English for Bio-Medical Engineers (self-study competence development). Учебное пособие

5.3.5 Describe one of the medical devices and define the class it belongs to according to the classification given in the text (Task 5.1.3).

6 Unit 6. Fundus photography

6.1 Text A. Fundus photography

6.1.1 Memorize the following words and word-groups from the texts of the unit:

6.1.2 Read the following words and word-groups:

fundography, interior, posterior, angiography, ophthalmologists, fundus, advantage, availing, recreate, handheld ophthalmoscopes.

6.1.3 Read and translate the text without the dictionary and say what fundus photography is used for.

Fundus photography (also called fundography) is the creation of a photograph of the interior surface of the eye, including the retina, optic disc, macula, and posterior pole (i.e. the fundus).

Fundus photography is used by optometrists, ophthalmologists, and trained medical professionals for monitoring progression of a disease, diagnosis of a disease (combined with retinal angiography), or in screening programs, where the photos can be analysed later.

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Compared to ophthalmoscopy, fundus photography generally needs a considerably larger instrument, but has the advantage of availing the image to be examined by a specialist at another location and/or time, as well as providing photo documentation for future reference. Modern fundus photographs generally recreate considerably larger areas of the fundus than what can be seen at any one time with handheld ophthalmoscopes.

6.2 Text B. Fundus camera

6.2.1 Memorize the following words and word-groups from the texts of the unit:

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6.2.2 Read the following words and word-groups:

doughnut, shaped aperture, magnified , retinal area, magnification, auxiliary lenses, ophthalmoscope, monocular, medium, simultaneously, cornea, towards, light source.

6.2.3 Read and translate the text using the dictionary. Be ready to speak on the topic.

Figure 7 – A non-mydriatic Topcon retinal camera

Fundus photography is performed by a fundus camera, which basically consists of a specialized low power microscope with an attached camera.

Optical principles. The optical design of fundus cameras is based on the principle of monocular indirect ophthalmoscopy. A fundus camera provides an upright, magnified view of the fundus. A typical camera views 30 to 50° of retinal area, with a magnification of 2.5x, and allows some modification of this relationship through zoom or auxiliary lenses from 15°, which provides 5x magnification, to 140° with a wide angle lens, which minifies the image by half. The optics of a fundus camera is similar to those of an indirect

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ophthalmoscope in that the observation and illumination systems follow dissimilar paths. The observation light is focused via a series of lenses through a doughnut shaped aperture, which then passes through a central aperture to form an annulus, before passing through the camera objective lens and through the cornea onto the retina. The light reflected from the retina passes through the un-illuminated hole in the doughnut formed by the illumination system. As the light paths of the two systems are independent, there are minimal reflections of the light source captured in the formed image. The image forming rays continue towards the low powered telescopic eyepiece. When the button is pressed to take a picture, a mirror interrupts the path of the illumination system allow the light from the flash bulb to pass into the eye. Simultaneously, a mirror falls in front of the observation telescope, which redirects the light onto the capturing medium, whether it is film or a digital CCD. Because of the eye’s tendency to accommodate while looking though a telescope, it is imperative that the exiting vergence is parallel in order for an in focus image to be formed on the capturing medium.

Since the instruments are complex in design and difficult to manufacture to clinical standards, only a few manufacturers exist: Topcon, Zeiss, Canon, Nidek, Kowa, CSO and CenterVue.

Modes. Practical instruments for fundus photography perform the following modes of examination:

-Color, where the retina is illuminated by white light and examined in full color.

-Red-free, where the imaging light is filtered to remove red colors, improving contrast of vessels and other structures.

-Angiography, where the vessels are brought into high contrast by intravenous injection of a fluorescent dye. The retina is illuminated with an excitation color which fluoresces light of another color where the dye is present. By filtering to exclude the excitation color and pass the fluorescent color, a very high-contrast image of the vessels is produced. Shooting a timed sequence of photographs of the progression of the dye into the vessels reveals the flow dynamics and related pathologies. Specific methods include

sodium fluorescein angiography (abbreviated FA or FAG) and indocyanine

green (abbreviated ICG) angiography.

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Indications. Fundus photography is used to detect and evaluate symptoms of retinal

detachment or eye diseases such as glaucoma.

In patients with headaches, the finding of swollen optic discs, or papilledema, on fundus photography is a key sign, as this indicates raised intracranial pressure (ICP) which

In patients with diabetes mellitus, regular fundus examinations (once every 6 months to 1 year) are important to screen for diabetic retinopathy as visual loss due to diabetes can be prevented by retinal laser treatment if retinopathy is spotted early.

In arterial hypertension, hypertensive changes of the retina closely mimic those in the brain, and may predict cerebrovascular accidents (strokes).

6.2.4 Say whether the statement is true or false and if it is necessary correct it.

1 Fundus photography is performed by a fundus camera, which basically consists of a specialized high power microscope with an attached camera.

2 A fundus camera provides an upright, magnified view of the fundus.

3 A typical camera views 30 to 50° of retinal area, with a magnification of 2.5x, and allows some modification of this relationship through zoom or auxiliary lenses from 15°, which provides 7x magnification, to 140° with a wide angle lens, which magnifies the image by half.

4 The light reflected from the retina passes through the un-illuminated hole in the doughnut formed by the illumination system.

5 When the button is pressed to take a picture, a mirror interrupts the path of the illumination system allow the light from the flash bulb to pass into the eye.

6 Specific methods do not include sodium fluorescein angiography and indocyanine green angiography.

7 Fundus photography is used to correct the symptoms of retinal detachment or eye diseases such as glaucoma.

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8 In patients with diabetes mellitus, regular fundus examinations are important to screen for diabetic retinopathy as visual loss due to diabetes can be prevented by retinal laser treatment.

9 In arterial hypotension, hypotensive changes of the retina closely mimic those in the brain, and may predict cerebrovascular accidents (strokes).

10 By filtering to exclude the excitation color and pass the fluorescent color, a very low-contrast image of the vessels is produced.

6.2.5 Answer the following questions:

1 What does fundus camera basically consist of?

2 What are optical principles of fundus camera?

3 What is fundus camera similar to an indirect ophthalmoscope in? 4 What does the light reflected from the retina pass through?

5 What are the manufacturers of fundus camera?

6 What modes of examination does fundus camera perform?

7 What are the specific methods of angiography?

8 What is fundus photography used for?

9 How often and why is it important to arrange fundus examinations in patients with headaches and diabetes mellitus?

10 May hypertensive changes of the retina predict cerebrovascular accidents (strokes)?

6.2.6 Speak on the main principles of operation and indications for fundus camera application.

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7 Unit 7. Types of Microscopes

7.1 Text A. History of the Microscope

7.1.1 Memorize the following words and word-groups from the texts of the unit:

7.1.2 Read the following words and word-groups:

experimented, edges, lentil, magnifier, object, curvature, contribution, marvel, affordable for, microscope manufacturer.

7.1.3 Read and translate the text using the dictionary. Outline the main stages in the microscope invention.

During the 1st century AD (year 100), glass had been invented and the Romans were looking through the glass and testing it. They experimented with different shapes of clear glass and one of their samples was thick in the middle and thin on the edges. They discovered that if you held one of these “lenses” over an object, the object would look larger.

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Someone also discovered that you can focus the rays of the sun with one of these special “glasses” and start a fire. These early lenses were called magnifiers or burning glasses. The word lens by the way is derived from the Latin word lentil, as they were named because they resembled the shape of a lentil bean (look up lens in a dictionary).

These lenses were not used much until the end of the 13th century when spectacle makers were producing lenses to be worn as glasses.

The early simple “microscopes” which were really only magnifying glasses had one power, usually about 6X - 10X. One thing that was very common and interesting to look at was fleas and other tiny insects. These early magnifiers were hence called “flea glasses”.

Sometime about the year 1590, two Dutch spectacle makers, Zaccharias Janssen and his father Hans started experimenting with these lenses. They put several lenses in a tube and made a very important discovery. The object near the end of the tube appeared to be greatly enlarged, much larger than any simple magnifying glass could achieve by itself! They had just invented the compound microscope (which is a microscope that uses two or more lenses).

Galileo heard of their experiments and started experimenting on his own. He described the principles of lenses and light rays and improved both the microscope and telescope. He added a focusing device to his microscope and of course went on to explore the heavens with his telescopes.

Anthony Leeuwenhoek of Holland became very interested in lenses while working with magnifying glasses in a dry goods store. He used the magnifying glass to count threads in woven cloth. He became so interested that he learned how to make lenses. By grinding and polishing, he was able to make small lenses with great curvatures. These rounder lenses produced greater magnification, and his microscopes were able to magnify up to 270X!

Anthony Leeuwenhoek became more involved in science and with his new improved microscope was able to see things that no man had ever seen before. He saw bacteria, yeast, blood cells and many tiny animals swimming about in a drop of

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water. From his great contributions, many discoveries and research papers, Anthony Leeuwenhoek (1632-1723) has since been called the "Father of Microscopy".

Robert Hooke, an Englishman (who is sometimes called the “English Father of Microscopy”), also spent much of his life working with microscopes and improved their design and capabilities. Little was done to improve the microscope until the middle of the 19th century when great strides were made and quality instruments like today’s microscope emerged. Companies in Germany like Zeiss and an American company founded by Charles Spencer began producing fine optical instruments.

Today, there are no microscope manufacturers in the US and most of the microscopes come from Germany, Japan and China. Toy plastic microscopes should be avoided as they do not achieve the level of quality of the basic instruments with metal frames and glass lenses.

Because of foreign production, quality microscopes have become affordable for all. Zaccharias Janssen, the inventor of the microscope would marvel at the quality of even the most basic microscopes found in schools today.

7.2 Text B. Microscope Glossary

7.2.1 Memorize the following words and word-groups from the texts of the unit:

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