Eye Examination Tools Curtis Kelly

Introduction to the Eye

The eyes are two if the most important organs in our body, as they have the responsibility of keeping our sense of sight
eye_with_labels.jpg
Here is a diagram of the human eye, including several of its vital structures
intact and properly functioning. Our sense of vision is the result of a complex process that involves all the parts of our eye coming together to create the image we see. Parts like the cornea, retina and **optic nerve** all have key roles in this procedure, and if even one of them isn’t functioning properly, the entire eye can be compromised. This is where the importance of eye examination tools can be seen; to ensure that our eyes stay working well for as long as possible. In this Wiki, you will learn about how doctors use some of these devices to keep our eyes safe from harm. (3, 4, 5)














Here is a short video about some parst of the eye and how it works,to get you strted with some of the infomation you need to know.

Ophthalmoscope

There are two types of the ophthalmoscope, the monocular direct (MO) and the larger binocular indirect (BIO). Here, the uses and purposes of both will be explained.

Monocular Direct Ophthalmoscope (MO)

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These are two of the many MO models


This is the smaller hand-held version, and it is used to examine the back of the eye, also known as the ‘**fundus**’. This instrument makes is possible to examine parts of the eye such as the optical nerve, **optic** **blood vessels**, and the macula for abnormalities. In addition, it can also detect alterations in clarity or obstructions of the optical media, which is normally completely transparent. This particular problem causes some of the light rays coming into the eye to be stopped or blurred, passing altered images on to the optic nerve. This then in turn causes us to only be able to see unclear or partial images. Ophthalmologists use this tool at various distances from the eye depending on the section of the organ they plan to examine: 20-60cm away for viewing the ocular media, and only a few millimetres to examine the back of the eyeball. (2)
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Here is an image of what occurs when a doctor uses an opthalmoscope. As can be seen, the light rays are manipulated to allow insight into the deep parts of the eye (eg. retina, optic nerve)


Binocular Indirect Ophthalmoscope (BIO)


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Shown here is and example of the BIO
This instrument is the larger counterpart of the MO, and is usually mounted on a doctor’s head or appears as a virtual reality type goggle that goes on the patient’s head. As it is larger, it has enough room to fit its own light source and optical system. Before examination, ophthalmologists will typically put water droplets in the patient’s eye to dilate the pupil, as this allows for a stereoscopic (3-D) view of the back of the eye. Due to the fact that this is a 3-D image, it provides a much larger view compared to the MO, however it is less magnified. Due to the wider viewing field, the BIO allows doctors to inspect parts of the eye that could not be seen with the MO, and also allows for more detailed pictures of some eye sections.
So, the decision between these two devices depends on the part of the eye being examined, and how detailed the image needs to be. (1,2)

Below you will find a video featuring the steps doctors take to perform a proper opthalmoscope exam:











Visual Fields Tester

This machine is usually automated so that the doctor doesn’t have to control the apparatus as it is performing the exam.
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Above shown is the usual appearance and operation of a visual fields tester
This particular tool is used to examine the retina and neurological parts of the eye, which means inspecting the visual pathways between the eyes and brain. This device is primarily used for detecting visual field loss resulting from diseases like: **glaucoma**, **retinal tears**, **artery and vein occlusions** and tumours along the **optic nerve pathway** and brain. It does by having the patient look at an oscillating bar pattern that appears in different locations on the video screen, and the patient presses a button if they see the image. Other tests are ones that place multiple pictures on the screen, and the patient must correctly count them. The aim of all these tests is to determine if any areas of the screen are can’t be seen by the person being examined, as this indicates there is a problem with the retina or neurological pathways. This is commonly used at the beginning of appointments as ophthalmologists will need to perform further diagnostic tests if the results of this machine come back with abnormalities. (2)

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This ray diagram shows how our eyes would see the images on the screen of a vision fields tester. As this machine focrces the patient's eyes to look at different angles, this means incident rays will come from various directions, making and blockages or damages to the eye apparent.

Recent Scientific Discoveries in Eye Testing

One of the newest additions to the world of eye examination is the Humphrey FDT unit. This particular tool is an improvement to the visual field testers because it is the first model to be computer assisted. This advancement allows the screening process to be faster, as well as more accurate because the FDT has much better comparative testing abilities. This machine works similar to the others by having the patient put their head inside the machine, and click a button then they see the target image. However, due to the advancements of this new Humphrey FDT unit, the screening process is shorter and more accurate. This cutting-edge technology is being used by more and more ophthalmologists each month because of its many advantages. (2)

Displayed above is a Humphrey FDT unit, a piece of cutting-edge eye examination equipment
Displayed above is a Humphrey FDT unit, a piece of cutting-edge eye examination equipment


Benifits to Society

When it comes to eye examination tools, the numerous benefits to society are obvious. The largest one of these is the reduction and elimination or eye diseases. These devices, along with many others, have drastically improved the amount of optical problems that are detected and fixed. By doing this, we have been able to preserve many people’s sense of sight, as well as in some cases even save their lives! We’ve allowed millions of people to go on living after an eye problem as if nothing had ever happened. Also, these machines have lead to many scientific breakthroughs in the field of optics. For example, we have learned many properties of light using discoveries made during eye examinations. Similarly, we have also made many improvements to glasses and contact (eye contacts) technologies that assists people who have trouble seeing. Lastly, there are many economic benefits this product provides. Not only does it create companies and jobs to produce these examination tools, but it also provides jobs for numerous doctors to specialize in the practise of ophthalmology. With all of the ways eye examination tools are beneficiary to our society, it is easy to say they have a large impact on out world today. (3, 4, 5)

Additional Fun Activity

If you've read the information on this site and have begun to wonder how good your eyesight is, use the following link to guide you to an online eye test that will tell you just how well your eyes are doing:
http://library.thinkquest.org/C005949/fun/eyechart.htm

Glossary

Cornea- A thin protective layer on the front of the eye that assists the intraocular lens with refracting light rays
Optic Nerve- Transmits visual information from the retina to the brain
Fundus- The general term used to describe the back of the eye
Optic Blood Vessels- Microscopic blood vessels that supply blood to various parts of the eye
Macula- An oval shaped area in the central retina that contains colour-sensitive rods; this is the point of our sharpest vision.
Optical Media- The term used to describe the middle area of the eye
Ophthalmologists- Physicians that study/treat the eye and diseases associated with it
Stereostematic- Means a view of the eye that has been created in a way that it can be viewed in a 3-D fashion, allowing all-angle vision.
Neurological- Describes the nervous system (brain & nerves) and all its functions in the body
Glaucoma- Abnormally high liquid pressure in the eye, usually caused by blockages in fluid channels
Retinal Tears- Rips that occur in the retinal tissue; can have very severe consequences
Vein Occlusions- The blockage or disruption of an ocular blood vessel
Optic Nerve Pathway- The path that image information takes along the optic nerve from the retina to the brain
Oscillating- Images that swing and move to and fro, akin to the movements of a pendulum
Ophthalmology- The study of eyes, eye diseases/infection, and other various ocular matters

Reference List

  1. Bickford, E. L. (n.d.). Ophthalmic Examination Instruments. Instruments Commonly Used for Examination of the Eye. Retrieved December 11, 2011, from http://www.eyecarecontacts.com/instruments.html
  2. OpthamologyWeb. (n.d.). Eye Examination Devices and Equipment | OphthalmologyWeb: The Ultimate Online Resource for Ophthalmologists. Home | OphthalmologyWeb: The Ultimate Online Resource for Ophthalmologists. Retrieved December 11, 2011, from http://www.ophthalmologyweb.com/Ophthalmic-Exam/5232-Eye-Examination-Devices-and-Equipment/
  3. Albert, D. M., Miller, J. W., & Azar, D. T. (2008). Albert & Jakobiec's principles and practice of ophthalmology (3rd ed.). Philadelphia: Saunders/Elsevier.
  4. The Basic Eye Exam. (n.d.). Docstoc – Documents, Templates, Forms, Ebooks, Papers & Presentations. Retrieved December 11, 2011, from http://www.docstoc.com/docs/33616340/The-Basic-Eye-Exam
  5. Cassel, G. H., Billig, M. D., & Randall, H. G. (2000). The eye book: a complete guide to eye disorders and health (Large print ed.). Baltimore: Johns Hopkins University Press.
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