Macular Degeneration: Losing your Sight in the Blink of an Eye
As a people progress throughout their life and then begin to grow old, a majority of them begin to experience health problems that are attributed to their age. One such problem that causes both physical and psychological damage to the person is the loss of their ability to see. Macular degeneration, a disease which significantly decreases a person’s ability to see using their central vision, is one such disease. Although there are two different and distinct types of the disease, the results are the same (6). A person diagnosed with macular degeneration losses their central sight over a period of time. Often times, legal blindness is an end result of the disease. Though there have been major strides in the identification of risk factors and treatments, a definite cause is unknown and for the majority of the cases, there is no cure because there is still little know about the disease. In addition, some of the treatments for it, such as the use of stem cells, are at the center of a raging debate (3). Regardless of the issues surrounding the disease, something must be done because today, macular degeneration is the leading cause of blindness in people over the age of 55 (4).
Macular Degeneration is a disease affecting the eye in which the person gradually loses their central vision as time progresses. The part of the eye that is responsible for perceiving the ‘fine visual details’, the macula, contains what are known as photoreceptors (9). These photoreceptors are light sensing cells that are responsible for converting light rays into electrical impulses. These impulses are then transferred to the brain via the optic nerve, which is located in the back of the eye. It is these photoreceptor cells that are affected by the disease which causes them to degenerate, which leads to the loss of the central vision (9). Usually, an individual’s peripheral vision is not affected by this disease. In most cases, there is a severe and often times irreversible loss of sight. People with this disease usually begin to notice a blurring of their central vision which can be accompanied with straight lines that look imprecise or warped (9). Soon afterwards, blind spots will begin to develop, greatly affecting many everyday tasks such as reading and driving.
Within the confines of the disease of macular degeneration, there are two separate and distinct types with different causes; “dry” and “wet” macular degeneration (6). “Dry” macular degeneration accounts for about 90% of all macular degeneration cases and blindness occurs gradually and usually over long periods of time (9). With this type of the disease, the macula is affected with yellow-white deposits called drusen, which are the waste products that are given off by the photoreceptor cells in the macular. These drusen deposits accumulate in the retinal pigment epithelium, otherwise known as RPE (9). The RPE is located directly beneath the macular. Too many drusen deposits underneath the macula cause it to become thin, dries it out, and eventually lose its ability to function properly. Consequently, the amount of central vision a person loses is directly related to the amount and location of the drusen deposits (6). There are no known cures for this type of macular degeneration.
The other type of macular degeneration is known as the “wet” type. This accounts for the remaining 10% of macular degeneration cases and can progress much faster then the “dry” type, thus usually causing more severe vision loss. With “wet” macular degeneration, there is an abnormal growth of blood vessels underneath the macular. These blood vessels leak fluid into the macular, which causes the macular to swell or protrude and damages the photoreceptor cells which lead to blindness (9). Again, peripheral vision is not usually affected. Although this type of the disease usually has more severe consequences, there are also a number of FDA (U.S. Food and Drug Administration) approved treatments. If caught and diagnosed early enough, the patient can have a laser treatment. Here, a laser is used to carefully destroy the unwanted leaking blood vessels (6). Even though multiple treatments are usually necessary, this is an improvement over previous laser treatments. In addition, the FDA recently approved the use of Lucentis, a new molecular entity, which is injected directly into the eye and is supposed to block new blood vessel growth and leakiness (2).
However, there has been a recent breakthrough in the development of treatments for macular degeneration. Researchers have taken a huge step forward in regards to the use of stem cells to help restore vision in those with macular degeneration (7). The team of researchers took human embryonic stem cells, derived RPE and photoreceptor cells from them, and transplanted them into rates with retinal degenerative diseases (7). The aim was to save the vision by producing growth factors, which are vision restoring proteins in the eye, and by implanting new photoreceptor cells. As a result, the RPE cells not only survived, but also continued to produce new growth factors (7). The results were uplifting, with reports saying that, “improvement in visual performance of the treated rats was 100 percent over untreated controls,” (7). In addition, a lead research said that, “When their eyes fully developed, the human cells survived, migrated into the sensory part of the eye and formed the correct cells,” (8). Now, the team is doing studies to see if it has the same effects on humans with retinal degeneration diseases.
Yet there is a large and over-shadowing problem with this new find. The use of stem cells is a hotly contested debate among people. This is especially so because the type of stem cells used in these studies were embryonic ones, meaning they are derived from 4 to 5-day old embryos that were destroyed in order to retrieve the necessary cells (3). The controversy rages over the question of weather the 4 to 5-day old embryos are considered alive. To those who see them as living beings, stem cell research is killing babies in order to harvest their stem cells. This rather extreme view is held by a number of people, including President Bush. To deal with this problem, he called for laws to ban what he calls “all human cloning” (1). This includes therapeutic cloning, which is simply another name for stem cell research. In his State of the Union address, Bush stated that “and because no human life should be started or ended as the object of an experiment, I ask you to set a high standard for humanity, and pass a law against all human cloning,” (1). Thus, he has essentially made it illegal to research or use stem cells.
One alternative suggested is to use adult stem cells instead of embryonic ones. However, these stem cells are used over adult stem cells for a number of reasons. The major reason embryonic stem cells are used is because scientists think that “embryonic stem cells have a much greater utility and potential than the adult stem cells, because embryonic stem cells may develop into virtually every type of cell in the human body,” (7). If adult stem cells were used, the chances of a successful transformation into the necessary photoreceptor cells are greatly reduced. Another reason embryonic stem cells are used is because they are relatively easy to grow in cell cultures (3). In addition, the chances of the new stem cells being rejected by the body are low. This has been personified by the fact that stem cells can be transferred from one species to another (from pig to rat) without being rejected (3). Nevertheless, more studies need to be performed in order to have a definite answer.
However, with the debate raging over stem cell research, people often lose sight of the true issue. It all comes down to the fact that people’s lives are being forever altered by a disease that strips them of their central eyesight permanently. For a disease where no definite causes are known and with very little treatments available, the potential success of stem cells is a saving grace to those afflicted with it. A person is not only devoid of their ability to physically see, but their psychological status is forever altered as well. Macular degeneration perpetually transforms a person’s ability to lead a normal and healthy life. To make matters worse, there is a potential life-altering cure available, yet certain individual’s religious views on what constitutes a life are stopping important scientific progress in its tracks. It is time to give people with macular degeneration their life back. Macular degeneration cases are increasing in numbers exponentially and are on the verge of becoming an epidemic with our nation’s senior citizens.
Works Cited Page:
1) Bush, George W. Address. State of the Union. The U.S. Capital, Washington D.C. 28 Jan. 2003. na <http://www.whitehouse.gov/news/releases/2003/01/20030128-19.html>.
2) "FDA Approves New Biologic Treatment for Wet Age-Related Macular Degeneration." FDA News. U.S. Food and Drug Administration. <http://www.fda.gov/bbs/topics/NEWS/2006/NEW01405.html>.
3) "Frequently Asked Questions." Stem Cell Research Foundation. <http://www.stemcellresearchfoundation.org/About/FAQ.htm>.
4) "Macular Degeneration - What Environmental and Behavioral Factors Increase the Risk?" Macular Degeneration. Foundation Fighting Blindness. <http://www.blindness.org/disease/riskfactors.asp?type=2>.
5) "Macular Degeneration General Information." Macular Degeneration Network. <http://www.macular-degeneration.org/home.htm>.
6) "Saving Sight through Research and Education." American Macular Degeneration Foundation. <http://www.macular.org>.
7) Shaberman, Ben A. "Investigators Pioneer Use of Stem Cells to Rescue Vision." Macular Degeneration. Foundation Fighting Blindness. <http://www.blindness/org/research.asp?id=288&type=2&print=1>.
8) "Stem Cells 'Could Restore Vision'" BBC News 25 Oct. 2004. <http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/3950827.stm>.
9) "What is Macular Degeneration?" Macular Degeneration. Foundation Fighting Blindness. <http://www.blindness.org/content.asp?id=46>.