Acquired Cataracts

It is divided the following kinds of acquired cataracts: senile, traumatic, radiational (thermal, X-rays), toxic, complicated.

Senile cataract. Last thirty years its level has grown 6 times as much (4-6 cases in one thousand of population). 30-40% of op­erations on the eyes are operations due to cataracts. Usually it aris­es at the age over 50, but last years cataract is met in younger age.

Etiology. Cataract is caused by topical and systemic disorders of metabolism. The cataractogenic factors are:

a) decrease of antioxidative enzymes activity with the age;

b) defects of microcirculation of the eye caused by diseases of cardiovascular system (hypertention, atherosclerosis);

c) defects of metabolism in liver and kidneys diseases, diabetes mellitus, a deficiency of vitamins C and B2.

Clinical course of the senile cataract. In the beginning of the dis­ease patients complain to:

— "flies" which move together with the eye. In fixed eye "flies" are immovable (opacity of the vitreous is mobile, in motionless eye it falls down);

— myopia in elderly age, often change of glasses for near dis­tance;

— monocular diplopia, polyopia.

Gradually a decrease of the visual acuity, mist before the eyes appears.

The visual acuity decreases from 1.0 up to a right perception of light.

Due to cataract only one visual function (visual acuity) is im­paired. The visual field, light sensitivity remain normal.

It is distinguished cortical and nuclear senile cataract. Cortical cataract is divided into four stages:

I. The incipient stage. At the periphery of the lens there appear
radial opacities ("spokes in a wheer). At the centre of the lens un­
der the capsule there are the transparent vacuoles, eye fundus can
be seen clear. The visual acuity is equal 1.0-0.3. The complaints
are "flies", "mist" before eyes.

II. Immature, intumescent cataract. Considerable opacities of­
ten have the form of sectors or "spokes in a wheel" which reach
the centre. There is the iris shadow in lateral illumination, there is
a reflex from eye fundus on periphery, but its details are not visi­
ble. The visual acuity is less than 0.2. The anterior chamber is shal­
low. There is complication — phacogenic (phacomorphic) glauco­
ma.

III. Mature cataract. The entire lens becomes opaque, there is no the iris shadow at lateral illumination, pupil is white or grey, there is no reflex from eye fundus, visual acuity is right percep­tion of light.

IV. Hypermature cataract. Fibre of the superficial layers of the lens break, cortex of the lens becomes white like milk liquid and partially resorlves. Therefore the anterior chamber becomes deep, tremulousness of the iris arises. The reflex from eye fundus and even low visual acuity may appear. The heavy nucleus falls downwards on the bottom of the anterior chamber. Complications: phacolytic secondary glaucoma, phacolytic iridocyclitis.

In nuclear cataract the opacity begins in the centre of the lens' nucleus. By lateral illumination the gentle opacity like a cloud is visible in the centre. In examination by a passage light the reflex is absent in the centre. It develops slowly, at once the visual acui­ty considerably decreases. It can be atypical form of the age cat­aract, i.e. brown or brunescence cataract. The pupil has a dark col­our, the reflex from eye fundus is absent. Lens is firm, brown, it has only nucleus, cortex is absent.

Treatment of cataract. The conservative treatment is carried out only in I stage with the purpose to delay the cataract progressing. It is used topically tauphon, vitamin drops (catachrome, sancata-lin, vita-iodurol, vitaphacol etc.).

Beginning with the II stage the surgical treatment is carried out, and the condition of the second eye is taken into consideration. If the visual acuity of the other eye is high, the operative treatment is used in decrease of visual acuity of the ill eye less than 0.3. If the visual acuity of a other eye is low or it is absent, the cataract is operated in visual acuity less than 0.1.

History of cataract surgery. Up to the middle of XVIII century there was carried out reclination of cataract. So-called reclinators made it. This operation caused blindness from glaucoma in 40%. The founder of modern methods of lens removal was Jacques Dav-iel, which has removed cataract through the cornea incision in Marseilles in 1745. At that time about 10% of the patients lost vi­sion due to intraocular infection.

At present there are applied the following methods of removal of cataract (only with microscope):

1. Extracapsular cataract extraction. The posterior capsule is not removed. It prevents loss and hernia of the vitreoum, ditach-ment of the retina. Due to microsurgical technique in the most cases it is possible to prevent the main defect of this method — develop­ment of a secondary cataract. Secondary cataracts are carried out by laser or knife discission.

2. Phacoemulsification is the most modern and effective meth­od. It is distinguished with a small incision, not very traumatic ope­ration, fast rehabilitation of the patient. Due to the new achieve­ment in phacoemulsification technique quality of the cataract sur­gery is very high. The main components of the method is automatic aspiration-irrigation system which supports constant intraocular pressure during the operation, high quality of coaxial microscope, viskoelastics for prevention of the cornea damage, small tunnel in­cision, adapted to a small incision of intraocular lens.

3. Intracapsular cataract extraction. It is carried out by means of a cryoprobe (cryoextraction) or with capsule forceps. This meth­od frequently gives complications: hernia of the vitreous, glauco­ma, ditachment of retina. Now it is carried out only in subluxa­tion of the lens.

Aphakia

Aphakia is absence of the lens. One of aphakia causes is opera­tion of cataract extraction. Clinical signs of aphakia: — the visual acuity is less, than 0.05;

— absence of accommodation;

— high hypermetropia — 10-12 D;

— deep anterior chamber;

— iridodonesis;

— absence of the lens complex at ultrasound examination.

Methods of aphakia correction

1. The intraocular lens (IOL). The first experimental implanta­
tion of IOL in rabbits was made by A. Kh. Mikhailov in 30s in
Sukhumi. In people the first implantation of IOL was carried out
by Ridley (England, 1949).

Now it is impossible to imagine cataract surgery without im­plantation of the intraocular lens. IOL are implanted almost to all patients after extraction of cataract. Contraindications are only diseases of the cornea, severe cases of diabetes mellitus. The mo­dels of the intraocular lens, its material are permanently improved. Now the posterior camera lens with intracapsular fixation are usu­ally applied. They are made from polymethylmetacrelate, silicon, hydrogel, acril. In our department the new models of intraocular lens with a carbon covering, has been worked out due to which trauma of eye tissue during implantation and excudative reaction have decreased, toxic effect of PMMA and damage effect of ul­tra-violet rays of light on retina were removed.

Last achievement in development of new models of intraocular lenses is multifocal lenses, which ensure the high vision at long and short distances.

2. Keratophakia — interlammelar refractive keratoplasty.

3. Contact lenses.

4. Iseikonia glasses (in monocular aphakia).

The old method. In binocular aphakia it is used glasses from + 10 to +12 D for a long distance and glasses from +13 to +15 D for a short distance (the eye refraction before operation will be ta­ken into account).

Date: 2014-12-21; view: 1415