Loss of vision is a disorder, also known as impairment or loss of ability to see, which cannot be eliminated with glasses and contact lenses . Ophthalmologists distinguish temporary loss of vision , when the symptoms are episodic and chronic - when irreversible changes have occurred with vision. For complete or almost complete loss of vision, the term blindness is used .
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Vision loss ranges
There are various scales for describing degrees of vision and loss of vision based on visual acuity . [1] In the first edition of the World Health Organization , the ICD describes a simple distinction between “legally sighted” and “legally blind”. [1] ICD-9, released in 1979, introduced the smallest continuous scale, which consisted of three levels: normal vision, poor vision, and blindness . [2]
Acute vision loss
Acute vision loss can have a sudden onset. It can be caused by clouding of refractive media, diseases of the retina , diseases of the optic nerve , visual pathway disorders or functional impairment, or it may be a sudden discovery of the fact of chronic vision loss.
Refracted Media Opacity
The opacity of the refractive media in the eyes, such as the cornea , the anterior chamber, the lens and the vitreous humor, can lead to acute loss of vision, resulting in blurred vision or decreased visual acuity. Although pupillary reflexes may be affected, these manifestations, as a rule, do not cause a defect in the relative afference of the pupils.
Causes of opacity include: corneal edema, hyphema , cataracts, and vitreous hemorrhage .
Retinal Diseases
Retinal diseases can lead to sudden loss of vision. Because if the retina is affected, then, as a rule, this is accompanied by a defect in the relative afference of the pupils. Reasons that affect or destroy the functioning of the retina include: retinal detachment ; degenerative diseases (for example, macular degeneration ); retinitis pigmentosa and vascular occlusion of the retina , the most important of which is occlusion of the central artery of the retinal artery. Modern research (2013) has brought closer the possibility of complete retinal regeneration. (see retinal regeneration )
Optic Nerve Damage
Diseases that affect the optic nerve can cause acute loss of vision. Symptoms include an abnormal pupil reflex, a pupil afference defect when the optic nerve lesion is unilateral. It can also be triggered with a strobe.
The condition of the optic nerve can depend on many diseases, including optic neuritis , papillitis , edema of the optic disc , glaucoma , ischemic optic neuropathy and arteritis of giant cells.
Hypoxia
The eye is very sensitive to oxygen restriction. Blurred vision ( brownout or greyout ) is accompanied by a loss of peripheral perception and may be the result of low blood pressure , shock , g-LOC (problems associated with aviation) or simply spontaneously, standing, especially if the patient is not completely healthy. Vision usually returns as soon as the causes that limit blood flow are eliminated.
Visual Disorder
Disorders of the visual pathways - any problems that may interfere with the functionality of the visual pathway. Rarely, acute visual loss causes homonymous hemianopsia and, even less commonly, cortical blindness.
In addition, traumatic causes can also lead to acute loss of vision.
Functional Disorder
The term functional disorder is currently used when the patient resorts to hysteria and simulation . This determines the inherent inability of the physician to identify the subjective experience of the patient (and thus determine whether the patient sees or not).
Notes
- ↑ 1 2 International Council of Ophthalmology. "International Standards: Visual Standards - Aspects and Ranges of Vision Loss with Emphasis on Popular Surveys." April 2002.
- ↑ World Health Organization. International Classification of Diseases, 9th Revision (ICD-9) , World Health Organization, Geneva, 1977.