Glaucoma is a chronic eye pathology characterized by increased intraocular pressure, the development of optical neuropathy and impaired visual function. Clinically, glaucoma is manifested by narrowing of the visual fields, pain, pain and a feeling of heaviness in the eyes, blurred vision, deterioration of twilight vision, in severe cases blindness. Diagnosis includes perimetry, tonometry and tonography, gonioscopy, optical coherence tomography, laser retinotomography. Treatment requires the use of anti-glaucoma drops, the use of laser surgery methods (iridotomy (iridectomy) and trabeculoplasty) or anti-glaucomatous operations (trabeculectomy, sclerectomy, iridectomy, iridocycloretraction, etc.).
Glaucoma is one of the most formidable eye diseases that lead to vision loss. According to available data, glaucoma affects about 3% of the population, and 15% of blind people worldwide have glaucoma as a cause of blindness. At risk for the development of this disease are people over 40 years old, but in ophthalmology there are such forms of the disease as juvenile and congenital glaucoma. The incidence of the disease increases significantly with age: for example, congenital glaucoma is diagnosed in 1 out of 10-20 thousand newborns; in the group of 40-45-year–olds – in 0.1% of cases; in 50-60-year-olds – in 1.5% of cases; after 75 years – in more than 3% of cases.
Disease is understood as a chronic eye disease that occurs with a periodic or constant increase in IOP (intraocular pressure), disorders of the outflow of IOF (intraocular fluid), trophic disorders in the retina and optic nerve, which is accompanied by the development of visual field defects and marginal excavation of the OND (optic nerve disc). The concept of “glaucoma” today unites about 60 different diseases with the listed features.
The study of the mechanisms development allows us to talk about the multifactorial nature of the disease and the role of the threshold effect in its occurrence. That is, for the occurrence of glaucoma, it is necessary to have a number of factors that together cause the disease.
The pathogenetic mechanism is associated with a violation of the outflow of intraocular fluid, which plays a key role in the metabolism of all structures of the eye and maintaining normal IOP levels. Normally, the watery moisture produced by the ciliary (ciliary) body accumulates in the posterior chamber of the eye – a slit-like space located behind the iris. 85-95% of IOF flows through the pupil into the anterior chamber of the eye – the space between the iris and the cornea. The outflow of intraocular fluid is provided by a special drainage system of the eye, located in the corner of the anterior chamber and formed by the trabecula and the helmet canal (venous sinus of the sclera). Through these structures, IOF flows into the scleral veins. A small part of the watery moisture (5-15%) flows off in an additional uveoscleral way, seeping through the ciliary body and sclera into the venous collectors of the vascular membrane.
To maintain a normal IOP (18-26 mmHg), a balance between outflow and inflow of watery moisture is necessary. In glaucoma, this balance is disturbed, as a result of which an excessive amount of IOF accumulates in the eye cavity, which is accompanied by an increase in intraocular pressure above the tolerant level. High IOP, in turn, leads to hypoxia and ischemia of the eye tissues; compression, gradual dystrophy and destruction of nerve fibers, decay of retinal ganglion cells and eventually to the development of glaucoma optic neuropathy and optic nerve atrophy.
The development of congenital glaucoma is usually associated with eye abnormalities in the fetus (dysgenesis of the anterior chamber angle), injuries, eye tumors. Predisposition to the development of acquired glaucoma is present in people with burdened heredity for this disease, people suffering from atherosclerosis and diabetes mellitus, arterial hypertension, cervical osteochondrosis. In addition, secondary glaucoma can develop due to other eye diseases: hyperopia, occlusion of the central retinal vein, cataracts, scleritis, keratitis, uveitis, iridocyclitis, progressive atrophy of the iris, hemophthalmos, wounds and burns of the eyes, tumors, surgical interventions on the eyes.
By origin, primary glaucoma is distinguished as an independent pathology of the anterior chamber of the eye, drainage system and OND, and secondary glaucoma, which is a complication of extra- and intraocular disorders.
In accordance with the mechanism underlying the increase in IOP, closed-angle and open-angle primary glaucoma are distinguished:
- with closed-angle glaucoma, there is an internal block in the drainage system of the eye;
- with an open–angle shape, the angle of the anterior chamber is open, but the outflow of IOF is violated.
Depending on the level of IOP, glaucoma can occur in the normotensive variant (with tonometric pressure up to 25 mmHg) or the hypertensive variant with a moderate increase in tonometric pressure (26-32 mmHg) or high tonometric pressure (33 mmHg and higher).
In the course of glaucoma, it can be stabilized (in the absence of negative dynamics for 6 months) and unstable (with a tendency to changes in the field of vision and OND during repeated examinations).
According to the severity of the glaucoma process , there are 4 stages:
- I (initial stage) – paracentral scotomas are detected, there is an expansion of the optical disk, OND excavation does not reach its edge.
- II (stage of advanced) – the field of vision is changed in the parenteral part, narrowed in the lower and/or upper temporal segment by 10° or more; OND excavation is marginal.
- III (stage of advanced) – there is a concentric narrowing of the boundaries of the field of vision, the presence of marginal subtotal excavation OND is revealed.
- IV (terminal stage) – there is a complete loss of central vision or preservation of light perception. The OND condition is characterized by total excavation, destruction of the neuroretinal girdle and displacement of the vascular bundle.
Depending on the age of occurrence, congenital glaucoma is distinguished (in children under 3 years old), infantile (in children from 3 to 10 years old), juvenile (in people aged 11 to 35 years old) and adult glaucoma (in people over 35 years old). In addition to congenital glaucoma, all other forms are acquired.
The clinical course of open-angle glaucoma is usually asymptomatic. The narrowing of the field of vision develops gradually, sometimes progresses over several years, so often patients accidentally discover that they see only with one eye. Sometimes there are complaints of blurred vision, the presence of iridescent circles in front of the eyes, headache and aching in the brow area, decreased vision in the dark. With open glaucoma, both eyes are usually affected.
During the closed-angle form of the disease, there is a phase of preglaucoma, an acute attack of glaucoma and chronic glaucoma.
Preglaucoma is characterized by the absence of symptoms and is determined by an ophthalmological examination when a narrow or closed angle of the anterior chamber of the eye is detected. With preglaucoma, patients can see rainbow circles in the light, feel visual discomfort, short-term vision loss.
An acute attack of angle-closure glaucoma is caused by the complete closure of the angle of the anterior chamber of the eye. The IOP can reach 80 mmHg and higher. An attack can be provoked by nervous tension, overwork, drug-induced pupil dilation, prolonged stay in the dark, long work with a bowed head. With an attack of glaucoma, there is a sharp pain in the eye, a sudden drop in vision up to light perception, hyperemia of the eyes, dimming of the cornea, dilation of the pupil, which acquires a greenish hue. That is why the disease got its name for a typical feature: “glaucoma” is translated from Greek as “green water”. An attack of glaucoma can occur with nausea and vomiting, dizziness, pain in the heart, under the shoulder blade, in the abdomen. To the touch, the eye acquires a stony density.
An acute attack of angle-closure glaucoma is an urgent condition and requires an early, within the next few hours, reduction of IOP by medication or surgery. Otherwise, the patient may face complete irreversible loss of vision.
Over time, glaucoma takes a chronic course and is characterized by a progressive increase in IOP, recurrent subacute attacks, and an increase in blockage of the anterior chamber angle of the eye. The outcome of chronic glaucoma is glaucoma atrophy of the optic nerve and loss of visual function.
Early detection of glaucoma has an important prognostic value that determines the effectiveness of treatment and the state of visual function. The leading role in the diagnosis of glaucoma is played by the definition of IOP, a detailed study of the fundus and OND, a study of the field of vision, an examination of the angle of the anterior chamber of the eye.
The main methods of measuring intraocular pressure are tonometry, elastotonometry, daily tonometry, reflecting fluctuations in IOP during the day. Indicators of intraocular hydrodynamics are determined using electronic tonography of the eye.
An integral part of the examination for glaucoma is perimetry – determining the boundaries of the visual field using various techniques – isoptoperimetry, campimetry, computer perimetry, etc. Perimetry allows you to identify even the initial changes in the fields of vision that are not noticed by the patient himself.
With the help of gonioscopy in glaucoma, an ophthalmologist has the opportunity to assess the structure of the angle of the anterior chamber of the eye and the condition of the trabecula through which the outflow of IOF occurs. Informative data helps to get an ultrasound of the eye.
The OND condition is the most important criterion for assessing the stage of glaucoma. Therefore, the complex of ophthalmological examination includes ophthalmoscopy – a procedure for examining the fundus. Glaucoma is characterized by deepening and widening of the vascular funnel (excavation) OND. In the stage of advanced glaucoma, marginal excavation and discoloration of the optic nerve are noted.
A more accurate qualitative and quantitative analysis of structural changes in the OND and retina is carried out using laser scanning ophthalmoscopy, laser polarimetry, optical coherence tomography or Heidelberg laser retinotomography.
There are three main approaches to the treatment of glaucoma: conservative (medical), surgical and laser. The choice of therapeutic tactics is determined by the type of glaucoma. The objectives of drug treatment of glaucoma are to reduce IOP, improve blood supply to the intraocular optic nerve, normalize metabolism in the tissues of the eye. Anti – glaucoma drops by their action are divided into three large groups:
- Drugs that improve the outflow of IOF: myotics (pilocarpine, carbachol); sympathomimetics (dipivephrine); prostaglandins F2 alpha – latanoprost, travoprost).
- Agents that inhibit the production of IOF: selective and non-selective beta-blockers (betaxolol, betaxolol, timolol, etc.); a- and beta-blockers (proxodolol).
- Drugs of combined action.
With the development of an acute attack of angle-closure glaucoma, an immediate decrease in IOP is required. The relief of an acute attack of glaucoma begins with the instillation of myotic – 1% of pilocarpine according to the scheme and timolol, the appointment of diuretics (diacarb, furosemide). Simultaneously with drug therapy, distracting activities are carried out – setting cans, mustard plasters, leeches on the temporal region (hirudotherapy), hot foot baths. To remove the developed block and restore the outflow of IOF, it is necessary to perform laser iridectomy (iridotomy) or basal iridectomy by surgical method.
Methods of laser glaucoma surgery are quite numerous. They differ in the type of laser used (argon, neodymium, diode, etc.), the method of exposure (coagulation, destruction), the object of exposure (iris, trabecula), indications for conducting, etc. Laser iridotomy and iridectomy, laser iridoplasty, laser trabeculoplasty, laser goniopuncture are widely used in laser glaucoma surgery. In severe degrees of glaucoma, laser cyclocoagulation can be performed.
Anti-glaucomatous operations have not lost their relevance in ophthalmology. Among the fistulizing (penetrating) operations for glaucoma, the most common are trabeculectomy and trabeculotomy. Non-fistulizing interventions include non-penetrating deep sclerectomy. Such operations as iridocycloretraction, iridectomy, etc. are aimed at normalizing the circulation of IOF. In order to reduce the production of IOF in glaucoma, cyclocryocoagulation is performed.
Prognosis and prevention
It is necessary to understand that it is impossible to completely cure glaucoma, but this disease can be kept under control. At an early stage of the disease, when irreversible changes have not yet occurred, satisfactory functional results of glaucoma treatment can be achieved. Uncontrolled course of glaucoma leads to irreversible loss of vision.
Prevention consists in regular examinations by an oculist of persons at risk – with a burdened somatic and ophthalmological background, heredity, older than 40 years. Patients suffering from glaucoma should be registered with an ophthalmologist at the dispensary, regularly visit a specialist every 2-3 months, and receive recommended treatment for life.