Structures of the eye and visual impairment during their lesions
Cornea — this is basic refractive surface of the eye. Surface of the cornea due to the nature of their structure and location is very sensitive to the effects. Therefore is possible next pathological conditions:
- corneal damage from the environment - direct trauma, drying, radiation and ionizing radiation;
- corneal damage by infectious agents - bacteria, viruses, especially herpes simplex virus and herpes zoster, fungi, parasites;
- damage of the cornea by inflammatory processes, sometimes in combination with common skin diseases - atopic dermatitis, scarring pemphigoid and erythema multiforme (Stevens-Johnson syndrome).
Inflammation and infection of the cornea called keratitis. Keratitis often accompanied by inflammation of the iris (iritis) or uveal tract, iris ciliary body and choroid (uveitis).
Being on the outer surface of the eye, the cornea is most susceptible to injury, dryness, infection.
Keratitis (cornea inflammation), in conjunction with uveitis (uvea inflammation) or iritis (iris inflammation) is usually observed with Reiter's disease (a consequence of Chlamydia trachomatis) and in some cases of Behcet's disease. Keratitis (cornea inflammation) and uveitis (uvea inflammation) can also occur in the case of herpes simplex lesions, sarcoidosis and collagen diseases.
Metabolic diseases in humans can also lead to of the cornea clouding, as it deposited substances present in excess in the patient's body:
- in the secondary hypercalcemia with sarcoidosis, hyperparathyroidism, or poisoning of vitamin D - phosphate and calcium carbonate is deposited beneath the epithelium of the cornea in the eye slit projection - the so-called band keratopathy;
- cystine crystals are deposited in the cornea during cystinosis;
- cholesterol esters are deposited in the cornea during hypercholesterolemia (gerontoxon);
- chloroquine crystals are deposited in the cornea during the treatment of discoid lupus erythematosus;
- polysaccharides are deposited in the cornea during the Hurler's disease;
- copper deposited in the cornea during hepatolenticular degeneration - Kayser-Fleischer ring.
In marked scarring and / or clouding of the cornea for the patient may be indicated operation keratoplasty (corneal transplant) to restore vision.
For the restoration of blurred vision in the case of corneal clouding is used the cornea transplant from a donor.
Pupil size determined by the intensity of light entering the eye. The size of the pupil identify the presence or absence of innervation of the eye trouble in various pathological conditions of the patient.
Normally mild asymmetry may occur pupils (anisocoria) of both eyes at the same time will have their reactions to light and accommodation. Pathologic anisocoria (pupil asymmetry) occurs in patients with lesions of the sympathetic (Horner's syndrome) or parasympathetic (internal ophthalmoplegia) innervation of the eye. Horner's syndrome is characterized by a normal reaction of constricted pupil to light on the affected side, partial ptosis, and in some cases, increased sweating on the face.
Internal ophthalmoplegia (III pair of cranial nerves) appears pupil dilation with no or weak response to light, after the instillation of a 1% solution of pilocarpine pupil narrows. Topical application of pilocarpine in different concentrations allows the physician to distinguish between paralysis of III pair of cranial nerves from mydriasis (pupil dilation), caused by the administration of drugs (atropine) or mystical pupil Eddie.
Depending on the size of the pupil and its reaction to light and accommodation, doctor neurosurgeon or neurologist can detect damage of the eye innervation in any disease case.
Glaucoma - a condition in which increased intraocular pressure (IOP). Increased intraocular pressure in glaucoma leads to damage to the optic nerve, part of the eyeball from the fundus. Intraocular fluid secreted by the epithelium of the ciliary body. Intraocular fluid provides metabolism in the lens and cornea, which lack their own blood vessels. The level of intraocular pressure (IOP) - the ratio between the rate of production of intraocular fluid and resistance to its outflow through the trabecular meshwork into Schlemm's canal and venous reservoirs. In most cases, the cause of glaucoma is not increased production of intraocular fluid, but the difficulty of its outflow from the anterior chamber of the eye.
Glaucoma takes the second place in the world among the causes of blindness. Glaucoma occurs in approximately 1 in 50 people over the age of 35 years. Most people already have glaucoma, unaware of its existence. Therefore, the detection of glaucoma, as well as measurement of blood pressure, is one of the necessary components during the inspection adult patients during routine medical examination. Measurement of intraocular pressure should bypass the eye exam. Intraocular pressure is elevated (IOP) when greater than 22 mm Hg.
In patients with glaucoma can be marked significant diurnal fluctuations in intraocular pressure (IOP), including in the normal range, so to confirm glaucoma is very important to examine the optic disc. Visual field loss is follows after progressive optic disc impression. This asymmetry of the optic nerve may be an early diagnostic sign of glaucoma. With the optic nerve damage, progression occurs nerve tissue death as result of its ischemia during compression. After that will develop atrophy of the optic nerve with the change of its contour (dent) and disc color (blanching).
Increased intraocular pressure in glaucoma leads to optic nerve damage, incoming the eyeball from the fundus.
Possible glaucomatous damage:
Optic nerve head
- Generalized depression
- Reduced color vision
- Cup-to-disc ratio >0.5
- Peripheral anterior synechiae
The main types of glaucoma, affecting the human eye include:
Open-angle glaucoma occurs as a complication of chronic difficulties reabsorption (suction) of intraocular fluid in the trabecular meshwork. Open-angle glaucoma occurs usually asymptomatic, but in rare cases develop pain in the eyeball and swelling of the cornea. Initially occurs loss of peripheral visual fields, visual acuity remains normal until late in the disease.
Open-angle glaucoma diagnosis made by detection of increased intraocular pressure (IOP) and the direct examination (gonioscopy) of the eye's anterior chamber angle. Clinical management of patients with open-angle glaucoma in the early stages is detailed re-examination with repeated measurements of intraocular pressure (IOP), visual field examination, a thorough inspection of the ocular fundus to identify the optic disc impressions.
Treatment of open-angle glaucoma begin with conservative methods. For the reduction of intraocular pressure (IOP) topically applied cholinergic drugs (pilocarpine or carbachol) and beta-blockers (timolol). Positive effect in the treatment of open-angle glaucoma may have diuretic medications - carbonic anhydrase inhibitors (diakarb).
In rare cases, there is a need of surgical treatment of open angle glaucoma. This prevents the development of persistent worsening of the patient eyesight. To do this, use the following steps:
- laser trabeculoplasty;
- form a fistula out of the anterior chamber in the subconjunctival space.
Initial approach to treatment of open-angle glaucoma:
Medical therapy first
Laser surgery first
Incisional surgery first
- Most patients
- Unlikely to tolerate medical therapy
- Same as for laser surgery but unlikely to respond to trabeculoplasty
Angle-closure glaucoma develops when the outflow of fluid hampered due to narrowing of the eye's anterior chamber. Tissue at the iris periphery is blocking the trabecular meshwork and obstructing output of intraocular fluid. Obstruction of the flow may occur suddenly, usually on one side. Patient's vision worsens. Chronic angle-closure glaucoma can lead to dilatation of the pupil, pain and loss of patient’s vision. In chronic and subacute angle-closure glaucoma is necessary to make a direct examination of the anterior chamber angle (gonioscopy) to determine the type of glaucoma.
The use of drugs that cause pupil dilation (mydriasis), may lead to the progression of closed-angle glaucoma. Since the restriction of the anterior chamber's angle causes the development of angle-closure glaucoma, so patients with age 50 years over should be carried out her examination (gonioscopy) before prescribing drugs that leads to mydriasis (i.e., pupil dilation).
Treatment of patients with acute angle-closure glaucoma requires urgent action. To reduce sharply increased intraocular pressure (IOP) are using preparations:
- intravenous injection - mannitol;
- parenterally - diakarb;
- pilocarpine or timolol administered topically.
After urgent measures may require surgical treatment of acute angle-closure glaucoma, it required creating connections between the front and rear chambers of the eye.
Congenital glaucoma - a rare form of open-angle glaucoma. Congenital glaucoma develops because of underdevelopment (dysplasia) of eye's anterior chamber angle. Congenital glaucoma can lead to blindness, increase the size of the eyeball and damage to the cornea. Early diagnosis of congenital glaucoma is essential for conservative and surgical treatment of this disease.
Secondary glaucoma develops as a complication of an existing patient or general disease as a local lesion of the eye. Among the common diseases and complications from taking drugs that may lead to the development of secondary glaucoma there are:
- blood diseases (leukemia, sickle cell anemia, Waldenstrom's macroglobulinemia);
- collagenosis (ankylosing spondylitis, rheumatoid arthritis, sarcoidosis);
- skin disease (allergic reactions to reception of corticosteroids, nevus of Ota);
- Infectious diseases (congenital rubella, onchocerciasis);
- metabolic disorders (amyloidosis, Weill-Marchesani syndrome);
- lesions of skeletal muscle (Conradi's disease, osteogenesis imperfecta);
- tumors (metastases in the trabecular meshwork);
- phakomatoses (neurofibromatosis, Sturge-Weber disease);
- lung disease (asthma, emphysema as a result of receiving corticosteroids);
- kidney disease (syndrome of Lowe - aminoaciduria), Wilms' tumor, a kidney transplant (as a result of receiving corticosteroids);
- drugs (amphetamine, corticosteroids, benzohexonium, reserpine, anticholinergics).
The local lesions of the eye, causing the development of secondary glaucoma in a patient, can be eyeball injury. Development of secondary glaucoma is also possible when the lens dislocation occurring in a patient with Marfan's syndrome or homocystinuria.
Cataracts - a clouding of the lens, which localized in its center (nuclear) in the superficial cortical region or in the posterior subcapsular region of the lens. Cataract develops in response to changes in the physical and chemical properties of environment inside the semipermeable capsule. Cataracts in origin can be congenital or acquired.
Cataracts - a clouding of the lens (normally it is transparent), which is inherited or occurs in aging, metabolism disorders, and trauma.
Congenital cataracts occur in patients with the following diseases:
- herpes simplex;
Acquired cataracts occur because of:
- the use of medications;
- metabolic disorders;
- elderly people (senile cataract).
Two types of cataracts detected in patients with diabetes mellitus:
- metabolic (like snow flakes);
Cataract by type of snowflakes commonly found in insulin-dependent diabetes. Development of snowflakes type cataract begins in the subcapsular region. Senile cataract develop in people with diabetes at an earlier age than in those who do not suffer from this disease, and mature faster.
Other metabolic disorders, often leading to the development of cataracts:
Cataracts, which are located in the rear part the lens, develops in more than one third of patients with myotonic dystrophy. Cataract formation in the posterior subcapsular region contributes to the systematic reception of corticosteroids. In addition to the development of cataract can cause the following diseases:
- chromosomal abnormalities (Alport’s syndrome, "cat crying" syndrome, Conradi’s disease, Crouzon's syndrome, Turner's syndrome);
- metabolism disease or nutritional disorders (aminoaciduria or Lowe’s syndrome, Fabry's disease, vitamin D hypervitaminosis, hypoparathyroidism, hypothyroidism, mucopolysaccharidosis, Wilson's disease);
- Infectious diseases (acquired cysticercosis, leprosy, onchocerciasis and toxoplasmosis);
- medication (corticosteroids, haloperidol and miotics).
Vision disorders in cataract appear by blurry vision with stored light perception, a doubling of the image (monocular diplopia), the change of color and decrease in visual acuity. Surgical removal of cataract can lead to full recovery of the patient.
Patients underwent cataract surgery for fully recover vision loss.
Lens luxation or subluxation (ectopia) occur in homocystinuria and Marfan syndrome. Under such conditions, the dislocation of the lens can accelerate the development of glaucoma.
With aging, the vitreous body undergoes significant physical and biochemical changes as the rest of the body's connective tissue.
In vitreous clouding types, the most common is benign "floating cloud." Benign "floating cloud" described by patients as a gray or white spots or elongated irregular objects moving at movement of the eyeballs.
Vitreous hemorrhage usually occurs from the retina vessels lumen and may distributed diffusely across the vitreous cavity. In the case of massive hemorrhage, vision will significantly reduce. Bleeding into the vitreous and membrane formation observed at the following diseases:
- diabetic retinopathy;
- in the case of retinal vein occlusion;
- in sickle cell retinopathy;
- in congenital anomalies of the retinal vessels;
- as a result of injuries;
- in discoid macular degeneration;
- in malignant melanoma of the choroid;
- subarachnoid hemorrhage in the case of traumatic brain injury or cerebral artery aneurysm rupture.
Asteroid hyalite (Benson's disease) characterized by formation in the vitreous body of tiny yellow clouding. These clouding composed of calcium soaps (palmitate and stearate). A similar condition, reflecting degeneration of the vitreous, may occur in patients with diabetes, as well as often in patients without obvious damage to the eyes. Vitreous clouding can take place in primary amyloidosis. When reticulosarcoma and retinoblastoma tumor cells can be detected, freely floating in the vitreous humor.
Vitrectomy surgery, the most important advance in the treatment of lesions of the vitreous body, used for cleaning vitreous opacities and reducing or preventing the vitreoretinal traction. In cases of suspected amyloidosis or reticulosarcoma useful information may be obtained by vitreous routine biopsy.
Lesions of choroid in clinical practice is rare.
For visualization of retina's blood vessels in a patient vein injected contrast agent, that enhances the visualization of the choroid.
If you have any questions, you can ask them to our neurosurgeon or neurologist: (499) 130–08–09
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