MINISTRY OF HEALTH OF THE REPUBLIC OF UZBEKISTAN
MEDICAL EDUCATION DEVELOPMENT CENTRE
TASHKENTMEDICALACADEMY
“Approved”by
Prorector on the academic work
Prof. Teshaev O.R.
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«_____»______2011 у.
Chair: EYE DISEASEES
Subject: OPHTHALMOLOGY
THEME:
Diseases of a vascular layer. A cataract.
(Forteachersand students of the higher medical institutions)
Educational-methodical workbook
(For teachers and students of medical HIGH SCHOOLS)
Tashkent-2011.
Authors:Abdurakhmanova U.M. -the assistant at eye diseasees chair
ТМА.
Reviewers:
Professor Karimova M. H. – the deputy director on scientific work of the EyeMicrosurgeryCenter
Yangieva N.R. – the senior lecturer of chair of Eye Deseases of the ТМА
THEME:Diseases of a vascular layer. A cataract.
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1.THE PLACE OF CARRYING OUT OF EMPLOYMENT
- Chair of eye diseasees;
-Thematic patients, magnifier 13 D, a desk lamp, ophthalmoscope, anti-inflammatorydrugs, antibiotics, midriatics, slides, video films
- slidoscope, TV-video.
2. Duration of the lesson
- 6 hours
3.The purpose
It is necessary to know such pathologies of organ of vision, as diseases of vascular layer and a cataract for doctors of any specialties. Very often it is local displayof many general diseases of an organism: rheumatism, diabetes, tuberculosis, chronic andacuteinfectious diseases, a thyroid gland pathology etc. Doctors should be ableto diagnose and treatpatients with the pathology. It is necessary as to be able to carry outpreventive measuresof the possiblecomplicationsarising at these diseases.
Problems
The student should know:
- Classification of diseases of vascular layer and cataract;
-Aethiopathogenesis and diagnostics of diseases of vascular layer and cataract;
- Clinic and principles of treatment of diseases of a vascular layer and a cataract;
- Complication and prophylaxisof diseases of vascular layer and cataract.
The studentshould be able:
Practicalskill – eyeball external examination, measurement of intraocular pressure by palpation.
4. Motivation
Diseases of vascular layer (iridocyclitis, chorioiditis) are frequentreasons low vision and blindnesses. Lens-dystrophic diseases leadto inpairementof properties of a crystalline lens - a transparency. Cataract are accompanied by sightfall, up to light sense. Low sight, as a rule, conducts to development of nistagmus and to a squint, and also to ambliopy. Unfortunately, cataract, is the most frequent reason of invalidisation of patients from the part of organ of vision.
The theme will allow students to acquire the basic signs of disease of lens and vascularlayer, their early diagnostics, ethiologic treatment and prophylaxisof complications and physical inability of patients.
5. Intersubject and intrasubject relations
Knowledge of students on the given theme should be characterised by sufficient width and depth, and also interpretation with related subjects on «verticals andhorizontals». The theme is integrated on a vertical with anatomy its section «nervous system andsense organs», with physiology – its section «physiology of nervous system», with histology –sections«ontogenesis and histology of nervous system and sense organs», with deontology – questionsof mutual relations of patients and doctors, with medical history, including ophthalmologicalhistory, withpharmacotherapyin ophthalmology.
Across the ophthalmology is related to:
- Otolaryngology (the anatomic neighbourhood and bilateral relation at various ENTpathology and eye diseases);
- With infections and their possible complications from the visual analyzer;
- With internal diseasees (diseasees of blood and kidneys, collagenoses andothersvarious combined diseases with defeats of the visual analyzer;
- With endocrinology - a diabetes, hypo-and hyperthirosis, diseases of a hypophysis and others endocrinopathies;
6. The content of the lesson:
6.1 Theoreticalpart
Diseases of the vascular (uveal) path. All three parts of a vascular path – iris, the ciliary body and actually vascular layer – directly pass each other. An inflammation of these structures name accordingly iritis, cyclitis and chorioiditis; the term «uveitis» means any inflammation of the uveal path. The inflammation of iris, iritis, usually is a consequence of other diseases if only there was no direct physical or chemical influence on iris itself. More often such diseases as rheumatic diseases, syphilis, tuberculosis, infection of paranasal bosoms, teeth or tonsils, gonorrhoea, gout, diabetes serve as the reason of iritis. The attack of iritis is shown by pains, reddening, lacrymation and photophobia. At long character of disease sight worsens. When the ciliary body is amazed also, an inflammation name iridocyclitis or to lobbies uveitis. Symptoms of this condition are heavier. The pupil decreases, iris sticks to a crystalline lens, and the watery moisture grows turbid. Treatment consists in expansion of a pupil by means of atropine and application of sulfanilamides, antibiotics, cortizone etc. Besides, spend treatment of the basic disease which has led to uveitis.
Inflammation of a vascular layer often mention also a retina. Thus there are no painful sensations, but the inflammation is dangerous, as sight can in the most various ways be broken. The reason of chorioiditis is usually tuberculosis or viral infection, hystoplasmosis or tumours.
Inflammatory diseases of a vascular layer are called uveitis. These are heavy enough diseases as they often happen the reason of blindness and considerable easing of sight (approximately in 25 % of all cases of blindness). The number of patients with uveitis during the last years has increased 5 times.
Uveitiscan be:
- anterior:
- iritis - An inflammation of iris
- Iridotcyclitis - inflammation of iris and of the ciliary body
- posterior:
- Chorioiditis-inflammation of actually vascular layer.
Inflammatory process of all vascular layer is called panuveitis. The retina and an optic nerve can be involved into process – neurochoreorhetinitis.
Genetically caused defects of immune system, long inflammatory processes in an organism, the centres of a chronic infection, organism easing at chronic diseases and metabolism infringements can be preconditions for development of uveitis.
Uveitis can sharply proceed, or to be chronic with frequent or rare relapses. The infection gets to a vascular layer of an eye at eye wounds, after operations on an eyeball. Often увеиты arise at cornea ulcers. The centres of a chronic or sharp infection in an organism can be an infection source. At suspicion on uveitis the patient should be carefully surveyed
Inflammatory processes concernanterior uveitis in iris (iritis), iris and a ciliarybody (iridocyclitis) and an inflammation only a ciliary body (cyclitis). The patient has complaints to pains in an eye, morbidities at eyeball movement, at pressing on an eyeball. Pains amplify at night and can sometimes be very expressed. There can be a photophobia, a frequent blinking.
Further sight decrease, a fog before eyes develops. Склера on cornea peripheryreddens, colour and colouring of an iris of the eye, a pupil from - 59d for a hypostasis iris changes is narrowed, its reaction to light slowed down. The pupil form can become rough.
Are often formed adhesion of iris with a crystalline lens. Sometimes the pupil absolutely grows. In this case the message between eye chambers is broken, outflow of an intraocular liquid is broken, intraocular pressure is thus often lowered. The intraocular liquid can become purulent. All it leads to infringement of a food of a crystalline lens, its turbidity and cataract development.
Back uveitis or chorioiditis usually proceed it is erased, it is languid, imperceptible for the patient. Pains in an eye does not happen. At survey of an eye bottom find out the individual or plural centres of the various form and the sizes with inflammatory limbus. The retina is involved into process (retinitis) and an optic nerve disk (papillitis).
Chorioiditis is always reflected in sight function. Depending on the location of the inflammatory centres can be found out loss of fields (sites) of sight or if inflammatory process grasps the central part of an eye bottom, there can be a sharp decrease in sight when the patient can distinguish light and darkness only.
Peripheral uveitis are inflammatory processes of a back part of a ciliary body anda peripheral part adjoining to it chorioidea (back cyclitis, basal uvearetinitis, parsplanitis). Features of this form of uveitis that children and people of young ageis more often fall illand at children illness proceeds especially hard. Thus inflammatory process proceeds imperceptibly, complaints at patients insignificant, at children they can be absent and the disease is reavealed late, in a stage of complications.
Peripheral uveitis it can be accompanied by separation of retina on periphery. In
process it is involved vitreous body that can be shown by turbidity vitreous bodies with sharp infringement of visual acuity. Often there is a complicated cataract at which cataract begins with its deep departments.Glaucoma occurrence can be one more complication
Visual acuity depends on a transparency of optical environments of the eye providing formation of the accurate image of subjects on a retina, safety of the visually-nervous device of a retina and the spending ways bearing visual impulses in the visual centres of a bark of a brain. If in any of these links there will be pathological changes - result will be this or that degree of decrease in visual acuity.
The cataract causes decrease in visual acuity at the expense of development turbidities in substance of a crystalline lens
The crystalline lens is one of the major components of optical system of the eye which basic function is carrying out of light and focusing of the image of subjects on a retina.
The cataract is the eye disease which basic sign is turbidity of the basic substance or a crystalline lens capsule (decrease in their transparency), accompanied by visual acuity fall.
In a translation from Greek, the word "cataract" means "falling" or "falls". Ancient Greeks believed, that grey colour of a pupil at a cataract represents a film which, like falls, falls from top to down (falls) on a pupil, as a result depriving of the person of sight.
In a translation from Greek the term the cataract means "falls"
At the expressed turbidity of substance of a crystalline lens the pupil gets grey colour
The cataract is one of the most widespread diseases of an eye. So, according to statistics a frequency of an age-related cataract makes 33 on 1000 population, and this figure essentially increases with the years and reaches in 70-80 years 260 on 1000 at men and 460 on 1000 at women. After the age of 80 years 100 % of the population suffer from cataract. Among a congenital pathology of an eye the cataract also occupies one of in the lead positions.
Prevalence of an age-related cataract in the various countries and world regions essentially differs. It communicates with weight of factors: a racial accessory, character of a food, impurity of environment, potable water structure, district level above sea level, a heredity, etc.
It is very difficult to consider all factors (toxic and beam influence, a trauma, hormonal infringements, etc.), leading to development of the got cataract. In the present review the reasons of development of an age (senile) cataract as the most widespread, the smaller attention will be given other types of cataracts will be in detail described.
Crystalline lens anatomy
The crystalline lens is the major part of optical system of an eye including a cornea, a liquid of anterior and posterior chambers and vitreous body.
The crystalline lens is located in an eyeball between iris and vitreous body. It looks like a convex lens with refracting force about 20 dioptries. At the adult person diameter of a crystalline lens is made by 9-10 mm, a thickness - from 3,6 to 5 mm, depending on accommodation (the concept of accommodation will be considered later). In a crystalline lens one distinguish forward and back surfaces, a line of transition of anterior surface in posterior which is called crystalline lens equator.
The crystalline lens is kept at the expense of fibres supporting it on the place with ligament of Zinn a sheaf attached circular in the field of equator of a crystalline lens on the one hand and to shoots cyliary body body with another. Partially crossing among themselves, fibres are strongly intertwined in a crystalline lens capsule. By means Viger’s sheaf originating from a back pole of a crystalline lens, it is strongly connected with the vitreous body. From different directions the crystalline lens is washed by the watery moisture developed by shoots of cyliary body.
The supporting device of a crystalline lens
While examining a crystalline lens under a microscope it is possible to allocate following structures: a crystalline lens capsule, epithelium of crystalline lens and proper substance of a crystalline lens.
Microscopic structure of a crystalline lens (a crystalline lens in a cut)
Crystalline lens capsule. From different directions the crystalline lens is covered by a thin elastic cover – a capsule. The part of the capsule covering its forward surface, is called as a forward capsule of a crystalline lens; a site of the capsule covering a back surface – a back capsule of a crystalline lens. The thickness of a forward capsule makes 11-15 microns, back – 4-5 microns.
Under a forward capsule of a crystalline lens one layer of cages – epithelium a crystalline lens which is stretched to equator area where cages get more extended form is located. The equatorial zone of a forward capsule is a growth zone (germinative zone) as during all human life from it epithelial cages there are a formation of fibres of a crystalline lens.
The fibres of a crystalline lens located in one plane, are connected by among themselves sticking together substance and form the plates focused in a radial direction. The soldered ends of fibres of the next plates form lenticular seams which, at connection among themselves like orange segments, form so-called lenticular "star" on a forward and back surface of a crystalline lens. The layers of fibres adjoining a capsule, form its bark, deeper and dense – a crystalline lens nucleus.
Feature of a crystalline lens is absence in it of blood and lymphatic vessels, and also nervous fibres. A crystalline lens food is carried out by diffusion or active transport through a capsule of the nutrients dissolved in an intraocular liquid and oxygen. The crystalline lens consists of specific fibers and water (on a share of last it is necessary about 65 % of weight of a crystalline lens).
The condition of a transparency of a crystalline lens is defined by feature of its structure and a metabolism originality. Safety of a transparency of a crystalline lens is provided with the balanced physical and chemical condition of its fibers and липидов membranes, the maintenance of water and ions, receipt and allocation of products of a metabolism.
The accommodation mechanism. As accommodation understand ability of a human eye equally accurately to see the subjects located both on close, and on far distance. It is provided at the expense of action cyliar muscle and elasticity of a crystalline lens. In a rest condition cyliary muscle is weakened, fibres of cyliary sheaves are tense. Force of a tension through a capsule is transferred to a crystalline lens which thus gets more flat form. It allows to focus on a retina parallel beams from the subjects which are in the distance, providing with that accurate sight afar. At the same time, dispersing beams from close located subjects, cannot be focused on a retina and gather in imaginary focus behind it, therefore in rest of accommodation of the image of close located subjects seem washed away.
Crystalline lens in a condition of rest of accommodation (a) and pressure of accommodation (b)
If necessary accurately to consider a subject which is close, there is a reduction cyliary muscles, fibres cyliary sheaves relax, and a crystalline lens, owing to the elasticity, gets a little more convex form. At the expense of increase in curvature of a surface there is an increase in its optical force. In such condition dispersing beams from the subjects which are close, can be focused on a retina, and images of the subjects which are in the distance, seem washed away.
Crystalline lens in a condition of pressure of accommodation (at the left) and rest of accommodation (on the right)
In a photo at the left images of subjects in the distance seem washed away, and close – accurate (the crystalline lens is in a condition of pressure of accommodation). In a photo on the right a return situation (the crystalline lens is in a condition of rest of accommodation).
Age-related changes of a crystalline lens. Throughout all life there is a change of size, the form, a consistence and a crystalline lens transparency. At the newborn it of practically spherical form, soft, transparent and colourless. With the years the crystalline lens gets the form of a convexo-convex lens, with more flat forward surface and becomes yellowish on colour, completely keeping thus the transparency. Intensity of a yellow shade increases with the years.
Formation of lenticular fibres occurs during all life, however the crystalline lens volume increases only to certain age. It is connected with consolidation of the central departments of the crystalline lens consisting of older fibres. As a result the nucleus density all time increases: from small and soft эмбрионального nucleuss at the newborn, to accurately differentiated at the adult (by 25-30 years), and then large, turned yellow and sclerosed at the elderly person.
Approximately to 60-year-old age ability to accommodation is lost practically completely. It is connected with consolidation and a sclerosis of a nucleus of a crystalline lens – phakosclerosis. In this connection to the person begins difficult to distinguish accurately the subjects which are at a short distance – after 40 years comes so-called presbiopic age. During this period in connection with infringement of a food of a crystalline lens, delay in it of a metabolism in its various layers initial turbidity may arise.
The reasons of development of a cataract
Now all over the world researches of the reasons and mechanisms of development of a cataract (cataractogenesis) are intensively conducted. It is especially actual because the cataract is one of principal causes of reversible blindness. After all to prevent cataract development much easier and more cheaply, rather than for years to spend its conservative treatment, or to carry out expensive surgical intervention.
The basic successes in this area are reached in studying of the physical and chemical processes leading to infringement of optical properties of a crystalline lens. At a senile cataract there are changes of a chemical compound of a crystalline lens. In an initial stage of development of a cataract the water maintenance increases, accrues disbalance of some ions, amino acids, the quantity of water-soluble fibers and vitamins, ATP simultaneously decreases. Activity of some the enzymes participating in process of a metabolism in a crystalline lens Besides, decreases, oxygen consumption sharply decreases, processes of peroxidation of lipids are broken, etc.