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... 1992). By comparison to the Beaver Dam Eye study with a predominantly Caucasian population, the Baltimore Eye Survey was a cross-sectional study with a multiracial population. In the Baltimore Eye Survey (Rahman et al, 1996) 5, 308 participants received an ophthalmological screening examination. Of this sample, 2, 395 were African American and 2, 913 were Caucasian Americans. OAG was defined on the basis of glaucoma tous optic nerve damage, abnormal visual fields or both.
IOP was not a criterion. For African Americans, prevalence rates were dependent upon age: 1. 2 % for those in the 40 to 49 year, and, 11. 3 % for those older than 80 years. For Caucasian Americans, the prevalence rates were also dependent upon age: 0. 9 % in the 40 to 49 year, and, 2. 2 % in those older than 80 years. The age-adjusted prevalence rate for African Americans compared with White Americans was 4 to 5 times higher underscoring a substantially higher risk for African Americans with respect to OAG. Gender did not influence prevalence in either African Americans or White Americans.
Although African Americans comprise 14. 7 % of the United States population, they comprise 25. 1 % of all patients with OAG (Quigley et al, 2001). Using a cohort size of 100, 000, 3. 9 % of the person-years in the African American cohort would be affected by glaucoma, about four times as many as a cohort of 100, 000 Caucasian participants. African Americans were shown to develop glaucoma about 6 to 10 years earlier than Caucasian Americans and had open angle glaucoma (OAG) longer than the average Caucasian American: African Americans = about 16 years, Caucasian Americans = about 13 years. In a population-based study of Hispanic subjects, detailed ocular examinations were conducted in eligible adults who lived in Nogales and Tucson, Arizona (Quigley et al, 2001). OAG was defined using threshold visual field defect and optic disc damage parameters (and not IOP). About 4, 800 subjects were examined.
The overall prevalence was 1. 97 % (95 % confidence interval, 1. 58 %- 2. 36 %). Prevalence rates were dependent on age. 0. 5 % in the 40 to 49 year, and, 12. 6 % in those older than 80 years. Only 36 (38 %) of the 94 subjects with OAG knew they had OAG prior to the study. If patients were screened using an IOP higher than 22 mm Hg as the only criterion, 80 % of the OAG cases would have been missed (Quigley et al, 2001).
The prevalence of OAG in Hispanic subjects is intermediate between Caucasian Americans and African Americans. In the Hispanic population sampled, glaucoma was the leading cause of bilateral blindness (Quigley et al, 2001). Prevalence Rate for People Age 40 and Over by State The map above reflects estimated state-by-state prevalence rates of vision impairment, including blindness. The overall national rate is 2. 85 %. When this rate is applied to the total U. S.
population age 40 and older of approximately 119 million, the result indicates that more than 3. 4 million older Americans are blind or vision impaired. Twenty-two states and the District of Columbia have rates above the national average, while 28 states have rates below the average. Iowa and North Dakota have the highest rates at 3. 73 % and 3. 74 % respectively. Alaska has the lowest rate at 1. 3 %. The largest majority of states (39 state and DC) are within the 2. 5 % to 3. 5 % range. Differences between states are likely due to demographic difference in age, race and / or gender distribution (National Eye Institute, 2002).
Future Perspectives on Glaucoma The current glaucoma treatment modalities involve administering eye drops and monitoring the disease, administering laser therapy and sometimes surgery to reduce IOP, but genetic research is taking a more prominent role in the delivery of evidence-based medical interventions. To date, eight genes have been identified that play a role in the development and progression of POAG (Richards & Lighter, 2005). Identified in the mid- 1990 s, the first gene was GLC 1 A. It was found to be responsible for mutations in the TIGR protein. The mutations in this gene are reported to affect 3 - 5 % of the general POAG population (Glaucoma Research Foundation, 2005). It is hypothesized that the TIGR protein may increase IOP by blocking aqueous flow through the trabecular meshwork. (Simmons, et al, 2004).
Only one commercial genetic test, Ocu Gene, is currently available and is considered complementary to current diagnostic interventions (Challa, 2003). It tests only 3 of the more than 40 mutations for GLC 1 A. Although it may help to identify a patient at risk for a more aggressive form of glaucoma, it is of limited use since only a small percentage of the adult POAG population is even affected by mutations on the tested gene. Still genetics research will play a major role in determining the glaucoma disease process and our understanding of it. Much research conducted today is aimed at patients diagnosed with glaucoma and their family members. Given the diversity of glaucoma genetics and the many families that do not map to any of the identified gene regions, it is likely that many other regions exist that are either causal or influential in the pathogenesis of glaucoma.
The identification of multiple glaucoma genes will enable the creation of a battery of tests to identify patients at risk for developing glaucoma (Challa, 2003). Initially, this genetic testing will allow for earlier intervention to reduce morbidity in the at-risk population (Gupta, 2005). Additionally, it is hoped that this genetic research will spur a commitment from pharmaceutical and medical supply companies to produce better therapeutic interventions that will target specific biomedical pathways for treatment. Pharmacogenetics, a new and exciting field of study, is emerging as a result of the human genome project. Scientists may someday use genetic information to understand how and why patients respond differently to the same medications. Not every patient has the same risk factors, develops the same symptoms, or responds to treatment the same way.
This has potentially far-reaching effects for physicians to acquire the ability to establish a risk profile and eventually tailor disease-specific treatment to an individual patient. In addition to early identification and therapeutic intervention of the at-risk population, further research will enable scientists to discover ways not just to treat glaucoma, but also to protect the eye from becoming diseased in the first place. This concept, neuro protection, is aimed at the cellular level. One of the characteristic symptoms of glaucoma is retinal ganglion cell death or apoptosis, which leads to deterioration of vision and potentially blindness. Many agents are hypothesized to have neuroprotective effects that may reduce a person's risk for developing glaucoma tous symptoms that lead to apoptosis. One such agent was discovered during a 2001 study conducted at the Weizmann Institute of Science in Rehovot, Israel.
It demonstrated that a vaccination with a synthetic compound known as Copaxone, normally used to treat multiple sclerosis, might be able to protect the optic nerve (Glaucoma Research Foundation, 2005). There are also some neuro corrective studies under investigation that involve infecting the trabecular meshwork, the ciliary epithelium, and the retinal ganglion cells by adenovirus, retrovirus and herpes virus vectors as a means of adding corrective DNA (Simmons, et al, 2004). The advantage of this delivery system is that it allows a safe and effective way to deliver genetic material to the specified target area. Gene therapy may someday allow physicians to control the production and outflow of aqueous, as well as prevent or slow the death of retinal ganglion cells (Harmon & Intrator, 2004). One theory under consideration for the distant future involves neurodegeneration. Researchers are optimistic that someday, the potential will exist to restore vision that has been lost to glaucoma.
Stem cell research may someday hold the key to reversing the damage from glaucoma by replacing the destroyed retinal ganglion cells (Harmon & Intrator, 2004). Policy Implications The science of genetics is growing at a rapid pace, and our ability to understand the implications it has on our society must also grow with it. With...
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Research essay sample on Optic Nerve African Americans
