POINTS

From Big Medical Encyclopedia

POINTS — the elementary optical device intended for correction of optical shortcomings of sight, protection of an eye against excessive visible and invisible radiation, wind, dust, snow, bruises and effect of chemically aggressive fluids, aerosols and other environments. Apply to correction of sight also contact lenses (see), put on directly a cornea or a sclera, and intraocular lenses — artificial crystalline lens (see).

Lakes consist of eyeglass lenses and the frame providing the correct provision of lenses concerning an eye.

O.'s invention is carried to the end of 13 century when in Italy the secret of receiving transparent glass was open. By 1280 the glory expatiated on the Venetian mirrors and glasses over the nearby countries. O.'s invention was preceded by works of the Egyptian scientist Ibn - al - Find fault - itself [latinizirovanny Alhazen], to-ry studied optics of an eye and magnifying effect of a spherical segment, and the English scientist R. Bacon. In Russia O. appeared at the end of 16 century; in 80 — the 90th 17 century the Russian merchants sold them to China.

The first eyeglass lenses (see. Optics ) were convexo-plane and biconvex, i.e. collective, positive (convex), and intended for correction of a hypermetropia (see. Far-sightedness ). In 150 years after their invention there were disseminating, negative lenses (concav) having concave surfaces for correction of a myopia (see. Short-sightedness ). The invention of bifocal (bifocal) lenses belongs to the end of 18 century when an amer. the scientist Franklin (V. of Franklin) connected halves of two lenses of various refractions. In 1837 bifocal lenses by a sticker of an additional lens on the main were made, and in 1908 in the main lens began to vpekat additional that allowed to create bifocal lenses with the invisible line of the section. In 1910 the trifocal lens (having three zones of optical action) was invented, and in 1959 — 1960 in France and GDR the transfocal lenses with smoothly changing refraction creating the best conditions for correction were offered presbyopies (see).

The cylinder lenses made in 1827 (their surfaces are parts of a side surface of the cylinder) allowed to korrigirovat astigmatism of an eye (see).

In 1908 Karl Tseyss released convexo-concave (meniscal) lenses of high precision (punctual lenses), and at the beginning of the 30th 20 century the same firm made positive eyeglass lenses of a high refraction with an aspherical surface.

At the beginning of 19 century connecting bridges of-point frames get various configuration; there was an oval form of rims, points eye-glasses, a nasal emphasis, and in the 70th 19 century new plastic material — celluloid became known, to-ry found broad application in production of-point frames. Along with metal and horn plastic frames appeared. The form of-point frames is considerably dictated by fashion.

From 50th 20 century there is a further improvement of a design and form of-point frames. There were combined-point frames from plastic (an atsetattsellyuloza, optit, Oestrolum) and metal with a decorative coating metals (gold, rhodium, palladium, etc.), colored varnishes and enamels. The sizes of light apertures increased.

The scientific and technological revolution and the related changes of conditions of visual activity of the person and steady growth of cultural level of the population caused the necessity of increase in production of O. E.g., production of products of-point optics to the middle of the 50th of 20 century in comparison with pre-war level increased in the USSR by 3 times. In 1980 in the USSR the St. 60 million lenses and more than 20 million frames was made. The main tendencies in development of-point optics — expansion of the range of difficult eyeglass lenses, increase in their diameter (in the nek-ry countries to 72 mm), production of easier lenses from transparent polymeric materials with the increased mechanical strength for deleting of a surface layer, use at morphogenesis of eyeglass lenses of zone surfaces (Fernel's surfaces), etc.

Depending on O.'s appointment are subdivided on corrective, special and protective.

A corrective spectacles

the Corrective spectacles is applied to correction of anomalies of a refraction, disorders of accommodation and correction of shortcomings of the muscular device of an eye.

O.'s variety and other means of correction and protection of sight is connected with significant difference in a condition of an organ of sight and influences of the environment (tab. 1).

Fig. 1. The schematic diagram of correction of sight one-focal stigmatic lenses (1 — negative, 2 — positive): the lens moves the image of a remote point F' on a retina of an eye (a point of F); 1 — at a myopia, 2 — at a hypermetropia.

The main anomalies of a refraction and accommodation of an eye are the myopia and a hypermetropia therefore the one-focal stigmatic (not astigmatic) positive and negative lenses having the identical refracting force (fig. 1) in each section are most widespread.

Fig. 2. Some types of eyeglass lenses: 1 — astigmatic lenses (— the radius of curvature of an inner surface; gt — the radius of curvature of a surface in meridional section; rs — the radius of curvature of a surface in sagittal section; d — thickness on the center); 2 — a lens with a zone surface (the surface of Fer-Nesle); 3 - a bifocal stigmatic integral eyeglass lens (and — for a distance — for a bliza); 4 — the bifocal stigmatic baked lens (and — for a distance — for a bliza).

Astigmatic lenses with a toric surface are applied to correction of an astigmatism. They have in two perpendicular relatively each other the main sections various refracting forces (fig. 2). Depending on a type of an astigmatism they are subdivided on: positive and negative — for correction of a simple and difficult gipermetropichesky and miopichesky astigmatism and otritsatelnopolozhitelny for correction of the mixed astigmatism. At the wrong astigmatism correction is carried out by the contact lenses compensating abnormality of a form of a cornea.

At a heterometropia (see) high degree full correction can be reached by the izeykonichesky lenses having the set coefficient of own increase and changing the size of the image received on a retina of an eye at the expense of the increased thickness. Izeykonichesky lenses are issued stigmatic, astigmatic and afocal.

At a presbyopy with reduction of volume of accommodation there is a need for correction of sight not only for a bliza, but also for a distance that is carried out by bifocal, trifocal stigmatic and astigmatic eyeglass lenses and lenses with smoothly changing refraction.

(See) apply positive eyeglass lenses of a high refraction to correction of an aphakia. However spherical lenses with such refraction have a big astigmatism of inclined bunches of beams (see. Aberration ), what sharply reduces their optical qualities. Reduction of an astigmatism is reached thanks to use in eyeglass lenses of aspherical surfaces (a hyperboloid, a paraboloid, an ellipsoid). Other lack of positive eyeglass lenses of high refractions is considerable narrowing of a field of vision that results in «tubular sight», or ring to scotoma (see). At an aphakia it is in most cases reasonable to appoint bifocal and trifocals with a difference of a refraction between a part for a distance and a part for a bliza from 3 dptr above. Aphakias it korrigirutsya by also contact and intraocular lenses (an artificial crystalline lens).

Fig. 3. Schematic diagram of correction of sight prismatic lens: And B of l — the line of a look of the left eye which is not needing correction; AiBn — the line of a look of the right eye (the image of a point And hits on a retina the nail of A2, but not on area of a macula lutea); P — a prism; ABP — the line of a look of the right eye, korrigirovanny a prism; in a rectangle — a prismatic eyeglass lens or a sferoprizmatichesky element (longitudinal section).

At squint and disturbances of muscular balance of eyes prismatic eyeglass lenses, and are applied to correction of solid vision at squint (see) and heterophorias (see) — The lake with sferoprizmatichesky lenses or sferoprizmatichesky elements pasted on lenses. The principle of action of prismatic lenses is shown in fig. 3. Are issued prismatic afocal, one - both bifocal stigmatic and astigmatic lenses.

Corrective O. shall meet the following requirements: the refraction of a lens or a prism (an axis of the cylinder or the main section of a prismatic lens) shall correspond to a copy-book of the recipe on O., the optical center of a lens — to match the center of a pupil of an eye, the top of the line undressed in bifocal lenses — to be 2 mm lower from the center of a pupil of an eye at a look afar, the eyeglass lens — to defend from an eye on 12 mm; standard deviations of a refraction of eyeglass lenses at value of a back vertex refraction (according to GOST 23265 — 78) to 6 dptr shall not exceed ±0,12 dptr, from 6 to 12 dptr — ±0,18 dptr, from 12 to 15 dptr — ±0,25 dptr, St. 15 dptr — ±0,35 dptr; the tsentrirovka allowed for lenses St. 2 dptr no more than 2 mm, from 0,5 to 2 dptr — from 7 to 2 mm; permissible deviations of provision of the first main section of an astigmatic lens (axis of the cylinder) or the main section (the line top — the basis) a prismatic lens from the provided receptomas on O. there have to be no more than 4 ° at lenses with an astigmatic difference (prismatic action) from 0,75 to 3 dptr (prismatic dioptries — prdptr), and at a lens St. 3 dptr (prdptr) — no more than 3 °; the form of a-point frame and its parameters shall correspond to an anatomic structure of the person and head of the patient, and also to meet the esthetic requirements; details of-point frames shall not make the irritating impact on face skin and to be convenient during the carrying.

Fig. 4. The form of the recipe on points: and — the face — the back.

Corrective O. are ordered according to the recipe (fig. 4), to-ry is given by the ophthalmologist after definition by means of ophthalmologic devices, napr, refractometers, skiascopy frames, sets of trial eyeglass lenses, tables of signs for a research of the visual acuity necessary for correction, measurement of center distance of pupils of eyes and some other parameters.

Corrective O. need to be stored in a case. O.'s lenses that not to scratch them, it is necessary to wipe with a suede or soft napkin. In the same purposes it is impossible to put O. lenses down on a solid surface.

Special glasses

apply Special glasses in cases when correction of sight by corrective O. does not give desirable effect.

Fig. 5. Points for visually impaired: and — bifocal monocular glasses for a bliza (1 — a frame, 2 — an upper part of a lens for orientation without increase, 3 — telescopic system with increase 2kh; 2,5kh; Zkh; 3,5kh; 4kh; 4,5kh; 5kh; 6kh; 4 — a nozzle for reading); — the unifocal monocular glasses for a bliza with an emphasis applied only to reading U — a frame, 2 — telescopic system with increase 6kh, 8u, diameter of a field of vision of 35 — 26 mm, 3 — a transparent plastic emphasis 38 — 27 mm long); in — the unifocal monocular glasses with the lighter for a bliza applied only to reading (J — a frame, 2 — a lens with increase 10kh, 12kh, 15kh, 20kh, diameter of a field of vision of 18 — 5 mm, 3 — the lighter); — a bifocal binocular distance spectacles — a telescopic spectacles (I — a frame, 2 — telescopic system with increase 2 x for a distance, z — the bottom of a lens for orientation without increase.

Points for visually impaired (fig. 5) are intended for persons with visual acuity from 0,2 to 0,05 and from 0,04 to 0,02 (residual sight). Such points are issued four types. Their selection is carried out by means of special set. The binocular points representing system from two lenses — collective and disseminating, strengthened in the general frame, are called telescopic.

A prismatic spectacles for reading lying include 2 prisms of total internal reflection changing a path of rays on 90e; if necessary are supplied with corrective nozzles.

The Stenopeic (perforated) spectacles applies in the postoperative period concerning amotio of a retina. They have opaque plates with a certain number of small openings that improves sight due to diaphragming.

Gemianopichesky (mirror) points apply to correction of sight at unilateral hemianopsias (see). The mirror and ground glass with a transparent zone to dia enter their design. 8 mm. The patient, observing through a transparent zone, sees only that a yole of sight, a cut it is formed by a mirror. At the same time its illusion of straight vision of objects is created.

Selection of a corrective spectacles. At selection of points use sets of trial eyeglass lenses and prisms of 3 types (in accordance with GOST 19872 — 74): small, average and big. Average set is most widespread, to-ry contains 34 couples of positive and negative stigmatic lenses (from 0,25 to 20 dptr), 20 couples of positive and negative astigmatic lenses (from 0,5 to 8 dptr), 6 steam rooms and 3 unary-point prisms (from 0,5 to 10 prdptr). For convenience of use rims of positive stigmatic and astigmatic lenses differ on color from rims of negative lenses. On the handle of each rim the refracting force of a lens in dioptries is specified; besides, on astigmatic lenses there are tags specifying the direction of an axis of the cylinder, and on-point prisms — the main section.

Fig. 6. A universal trial frame to a set of trial eyeglass lenses and prisms.

For installation of lenses during O.'s selection the universal trial frame (fig. 6) allowing to change lenses, to rotate them, to move across and verticals that is necessary as for the correct tsentrirovka of lenses concerning eyes, and for giving of an axis of an astigmatic lens or to the main section of a-point prism of the necessary inclination is applied to a set of trial eyeglass lenses and prisms. For counting of provision of an axis of an astigmatic lens or the main section of a-point prism on a rim of a trial frame there are divisions in degrees. At O.'s selection the lens shall be at distance of 12 mm from a front surface of a cornea since for such distance the refracting force of lenses at O.'s production according to the recipe is calculated. In big set there is a trial frame for O.'s selection to children.

Process of selection of O. consists of the following stages: define visual acuity of each eye (see. Visual acuity ), carry out test with positive and negative stigmatic lenses for approximate identification of species and degree of an ametropia; if necessary appoint the means (e.g., 1% solution of Atropini sulfas, to children up to 6 years of 0,5% solution) weakening accommodation (at persons 35 — 40 years medicamentous relaxation of accommodation are more senior make only in extreme cases after preliminary measurement of intraocular pressure); make objective definition of a refraction in the conditions of a tsikloplegiya (see. Refraction of an eye ), check visual acuity of each eye without diaphragm with lenses, completely corrective ametropia (see), also in the conditions of a tsikloplegiya; after cancellation of tsiklo-plegichesky means on the basis of results of the previous stage of inspection, the general rules of appointment of O. at different types of an ametropia and trial glasses wearing within 15 — 20 min. finally resolve an issue of rational optical correction.

The indication to O.'s appointment at a hypermetropia (see. Far-sightedness ) asthenopic complaints serve (see. Asthenopia ) or decrease in visual acuity at least one eye. In such cases, as a rule, appoint constant optical correction on subjective portability with a tendency to the maximum correction of an ametropia. If such correction does not give relief, then for visual work at a short distance write out stronger (on 1 — 2 dptr) lenses. At small degrees of a hypermetropia and normal visual acuity afar it is possible to be limited to purpose of points only for work at a short distance.

At a myopia (see. Short-sightedness ) to 6 dptr for a distance full correction is, as a rule, recommended. In case of a myopia 1 — 2 dptr correction can use only if necessary. Rules of optical correction for work at a short distance are defined by a condition of accommodation: if it is weakened, then appoint weaker lenses.

At the astigmatism of all types which is followed by decrease in visual acuity constant glasses wearing is shown. The astigmatic component of correction is appointed on subjective portability with a tendency to full correction of an astigmatism. The spherical component of correction is written out according to the general rules of purpose of points at a hypermetropia and a myopia.

At a presbyopy additional correction is recommended. For selection of points it is possible to use an approximate formula: DB = = Dd + (A - 30)/10 where DB — force on lozhitelny lenses for work close, dptr, Dd — force of a lens, corrective sight afar, dptr', And — age of the patient.

Correction aphakias (see) it is carried out not earlier than 4 weeks after operation. In the beginning write out a distance spectacles, and after accustoming to them — and for work at a short distance — on 3 — 4 dptr is stronger, than for a distance. Especially carefully it is necessary to korrigirovat an astigmatism. At a unilateral aphakia because of existence of an aniseikonia the best way of optical correction will be contact lenses.

The optical power of lenses and compliance to their recipe at issue to the customer O. are checked with the help dioptrimetra (see). It is possible to use also a method of neutralization of positive lenses negative and vice versa.

Safety spectacles

Safety spectacles are intended for individual protection of eyes from influence of dangerous and harmful factors (dust, solid particles, splashes of liquid and molten metal. the corroding gases, ultraviolet, infrared, laser radiation, Svchizluche-niya, the blinding brightness and radio waves).

Protective O. consist of a frame or the case (for deduction of ocular glasses in the situation demanded at operation), ear arms or a natolovny tape (for fixing of points on the head) and ocular glasses. They can be with single-layer, two - and triplex colorless glasses, and also with glasses light filters (silicate or organic). Light filters have various optical density and coloring depending on purpose of the Lake. Points with light filters often use also for the cosmetic purposes, and also as sun-protection.

Fig. 7. Safety spectacles: and — open 012-72 — open, folding forehead К1-(Д-1), in — open folding 002-76 — open double OD2-72-G1, d — ZP8-84 closed with direct ventilation, e — ZI4-72 closed with indirect ventilation — the double ZND2 closed with indirect ventilation, z — the closed tight PO-2; 1 — a-point frame, 2 — protective glass, s — side guards, 4 — ear arms, 5 — a head-mounted elastic tape for fixing of points, 6 — the ventilating device? — a nalobny plate for fastening of points, 8 — the rotary fixing device, 9 — a folding stekloderzhatel with light filters, 10 — the device for fastening of points to a helmet or a visor.

Exist adjacent opened (fig. 7, a) or the closed safety spectacles, i.e. O. adjoining to the person a part or all contour of the case, and also not adjacent — the cases which are not adjoining to the person on a contour, napr, forehead points (fig. 7, b), a protective lorgnette. Folding points (fig. 7, e) can lean back thanks to the nalobny device with the special hinge up. Open double O. (fig. 7, d) have two appearance of ocular glasses: colourless and light filter.

The adjacent closed O. are divided into points with direct ventilation (fig. 7, e) when air comes to sub-point space without changing the directions, and points with indirect ventilation (fig. 7, e, g), in to-rykh the direction of air changes thanks to existence of special devices. Earlier being issued scaly, driver's and flight Lakes treat O. of this kind. Tight points (fig. 7, h) completely isolate eyes and sub-point space from the environment.

Types of the protective O. which are released in the USSR and their appointment are determined by GOST 12.4.003 — 80 (tab. 2).

Protective O. with usual silicate glasses provide protection of eyes against the flying solid particles with energy to 0,4 J, with the strengthened silicate glasses — to 0,6 J, with glasses triplex or double organic — to 1,2 J.

Light filters — ocular glasses for decrease in intensity of harmful and dangerous radiation — are selected depending on brightness and character of radiation, duration of the performed work, the general illumination indoors, and also from specific features of the sight working. According to GOST 12.4.080 — 79 at flame welding workers use light filters of designations: G-1, G-2, G-3, during the auxiliary welding works — B-1, V-2, V-Z, during the work at blast, heating furnaces, rolling mills - D-1, D-2, D-3, during the work at steel-smelting and other metallurgical furnaces - P-1, P-2, P-3, etc. Since 1980 O. for protection against pulse and continuous laser radiation with various lengths of waves are issued. As light filters blue-green glasses of the SZS-22 brand, and also organic colored glasses are applied. The given marking on glasses light filters is put at distance of 2 — 3 mm from their edge.

The intercenter distance at protective O. is usually equal to 72 mm. However, if in protective O. lenses light filters are used, nek-ry models O. make with the adjustable crossing point allowing to change center distance from 64 to 76 mm.

Efficiency of use of protective O. depends not only on a right choice, but also on individual adjustment, their reliable fixing on the head. Tight O. adjust by means of a rubber tape and adjusting buttons.

In case of fogging of glasses O. apply special pencils or glycerin soap, to-rye apply from within on dry pure glass with several strokes and pound a soft tissue to transparency.

Protective O. store in special cases or cardboard boxes far from oil products, acids, alkalis and other pyretics. Periodically it is necessary to make cleaning of glasses, being in operation (to wash out a brush a frame, glasses, ear arms, the case in hot water with soap); it improves transparency of glasses and outward of points, excludes an opportunity inf. infections of eyes.

Tables

Table 1. Condition of an organ of sight and means of correction and protection



Table 2. Types and purpose of some safety spectacles




Bibliography: Avetisov E. S. and Rozenblyum Yu. 3. What shall be optical correction of short-sightedness? Vestn, oftalm., No. 6, page 31, 1970; A v i z about n i s P. History of points, Arkh. oftalm., t. 2, p.1, page 48, p. 2, page 197, p. 3, page 372, 1926; V. V. Wolves, about r and N A. I. and D and l and and sh in both l and O. A. Klinicheskaya vizo-and refractometry, JI., 1976; Gayevy L. A. Individual protection equipment of eyes and the person on production, M., 1980; Galkin H. N. Posobiye on selection of points, L., 1960; The expert owls with to and y L. N. both To r and in about sh and-p about in and L. V. Multifocal ocular glasses, It is new. medical technicians, No. 2, page 47, 1961; Denisenko O. N. Points and guards for protection against mechanical influences, the Mechanician, No. 1, page 41, 1980; To r and with at c to and y F. K. Influence of individual protection equipment on reduction of a field of vision, Safety of work in prom-t, No. I, page 58, 1976; Model D. M. Short reference book of the medical optician, L., 1970; M at r and sh-to and a certain V. E., etc. Oftalmolo-gichesky optics, L., 1928; Page about S. L pain. Points in Russia in the 17th century, in book: Probl, fiziol, optics, under the editorship of L. A. Orbeli, t. 7, page 111, M. — L., 1949; At r m and x e r L. S. Reference book on ophthalmologic optics and devices, M., 1971; To Tsepa of l ev Yu. A. and And y-zenshtat L. I. Rol of the optical-mechanical devices and devices in development of new diagnostic methods and treatments, the Medical equipment, No. 5, page 29, 1977.


L. I. Ayzenshtat; E. S. Avetisov (oft.), O. N. Denisenko, M. E. Tsutskov (gigabyte.).

Яндекс.Метрика