Age Related Macular Degeneration (ARMD)
One thing that you should be aware of and prepared for are questions regarding your 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 Grid
Amsler Grid provides a very useful test for discovering central vision disturbances. The standard Amsler 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.
Amsler Grid is a useful observation device for anyone concerned about ARMD or other macular diseases. Acquire your own Amsler Grid for home monitoring.
Procedure for Amsler Grid test
Wear your glasses or contacts if you have any and hold the grid at arm’s length facing you so you can read side 1. Cover your left eye.
With your eye still covered, fix your vision on the dot in the middle of the grid and bring it toward you.
Keep bringing the card toward you until the large diamond has disappeared from peripheral sight. It is important that you continually stare at the dot and not try to look at the diamond.
- Did you see any lines that appeared wavy? If so shade them in with a pencil.
- Did you see any dark spots or blurry areas? If so shade them in with a pencil.
- Did all of the squares appear normal in size and equal to one another? If not, shade these areas in with a pencil.
After you have done this for the right eye, flip the grid over and examine your left eye. Repeat steps 2 and 3.
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 Grid with your shadings to help explain what you saw.
- Color vision
Color vision defects are common, especially 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 assessing 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 someone who is dichromatic (for whom two colors appear to be the same, like red and green) will not see the figure. A person with normal color vision should be able to distinguish three different numbers in the color plates.
- Retinal examination
This is a very safe, noncontact examination of the inside of the eye and retina. The instrument used is a small handheld device called an ophthalmoscope. The head of the tool contains many lenses and projects light through a variably sized aperture. This is attached to a handle that serves as the power source. The beauty of the ophthalmoscope 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 too 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 patient’s eye, and aperature size, the doctor can survey the iris, crystalline lens vitreous, retina, and optic disc.
Binocular indirect ophthalmoscopy
Like its direct counterpart described above, binocular indirect ophthalmoscopy is used to inspect the retina. However, with this technique a large area of the retina can be viewed instead of a only a small portion as seen with direct ophthalmoscopy. The device consists of a headband, an optical viewing system, and a controllable illumination source. The lens system has eyepieces that are adjusted depending on the practitioner’s distance from the patient. In addition, a condensing lens held in the doctors hand near the patient’s eye is used to generate an image of the retina. With binocular indirect ophthalmoscopy 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.
Biomicroscopy (90 D Lens)
The 90 Diopter (unit of refracting power for lenses) lens is another noncontact, well-illuminated, retinal evaluation procedure. Similar to binocular indirect ophthalmoscopy, the 90 D exam uses a powerful condensing lens to produce a magnified image. A biomicroscope is used to magnify the image, enabling easy illumination and viewing. Similar to the binocular indirect exam, the condensing lens is held in front of the patient’s 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.
Fluorescein angiography is generally used to discover vessels that have been compromised in the retina, choroid, and/or optic nerve. It also measures 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 that 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 patient’s 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 choriocappillaris 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 retinal pigment epithelium 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.
By comparing the patient’s examination to standards, such as time of normal blood flow, normal vascular patterns, and impermeability to fluorescein, practitioners can identify troubled areas. In the case of wet ARMD, fluorescein angiography is used to locate new subretinal 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 patient dislike of the camera flash or a phobia concerning injections. In the latter case, oral fluorescein angiography may be a reasonable alternative. Despite these minor complications, fluorescein angiography is a valuable technique for evaluating the retina, optic nerve, and choroid.