THE UVEAL TRACTAND ITS DISEASES

Anatomy of the Lacrimal Organs

The lacrimal organs consist of the lacrimal gland, which forms a tear, and organs which conduct it, — lacrimal passage.

The lacrimal gland (glandula lacrimalis) lies in the frontal part of the outer-upper segment of the orbit, into the pit of the same name (fossa glandulae lacrimalis). The tendon of muscle, that lifts an upper eyelid, divides the lacrimal gland into the orbital and palpebral parts. The excreting channels of the orbital and palpe bral parts of the lacrimal gland are opened in the conjunctival sac. In conjunctival mucose there are accessory lacrimal glands — Krause's and Waldeyer's glands.

The lacrimal gland is innervated by the lacrimal nerve (n. lac­rimalis) — a branch of the trigeminal nerve which has secretory fibres in the composition. The lacrimal gland has sympathetic in­nervation. Likable fibres get to the gland with vessels from inter­lacement near an internal carotid.

The secret of the lacrimal gland is a tear (lacrimae) — is trans­parent, a little opalescent liquid. Besides of insignificant quantity of albumen and mineral salts, it contains lysozym which has great bactericidal action.

Under normal conditions the amount of tears, secreted by the accessory Krause's glands is sufficient to moisten the eyeball. The basic lacrimal gland begins to function when it gets irritated re-flexly as a result of eye disease under the influence of psychical moments (weeping).

The lacrimal passage consists of lacrimal puncta, lacrimal ca-naliculi, lacrimal sac and nasolacrimal duct, that is opened in the cavity of nose in inferior nasal meatus, under inferior nasal con­cha.

The lacrimal puncta are two openings lying near the posterior margin of each lid, near the inner conthus. The lacrimal canalicu­lus joins the punctum to the lacrimal sac. It first passes vertically, then horisontally and falls into the lacrimal sac.

The lacrimal sac lies in the lacrimal fossa, formed by the lac­rimal bone and the frontal process of the maxilla. The upper por­tion of the sac, fundus extends above the medial palpebral lega-ment. The lower end continues as nasolacremal duct.

Diseases of the Lacrimal Organs

Inflammation of the lacrimal gland — dacryoadenitis is, as a rule, bilateral. It begins with sharp pains and swelling of the ex­ternal part of the upper eyelid, in the area of the lacrimal gland, and also lacrimation. The disease is sometimes accompanied by dis­placement of the eye to bottom and inward, diplopia occurs. At drawing of the upper eyelid, a palpebral part of the lacrimal gland, which comes forward in a transitional fold, is well visible. The clini­cal course of the disease is benign, the infiltrate resolves during 10-15 days, but in weakened patients it can result in formation of ab abscess and even phlegmon of the orbit. As a rule, the disease is accompanied by fever.

Etiology. Inflammation of the lacrimal gland is complication of infectious diseases, such as flu, angina, pneumonia. More frequent bilateral acute dacryoadenitis is observed in parotitis. Quite often orchitis joins the disease.

Treatment. Treatment of general disease is conducted (antibio­tics, sulfonamides, analgetics, antihistamins). Physiotherapy is used locally (dry heat, UHF-therapy), washing of conjunctival sac with warm antiseptics and anesthetics, application of ointments with an­tibiotics and sulfonamides. At abscess dissection is performed.

Inflammation of the lacrimal sac — dacryocistitis. When there are inflammatory processes in the mucous of nasolacremal duct, and also different processes in the nose, for example, hyperplasia of mucous tunic, atrophy processes in it and nasolacremal duct, nasal septum deviation, formation of polyps, nasolacremal duct is narrowed or is fully closed. Microflora which gets into the lacrimal sac with a tear propagates and irritates its walls, mucous of which begins to product a secret, a sac is full of mucous, mucous-fester­ing or only festering discharge. Chronic inflammation of the lac­rimal sac develops (dacryocistitis chronica). At pressure on the the lacrimal sac area festering contents is discharged from the lac­rimal punctum. An eye is always moistened. Margins of eyelids, conjunctiva, lacrimal caruncle and half-moon fold are, as a rule, reddening. At the prolonged course of the disease the lacrimal sac stretches (ectasia sacci lacrimalis), near the internal corner of eye a tumour becomes noticeable. In the course of time sac's mucous can atrophy and the track to canalicula can be closed, the locked sac filled with a liquid is formed as a result, that does not become empty at pressure — hydropsy of the lacrimal sac (hidrops sacci lacrimalis).

Quite often inflammation passes outside a sac on the surround­ing tissue, causing its acute inflammation — phlegmon of the lac­rimal sac. Redness and oedema of the skin in the sac area appear, then spreading on eyelids, cheek and a corresponding side of the nose. In a few days a tumour grows soft and pus breaks through outside. A fistula, that appears after opening, is rarely closed, more frequently it remains (fistula sacci lacrimalis).

Inflammation of the lacrimal sac is dangerous for the eye, be­cause in case of the least damage of the corneal epithelium the cor­neal ulcer serpens can develop.

Treatment. If discharge from the sac are insignificant, it is rec­ommended to wash the lacrimal ducts 1-2 times, if they were stopped up by the clot of mucus. When washing does not give an effect, the operation should be performed.

Dacryocystorhinostomy is usually used, that forms connection between the sac and nasal cavity.

Dacryocystitis of newborns. The lower end of the nasolacrimal duct in the antenatal period is closed by a thin membrane which disappears only shortly before birth. If it does not happen dacryo­cystitis occurs. A gentle pressure over the lacrimal sac produces the reflux of purulent discharge from the lower punctum.

Treatment. It is needed once or twice a day to squeeze content from the sac (descending massage) and wash an eye by solution of boric acid, instill 20% solution of sulfacyl natrium or antibiot­ics. If in a week suppuration is not stopped the probing of the lac­rimal ducts should be performed.

Consequently, the disease of the accessory apparatus of the eye can lead to the severe damages of the eyeball, especially the corne­as, therefore they should be cured in time and eliminated.

THE UVEAL TRACTAND ITS DISEASES

Anatomy of the Uveal Tract

The uveal tract consists of three parts: the iris, the ciliary body and the choroid.

An arbitrary distinction has been made between the anterior uveal tract (iris and ciliary body) and the posterior uveal tract (choroid).

The iris regulates the amount of the light, which enters the eye through the pupil. Diaphragm is composed of the iris and lens, which divides the anterior chamber from the vitreous cavity and the posterior chamber.

The iris consists of the anterior mesoderm layer (with numer­ous chromatophores in dark-eyed people) and a posterior pigment layer derived from ectoderm and contains sphincter and dilatator muscules of the pupil.

The ciliary body is inaccessible for examination, can be inspected by palpation. It extends anteriorly to the scleral spur and looks like a ring with width of about 8 mm. The posterior zone is smooth and is known as pars plana. The ciliary body is composed of unstriped ciliary muscle fibres, stroma and blood vessels

The choroid is a thin vascular membrane extending from the optic nerve to the ora serrata. It consists of five layers: suprachoroid, layer of large vessels, layer of small vessels, choriocapillaris and lamina vitrea elastica (the Bruch's membrane). It makes trophical function.

The short posterior ciliary arteries supply the choroid. The long posterior ciliary arteries and the anterior ciliary arteries supply the iris and the ciliary body.

Diseases of the Uveal Tract

There are distinguished the following groups of the uveal tract diseases: 1) developmental abnormalities; 2) inflammations (uvei­tis); 3) dystriphies; 4) tumours.

Developmental Abnormalities

Albinism. The iris appears pink because of the absence of the pigment, and examination of the retina reveals that the choroidal 1 vessels stand out prominently owning to the absence of the pig- I ment in the retinal pigment epithelium. Patients have poor vision (0.01-0.05), often nystagmus and photophobia occur.

Treatment. Correction of refraction anomaly, pleoplastic.

Congenital colobomas of the iris. These are usually found in the inferonasal quadrant, and may sometimes be associated with colo­bomas of the ciliary body and choroid.

Treatment. Iridoplasty.

Persistent papillary membrane forms a net in front of the pupil as a result of incomplete reabsorption of the fetal capillary vascu­lar system has no other pathological significance.

Aniridia (absence of the iris). Complaints to poor vision, photo­phobia.

Treatment. Iridoprothesis, contact lens.

Inflammations of the Uveal Tract (Uveitis)

Clinically uveitis may be anterior (iridocyclitis), posterior (choroiditis) and total (panuveitis) depending on which part of the uveal tract is affected.

Iridocyclitis. Acute and chronic forms are recognized. The pa­tient complains of photophobia, lacrimation, dull pain and reduc­tion of vision.

Clinical features:

— pericorneal vascular injection;

— hyperemia of the iris and the presence of the iris nodules;

— the pupil is constricted and react poorly to light;

— aggregates of cells adhere to the corneal endothelium (keratic precipitates).

— In severe cases pus develops in the anterior chamber (hypopyon). There are also pain while touching and reduced accommodation.

— Complications. Posterior synechiae formation (adhesions be­tween the posterior surface of the iris and the anterior lens cap­sule). If adhesions form all around the papillary margin aqueous humour secreted by the ciliary body cannot enter the anterior chamber. The iris root is therefore pushed forward to come in con­tact with the corneal periphery (peripheral anterior synechiae), blocking of the drainage angle, and the intraocular pressure raises (secondary pupil block glaucoma). Following the use of mydriaticts the pupil margin may assume a scalloped contour in cases where posterior synechiae have formed. If mydriaticts are not employed a membrane may occlude the pupil.

— Differential diagnosis is conducted with acute glaucoma, acute conjunctivitis (Table 4).

— Table 4. Differential diagnosis of acute iridocyclitis with acute glaucoma and acute conjunctivitis

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Choroiditis. Inflammation of the choroids, which almost invari­ably spreads to the retina (choroidoretinitis).

Etiology. Exogenous factors: consequences of perforating inju­ries, toxins liberated from the corneal ulceration, chemical burns, etc.

Endogenous factors: choroidoretinitis often occurs as a result of septic emboly arising elsewhere in the body.

Uveitis commonly occurs in the following systemic diseases: col-lagenosis, particularly the juvenile rheumatoid arthritis, ankylos­ing spondilitis, Reiter's disease; tuberculosis, secondary syphilis, sarcoidosis, Behcet's disease (hypopyon — iridocyclitis, aphtous ulceration of the mouth and ulcerative lesions of external genital organs), brucellosis, toxoplasmosis, etc.

Treatment. To reveal the foci of infection it should be carried out the examination of the whole organism. Cycloplegics and my­driatics are used to relieve pain from ciliary spasm to dilate the pupil to prevent the formation of posterior synechiae. Antibiotics, sulphonamides are alministered as well as corticosteroids, antiin­flammatory and desensitising drugs.

Date: 2014-12-21; view: 1298