One thing that patients should be aware of and prepared for are questions regarding their eye health history. Some of these may include your family's history regarding vision or eye difficulties, hobbies, lifestyle, and health status. Each of these questions aids the physician in discovering what may be affecting your eye. In addition to the aforementioned questions, inquiries into childhood diseases and allergies to any medications may also be asked.
Amsler's Grid provides a very useful test for discovering central vision disturbances. The standard Amsler's Test consists of a perfectly squared grid on a white background. A black dot appears in the middle of the grid and is used as a focusing instrument. Sometimes, another symbol, usually a diamond, will appear to the right or left of this dot. Essentially, a patient with a healthy macula will see the described grid without aberration. In an unhealthy macula a patient may observe spots, wavy lines, blurring, or distortion.
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Amsler's Grid is a useful observation device for anyone concerned about ARMD or other macular diseases. To acquire your own Amsler's Grid for home monitoring follow the Amler's Grid Test link.
NOTE: If you had to shade in any areas upon answering questions 1, 2, or 3 then you should make an appointment with your eye-care practitioner immediately. When you visit be sure to take in the Amsler's Grid with your shadings to help explain what you saw.
Color vision defects are common, expecialy for males. The most familiar color vision problem involves confusing reds and greens. Some individuals may also have problems with colors in the blue-yellow range. The standard test for assesing color vision defects is the Pseudoisochromatic plates. This test is contained in a book and consists of a variety of color plates. The plates have different patterns such as numbers, letters, figures, or a winding path within a series of dots that vary in hue and brightness from the background. For example, one plate may have a background of orange dots and the figure will be in olive dots. To a person with normal color vision, this is easily distinguished but to someone who is dichromatic (two colors appear to be the same like red and green) no figure will be seen. For the color plates below a person with normal color vision should be able to distinguish three different numbers.
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This is a very safe, non-contact examination of the inside of the eye and retina. The instrument used is a small handheld device called an opthalmoscope. The head of the tool contains many lenses and projects light through a variably sized aperature. This is attached to a handle which serves as the power source. The beauty of the opthalmoscope is that it uses the eye as a simple magnifier producing a magnified image for the eye-care physician to view. To obtain the best results from this analysis, lights in the exam room are generally dimmed allowing the pupil to maximally dilate. If the pupil is still to small, a topical mydriatic solution may be used to aid in dilation. The patient is then asked to fixate on a target. By varying the lenses, the distance from the patients eye, and aperature size; the doctor can survey the iris, crystalline lens vitreous, retina and optic disc. |
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Like its Direct counterpart described above, Binocular Indirect is used to inspect the retina. However, with the this technique a large area of the retina can be viewed instead of a only a small portion as seen with Direct Opthalmoscopy. The device consists of a headband, an optical viewing system, and a controllable illumination source. The lens system has eyepieces which are adjusted depending on the practitioners distance from the patient. In addition, a condensing lens held in the doctors hand near the patiens eye is used to generate an image of the retina. With Binocular Indirect Opthalmoscopy the eye-care practitioner has the advantages of a large field of view, bright illumination, a comfortable working distance from the patient, and little periphery view distortion. The pupils are dilated prior to performing this test. |
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The 90 Diopter (unit of refracting power for lenses) Lens is another non contact, well illuminated, retinal evaluation procedures. Similar to Binocular Indirect Opthalmoscopy, the 90 D exam uses a powerful condensing lens to produce a magnified image. A biomicroscope is used to magnify the image allowing easy illumination and viewing. Similar to the binocular indirect exam, the condensing lens is held in front of the patients eye. The 90 D lens examination provides high quality 3-D evaluation of the optic disc in addition to detailed inspection of the posterior portion of the eye.
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Fluorescein Angiography is generally used to discover vessels that have been compromised in the retina, choroid, and/or optic nerve. It is also utilized to measure the success of laser treatment on leaking vessels. The key component to this technique is Fluorescein, a stable and inert vegetable dye. It is injected intravenously where most of it binds to plasma proteins. The remaining unattached Fluorescein moves through the veins and capillaries and fluoresces only under illumination of certain wavelengths of light. Excitation occurs in the blue wavelength which is achieved by placing a blue filter over a direct light source. As the dye begins to fluoresce to its peak point, a special camera is used to take pictures of the areas in question.
The reason this technique works so well is that the small Fluorescein molecule cannot passively diffuse out of retinal vessels. In contrast, the other vessels in the body allow Fluorescein to pass through which may cause the patients skin to appear jaundiced in color. Other areas that allow Fluorescein to diffuse out are found behind the retina in the choroid. In this region choriocappilaris endothelial cells have small openings that allow Fluorescein to leak out giving rise to a fluorescent flush that can be seen in the developed pictures. When healthy, the RPE limits the amount of this choroidal flush because it does not allow Fluorescein to pass through it. In particular, the macula which contains a high quantity of melanin, hardly allows any transmission of fluorescence. As a result this region appears as a dark spot in photographs. If brightness is observed in the macula or other areas there is probably RPE damage.
Physicians who use this technique are aware of several certainities such as the time of normal blood flow, normal vascular patterns, and that healthy retinal vessels are impermeable to Fluorescein. By comparing the patients examination to normal standards practitioners can identify troubled areas. In the case of wet ARMD, Fluorescein Angiography is used to locate new sub-retinal vessel growth and/or identify leaking vessels. The importance of catching these problems early far outweighs the drawbacks of Fluorescein Angiography. Some of these include patients who dislike the camera flash or have a phobia concerning injections. In the latter case, oral fluroescein angiography may be a reasonable alternative. Despite these minor complications, fluorescein angiography is a valuable technique for evaluating the retina, optic nerve, and choroid.
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