MacularDegeneration
by AshleyDockx
Stephen F. AustinState University, Spring 2000
Return to Perception: Spring 2000frontpage.
Robert, a 65 year-old male, has troublereading fine detail, especially out of his central vision. Hecomplains that his vision is blurred and that it is harder to seewhile operating a motor vehicle. In addition, sometimes objectsappear wavy or crooked, which impairs his vision. His worst symptomswere that he occasionally lost the ability to distinguish between thefeatures of familiar faces and he had a localized blind spot. Robertis not alone; many people suffer from symptoms related to loss anddistortion of the visual field. He suffers from macular degeneration,the leading cause of decreased vision loss in the United States,especially for people over the age of 50 (Philippi, 2000).
Macular degeneration also known as late,aged-related maculopathy is an eye disorder which causes a decreasein the visual field known as the retinal macula (MedicalEncyclopedia, 2000). The majority of people who are affected arepeople over the age of 65, but occasionally it develops earlier inpeople 40-50 years old (Philippi, 2000). The majority of the visualloss is located in the central part of the visual field, while theperipheral vision is unharmed. There are also two types of maculardegeneration, the "wet" and "dry" forms. The "dry" form of thisdisease is the most popular, affecting 90% of the cases (AmericanAcademy of Ophthalmology, 1997).
Macular degeneration in general can affectmany people in minor or drastic ways. People who experience this formoften complain of vision loss when they are in dim light, especiallywhen they are reading. The "dry" type is often characterized by amore gradual loss of vision compared to the "wet" type. Signs of thisdisease include an increase in drusen, which is an accumulation of ayellow-white substance, in the underside of the macular retina. Aloss of cells can be seen in the macula. The macula is our sensitivesight region, where intricate detail can be seen. Thus, vision inthis area is helpful and necessary to drive, read, focus on smalldetails, and recognize familiar faces. The macula is located in theback of the eye known as the retina. The macula is only about 5 mm indiameter, and includes the fovea, which gives us our detailed centralvision. If a person suffers from the "dry" form in one eye they willbe more likely to develop it in the other eye as well.
In addition to, the "dry" form of maculardegeneration, we must consider the "wet" form. Affecting 10% of thepersons with macular degeneration this form can be very detrimentaland severe (American Academy of Ophthalmology, 1997). The wet form isalso referred to as the neovascular or exudative type (Cincinnati EyeInstitute, 2000). This particular form takes a more progressive pathand can affect the person more rapidly than the "dry" form. Also in alayer behind the retina, new blood vessels form in the choroids. Thenew blood vessels that develope tend to be on the outer side of themacula extending to the fovea. This process is known as choroidalneovascularization or a chorodial neovascular membrane (CincinnatiEye Institute, 2000). Once the new vessels have developed they thenbegin to leak, which causes the separation of the layers, which thencauses a retinal detachment. The gentleman mentioned at the beginningof this report, Robert, most likely experienced this form of maculardegeneration, especially since he suffered from blurred vision and alocalized blind spot in this visual field.
Both forms of macular degeneration have beenlinked to other family members, which makes this disease familial.Since scientists still today do not know the extent of this, we needto keep researching so perhaps we can stop this cycle before itaffects more and more people.
Treatments are being developed everyday inthis field of visual loss. The dry type of macular degeneration canbe treated by the use of laser treatments (Medical Encyclopedia,2000). Currently there is no known treatment to completely stop theformation or intensity of the dry form of macular degeneration. Thereis, however, research being done to see if vitamins and minerals willbenefit the person affected with this disease. Also, researchers havebegun to investigate if consuming dietary spinach or other greenleafy vegetables can slow down the dry form of AMD (Cincinnati EyeInstitute, 2000). On the other hand, new treatments of the wet formof macular degeneration are available and give people who suffer withthis disease a sense of hope. According to the National EyeInstitute, the treatment most commonly used to correct to reduce wetAMD is called laser photocoagulation (Philippi, 2000). In this laserprocedure a small, vigorous light ray is directed into the eye,focusing on a tiny location on the macula. This focusing of lightpreserves the vision by destroying any unwanted blood vessels thathave formed (Philippi, 2000). In this particular study vision losswas prevented and in some cases diminished extensively in over 50% ofthe cases. It is not the best solution for everyone who has thisproblem but has been known to help some. Using laser surgery is bestif the problem is detected early on, so that the fovea is not damagedseverely. This form of laser surgery is not used and will not help todiminish or extinguish the "dry" type of macular degeneration.Society will have to wait for later developments and research Thislaser surgery can not restore any previously lost vision, so if itwas damaged badly there is no chance of visual recovery (Philippi,2000). Also if a person with this disease goes through with the lasersurgery, then continued treatments will be necessary so thatadditional growths on the retina can be detected (Cincinnati EyeInstitute, 2000). The best way to decrease a person's chance ofhaving progressed macular degeneration is to see an eye specialist ifany symptoms occur or persist.
In the case of having the dry form ofmacular degeneration the person can not see with the naked eye thebuild up of drusen, so they should have a visual specialist examinetheir eye. Drugs can even be given to perhaps reduce this disease,for example thalidomide and antioxidant vitamins (Dr. Koop, 1999). Ifthese techniques do not work perhaps radiation therapy or bloodfiltration procedures would be beneficial. Radiotherapy has also beeninfluential in treating patients with choroidal neovascularizationalso known as CVN (Mauget-Faysse, et. al., 1999). Individuals alsocan check out their own eyes by using the Amsler Grid. This grid willgive people a patterned grid, which a normal person can distinguishbetween but someone with AMD will see distortions. The person shoulduse this technique on a daily basis so that they can realize changessooner.
Current research supports the idea thatmacular degeneration may be a result of "overeager repair of mildinjuries to retinal cells." An unhealthy, fatty diet may alsoincrease the immune overreaction due to high concentrations of fat inthe bloodstream.
On the other hand some research has beendone to see if the result of the disease is influenced by "thegradual starving of retinal cells." (Seppa, 1999) Blood formation wasa potential trigger for the formation of macular degeneration aswell. At the University of Pennsylvania in Philadelphia researchersreported that patients with the "dry" form of AMD had a lower-thannormal blood flow to the retina. This is perhaps due to the fact thatpoor circulation prevents nutrients from getting to the targetedarea. This can also explain the idea that healthy people are lesslikely to develop the "wet" form of AMD if they already haveexperienced the "dry" form of this disease (Seppa, 1999). Anadditional study was done to test whether or not neovascularage-related macular degeneration is related to oxidative stress(Frank, Amin, & Puklin, 1999). They found that oxidative stressdid in fact cause a pathologic upregulation of the enzymes hemeoxygenase and lysosomal antigen. They also found diminishing catalaseactivity in both the macular and peripheral areas of the eye,especially with age (Frank, et al., 1999). Not only has research beendone on macular degeneration in the United States but it has alsobeen studied in European countries and even Japan (Kadonosono,Yazama, Itoh, Sawada, & Ohno, 1999). Their research provides uswith the idea that choroidal neovascular membranes are responsiblefor the severe vision loss known as macular degeneration. This isbecoming a growing problem with people who are becoming legally blindin areas like Japan (Kadonosono, et. al, 1999). Additional researchalso supports the finding that perhaps hypertension is a factor thatimpacts the outcome of poor vision (Owens, Guymer, Gross-Jendroska,& Bird, 1999). Perhaps if we knew more about what causeshypertension we could reduce our chances of getting a form of maculardegeneration.
If someone suffers from macular degenerationthey should be informed of the risks, prevention and devices used toadapt to a new lifestyle. There is really no known prevention, but ifmacular degeneration runs in a family consider a smoke-free lifestyleif you smoke currently (Yahoo Health, 2000). There are also manydevices that help people with visual impairments manage everydayliving more easily. People can use low-vision aids, which can enhancethe images so that people can view slightly larger objects. Eventhough there is an extensive amount of information about maculardegeneration, there is still more to be understood. Especially,because the magnitude of the problem is considerable.
References
Frank, R.N., Amin, R.H., & Punklin, J.E.(1999). Antioxidentenzymes in the macular retinal pigment epithelium of eyes withneovascular age-realted macular degeneration. American Journal ofOphthalmology, 127 694-704.
Kadonosono, K., Yazama, F., Itoh N., Sawada, H., Ohno, S. (1999).Expression of Matrix Metalloproteinase-7 in Chroroidal NeovascularMembranes in Age-related Macular Degeneration. American Journal ofOphthalmology, 128,382-384.
Mauget-Faysse, M., Chiquet, C., Milea, D., Romestaing, P., Gerard,J.P., Martin, P., Koenig, F. (1999). Long term results ofradiotherapy for subfoveal chorodial neovascularisation inage-related macular degeneration. American Journal of Ophthalmology,128,781-782.
Owens, S.L, Guymer, R.H., Gross-Jendroska, M., & Bird A.C.(1999). Fluorescein Angiographic Abnormalities after ProphylacticMacular Photocoagulation for High-Risk Age-related Maculopathy.American Journal Of Ophthalmology, 127,681-687.
Philippi, K.,(2000). Macular Degeneration. The Health Connection.
Seppa, N. (1999). Physicians find clues to vision deterioration.Science News, 156, 215.
Websites:
Http://go.drkoop.com/conditions/macular_degeneration/page_49_238.asp
Http://www.cincinnatieye.com/laservisioncorection/eyedisordersand.htm
Http://209.64.11.10/Disease%20Cener/diseases/amd.asp