Ophthalmic fluid. The structure of the eyeball (continued) Intraocular fluid is produced

Aqueous moisture is formed in the eye at an average rate of 2-3 µl/min. Essentially all of it is secreted by the ciliary processes, which are narrow and long folds protruding from the ciliary body into the space behind the iris, where the lens ligaments and the ciliary muscle are attached to the eyeball.

Due to folded architecture of ciliary processes their total surface area in each eye is approximately 6 cm (a very large area considering the small size of the ciliary body). The surfaces of these processes are covered with epithelial cells with a powerful secretory function, and directly below them there is an area extremely rich in blood vessels.

Aqueous moisture almost completely formed as a result of active secretion of the epithelium of the ciliary processes. Secretion begins with the active transport of Na+ ions into the spaces between epithelial cells. Na+ ions pull SG and bicarbonate ions with them to maintain electrical neutrality.

All these ions together cause osmosis water from blood capillaries, lying below, in the same epithelial intercellular spaces, and the resulting solution flows from the spaces of the ciliary processes into the anterior chamber of the eye. In addition, some nutrients, such as amino acids, ascorbic acid and glucose, are transferred through the epithelium by active transport or facilitated diffusion.

Outflow of aqueous humor from the chambers of the eye

After education aqueous humor It first flows through the ciliary processes (fluid flow) through the pupil into the anterior chamber of the eye. From here, the fluid flows forward to the lens and into the angle between the cornea and iris and, through a network of trabeculae, enters Schlemm's canal, which empties into the extraocular veins. The figure demonstrates the anatomical structures of this iridocorneal angle, where the spaces between the trabeculae can be seen extending all the way from the anterior chamber to Schlemm's canal.

The latter represents a thin-walled vein, which runs around the eye along its entire periphery. The endothelial membrane of the canal is so porous that even large protein molecules and small solid particles, up to the size of red blood cells, can pass from the anterior chamber of the eye into Schlemm's canal. Although Schlemm's canal is a true venous blood vessel, it usually has so much aqueous humor flowing into it that it becomes filled with that moisture rather than blood.

Small veins, going from Schlemm's canal to the great veins of the eye, usually contain only aqueous humor, and they are called aqueous veins.

There are several types of glaucoma, the treatment of which is approached from different directions.

Glaucoma is a large group of ophthalmological diseases, varied in their causes, which lead to increased intraocular pressure and gradual atrophy of the optic nerve.

Treatment consists primarily of normalizing intraocular pressure, which can increase for the following reasons:

• violations of the removal of intraocular fluid (IOH) through special channels to the outside;
• increased production of intrauterine fluid in the ciliary body;
• changes inside the eyeball, leading to disruption of the movement of the intraocular fluid.

For these purposes, there are a large number of pharmaceutical drugs for glaucoma, which can be divided into several groups based on their mechanism of action:

1. Drugs that enhance the outflow of intraocular fluid.
2. Agents that reduce the production of intrauterine fluid.
3. Combination drugs.

Mechanism of action

Most of the drugs from are drugs that increase the excretion of intrauterine fluid:

• Prostaglandin analogues - a group represented by substances such as latanoprost, travaprost, tafluprost, bimatoprost.
• M-cholinomimetics - this group is represented by a single drug - pilocarpine.

The hypotensive effect when using prostaglandin analogues is achieved by improving the outflow of intraocular fluid along the uveoscleral pathway, which is an alternative (“spare”) pathway. This is especially important in cases where the main route of elimination, the trabecular tubule system, does not function properly.

The very mechanism of action of prostaglandins, due to which there is an increase in outflow, and accordingly a decrease in IOP, is currently not fully understood.

M-cholinomimetics, when used in the form of eye drops, lead to a significant constriction of the pupil by stimulating the muscles of the iris and ciliary body. This effect leads to the opening of the anterior chamber angle in both open-angle and closed-angle glaucoma, thereby increasing the outflow of intraocular fluid into Schlemm's canal and fountain spaces.

Indications for use

Preparations from the prostaglandin group are used primarily for the most common form of glaucoma - open-angle. It is also possible to use these medications for angle-closure and secondary glaucoma, but with some restrictions.

Pilocarpine is mainly used in the treatment of . The drug also shows good results when used for the treatment of secondary glaucoma and open-angle glaucoma.

Contraindications for use

One of the ways to treat glaucoma is surgery.

Prostaglandin analogs are natural substances in their structure, i.e. they are produced in the human body. In this regard, these drugs have high safety, bioavailability combined with high efficiency. For the same reasons, drugs in this group belong to the drugs of first choice, i.e. they are appointed first.

There are no absolute contraindications or significant side effects for these medications. It is not recommended to use drugs from the prostaglandin group for the following ophthalmological diseases:

1. Inflammatory and infectious diseases of the eye, especially iridocyclitis and.
2. It should also not be used after operations for keratoplasty, corneal transplantation, cataract extraction (the limit in this case is up to 1-1.5 months).
3. Presence, or high risk of possible occurrence of macular edema. This limitation is especially important for patients with diabetes.
4. The presence of secondary neovascular or diabetic glaucoma, with preserved visual functions.

Pilocarpine, as a treatment for glaucoma, is currently used less and less.

This fact is due to the fact that m-cholinomimetics have a significant number of various side effects and contraindications:

• Inflammatory diseases of the eyes, in which constriction of the pupil is unacceptable - and uveitis.
• High myopia, due to the high risk of developing retinal detachment.
• Retinal detachment present at the time of treatment or in history (operated).

When using pilocarpine, systemic effects on the body are possible with the development of the following undesirable effects:

1. Decreased heart rate and conductivity. Therefore, it is not used for certain heart diseases.
2. Bronchospasm - not used for bronchial asthma and COPD.
3. Increased secretion of gastric glands - use is not recommended for peptic ulcers and gastritis.

Use in children and pregnant women

The use of Pilocarpine in children and pregnant women is not allowed due to side effects and the possible systemic effect of the substance.

The use of Latanoprost, as a representative of prostaglandins, in pregnant women and children is acceptable. Numerous studies have been conducted, both in laboratory conditions and on volunteers, confirming its safety for individuals of these groups. Other representatives of this group are not used due to the insufficiently studied effect in children and pregnant women.

Special instructions for use

When combining several drugs, do not forget to indicate this to your doctor

It should be noted that drugs from the group of prostaglandin analogues are used only once a day, and the greatest effectiveness is achieved when used in the evening. More frequent use leads to a decrease in the hypotensive effect, causing redness, swelling, and burning of the eyes.

Pilocarpine is used 2-3 times a day, depending on the IOP level. More frequent use is acceptable when stopping an acute attack of glaucoma. In this case, it is used according to a special scheme.

Most often, pilocarpine is used as part of complex treatment together with one of the representatives of beta-blockers (Timolol, Betaxolol).

Sales representatives and prices

Representatives of the prostaglandin group:

• — 650 rubles;
• Prolatan - 510 rubles;
• Glauprost - 520 rubles;
• — 680 rubles;
• Taflotan - 850 rubles;
• Xalatamax - 450 rubles;
• Glaumaks - 410 rubles.

Representative of the group of m-cholinomimetics:

• — 20 rubles;
• Pilocarpine-DIA - 25 rubles.

Glaucoma treatment should be approached judiciously. Due to the large selection of drugs, the doctor must individually determine which drug is most suitable for you and choose the dosage. If you have an unexpected reaction to the drug, contact a specialist immediately!

Aqueous moisture is a colorless jelly-like liquid that completely fills both.

The composition of aqueous humor is similar to that of blood, only with the lowest protein content. The speed at which a clear liquid is formed is 2-3 µl per minute. During the day, 3–9 ml of liquid is formed in the human eye. Secretion is carried out by ciliary processes, which in their shape resemble long and narrow folds. The processes protrude from the area behind the iris, where the ligaments attach to the eye. The outflow of aqueous humor is carried out through the trabecular meshwork, episcleral vessels and uveoscleral system.

How does aqueous humor circulate in the eye?

Pathway of aqueous humor outflow is a complex system in which several structures are involved at once. After aqueous humor is formed by the ciliary processes, it flows into the posterior chamber, and then through into the anterior chamber. Due to the high temperature regime on the front surface, aqueous humor rises to the top and then falls down along the rear surface, which has a low temperature. After this, it is absorbed in the anterior chamber and, through the trabecular meshwork, enters Schlemm’s canal and again into the bloodstream.

Functions of the aqueous humor of the eye

Aqueous moisture The eye has essential nutrients for the eye, such as amino acids and glucose, which are necessary to nourish the avascular structures of the eye.

Such structures include:

Lens
- anterior section
- corneal endothelium
- trabecular meshwork

The aqueous humor of the eye contains immunoglobulins, through which the protective function of the internal parts of all structures of the eye is carried out.

The constant circulation of these substances neutralizes various factors that can lead to damage to all eye structures. Aqueous moisture is a medium that refracts light. due to the ratio of formed and excreted aqueous humor.

Diseases

A decrease or increase in aqueous humor leads to the development of certain diseases, such as, for example, which is characterized by an increase in intraocular pressure, that is, an increase in the amount of aqueous humor due to impaired outflow. Unsuccessful operations or eye injuries can lead to a decrease in the aqueous humor content, as a result of which there is an unhindered and uncontrolled outflow of fluid.

Intraocular fluid or aqueous humor is a kind of internal environment of the eye. Its main depots are the anterior and posterior chambers of the eye. It is also present in the peripheral and perineural clefts, suprachoroidal and retrolental spaces.

In its chemical composition, aqueous humor is analogous to cerebrospinal fluid. Its amount in the eye of an adult is 0.35-0.45, and in early childhood - 1.5-0.2 cm3. The specific gravity of moisture is 1.0036, the refractive index is 1.33. Consequently, it practically does not refract rays. Moisture is 99% water.

Most of the dense residue consists of anorganic substances: anions (chlorine, carbonate, sulfate, phosphate) and cations (sodium, potassium, calcium, magnesium). Most of the moisture contains chlorine and sodium. A small proportion is accounted for by protein, which consists of albumins and globulins in a quantitative ratio similar to blood serum. Aqueous humor contains glucose - 0.098%, ascorbic acid, which is 10-15 times more than in the blood, and lactic acid, because the latter is formed during the process of lens exchange. The composition of aqueous humor includes various amino acids - 0.03% (lysine, histidine, tryptophan), enzymes (protease), oxygen and hyaluronic acid. There are almost no antibodies in it and they appear only in secondary moisture - a new portion of liquid formed after suction or expiration of the primary aqueous humor. The function of aqueous humor is to provide nutrition to the avascular tissues of the eye - the lens, vitreous body, and partially the cornea. In this regard, constant renewal of moisture is necessary, i.e. outflow of waste liquid and influx of freshly formed liquid.

The fact that intraocular fluid is constantly exchanged in the eye was already shown in the time of T. Leber. It was found that the fluid is formed in the ciliary body. It is called primary chamber moisture. It mostly enters the posterior chamber. The posterior chamber is bounded by the posterior surface of the iris, the ciliary body, the zonules of Zinn, and the extrapupillary portion of the anterior lens capsule. Its depth in different sections varies from 0.01 to 1 mm. From the posterior chamber, through the pupil, the fluid enters the anterior chamber - a space limited in front by the posterior surface of the iris and lens. Due to the valve action of the pupillary edge of the iris, moisture cannot return from the anterior chamber back to the posterior chamber. Next, the waste aqueous humor with tissue metabolic products, pigment particles, and cell fragments is removed from the eye through the anterior and posterior outflow tracts. The anterior outflow tract is the Schlemm's canal system. Fluid enters Schlemm's canal through the anterior chamber angle (ACA), an area limited anteriorly by trabeculae and Schlemm's canal, and posteriorly by the root of the iris and the anterior surface of the ciliary body (Fig. 5).

The first obstacle to aqueous humor leaving the eye is the trabecular apparatus.

Aqueous humor is produced by the ciliary body, enters the posterior chamber of the eye, and then passes through the pupil into the anterior chamber. On the anterior wall of the angle of the anterior chamber there is an internal scleral groove through which the crossbar is thrown - trabecula. The trabecula looks like a ring and fills only the inner part of the groove, leaving a narrow gap outward - scleral sinus (Schlemm's canal). Aqueous humor seeps through the trabecula into Schlemm's canal and flows out from there through 20-30 thin collector tubules V intra- and episcleral venous plexuses. The latter are the final point of outflow of intraocular fluid.

The fluid is continuously produced by the ciliary crown with the active participation of the non-pigmented retinal epithelium and, in smaller quantities, in the process of ultrafiltration of the capillary network. Moisture fills the posterior chamber, then enters the anterior chamber through the pupil (it serves as its main reservoir and has twice the volume of the posterior chamber) and flows mainly into the episcleral veins through the drainage system of the eye, located on the anterior wall of the angle of the anterior chamber. About 15% of the fluid leaves the eye, seeping through the stroma of the ciliary body and sclera into the uveal and scleral veins - the uveoscleral outflow pathway of the fluid. A small part of the liquid is absorbed by the iris (like a sponge) and the lymphatic system.

Regulation of intraocular pressure. The formation of aqueous humor is under the control of the hypothalamus. A certain influence on secretory processes is exerted by changes in pressure and the rate of blood outflow in the vessels of the ciliary body. The outflow of intraocular fluid is regulated by the ciliary muscle – scleral spur – trabecula mechanism. The longitudinal and radial fibers of the ciliary muscle are attached to the scleral spur and trabecula with their anterior ends. When it contracts, the spur and trabecula move posteriorly and inwardly. The tension of the trabecular apparatus increases, and the openings in it and the scleral sinus expand.