Media are tools and technologies which facilitate the teaching learning process.

Overhead projection, slides, video, computer and internet are some of the more important media used in medical education. We will outline their attributes and describe their applications.

Overhead projection (OHP)

The overhead projection (OHP) is a versatile instructional medium designed primarily for teaching. It is not an alternative to the chalk - board, but has its own unique features, capabilities and merits. Although designed way back in the 1930's, it is only during the last three decades that is has emerged the most popular medium in education the world over. It provides effective support for instruction aimed at recognition, rules , concepts and discrimination. The most significant attribute of overhead projection is that it can be used with the room lights on. This enables the teacher to maintain eye contact with audience and there by ensure an interactive learning environment. OHP is also a very user - friendly system. The presenter can easily make her / his own transparencies using color pens (and not depending on the audiovisual units ) at an affordable cost.

Preparing Transparencies

The standard transparencies used for overhead projection are made of clear acetate or polyster. Other transparent materials like a washed x - ray film or cellophane can also be used so long as it is possible to write on them.

Transparencies are either square or rectangular in shape. Regardless of the shape, the visual information should occupy only the central area not exceeding 18 cm vertically and 24 horizontally.

Legibility is an important consideration of any visual presentation. The audience sitting in all parts of the room should be able to read the information on the screen. For most situations, the vertical height of the letters on the transparency should be at least 1 to 1.5 cm. In the case of printed matter, the letter size should at least be 18 points.

A single transparency should not contain too much information. This will inevitably clutter the visual. This is irritating to the viewer who may lose track of the presentation. Confine each transparency to a single concept expressed in just the key points. Several presenters write a page full of running text. This is a sure to kill you presentation.

Always use a combination of capital and small letters in your visual. The use of only upper case or capital letters in any visual presentation impairs the readability severely. The process of reading and assimilation is facilitated by the use of a mixture of capital and small letters, as is the case with normal text in newspapers and books which we read everyday.

One feature of the overhead projection system that makes it the most practical of all instructional media is that the transparencies can be easily handwritten. The presenter does not have to depend on the illustration units to prepare the material.

Special pens are used to write on the transparencies. Their ink is of two types, namely water based and spirit based. Before selecting the pens, make sure that the ink is translucent and the label says that they are meant for overhead projection. Pens with opaque ink will not project in color, but only in black. The transparency written with water - soluble ink can be wiped clean by a wet swab, while the material written with spirit - based ink can be removed by using alcohol or sprit. The best colors to use are black, purple, blue and red.

While making a hand written transparency, it is a good idea to place a ruled paper underneath. This helps in writing in straight lines, which may not be otherwise easy for many of us. Overhead transparencies can also be conveniently prepared using the electrostatic photocopier machines, even in color. However, only polyester transparencies with thickness of at least 100 micron can be used for this process. This method also makes it possible to enlarge the visual to a suitable size. Ready - made sets of multicolor transparencies on several medical subjects, such as anatomy and physiology are also available commercially.

If a transparency is likely to be used again and again, it is wise to mount it on a cardboard frame for better storage. Framed transparencies also make it convenient to use overhead and masking techniques. Such frames are a available commercially, but can also be improvises using cardboard which your children use for craft - work in school.

The information on a transparency can be highlighted to emphasise key points. This can be achieved in several ways - by underlining, by encircling and by using different colors. An impressive method of highlighting information is to use an overlay of a coloured transparency with a cut out which lets the visual within it stand out.

OHP Techniques

OHP based presentation can be made more effective by using masking and overlay techniques.

Masking means uncovering only a part   of the information available on a transparency at a time, the rest of the visual being shielded using an opaque paper or a card. Masking achieves two purposes. Firstly, the teacher presents just as much information as she / he is referring to, thus enabling the students to assimilate it properly. Secondly, it ensures that students do not read ahead of the points being covered by the teacher. Tendency to drift ahead conflicts with the audio and visual channels of communication which can adversely affect the teaching / learning experience.

How do we carry out masking ? A simple and practical method of masking is to place a paper or a card on the transparency and move it gradually as the presentation progresses. Some presents find it difficult to control the masking in this way. A more organized approach is to cut one or more strips of a card and paste them to the frame of the transparency. The presenter then lifts the strips one by one, uncovering the visual in steps. Masking should not be over - done. If all that is written on the transparency is a single message, it is not advisable to mask it.

The second OHP technique used extensively is the overlay. This fascinating technique is a unique feature of this medium. In it possible to create a full story by superimposing two or more transparencies, each carrying part of information. In this technique, you place one transparency on the projector then superimpose another one carrying and additional message over the first one. The projection now shows a composite picture that has developed in two stages. A third transparency may be placed on the firs two to develop the visual further, and so on.

This technique allows us to explain structure, describe procedures, emphasise a part of the visual and , above all, to build up complex information bit by bit. Sequential information is delivered more effectively by overly system rather than by masking technique. Overlay technique has more drematic effect than masking.

OHP also provides other applications. Using a moving line screen, it can be used to simulate motion (animation). It can be used to make or enlarge a sketch. By projecting the image on a poster, the artist can draw the sketch thereon. Overhead projection has been adapted to display computer panel which is placed comes on the transulcent LCD projection panel which is placed on the platform and the computer output, in colour or monochrome, in real time can be displayed on the screen.

Case of the Equipment :

OHP Projector should be carefully maintained. All glass surfaces tend to collect dust and finger print smudges. These should be cleaned properly. The projector should be covered when not in use. To prolong the life of the bulb, the switched off lamp should be allowed to cool by running the fan so long as warm air is emanating from the fan to be operated on its own.

The screen size should be related to the size of the room. A general rule of thumb is the so called 2 by 6 rule. it means that the nearest viewer should not be closer than a distance equaling 2 screen widths ; and the farthest one should not be more than 6 screen widths away. This approach ensures that all members of the audience get an optimum view of the projection.

In most cases, a centrally placed screen is quite acceptable. However, a screen thus placed tends to dominate the scene at the expense of the speaker. A corner placement, therefore may be a better choice. This way a larger area gets a good view of the screen. This is particularly useful if the lecture room is square.

The projector should be placed such that its beam makes a perpendicular with the screen. This requires the mounted lens of the projector to be at the level of the middle of the screen. The distance between the projector and the screen should be such that the images fills the screen fully. Keep in mind that the image becomes larger, but less brilliant, with increasing projector screen distance.

Improper positioning of the projector or the screen produces a very common distortion of the image called the Keystone effect. This effect may be vertical or horizontal. The vertical keystone effects is due to the fact that the projection beam is not prependicular to the screen. This happens because the projector is at a lower plane with respect to the screen. The vertical keystone effect can be eliminated by raising the projector or by tilting forward the screen top (such that it makes an acute angle with the vertical axis of the wall).

Horizontal keystone is less commonly encountered. It occurs because the projection beam is not at the perpendicular axis of the screen. It can be easily eliminated by bringing the projector in live with the plane of the screen.

Practical Tips

Here are some practical tips for improving your OHP presentation.

• Stand on one side of the projector so that you don't obstruct the view of the screen.

• Don't dilute the impact of your presentation by switching off the room lights. Overhead projection is meant to be used with lights on.

• Place the transparency properly on the stage before switching on the projector. It looks very amateurish to put on the projector first and then struggle with the transparency. This precaution is particularly important if masking technique is being used.

• Never leave a  visual on the screen after a point has  been made. Equally important, switch off the projector if no transparency is being projected. The bright glare can seriously distract the audience.

• It is generally advisable to use a pen or a pencil as a pointer on the overhead projection system. You are thus able to maintain eye contact with the audience. However, if you feel you would have more impact by using pointer on the screen, it is quite all right to do so.

• If you use cardboard framed transparencies, it is a good idea to write lecture cues on the frame as an aide memoir.

• It may be a good idea, at times, to add extra information to a prepared transparency at the time of presentation. It gives an element of spontaniety and helps draw better attention of the audience. If the transparency is valuable and cannot be written on, you may superimpose a blank transparency and use that for writing.

The 35 mm Slides

Projection slides (35mm) are a popular media among medical scientists and teachers. They improve the delivery of the spoken message by visual reinforcement of the key points. They are particularly suited to large audiences. Good slides enhance the range, the speed and the depth of presentation. Slides can bring the remote and inaccessible to classroom. Full colour capability makes the slide presentations highly absorbing. Slides can be coupled with taped text and used as a tape - slide program.

Slides should be prepared careful. Poorly prepared slides can kill the rapport of the speaker with the audience

Here are important attributes of a good slide.

A good slide is simple : Each slide should depict just one idea. It is better to build one's message by showing several slides, rather than dwell endlessly on a single detailed slide carrying all the information. It should be possible to absorb the information on a given slide in 4 seconds. This is as long as long as it takes an average person to both look and listen with reasonable comprehension.

A good slide is legible : In a typical text slide the typed area should not exceed 17 mm x 21 mm, number of words should not exceed 35, and number of lines should not exceed 6. Capital letters should be used sparingly. The slides with all capitals are not legible. Capital letters can however be judiciously used for short heading (as above) or for EMPHASIS.

For heading, larger point size is the ideal method. Underlining is genereally not recommended in a slide. Avoid the use of full stops. Other punctuation marks are also used sparingly. Placing cueing marks (bullets) alongside a new item helps in improving the legibility.

The material for slides should be printed bold and clear. Preferably use a laser. If routine typewriters are employed, use a good quality ribbon. Placing a reversed sheet of carbon behind the tying paper produces a denser image which is more suited for a slide.

In Non - Text slides, maintain a ratio of 2 : 3 in the illustration Do not put complex tables on a slide. Simplify the information and use only 2 or 3 columns and rows. If graphs are used, only minimum information should be put. Data points and lines should be bolder than the axis lines. Diagrams should and lines should be bolder than the axis lines. Diagrams should be kept as simple as possible.

A good slide is accurate : Do not make spelling mistakes or factual errors. Remember, a large number of  intelligent persons will be scrutinizing your presentation.

A good slide is appropriate : The projected material must be in true with what is being spoken. Choose the best visual depiction for your idea. Often , a picture is worth a thousand words ! And, may be a flow chart gives a better idea of what you wish to convey.

Video depicts pictures as well as sound. Unlike 35mm slides it display movement and is therefore a live medium. Real life situation can easily captured, played and replayed. The remote (an experiment in Antarctica), the inaccessible (an endoscopic visual of the duodenum), the delicate (care of a tiny baby in an intensive care demonstrated by the video. Unlike most other media, video can be used to change the attitude of the audience (e. g. by showing the dedicated care of the sick children by Missionaries of Charity) and motivate them for a cause. Video is highly effective in explaining procedures.

Video is a self - learning tool as well as an adjunct to teacher's presentation. It can be combined with a workbook containing objectives of the film and self assesment questions.

making a video film is time consuming and costly. However, the films can be easily copied and distributed extensively at an affordable cost. There is a need to create educational films for medical students based on our local needs and problems.

Computers

Computers have revolutionized several facets of life already. Education comprises of information, first and fore most, and will therefore be profoundly affected by the continuing advances in information technology. The advent of the personal computer has placed the most versatile of the contemporary media to the desk top (or lap top ) of the learner.

Computer, in many ways is a dream facilitator of learning. We know that learning is an individual matter occuring at an individual pace. Learning through computers is indeed an individual affair and the learner is in control of her / his learning. Perhaps the most unique attribute of computer and learning is interactivity. Computer gives instructions. A well designed package can readily augment the motivation of the learner by adjusting to the needs of the learner by providing her / him  progress towards the learning goals and perform analysis of the shortcomings upon receiving the feedback.

All learning, especially professional, blossoms when it is contextual. Medical teachers know it too well that best setting for the student to learn medicine is the ward, the clinic and the community. An alternative of a real life situation is a simulated situation. Computers are excellent tools providing simulated situations.

Through multimedia applications, computers can provide not only text but also graphics, pictures ( of real patients), sound (e. g. heart murmur) and animation. Using virtual reality techniques, in future, it will be possible to train students in sophisticated skills. The ability to combine many media together is a unique attribute computers. Computers can handle linear as well as branching  information. It allows the learner to browse and navigate through the package and access information at random. CAL is an excellent method to train the students in problem solving ability. It can train a novice to think and decide like an expert. A computer consists of hardware and software. Hardware is the machine, itself. For a personal computer, it consists of a monitor, a keyboard, a central processing unit and a mouse. It may also be a multi media kit consisting of CD - ROM disc, speakers, microphone etc. The software is the electronic information that drives the hardware itself or runs the applications (such as text, graphics, data handling, statistics, simulation, communication and so on). The CAL packages are computer software meant primarily for education. Most CAL packages are run through CD-ROM (Compact disc-read only memory) system. Each CD-ROM stores enormous information, often in multimedia format, that can be read, displayed or unloaded on to a printer. Computer can be used to make slides. Computers can be used for making full color images projecting the visual on the monitor over a full screen. Combining it with digital video disc (DVD), it is becoming possible to combine the best attributes of video with that of computers.

Computer is undoubtedly an excellent tool for teaching, learning and assessment. In the words of Bill Gates, the icon of the information age, computers have made it possible to 'learn more easily, enjoyable and successfully than even before."

Already hundreds of software packages on medical education have appeared in the international market. Computers labs are becoming a norm in most medical schools in the developed countries. Students are using lap top computers for talking notes in the class. The teachers bring their lectures on a floppy disc in their pocket and make presentations using the computer and data projector to a full class. Through internet, the computer places the student in a global classroom, literally.

In India, computers have yet to make much inroads into medical colleges, but we will not remain untouched by this revolution. It is just a matter of time. Hence, dear teachers, do not ignore the computer, master it !

The Internet

Several computers when interlinked with each other are called a network. This link may be by cables, telephone lines and / or the satellites. A user of any terminal of the network can share information from all the other terminals. Networks are created by individuals interested in sharing information. A network may thus encompass several or all computers of a hospital (e. g. linking laboratories, wards, blood banks, pharmacy etc.) or of ten libraries in the country or a hundred medical schools in five continents. A very large network may have several constituent networks.

Internet is the global network of network. It consists of over 30,000 networks in nearly a hundred countries. It is an outgrowth of a governent network called ARPANET created by the US defence department in 1969. Its designers started providing access to university scientists and industry engineers. It soon evolved into a vital communication link among collaborators located world wide. Currently, over 50 million people globally use the Internet today. This number will grow to 300 million by the year 2005 A. D. Indeed, with Internet, the information age has truly arrived.

Internet's most popular application relevant to us is World Wide Web or www in short. It is a network of servers which offer pages of information which is not only text but also graphic as well as audio. Form your home or office, you can not only browse a newspaper or a journal, but also see and listen to astronauts on the space shuttle mission. You can  download pictures of Mars taken by Pathfinder or record the speech of JF Kennedy on to your personal computer from the Internet.

You may be wondering what has all this got to do with medical education ! Well, a lot !! There are many Web sites related to medical sciences such as nih, healthfront and medguide etc. Internet web sites include those put by hospitals, universities, international agencies, health care foundations and libraries. The internet is bound to affect the lives of present and future generations of clinicians, teachers and students.

Here are some relevant applications of the Internet.

• Internet is the largest store of information. It uses the interactive hypertext environment for information exchange. The user can seek initial information and then go across to a sub topic and onto related information, and so on. The search and access is not linear, but branching with loops for feedback. This becomes a unique learning medium.

• It can help medical teachers to share information about various aspects of education. For instance WHO plans to put the bibliography of publications on bioethics on the Internet for access by any one.

• It is an unmatched tool for distance education. Periodically updated information (say on management of dengue) can be put on Internet for rapid global dissemination.

• Using E - mail facility of the Internet, you can communicate with people across the world and seek information on areas of concern. For instance, you may like to learn how to set up an OSCE (Objective Structured Clinical Examination) test on communication skills. This enquiry can be put on the Internet for anyone to provide information.

• You can browse through university libraries and conduct online search of literature.

• It is a publication medium also. The Cochrane network publishes scientific papers on meta - analysis of various clinical trails on Internet (without written publication). These are counted as publication by the concerned authors. The book in your hands is a available on the Internet also.

• Internet is also hands is available for telemedicine, telesurgery and teleconferencing.

In India, Internet access is available through Videsh Sanchar Nigam Ltd. for a fee. It is also available through many private companies. You need a telephone line and modem apart from a personal computer.

Internet revolution is just beginning to take off in India. Future students will be very well versed with Internet. It is time that medical teachers also familiarise themselves with the emerging importance, educational potential, reach and versatility of the information superhighway of which Internet is a mere harbinger !