Please create an account to participate in the Slashdot moderation system


Forgot your password?

Comment AMD Explained (Score 1) 68

AMD is the abbreviation for Age-related Macular Degeneration, and it is one of the main causes of vision loss in first world countries among people age 65 and older. At this point there is no cure for AMD, and doctors still aren't completely sure what causes it.  Perhaps, since we are living longer than generations before us did, our macula, which is responsible for straight-ahead, central, 20/20 detailed vision, is simply degenerating.  Maybe before they were able to recognize and name this disease, it was something like this:  "Grandma is really getting up in age (say 66 year old, when most ppl died around 60 years of age on average) and has now gone blind".   Anyone ever hear that said about older and prior generation family members?  There's a good chance that "Grandma" had AMD, there just wasn't a name for it yet.... besides "old age".

Some doctors now believe that there may be a genetic component to AMD as well, as it seems to run in families.  Siblings may get AMD, and perhaps one of their parents had it too (or most likely did).  Unfortunately there is currently no cure for AMD, only some treatment to arrest the progression of the disease and rehabilitation therapy skills and devices to teach patients how to "work around" and "live" with AMD, while still maintaining as much as the same quality of life before the vision loss.

Though the term "blind" is often used, generally, people who get AMD do not go completely blind (unless they have some other accompanying eye disease, such as glaucoma.  Because AMD mainly affects the central 20 degrees or so of vision (which is the vision we use for reading, writing, driving, recognizing someone's facial features....) they will still have use of their peripheral vision.  AMD can and often does result in legal blindness (only being able to see the "big E" on the standard Snellen eye chart, (if even that), and nothing smaller on the chart when sitting 20 feet away from it in a well lit area.

AMD can NOT be corrected with conventional eyeglasses or conventional contact lenses, as it is the degeneration or breaking down of a vital part of the retinal nerve which enables us to see centrally.  The vision loss caused by AMD creates a blurry or even dark spot in the middle of your vision.  For instance, if someone comes to the door and a person with AMD goes to answer the door, they may look at the person's face to see who it is, but not be able to make out the facial features enough or at all so as to identify who is standing at their door.  To see an example of what someone with AMD might see when looking at a picture of two boys holding a soccer ball and a basket ball, go here:

There are two types of AMD: Wet AMD, which the macula (at the back center of the retina, which lines the inside of the eye and goes to the back of the eye to become the Optic Nerve) has blood vessels which begin to leak blood into the center of the eyeball, which contains a clear jelly like substance.  With blood leaking into that clear area, called the vitreous, it creates vision loss, and Wet AMD can occur suddenly and without warning.  Often times, a patient will wake up and find that straight lines (like the door jam, or a telephone pole) appear to be "squiggly" as they see it.  That is a main indicator that there is now bleeding into the eye and it is an emergency situation.  If the patient can get into the Ophthalmologist right away, often the doctor can cauterize the bleeding vessels, thereby stopping the bleeding.  In time the eye may be able to flush the blood out of the vitreous area, thereby clearing up the vision.

The slower, generally less aggressive form of AMD is called Dry AMD.  This is the macula breaking down, and being reduced in its ability to see clearly.  Often however, Dry AMD can suddenly become Wet AMD, so doctors will often have an AMD patient look at an amsler grid daily to ensure that they can see the dot on the grid and that the grid lines are straight.

(For a picture of an amsler grid, go here:

If the lines do not appear straight or appear to be bending in towards the center dot, or the center dot, which is what the person's focus is to be on, is not seen, then likely Wet AMD has occurred and it is an emergency situation.

Perhaps the easiest way to explain the effect of AMD on a person's vision is to give an example.  Because a patient's central vision is affected, they likely will have difficulty reading, because they have that central "blurry" or "blind" spot, which is called a scotoma.  Scotomas can vary in shape and size, depending on the extent of the damage to the macula.   Without a cure, patients can only learn skills and utilize special magnifying equipment to read with the AMD scotoma.

Here's an example:  Place a silver dollar (or quarter) on part of a newspaper article.  That coin will likely block the viewing of parts of a few lines of the article and several letters in a few words.  The coin is representative of a scotoma.    Now, place a smaller coin, say a dime, on that exact same spot of newsprint.  Less lines and less of the lines/words are covered by the dime.  One may even be able to figure out (using context clues and what they can see around the dime's area) what is written on the newspaper under the dime.   The dime represents magnification.   If the print can be magnified so that it is larger than the person's scotoma caused by AMD, that person can likely read the text.    Currently there are hand held magnifiers that work well for some people with AMD so they can read "regular print" and there are also electronic devices which can magnify the text 36 times or even larger, thereby having their scotoma (like the dime) block out only a small portion of a letter, which the brain can automatically complete what that letter looks like, even with the missing area.    Unfortunately, the main electronic magnification devices, called Closed Circuit Televisions, or CCTVs,  are NOT portable.   There are some portable CCTVs on the market, but they may not be able to provide enough magnification for some people, as, due to their portability, their screen is rather small, thus limiting how big the print they wish to read can be made.  Size does matter in this case!  The non portable CCTVs can have a 21 inch (diagonally measured) or greater screen size (which is why they are not portable, not to mention the need for an electrical outlet and the sheer weight of the device), whereas the portable "CCTVs" may only have a screen size of 6 to 8 inches diagonally.

To view an example of a CCTV and of a portable CCTV go here:

(Note there are various manufacturers of CCTVs with different names and features.  The link is just to one of them as an example, not an endorsement of any particular device over another.)

So, the idea of having telescopic contact lenses with switchable magnification amounts sounds wonderful, in theory.  While I'm not sure even the developer has worked out all the details of how such a contact lens would work, my guess is that to have different magnification amounts, a person would have to have a different contact lens to utilize based on the magnification level desired and the focal length, or distance from what they are looking at at which the item is in clear focus.  To have one (or one set of) contact lens that can vary in magnification amounts say even from 4x to 8x sounds amazing (and un-doable) to me.

But, with a better understanding of the disease of AMD and the way to live and function as independently with AMD, one can see the draw to a telescopic varied magnification level contact lens!!  No handheld magnifiers to remember to bring with you to read a restaurant menu, no monocular telescope or binocular hanging around your neck for clearer distance viewing, and no aesthetic issues, such as feeling like others are staring at you (and they probably are!) because you are using some kind of device to read something that most other people can read.  Not to mention, extreme portability!!  What a wonderful thing!!  I hope the developer is able to create such a contact lens and that they are not cost prohibitive to our ever-growing senior citizen population with AMD!!

I hope some of you have found this information to be helpful...

Amy K. Brown   MS, CLVT, CVRT
Masters of Vision Rehabilitation
Certified Low Vision Therapist
Certified Vision Rehabilit

Slashdot Top Deals

How long does it take a DEC field service engineer to change a lightbulb? It depends on how many bad ones he brought with him.