Retinal diseases

Retinal diseases are very diverse. Retinal diseases are caused by the impact of various factors leading to pathological and pathological physiological changes, which in turn determines visual function disorders and the presence of characteristic symptoms. Among retinal diseases, hereditary and congenital dystrophies, diseases caused by infections, parasites and allergic agents, vascular disorders and tumors are distinguished. Despite the diversity of retinal diseases, pathological and pathological physiological manifestations may be similar in different nosological forms.

Pathological processes observed in the retina include dystrophies, which can be genetically determined or secondary, inflammation and edema, ischemia and necrosis, hemorrhages, deposition of hard or soft exudates and lipids, retinoschisis and retinal detachment, fibrosis, proliferation and formation of neovascular membranes, hyperplasia and hypoplasia of the pigment epithelium, tumors, angioid streaks. All these processes can be detected by ophthalmoscopy of the fundus.

The retina has no sensitive innervation, so pathological conditions are painless. Subjective symptoms in retinal diseases do not have any specificity and are associated only with dysfunction, which is typical for diseases of not only the retina, but also the optic nerve. Depending on the localization of the pathological process, the function of central vision, peripheral vision is impaired, limited loss in the field of vision (scotomas) are detected, and dark adaptation is reduced. There are no painful sensations with damage to the retina.

The ophthalmoscopic picture in retinal diseases essentially consists of four elements:

1. changes in blood vessels, their walls, caliber, and their course in the retina;
2. hemorrhages in different layers of the retina;
3. opacities of the normally transparent retina in the form of diffuse, large areas or limited white spots - foci;
4. retinal pigmentation in the form of small dots and large dark spots.

Inflammatory diseases of the retina (retinitis, retinovasculitis). Inflammatory processes in the retina (retinitis) never occur in isolation due to the close contact of the retina and the choroid. Having begun as retinitis, the process quickly spreads to the choroid and vice versa, therefore, in clinical practice, chorioretinitis and retinovasculitis are observed in most cases.

Retinal diseases are caused by various endogenous factors, such as:

1. infections (tuberculosis, syphilis, viral diseases, purulent infections, toxoplasmosis, parasites);
2. infectious and allergic processes in the retina (rheumatism, collatenosis);
3. allergic reactions;
4. blood diseases.

Retinovasculitis is divided into primary and secondary. Primary ones develop in the retina as a result of a general allergic reaction without previous general ocular manifestations.

Secondary - a consequence of some inflammatory process (uveitis). The retina is involved secondarily.

Various etiological factors causing inflammatory changes in the posterior pole of the fundus cause multifocal involvement of the retina and choroid in the pathological process.

Often, the ophthalmoscopic picture of the fundus plays the main role in diagnosis, since there are no specific diagnostic laboratory tests to identify the cause of the disease.

Acute and chronic inflammatory diseases of the retina are distinguished. Anamnestic data are very important for establishing a diagnosis. Histologically, the division of the inflammatory process into acute and chronic is based on the type of inflammatory cells found in tissues or exudate. Acute inflammation is characterized by the presence of polymorphonuclear lymphocytes. Lymphocytes and plasma cells are detected in chronic nematous inflammation, and their presence indicates the involvement of the immune system in the pathological process. Activation of macrophages and giant inflammatory cells is a sign of chronic granulomatous inflammation, so immunological studies are often essential not only for establishing a diagnosis, but also for choosing treatment tactics.

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Symptoms of retinal diseases

1. Decreased central vision is the main symptom. Patients with macular disease report impaired central vision, which is confirmed by perimetry (positive scotoma). In contrast, with optic neuropathy, patients do not complain of changes in the visual field (negative scotoma).
2. Metamorphopsia (distortion of the perceived image) is a common symptom of macular pathology. It is not typical for optic neuropathy.
3. Micropsia (a decrease in the size of the perceived image compared to the actual one) is a rare symptom caused by the “rarefaction” of the foveal cones.
4. Macropsia (an increase in the size of a perceived object compared to the actual one) is a rare symptom caused by “crowding” of the foveal cones.

Impaired color vision is a common symptom of early stage optic nerve diseases, but it is not typical for mild forms of macular pathology.

Vision decreases, metamorphopsia, macropsia, micropsia, and photopsia are observed.

In peripheral vision - scotomas of various localizations. If the lesion is located on the periphery, then hemeralopia is typical. There is always a lesion (a cluster of cellular elements) on the fundus. If the lesion is localized in the outer layers, a small pigment deposit may occur in the com. If the lesion is located in the inner layers, then the optic nerve disc may be involved in the process (edema, hyperemia).

With rhinosculitis, the transparency of the retina is impaired, and swelling of the interstitial substance occurs in the area of the lesion. Hemorrhages may appear in the pre-retinal layers - large, massive. This is the so-called "inverted bowl syndrome". If in the inner layers the hemorrhages look like a streak, then in the outer layers they are deep - in the form of dots. The appearance of pigment in the lesion area indicates chorioretinitis (i.e. the vascular membrane is affected).

If the retinal vessels are involved, retinovascular disease occurs.

The inflammatory process of arteries is called arteritis. There are endoarteritis, periarteritis, panvasculitis.

Endoarteritis is a thickening of the arterial wall. The lumen of the vessels is narrowed, the blood flow is slowed, sometimes complete obliteration occurs, and ischemic edema occurs.

Periarteritis - the cuff (loose accumulation of exudate) around the vessel becomes inflamed. It covers the vessel, so it cannot be traced along its entire length.

Panarteritis - all vessel walls are affected.

Thus, changes in the retina occur as a consequence of damage to its vessels, especially capillaries. The most common pathological changes in the vessels of the retina are atheromatosis, atherosclerosis, inflammatory changes in the walls of the vessels and dystrophic disorders.

In atheromatosis and atherosclerosis, the walls of the arteries thicken, the lumen narrows, the strip of translucent blood flow becomes thinner, and the white stripes (the walls of the artery) widen, the color of the blood through the thickened wall seems yellowish (the arteries resemble copper wire). Strongly thickened walls of the arteries, especially third-order arteries, become opaque, the blood flow does not shine through, they resemble a shiny silver wire. In atherosclerosis, the walls of the arteries become denser, and in the places of crossing, where the artery lies on the vein, the artery squeezes the vein and disrupts the blood flow in it. Atherosclerotic changes in the walls of the vessels are uneven, as a result of which small aneurysms are formed in places along the course of the vessels. The capillaries also change and at first begin to allow formed elements of blood and plasma to pass into the layers of the retina, and later become completely obliterated.

In periphlebitis, veins are surrounded by delicate opacities in the form of cuffs, dressing the vessel to a greater or lesser extent. The outer layers of the vein grow due to inflammatory infiltration with subsequent organization into connective tissue adhesions. The caliber of the vein becomes uneven, in places the vessel disappears, hiding in inflammatory infiltration or in the connective tissue adhesions. When the wall of the vein is destroyed, hemorrhages appear in the vitreous body, sometimes so significant that ophthalmoscopy is impossible.

Retinal hemorrhages

Vascular lesions are accompanied by hemorrhages in the retina. Depending on the shape and size of the hemorrhages, it is possible to determine the localization of hemorrhages in the layers of the retina. When blood flows into the outer or middle layers of the retina, the hemorrhage has the form of small circles, since it occupies the space between the glial supporting fibers in the form of columns perpendicular to the plane of the retina, which in its plane look like round spots. When hemorrhages pass from the capillaries into the inner layer - the layer of nerve fibers, the blood is distributed along these fibers and has the form of streaks. Around the central fovea, as well as around the optic disc, hemorrhages into the inner layers are located in radial stripes. Blood from large vessels, the innermost layers of the retina, flows out between the retina and the vitreous body in the form of a large (4-5 diameters of the optic nerve disc) round “puddle”, the upper part of which is lighter due to the accumulation of blood plasma, and the lower part is darker due to the descended clot with formed elements, which often forms a horizontal level.

Types of retinovasculitis:

1. hemorrhagic - hemorrhages and external circulation in the retina;
2. exudative - exudation phenomena predominate;
3. proliferative - the outcome of angiitis, which is accompanied by circulatory disorders (ischemia gives impetus to proliferation - the formation of connective tissue). The prognosis is severe.

Diagnosis of retinal diseases

1. Visual acuity is the most important test of the state of macular function and is extremely quick to perform. In patients with macular pathology, visual acuity is often lower when using the diaphragmatic opening.
2. Biomicroscopy of the fundus with a contact or strong convex lens allows for a good view of the macula. Monochromatic light is used both for general ophthalmoscopy and for detecting the most subtle disorders. The use of green (red-free) light allows for the detection of superficial retinal damage, folding of the internal limiting membrane, cystic edema, and subtle contours of serous neurite detachment. Lesions of the retinal pigment epithelium and choroid are best detected in the light of the final part of the red spectrum.
3. The Amsler grid is a test that evaluates the central 10 fields of vision in screening and monitoring macular diseases. The test consists of 7 cards, each containing a square with a side of 10 cm:
   • Map 1 is divided into 400 small squares with a side of 5 mm, each of which is perceived at an angle of 1 when the grid is presented from a distance of 1/3 meter;
   • Map 2 is similar to Map 1, but has diagonal lines to help a patient with low vision focus their gaze;
   • Map 3 is identical to Map 1 but contains red squares. The test helps to identify color vision disorders in patients with optic nerve diseases;
   • Map 4 with randomly located dots is rarely used;
   • Map 5 with horizontal lines is designed to identify metamorphopsia in a specific meridian, which allows for an objective assessment of such a complaint as difficulty reading;
   • Map 6 is similar to Map 5, but has a white background and the central lines are closer together;
   • Map 7 contains a finer central grid, each square of which is perceived at an angle of 0.5. The test is more sensitive. The testing is carried out as follows:
   • the patient, if necessary, puts on reading glasses and closes one eye;
   • The patient is asked to look directly at the central dot with one eye open and report any distortions, blurry lines, or solid spots anywhere on the grid;
   • Patients with maculopathy often report that the lines are wavy, whereas in optic neuropathy the lines are not distorted but are often absent or become fuzzy.
4. Photostress. The test can be used in the diagnosis of macular pathology with unclear ophthalmoscopic picture and in the differential diagnosis of maculopathy and optic neuropathy. The test is performed as follows:
   • correction of distant visual acuity is mandatory;
   • the patient observes the light of a penlight or indirect ophthalmoscope from a distance of 3 cm for 10 seconds;
   • the recovery time after photostress is equal to the time required for the patient to read any three letters from the line read before the test. Normally - 15-30 sec;
   • The test is then performed on the other, presumably healthy eye and the results are compared.

The recovery time after photostress is prolonged compared to a healthy eye in macular pathology (sometimes 50 seconds or more), but is not typical for optic neuropathy.

5. The pupillary reaction to light in diseases of the macula is usually not impaired, but with mild damage to the optic nerve, impaired consensual pupillary reaction to light is an early symptom.

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