What is the difference between a magnifier and a lens?

Features of the binocular loupe

Doctors use binocular devices to get a clearer image, magnified several times. With the help of the device, eye strain is reduced and visual acuity is increased, thanks to which the specialist can examine the area of ​​interest in detail.

Optical devices differ in magnification ratio, depth of field and working distance. There are binocular loupes with an image magnification of two, two and a half and even six times. During the examination of the patient, the doctor most often uses a device with a maximum magnification. Trainees in medical institutions examine patients with binocular loupes with a double approach of the area being examined.

The characteristics of the optical device are related to each other, therefore, with a large expansion, the field of view narrows and the specialist will be able to consider not the entire object, but only small parts of it. Also, if a device with a sixfold magnification is used during examination, it must be remembered that this significantly decreases the depth of the perceived space. Therefore, when using a binocular loupe in surgery and dentistry, you need to ensure that all necessary objects fall into the field of view and are not blurred.

To view the area of ​​interest more clearly, you need to adjust the working distance, for example, using the device settings or approaching or moving away from the surveyed area. A magnifier with the same distance but different magnification will have different depth of field and field of view.

For example, if you examine a patient using a device with 2x magnification at a distance of 3.4 centimeters, then the field of view and depth of field will be the same - 1.3 centimeters. In the case when the doctor examines the object using a magnifying glass with an approximation of 2.5 times at the same distance, the field of view will be 0.9 centimeters, and the sharpness - 1.1 centimeters. When examining with a magnifying glass with a sixfold magnification at the same working distance, the sharpness will be 0.3 centimeters, and the field of view - 0.4 centimeters.

If the instrument is used with a sixfold magnification, the amount of light passing through the optics will be reduced. In this case, it is necessary to use the device only in an office with good and high-quality lighting. For an optical device with a small magnification, you need to use an LED source, and for a magnifier with a large magnification, a halogen illuminator is suitable.

A binocular lens with an approximation of two and a half times is considered the classic and most convenient. It is quick to set up and has a medium depth of field, so there is no need to constantly change the working distance. It is quite easy to get used to working with a binocular device, since the mechanism is easy to use. Optical devices with sixfold magnification are most often used in conventional surgery and neurosurgery during surgical interventions.

Spheres

It has been speculated that ancient cultures may have had telescopes because they made small balls of glass. The problem is that it is not known what they were used for, and they certainly could not form the basis of a good telescope. The balls could be used to enlarge small objects, but the quality was hardly satisfactory.

The focal length of an ideal glass sphere is very short and forms an actual image very close to the sphere. In addition, aberrations (geometric distortions) are significant. The problem lies in the distance between the two surfaces.

However, if you make a deep equatorial groove to block the rays that cause image defects, it goes from a very mediocre magnifier to a beautiful one. This decision is attributed to Coddington, and his name enlarger can be purchased today in the form of small handheld magnifiers for examining very small objects. But there is no evidence that this was done before the 19th century.

Comparison and Differences

The glasses do not come into contact with the surface of the eye. They can be taken off or put on at any time. The lens is put on directly on the cornea and remains on it throughout the day.

Positive aspects of using glasses:

• Ease of care: just wipe it and put it in a specially designated place or cover.
• Lack of contact with the eyeball.
• The ability to choose the shape of glasses and frames for the style of clothing, create a special image, assemble a collection for a wardrobe or mood.
• Use only when necessary: ​​read a book, work at a computer.
• Replacement is only necessary in case of visual impairment or loss. For neat people, glasses can last for years.
• Good eye protection from dust, debris, insects.

Advantages of lenses:

1. During the day, you can forget about the lenses: they are not felt at all.
2. The field of vision is complete.
3. Do not change their appearance.
4. Weather phenomena are not terrible: there is no influence of temperature drops or rain.
5. You can comfortably go in for sports and even swimming.
6. Does not interfere with the use of sunglasses.

Disadvantages of glasses:

• Limited peripheral vision.
• Depends on weather conditions: when it rains, drops fall on the glass and limit visibility, when the temperature drops, the glass fogs up.
• To wear on bright days, you need to purchase prescription sunglasses.
• You can lose or break at the most crucial moment.
• It is not always convenient to play sports.
• Changing the appearance "for an amateur", some people may develop a complex due to the need to correct vision by this method.
• With different diopters on the right and left eye, it may be necessary to make custom glasses.

Negative aspects of wearing lenses:

1. The need for daily care: taking off and dressing, cleaning.
2. Putting on: wash your hands, wipe them dry, rinse the lenses in a special solution. The procedure itself can also cause difficulties and negative feelings.
3. There may be a sensation of a foreign body: something could have entered the lens or it was not worn correctly. Then the entire donning procedure will have to be repeated.
4. It can be lost or broken.
5. Development of allergic reactions is possible.
6. For some diseases (colds, conjunctivitis), use will have to be discontinued.
7. If not removed before bedtime, dryness and redness of the eye may appear in the morning.
8. They require constant planned replacement.

When glasses are prescribed

Glasses consist of a frame and spectacle lenses. They should be selected by an ophthalmologist. This accessory is required to improve and correct vision.

What are the indications for wearing glasses:

• Astigmatism. With this disease, objects are bifurcated in the eyes, sometimes they are seen twisted. Clarity is lost, eyes get tired quickly during work. Overwork headaches may occur. With this pathology, the shape of the cornea or lens is disturbed.
• Myopia, or myopia. A person does not see distant objects clearly, but close up well. Focusing occurs in front of the retina.

• Hyperopia, or farsightedness. The gaze is focused behind the retina, so a person can see well in the distance, and close objects are blurred.
• Aniseikonia. It is very difficult to read, perceive the relationship of objects. Since the same image has different magnitudes on the retina of the right and left eyes. It is accompanied by increased vision fatigue.
• Heterophoria, or latent squint. The eyeballs deviate from the parallel axes.
• Presbyopia. Age-related or senile hyperopia.

Consider when a doctor might recommend lenses.

How to decipher a prescription for glasses

During the consultation with an ophthalmologist, diagnostic tests are performed. Visual acuity, refractive ability and other indicators are determined using diagnostic tables and autorefractometry.

After completing all examinations, the patient is given a prescription for glasses. It contains designations consisting of Latin letters. Each of them has its own definition:

• OD. Indicates all indicators for the right eye.
• OS. Left eye designation. All criteria are just below the right eye designation.
• OU. Disorders that are determined for 2 organs of vision at the same time.
• Sph. Show detected using diagnostic tables. It means the presence of myopia or hyperopia, which is respectively defined with a minus or plus sign.
• Cyl. With the help of this indicator, the optical power of the lens is revealed, which is necessary for the correction of astigmatism. A cylindrical lens type is selected.
• Prism. This designation is prescribed in the event that a person needs to choose prismatic lenses. They correct myopia, that is, myopia.
• Ax. The indicator indicates the cylindrical tilt of the lens, which is expressed in degrees, ranging from 0 to 180.
• Add. Designation of the difference between the nearest and farthest point, which a person sees clearly. This measurement is necessary for those people who simultaneously develop myopia and hyperopia. In this case, bifocal or progressive lenses are selected.
• Dd. Designation for the distance between two pupils. This is necessary to identify the center of the lens through which the pupil will look.

An ophthalmologist determines the degree of visual acuity of a person and writes a prescription. To get glasses, you need to go to the optician with this prescription. There will be made optical devices individually for the patient.

How to choose?

Of course, when choosing a magnifying glass, it is necessary to determine the purpose of the device.

For people working in the medical field, the main thing is to choose a reliable mount. It is better to select samples in the form of a helmet or rim. It is not recommended to use models with spectacle frames: the device may slip off when the head is tilted.

For a more detailed examination of small details, you should choose models with backlight. They are most often used by dentists and ENT specialists.

There are several main criteria for choosing binocular loupes.

• Multiplicity of magnification. The parameter is responsible for the degree of magnification of the object.
• Focal length. In this case, we mean the distance of the object under consideration from the lens.
• Distance between the pupils. Comfortable work depends on this value. For people with small pupil distances, using eyepieces can cause fatigue and burning sensation. This is due to the presence of a partition between the panes. If the interpupillary distance is 64 mm or more, then the possibility of discomfort is minimal.

When choosing, it should also be understood that high magnification is not always the best option. The parameter value should be optimal for each type of work. Too high magnification can blur the image.

The size and shape of the glasses are also considered the main features when choosing a magnifier. The larger the glass, the less bulky details can be viewed. But the large size of the eyepieces increases the size of the structure itself.

The classic round lens is easy to manufacture, but less convenient to use than quadrangular lenses. In forehead magnifiers, magnifying glasses, helmets, they use just the same quadrangular shape. This greatly simplifies and speeds up the change of glasses.

The binocular loupe is the main tool for various types of work. The device can be found in everyday life of medical institutions. It is also used for domestic purposes.The choice of the device depends directly on the purpose and some parameters. These recommendations will help you choose the optimal device for a particular type of work.

For a video review of the Magnifier 81007a binocular loupe, see the following video.

Material

Two materials are used to make lenses:

• glass;
• plastic.

Glass is otherwise called mineral. Plastic have another name - polymer. In order to decide which material is best suited, you need to know the main advantages and disadvantages of each type.

Mineral or glass

Several advantages:

• Durability - they can be used for a long time and they do not undergo deformation, the glass remains clear and unclouded.
• Protection of the retina from ultraviolet rays - therefore it is well suited for those who are exposed to sunlight for a long time (drivers, pilots, parachutists).
• High transmission capacity - this parameter is maintained at any degree of illumination (this also allows you to apply a polarizing, anti-reflective or antireflection coating to their outer part).

A number of disadvantages:

• Low shockproof properties (in this regard, glasses with lenses must be protected and treated carefully).
• Possible discomfort while wearing - glasses with glasses are quite heavy, because of this, many experience discomfort in the nose bridge when wearing them. In addition, in this place, traces of frame souls often remain.
• A slow change in light transmission characteristics - this drawback is clearly manifested in glasses with photochromic lenses, which have various types of dark shades.

Plastic or polymer

Pros:

• Light weight - much lighter than glass.
• Impact resistance - several hundred times stronger than glass counterparts.
• Preservation of optical properties under extreme conditions. Plastic lenses are not exposed to abnormally high temperatures. An excellent option for those whose work activity is associated with similar conditions (for example, a worker in the metallurgical industry).
• Enhanced security. Compared to glass, organic lenses are the most resistant to impacts and drops. They break much less often, however, if they break, then their fragments are less traumatic. This option is great for people with an active lifestyle.
• They allow you to show your individuality. they are easy to process, which allows them to be produced in various variations of shapes and colors.

Minuses:

This type has one drawback - the plastic is easily scratched, leaving traces of deformation on itself. Because of this, distortion of the picture in the field of view may occur.

Lenses made from organic materials are divided into three subtypes:

Reaktoplasts

These are organic compounds that become solid when exposed to ultraviolet radiation. As a result of this process, a three-dimensional structure is formed, which does not change its characteristics and shape when it is subsequently exposed to heat. This material is used more often than others.

Thermoplastics

Polymers which, when exposed to heat, transform into a viscous and flowing substance. Because of this, large molecules do not change their original chemical structure. Lenses from this material are manufactured in the injection molding process.

Quasi-reactoplasts

Otherwise, they are also called quasi-thermoplastics. This is a set of plastics, which in their properties are considered an intermediate state between thermosetting plastics and thermoplastics. They combine all the positive properties of both subspecies.

Knowing the main differences between mineral and polymer types, we can determine which lenses for glasses to choose in order to ensure maximum comfort.

Important differences

Be very careful to distinguish convergence or divergence of rays from convergence or divergence of the lens. Lenses and light beams may not match.Rays associated with an object or image point are called diverging if they "scatter" and converging if they "come together". In any coaxial optical system, the optical axis is the path of the beams. The beam travels along this axis without any change in direction due to refraction. This is, in fact, a good definition of the optical axis.

A ray that moves away from the optical axis with distance is called diverging. And the one that gets closer to her is called convergent. Beams parallel to the optical axis have zero convergence or divergence. Thus, when talking about the convergence or divergence of one ray, it is related to the optical axis.

Some types of lenses, the physics of which is such that the beam is deflected more towards the optical axis, are converging. In them, the converging rays approach each other even more, and the diverging ones move away less. They are even able, if their strength is sufficient for this, to make the beam parallel or even convergent. Likewise, a diverging lens can separate diverging beams even more, and converging beams parallel or divergent.

Rating of the best manufacturers

In addition to the physical characteristics, it is necessary to select lenses from a certified and trusted manufacturer. The following brands are considered market leaders:

• Ray-ban;
• Maxima;
• Glance;
• Essilor
• Relax;
• Carl Zeiss;
• Rodenstock;
• Seiko.

These manufacturers produce high quality products that are manufactured using the latest technologies in the field of optics.

Essilor

The French company was founded in 1849. Under her leadership, 19 factories around the world produce spectacle lenses that are necessary for correct vision correction. Essilor is focused not only on product development but also on research in the field of optics.

The company conducts monitoring and testing to improve the quality of its products in 390 laboratories. Therefore, before mass production of any product, it will be tested by about 15,000 volunteers under the close supervision of independent experts.

The company allocates 150 ml of euros annually for research. With this approach, Essilor has developed a unique Crizal Prevencia coating that partially absorbs the blue spectrum. The latter negatively affects the work of the photosensitive cells of the retina.

Rau-Ban

The Italian corporation Ray-Ban is the leader in the quality of sunglasses. Lenses for vision are also of high quality, but they are not the main purpose of production. Glasses from this brand not only actively protect the eyes from ultraviolet light, but also do not harm the retina.

The eyes get tired less at work, the person does not experience discomfort when wearing glasses and does not feel a headache. The company's most popular product is mirror coated lenses.

The main disadvantage of Ray-Ban is the high cost of the manufactured goods. But the big price pays off due to the wear resistance of the products, good sun protection, wide assortment and fashionable design.

Maxima

Products from Maxima are manufactured in the UK. The company manufactures not only spectacle lenses, but also eye care products. Any product from this corporation is considered hypoallergenic. Products made from natural materials are especially popular. Unlike the world market leaders Essilor and Ray-Ban, Maxima products are sold at an affordable price.

Glance

The Glance brand is considered a young brand in the field of optics, therefore it is just beginning to gain popularity. The company's products are made of polymer material. A distinctive feature of spectacle lenses is their ultra-thin structure and pale green tint. The German company Glance is of high quality.

Zeiss

The more senior representative of German production in the field of optics is the Carl Zeiss corporation. The company was founded in 1846.Thanks to its developments, the company produces a wide range of lenses not only for spectacles, but also for medical equipment, telescopes and cinematographic devices.

Expert opinion
Nosova Yulia Vladimirovna

Ophthalmologist of the highest category. Candidate of Medical Sciences.

Glasses for glasses are recommended for people who spend a lot of time behind the wheel. The lenses have both a sunscreen, anti-reflective coating and a hydrophobic film. Such a product allows you to simultaneously prevent glass fogging and the ingress of a large amount of ultraviolet rays on the retina. A multi-layer coating is essential for maximum eye health protection.

Relax

The Korean company Relax produces sunglasses and sports glasses featuring large lenses with a blue tint. They provide 100% UV protection and have ventilation holes. The latter prevent glass fogging.

Bandwidth

Depending on the type of lens, the light rays pass through them differently. Therefore, the criterion is distinguished by the main types of optical means:

• transparent - they transmit absolutely all rays, a slight delay in ultraviolet radiation is possible, therefore the internal structure of the eyes is not protected;
• tinted - protection of the eyes from ultraviolet radiation, which prevents the risk of damage to the retina;
• photochromic - such models, in the absence of bright sunlight, remain transparent, but if it occurs, they become darkened, therefore they do not transmit harmful ultraviolet light;
• polarizing - protection of eyes from the negative effects of long-wave rays arising from reflection from the surface.

Clear lenses are used to improve visual acuity if models have diopters. If the product does not correct vision, clear lenses are used to improve the image. Any frame can be inserted into them, so they are versatile.

Tinted lenses can be painted in a certain color, therefore, they have a different effect on the organs of vision:

• brown, black - most well protect the organs of vision from ultraviolet radiation and exposure to bright rays;
• green - designed to protect the eyes of a person suffering from increased intraocular pressure, additionally calm the nervous system;
• gray - glasses capable of uniformly protecting the eyes from the action of bright light throughout the lens;
• orange - enhancement of contrast and color rendering of surrounding objects;
• pink, red, yellow - excite the nervous system, wearing is not recommended in the presence of ophthalmic diseases, overloads the eyes.

Chameleon glasses are suitable for people who partly spend time indoors, for example, in an office, at other times they are outdoors under the influence of bright sunlight. Polarized models are chosen by car enthusiasts.

Eyeglass tips

Before purchasing glasses, you must adhere to the following recommendations:

Visit an ophthalmologist. If after a visit to the doctor it turned out that you need to purchase lenses of low refraction, you can buy frames made of metal or plastic. Such glasses are thin and lightweight.

Therefore, even the purchase of rimless products is allowed.
It is important that the frame does not cause discomfort. Uncomfortable stiff arches of glasses can pinch blood vessels, rub the thin skin above the auricle and often irritate the skin.
You should not be guided by fashion when choosing thick frames

This design is quite heavy, so while wearing glasses, your ears will get tired faster. The person will experience discomfort and pain. In addition, the horn frame is designed for thick lenses, which will only add extra weight to the glasses.
Progressive and bifocals can be worn with narrow frames. It made it possible to improve the quality of vision in case of myopia.
For lenses of high refraction, it is recommended to select a plastic frame to compensate for the large weight of the glass.
Photochromic glasses are not suitable for drivers, because they darken only under the influence of direct sunlight. They will not save your eyes from bright light reflected from the road or signs. Tinted lenses are recommended for people with cars.
If there is a large difference in diopters when changing glasses, the person will experience discomfort and dizziness. The unpleasant sensations will go away on their own in 3-4 days.

IMPORTANT. If it was decided to buy a thick frame, it is recommended to choose products with wide arms.

They partially compensate for the discomfort.

Do I need to go to the doctor?

You don't have to make an appointment with an ophthalmologist to get a prescription. In salons, opticians check their eyesight for free. Experts determine the necessary vision correction and give recommendations on the choice of lenses and spectacle frames.

The exclusion group includes children under 16 years of age. During this period, the organs of vision continue to form. In addition, prolonged exposure to textbooks or a monitor can cause an accommodation spasm - an overstrain of the muscles responsible for focusing the image. In such a situation, glasses are not required.

When corrected with lenses, a spasm of accommodation can provoke the development of myopia. A pediatric ophthalmologist can accurately diagnose the pathology. The doctor conducts a step-by-step study, constantly changing the recipe, depending on the dynamics of the pathology treatment.

How do you know if the glasses don't suit you?

If the wrong lenses were selected, the person may experience:

• dizziness;
• acute headaches with prolonged wearing of glasses;
• discomfort in the eyes;
• there is a feeling of squeezing of the organs of vision;
• loss of orientation in space;
• sense of anxiety;
• pain in the eyes;
• deterioration in visual acuity.

You need to tell an ophthalmologist or an optician about your feelings.

Coating

In ophthalmology, a wide range of additional coatings are used, which allow not only to maintain eye health, but also to improve the comfort when wearing glasses.

The main coatings are:

Hardening

The most common type. The coating is applied on both sides, that is, on the outside and on the inside. Lenses with such a coating are less exposed to mechanical stress, which prolongs their life.

Enlightening

Apply it once or several times. Due to its physical parameters, the reflection of light rays is reduced, which improves the brightness and clarity of the image. The anti-reflective properties change depending on the number of layers.

Mirrored

This type is applied for a cosmetic effect. The mirror finish gives the glasses a modern, stylish look. It does not affect the optical parameters in any way.

Antireflex

Glare on glasses does not look aesthetically pleasing. In addition, their presence makes it difficult to create eye contact with the interlocutor in such glasses. To prevent this from happening, an anti-reflective coating is applied to the lens surface. It improves the quality of the picture in the visual field, so that the eyes can receive 10% more light. Along with this, visual acuity rises, tension in the eyes decreases.

Anti-glare

It is an ideal choice for those who are often exposed to bright flashes, be it cameras or the bright lights of vehicles at night.

Hydrophobic

Glasses with an anti-reflective coating are often not resistant to dirt. Therefore, in order to prevent dirt and water from contaminating the surface of the glasses, a hydrophobic coating is applied. It does not allow foreign reagents to adhere to the surface. In addition, this type of coating prevents them from fogging up when the temperature changes.

Multifunctional

These are coatings that combine several types. The effect of such a combination helps to increase the value of the lenses at times.

Galileo's trumpet

During the time of Galileo (early 17th century), glasses were widely available in Europe. They were usually made in Holland and distributed by street vendors. Galileo heard that someone in the Netherlands placed two types of lenses in a tube to make distant objects appear larger. He used a long focus converging lens at one end of the tube, and a short focus diverging eyepiece at the other end. If the focal length of the lens is f_o and eyepiece f_e, then the distance between them should be f_o-f_e, and the force (angular magnification) f_o/ f_e... This is called the Galileo tube.

The telescope has a magnification of 5 or 6 times, comparable to modern hand-held binoculars. This is enough for many exciting astronomical observations. Lunar craters, the four moons of Jupiter, the rings of Saturn, the phases of Venus, nebulae and star clusters, and faint stars in the Milky Way can be easily seen.

Glasses

The first glasses invented by our ancestors served as protection from the sun. It was only in the 13th century that the first developments for improving vision appeared. But these glasses were intended only for farsighted people. The short-sighted citizens had to wait until the sixteenth century.

Previously, glass was used to make glasses. Plastic is now used because it is lighter and easier to work with.

Frames come in plastic, metal and natural materials. According to the production method, plastic frames are cast and milled. Steel, aluminum, bronze, titanium and precious metals are used for metal frames.

Compared to plastic, such frames are more vicious, and their thickness can be minimal. Do not forget about horn frames, because for their manufacture you need a real master who will process the horn.