and juvenile glaucoma is more often hereditary, but there are also spontaneous cases of glaucoma in this category of patients. But still the genetic predisposition to the development of high intraocular pressure and the risk of developing glaucoma sometimes, even under normal intraocular pressure, are not denied and are of great importance.

Atherosclerosis is one of the main health problems in modern society. The blood vessels of the eye, like any other vessels, can suffer from atherosclerosis. Atherosclerosis more often and at an earlier age develop cataracts and macular degeneration (age changes in the central zone of the retina). Studies show that atherosclerosis does not increase the risk of developing glaucoma, and yet there is a weak relationship between atherosclerosis and increased intraocular pressure. People with atherosclerosis are more likely to have increased intraocular pressure compared to healthy people of the same age.

Myopia and hyperopia. Healthy farsighted and myopic eyes have the same average intraocular pressure. However, with hyperopia, the risk of developing a closed-angle glaucoma is higher, while near-sightedness is more likely to cause pigmented glaucoma. Such eyes are more sensitive to the effects of increased intraocular pressure.

Disturbances of the ocular circulation. The fact that the reduction in ocular blood flow is usually observed earlier than glaucomatous lesions, and patients with glaucoma often have circulatory disorders in other organs, indicates that some of these disorders are causative,

Some glaucoma patients experience a change in circulation even at rest, but especially after physical exertion, emotional stress or cold. There are various signs that are most likely due to vascular dysregulation, rather than atherosclerotic circulatory disorders. It is proved that patients with glaucoma are much more likely to suffer from various circulatory disorders than healthy people of the same age. With low intraocular pressure, at which glaucomatous lesion develops, there is a possibility that in the pathological process blood circulation is also involved. In the most serious cases, insufficient blood circulation (ie, feeding the optic nerve) can lead to structural damage, sometimes even at sufficiently low levels of intraocular pressure. The most common cause of decreased blood supply is atherosclerosis. It can lead to constriction of blood vessels, thrombosis and embolism. The main cause of worsening of the eye blood flow in glaucoma is disruptive disorders in the blood vessels, including the vessels of the eye. In patients who suffer from vascular disregulation, there is a tendency to lowered arterial pressure (hypotension), especially at night, and the development of vasospasm.

Blood pressure. Elevated blood pressure - hypertension - represents a known health risk. Constant blood pressure does not exist. It can vary throughout the day, depending on the physical load, the position of the person (horizontal or vertical), eating and using medicines.

Glaucoma is often combined with normal blood pressure during the day, but at night it can either decrease or rise, which does not happen in healthy people.

For patients with glaucoma, a significant orthostatic pressure drop (with a change in the position of the body from horizontal to vertical) can be quite dangerous.

The high blood pressure in glaucoma is not so serious, but a chronic increase in blood pressure leads to the progression of atherosclerosis, which is the consequence of the development of ophthalmopathology, including glaucoma.

Temporary blood pressure drops are common among patients who suffer from a vasospastic syndrome, because the eye blood circulation in them is very sensitive to lowering the blood pressure level.

The blood vessels of the eye provide nutrition to various parts of the eyeball. Active regulation of the eye blood flow is as follows. When light enters the eye of a healthy person, the blood supply to the retina and optic nerve immediately increases. This leads to a decrease in blood pressure in the vessels at the entrance to the retina and causes a shortage of blood supply. To compensate, this deficit, the vessels expand. Thus, the regulation of the ocular blood flow is carried out.

Diabetes mellitus. Diabetes can cause irreversible damage to the eyes, especially with the development of glaucoma. With diabetes, a significant increase in intraocular pressure is possible, which is regarded as a complication of glaucoma. There was evidence that with diabetes, glaucoma is less common.

Thus, the primary risk factors for increasing intraocular pressure and, as a consequence, the development of glaucoma, are age, heredity, race, atherosclerosis and nearsightedness. Primary risk factors for the development of glaucomatous lesions are increased intraocular pressure, vascular dysregulation with systemic hypotension and vasospasm, female gender and race.

Additional factors (anatomical predisposition to the development of glaucoma)

1. Myopia and hyperopia. Healthy hypermetropic and myopic eyes have average intraocular pressure. However, with farsightedness, the risk of developing a closed-angle glaucoma is higher, and when the cup is short-sighted, pigment glaucoma is observed. Such eyes are more sensitive to the effects of increased intraocular pressure.
2. Small before not the posterior axis of the eye.
3. Rear location of the helmet canal.
4. Small front camera.
5. The big crystalline lens.
6. The small curvature of the cornea leads to a shallow anterior chamber.
7. Atopy of the ciliary body, weakening of the muscle of the Brücke, which stretches the scleral spur, which leads to the fall of the graduates.

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