Anatomy, Physiology, and Pathology of the Organs of Hearing, Vision, and Speech - Shvetsov A.G. 2006

Anatomy, Physiology, and Pathology of the Visual Analyzer
Pathology of the Visual Analyzer
Retinal Pathology

It is associated with diffuse and localized opacities, hemorrhages, and pigmentations of the retina. Objectively, retinal pathology is established only during fundus examination, while indirectly it manifests as a decrease in central and peripheral vision, impaired Color Vision, impaired dark adaptation, and visual field defects. Their nature and severity depend on the localization and extent of the pathological process.

Retinal developmental anomalies that severely impair its photosensitive function are extremely rare (e.g., retinal albinism) and are congenital in nature.

The most common causes of a sharp decline in, or even loss of, visual function are retinal detachment, retinal contusion edema, tears and dialyses, and hemorrhages into its layers.

Primary retinal detachment occurs in approximately 1 in 10,000 people and, without Treatment (usually surgical), leads to blindness. Its causes can include retinal inflammation and dystrophy; retinopathies of various origins; degenerative ischemic Changes in the peripheral retina combined with elongation of the globe in high axial myopia; vitreous shrinkage; indirect bodily trauma (falls, HEAD injuries, sudden heavy lifting, etc.), and others. An indispensable prerequisite for primary retinal detachment is a breach of its integrity, i.e., a tear, which can vary greatly in size, followed by the penetration of fluid beneath it.

Secondary retinal detachment is much more common and occurs As a result of various inflammatory eye diseases, neoplasms, penetrating eye injuries, and retinal vascular lesions due to comorbidities (diabetes, Hypertension, Preeclampsia, etc.). Complaints of vision loss in retinal detachment depend on its localization and extent.

Retinal Circulatory Disorders play a major role in its pathology. As a result of spasm or occlusion of a Blood vessel, partial or complete vision loss occurs suddenly, with subsequent incomplete recovery. In retinal vein occlusion, visual acuity does not decrease as sharply as in arterial occlusion. Patients complain of flashes of light and a gradual increase of fog before their eyes. The resulting severe congestion leads to multiple small hemorrhages throughout the fundus, especially in the optic disc area. Developing edema and optic atrophy can lead to permanent vision loss. Dystrophic changes of the retina (retinal dystrophies) are characterized by a gradual loss of visual acuity and peripheral vision. One of the first symptoms of this hereditary disease is night blindness. Retinal degeneration (dystrophy) is a common pathology in the elderly, but in children, it is a relatively rare phenomenon, usually of a congenital or hereditary nature. Their course is slow but progressive; they lead to low vision and blindness. The process is irreversible.

Retinitis pigmentosa is characterized by so-called nyctalopia ('night blindness'), i.e., a sharp deterioration of visual Functions at dusk. Objective Examination of such patients reveals a narrowing of the visual field boundaries and a sharp decrease in dark adaptation. It is a hereditary disease, usually associated with Hearing loss and endocrine disorders (dwarfism, obesity, intellectual disability).

Retinal inflammation (retinitis) occurs due to bloodborne infection in Sepsis, involvement of the choroid itself due to tuberculosis, rheumatism, Toxoplasmosis, etc., traumatic eye injuries, or exposure of the eyes to ultraviolet or ionizing radiation.

Retinal opacities (retinopathies) can occur either independently or as a result of Metabolic Disorders of a neurocirculatory nature, such as in diabetes, inflammatory Kidney diseases, or hypertension. Patients complain of decreased visual acuity and dark spots before their eyes, although externally the eyes of such people appear quiet and the refractive media are clear. Most often, retinopathies are detected during objective fundus examination, presenting a characteristic pattern of pathological retinal changes.

Color vision deficiency, in the form of its complete absence (color blindness) or impaired color perception (color anomaly), is caused by a decrease in the sensitivity of one of the receptor types. Congenital color vision deficiencies are more common in men. They are usually stable, present in both eyes, and inherited. Most often, sensitivity is reduced to red or green. Congenital color vision disorders are commonly referred to as Daltonism, named after the English scientist John Dalton, who suffered from red color blindness and described this phenomenon. About 8% of men and 0.5% of women worldwide suffer from color blindness.

Congenital color vision deficiencies are not accompanied by impairment of other visual functions. Individuals suffering from this condition usually have no complaints, and their color vision deficiencies are detected only during specialized testing.

Acquired color vision disorders occur in inflammatory or dystrophic Diseases of the retina, Optic nerve, or Central Nervous system. They can be observed in one or both eyes, are usually accompanied by impaired perception of all three primary colors (red, yellow, blue), and occur in combination with other visual function disorders. Acquired color vision disorders can manifest as:

§ xanthopsia — seeing the surrounding world only in yellow (in jaundice, poisoning with certain substances and medications);

§ cyanopsia — perceiving the surrounding world in blue (for example, after cataract removal);

§ erythropsia — perceiving the surrounding world in red (after cataract removal, or during prolonged fixation of gaze on a bright light source rich in ultraviolet rays);

§ chloropsia — perceiving the surrounding world in green (in case of poisoning with certain medications or nicotinic acid).

Unlike congenital color vision deficiencies, which are permanent, acquired disorders normalize as the underlying disease that caused them is cured.

In complete color blindness, a person perceives the world in shades of gray. Contemplating the diverse colors of nature, paintings, color photographs, color films, and color television brings aesthetic pleasure. Impairments in color perception primarily impoverish the emotional aspect of vision, which in children affects The Development of the psycho-emotional sphere.

Color discrimination helps us better understand the world around us. Without it, traffic control and many color-based studies, including those in medicine, would be impossible. Even a person's productivity and well-being depend on the color scheme and lighting of the rooms where they work, live, Sleep, etc.

An essential component of good vision is the full range of coordinated Eye Movements. Each eye must be able to track a moving object and easily and accurately change its point of fixation. Since tracking ability depends on the clarity of the image of the observed object, an eye with refractive errors usually becomes a poor observer. Impairments in Eyeball movement can be caused by changes both within THE EYE AND in other PARTS OF THE visual analyzer.