Most people with good vision from birth, perceive it as a given and usually give little thought to its value.Valuing of human begins usually when first confronted with the limitations of their opportunities against the background of falling.
The fact that the lost opportunity to see clearly, often frustrating person, but usually not for long.If preventive measures or conservation efforts of some time and efforts, the situation will soon corrected or smoothed spectacle lenses, and prevention stops.
Perhaps only expensive surgery makes people more seriously to preserve the achieved surgical results.What are the causes of the fall?What situations can be dealt with in the normal manner, and which require urgent visit to the doctor and emergency?
options visual impairment
- Reduced visual acuity
- Double vision
- binocular vision Pathology fields of
- Disorders of color
Reduced sharpness of vision
Norma visual acuity for children, crossed the five-year milestoneand adults is 1.0.This means that the human eye is able to clearly distinguish between two points located at a distance of 1.45 meters, provided that the owner looks at them at an angle of 1/60 degree.
Clarity of vision is lost for myopia, hyperopia, astigmatism.These violations relate to refractive error, ie, a state where the image is projected onto the retina is.
Under myopia or nearsightedness realize a state where the light rays projected image to the retina.At the same distance vision deteriorates.Myopia can be congenital (against the background of an elongated eyeball, when there is a weakness or ciliary eye muscles) or acquired.Acquired myopia caused by unsustainable visual load (reading and writing in the supine position, while non-compliance with the best distance vision, with frequent eyestrain).
Basic pathology, leading to the acquisition of short-sightedness - a spasm of accommodation, increased corneal thickness, traumatic dislocation and subluxation of the lens and its multiple sclerosis in the elderly.Also, short-sightedness may be of vascular origin.The weak myopia is considered to minus three.High degree - from minus 3.25 to minus six.Anything more - severe myopia.Called progressive myopia, when its numbers are growing in the background stretching back of the camera eye.The main complication of severe myopia - exotropia.
- the inability to see near normal.Opticians call it hyperopia.This means that the image will be formed at the retina.
- congenital hyperopia is natural and is caused by a small longitudinal dimension of the eyeball.It can disappear as the child grows yl survive.In cases of an abnormally small eye size, the lack of curvature of the cornea or lens.
- Senile (when fall vision after 40) - a consequence of reducing the ability of the lens to change its curvature.This process goes through presbyopia step (first time in individuals between 30 and 45), and then the constant (after 50-60 years).
Age-related loss of vision after 65 is because the accommodation of the eye (the ability to adjust the curvature of the lens by the lens of human needs) is virtually absent.
This fault as the lens (losing elasticity or changing the curvature) and the ciliary muscle, which is no longer able to bend the lens properly.In the early stages of presbyopia can compensate for bright lighting.In the later stages and does not save it.The first manifestations of the pathology becomes impossible to read the font close ms comfortable distance vision (25-30 cm), subjects with fast motion blur looks from distant subjects to close.Farsightedness can be complicated by an increase in intraocular pressure.
in primitive explanation - a different visual acuity horizontally and vertically.In this case, any point is projected into the eye so that from it get blurred ellipse or eight.The pathology associated with impaired lens shape of the cornea or the entire eye.Besides blurred vision of astigmatism is accompanied by a doubling of objects, their vagueness, rapid eye fatigue.It can be combined with myopia (compound myopic) or farsighted (hyperopic complex), as well as being mixed.
This condition is called diplopia.When it visible object can be doubled horizontally, vertically, diagonally or two images are rotated relative to each other.Blame around the oculomotor muscles whose work is not synchronized and which do not allow the eyes to converge to the target as it should.Often muscle damage themselves or provide their nerves in systemic diseases begins with diplopia.
- Classical cause of double vision - Strabismus (divergent or convergent).This man did not manage to both the central fovea of the retina send strictly for the course.
- second typical pattern - alcohol poisoning.The toxic effect of ethanol frustrating combined movement of the eye muscles.
- Temporary diplopia repeatedly beat in the movies and cartoons: when struck on the head of the hero is often not just pouring from his eyes sparkle, and are leaving the picture before my eyes.
all examples binocular (two eyes) diplopia.
- Double vision in one eye may occur when too convex cornea, lens subluxation, when struck calcarine sulcus of the occipital region of the cerebral cortex.
Disorders of binocular vision
ability to see two eyes allows a person to expand the field of view by 40% to improve its clarity, see the three-dimensional object, assess its approximate size and shape.This stereoscopic vision.Another of its important purpose - to estimate the distance.If one eye does not see, or the difference in the eyes of a few leaves dioprtry weaker eye which can cause diplopia begins to forcibly turn off the bark from the process view.
first lost binocular vision, and then the weak eye can and does go blind.In addition to nearsightedness and farsightedness with a large difference between the eyes to podlobnomu phenomenon leads uncorrected astigmatism.It is the failure to assess the distance without spectacle correction forces driving many to use glasses or lenses.
more often absent binocular vision in strabismus.Frankly, the perfect balance between the position of the eyes, there is almost no one, but because even with deviations in muscle tone binocular vision is maintained, it does not require correction.If the convergent divergent vertical squint or deprives a man of vision with two eyes, we have to have surgery, or at best to wear sunglasses.
distortion of visual field
fixed eye visible part of reality - is the field of view.In spatial terms, this is not the field, but rather a 3D hill on top of which the highest visual acuity.The deterioration of the foot over the hill near the nose and smaller in the temporal.Limited field of view of the anatomical projections of the facial skull and the optical layer - features of the retina.
For white normal field of vision are: inwards - 55 degrees up - 50 down - 65, outwards - 90. (see field of view image.).
for one eye field of view is divided into two vertical and two horizontal half.
change the field of view may be the type of cattle (dark spots) in the form of concentric ilil local restrictions (hemianopsia).
- scotoma - this is the spot in which nothing can be seen, if it is absolute or seen blurry if it is relative.It can be mixed with absolute scotoma black inside and on the periphery of relativity.Positive scotoma is felt by the patient.Negative detected only at inspection.An example of a physiological scotoma - a blind spot Mariotte in the outer part of the visual field (the projection of the optic disc, where there are no cones and rods).
- atrophy of the optic nerve - loss in the central part of the field talk about the degeneration macular or optic nerve atrophy, often age.
- Detachment of the retina - if you would like a curtain fences off the peripheral part of the visual field with a hand, it is a question most likely of retinal detachment (then there may be a distortion of lines and shapes, floating image).Detachments The reasons are the high degree of myopia, trauma or degeneration of the retina.
- bilateral loss of external halves fields - a frequent sign of pituitary adenomas, interrupting the optic tract in the place of crossing.
- Glaucoma drop half the fields close to the nose.They can be combined with a rainbow at the sight of the light mist in the eyes.The same loss occurs in pathologies neperekreshchennymi fiber optic chiasm in the field (for example, an aneurysm of the internal carotid artery).
- Cross-loss pieces fields (for example, an internal one side and the other outdoor) is more common in tumors, hematomas or inflammatory processes in the central nervous system.In addition to the half field may fall and a quarter (quadrant hemianopsia).
- If precipitation in the form of a translucent curtain - is evidence of changes in the transparency of the eye media: the lens, cornea, vitreous body.
- pigment degeneration of the retina gives concentric narrowing of visual fields or tubular vision.In the center of the field there is a high visual acuity and peripherals nearly falls.If concentric vision develops evenly, the blame for this probably glaucoma or cerebrovascular accident.Concentric narrowing is characteristic for peripheral chorioretinitis (inflammation of the posterior section of the retina).
Deviations in color perception
- blindness - did not realize sick birth defect distinguishing red and green.Most often diagnosed in men.
- time shift in the perception of white - a consequence of surgery to remove the cataract affected lens.Can develop shifts toward blue, yellow, red colors, ie white to bluish.yellowish reddish like unregulated monitor.
- after cataract surgery may change the brightness and color : blue becomes more saturated, while yellow and red fade, fade.
- shift perception toward longer wavelengths (yellow, red objects) may indicate retinal degeneration or optic nerve.
- discolors the items under the old macular degeneration, which is no longer progressing.
most common disorders affecting the central part of the color visual field (within 10 degrees).
In the absence of the eye (or congenital) acquired, with full detachment of the retina, optic nerve atrophy blindness called amovrozom.If the eye has seen previously suppressed bark on the background of strabismus, a big difference in diopters between the eyes, with eyes opacity environments syndromes Kaufmann and Ben Tre, ophthalmoplegia with strong ptosis (lowering century), developing amblyopia.
Causes of visual impairment
- Changes transparency eye media (cornea pathology of the lens).
- Muscle pathology
- Abnormalities in the retina
- lesions of the optic nerve
- Abnormalities in cortical center
Normally transparent medium of the eyeball (cornea, lens, vitreous body) is passed and refract the rays of light like a lens.Under pathological infectious and inflammatory, autoimmune or degenerative processes in these lenses change their degree of transparency, which becomes an obstacle in the path of light rays.
Pathology of the cornea, lens
keratitis - inflammation of the cornea.Bacterial often becomes a complication of untreated conjunctivitis, a consequence of infection during eye surgeries.Especially dangerous Pseudomonas aeruginosa, which often led to cases of mass outbreaks of keratitis in ophthalmic hospitals with inadequate aseptic and antiseptic (more on Pseudomonas aeruginosa and its treatment).
- for pathology characterized by clouding, corneal ulceration, pain and redness in the eye.
- Also present photophobia.
- Tearing and decreased corneal shine up to the formation of an opaque whiteness.
More than half of viral keratitis accounts for a share of herpes (keratitis tree).In the eye of a branch of a tree is seen damaged nerve trunk.Creeping corneal ulcer - the outcome of herpetic lesions or chronic injury corneal foreign bodies.Often it leads to ulcers amoebic keratitis, which suffer lovers of cheap low-quality lenses and those who do not comply with hygiene rules lens use.
When the eye "fired" by welding or watching the sun naked eye, develops photokeratitis.Apart from ulcerative keratitis is non-ulcer.The disease may affect only the superficial layers of the cornea or be profound.
corneal opacities - is the result of inflammation or degeneration, cataract - a scar.Opacities in the form of clouds or patches decrease visual acuity, causing astigmatism.Walleye limits vision to light perception.
Cataracts Cataracts - a clouding of the lens.At the same time it disturbed metabolism, structural proteins are destroyed, lost elasticity and transparency.Congenital disease - the result of viral, autoimmune or toxic effects on the fetus in utero or genetic abnormality.
Sold clouding of the lens, as age dystrophy, the result of mechanical or chemical injury, radiation exposure, poisoning mothballs ergot, vapors of mercury, thallium, trinitrotoluene).Posterior subcapsular cataract - a lot of people over 60, who are quickly losing sight nuclear gradually increases the degree of myopia, age makes the surrounding cortical vague.
vitreous opacities (its destruction) is perceived by the patient as a thread or point of floating before the eye when moving sight.This is due to the thickening and loss of transparency of the individual vitreous fibers that develop with age degeneration, hypertension and other vascular disease, diabetes mellitus, when hormonal changes or treatment with glucocorticoids, blurred perceived as a simple or complex (webs, beads, plates) figures.Sometimes portions perceived retina degeneration, and then flashes occur in the eyes.
vision depends on the ciliary and eye muscles.The disorder impairs their performance and vision.The whole range of the eyeball movements provide a total of six muscles.They are stimulated by 6, 3 and 4 pairs of nerves traumatic brain area.
ciliary muscle helps bend the lens to be involved in the outflow of intraocular fluid and stimulates blood flow to certain parts of the eye.Violate muscles work vascular spasm in the brain vertebro-basilar basin (eg, vertebral artery syndrome in osteochondrosis), hypothalamic syndrome, scoliosis of the spine, and other causes of cerebral blood flow disorders.The reason may be, and traumatic brain injury.This leads initially to a spasm of accommodation, and then to the development of myopia.In some works of local ophthalmologists revealed the relationship between cervical spine injuries during childbirth and fruit development in children of early forms of acquired myopia.
oculomotor nerve and the muscles responsible for eye movement
oculomotor nerves regulate not only the muscles that control the eyeball, but also the muscles, narrowing and expanding the pupil, as well as the muscle that lifts the upper eyelid.