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... s what lessons were learned from these three particular studies? The answer lies with lowering the IOP. The Ocular Hypertension Treatment Study evaluated whether "lowering IOP was effective in delaying or preventing glaucoma in patients with ocular hypertension" (Johnson & Brandt, 2005). This study was designed to identify the characteristics in progression of disease in patients.
Also identified as major predictive factors for development of glaucoma was optic nerve anatomy and central corneal thickness (CCT). Study results concluded "only 4. 4 % of OHT study participants who received treatment developed glaucoma within five years. In comparison, 9. 5 % of individuals who were not medicated went on to develop glaucoma within five years" (Harmon & Intrator, 2004). The participants without treatment developed glaucoma at more than twice the rate of the treated group. Treatment is introduced earlier in these individuals than before this study.
An interesting fact is that this study was really the first well-conceived attempt to introduce the concept of risk assessment and analysis. The OHTS trial confirms the importance of IOP control in the treatment of glaucoma. The Collaborative Initial Glaucoma Treatment Study (CIGTS) measured whether medication or filtration surgery was better for the treatment of POAG (Johnson & Brandt, 2005). Patients have reported a decline in symptoms over time, but the surgery group experienced more foreign body sensation and ptosis which is defined as "drooping of one or both upper eyelids; it may be congenital or result from damage to the oculomotor nerve, myasthenia gravis, or other disorder" (Rothenberg, 2000).
CIGTS is an important study. It confirmed that no matter how the IOP was lowered in patients with newly diagnosed primary open angle glaucoma, physicians could stabilize the visual field and stop progression. The Early Manifest Glaucoma Trial was "conceived before the role of IOP reduction in delaying or preventing glaucoma tous visual field loss was well established" (Johnson & Brandt, 2005). The evaluated efforts of immediate treatment or no treatment on early-stage open angle glaucoma was tested. The progression rates for glaucoma seen in this study are higher than other studies.
This could be explained that progression was defined very sensitively, so that any subtle change in the visual field was considered to be from progression. The highlights from glaucoma clinical trials are in lowering intraocular pressure (IOP) that may delay or prevent glaucoma, medication or surgery as initial treatment as an effective way to long term IOP lowering, and in treating glaucoma early may lower the risk of progression of disease. Today physicians are searching for scientific evidence with regard to whom to treat, when to treat, and how aggressively to treat. These decisions about glaucoma therapy can be based on the results of these and many other clinical trials. Prevalence and Incidence of Glaucoma in the United States Studies have shown that glaucoma is the second leading cause of blindness in the United States (Leske, 1983) as well as the second leading cause of bilateral blindness in the world (Quigley, 1996). According to Healthy People 2010, glaucoma is a major public health problem in this country.
An estimated 3 million people in the United States have the disease; (Rahman et al, 1996) of these, as many as 120, 000 are blind as a result (Kahn & Moorehead, 1973). Furthermore, glaucoma is the number one cause of blindness in African Americans. However, at least half of the people who have glaucoma are not receiving treatment because they are unaware of their condition. Blindness from glaucoma is believed to impose significant costs annually on the Federal Government in Social Security benefits, lost tax revenues, and health care expenditures (Healthy People 2010). Healthy People 2010 also stated that, more than two-thirds of visually impaired adults are over age 65 years. Although no gender differences exist in the number of older adults with vision problems, more women are visually impaired than men are because, on average, women live longer than men do.
By 1999, almost 34 million persons in the United States were expected to be over age 65 years; that number is expected to more than double by the year 2030 (U. S. Bureau of the Census, 1999). As the population of older adults grows larger, the number of people with visual impairment and other aging-related disabilities is expected to increase. Anyone can develop glaucoma. Some people are at higher risk than others.
They include: African Americans over age 40, everyone over age 60, especially Mexican Americans, and people with a family history of glaucoma. A comprehensive dilated eye exam can reveal more risk factors, such as high eye pressure, thinness of the cornea, and abnormal optic nerve anatomy. In some people with certain combinations of these high-risk factors, medicines in the form of eye drops reduce the risk of developing glaucoma by about half (National Eye Institute, 2004). African Americans are twice as likely to be visually impaired as are Whites of comparable socioeconomic status. Studies conducted in the United States and the West Indies have shown that primary open-angle glaucoma exists in a substantially higher proportion of Caribbean Blacks and African Americans than in Whites (Klein et al. , 1992); (Leske et al. , 1983). Hispanics have three times the risk of developing Type II diabetes as Whites, and they also have a higher risk of complications (Novella, Wise, and Kleinman, 1991).
This is significant since diabetes may be a risk factor for glaucoma. Many barriers still need to be overcome in reducing vision disorders. Among the major prevention strategies are educating health care professionals and the general population about the benefits of prevention, improving access to quality health care across socioeconomic classes to decrease disparities, and gaining cooperation of families in the screening and treatment of infants and children (Healthy People 2010). Prospective Study In a random sample from Salisbury, Maryland, 2, 520 Medicare patients agreed to participate in a prospective study and have their eyes tested (Munoz et al, 2000). The presence of bilateral visual insight less than 20 / 40 increased from 4 % in those 40 + years old to 16 % in those 80 + years old. Of all participants, 21 (0. 83 %) were bilaterally blind.
Of theses 21 patients: 43 % were blind from age related macular degeneration, 10 % were blind from diabetic retinopathy, 10 % were blind from glaucoma, and, 37 % were blind from other causes. In the United States, glaucoma is a common reason for patients to visit their ophthalmologist. Among patients 40 + years of age, between the years 1991 and 1992 glaucoma was the third most frequently reported reasons for a visit to the physician for a disease amongst all diseases (Schappert, 1995). It was estimated that in 2000, United States residents would make 8. 8 million office visits for glaucoma (Quigley et al, 1997). In 2000, the number of people in the United States with primary open angle glaucoma (POAG) was estimated to be 2. 47 million, i.
e. 1. 84 million Whites and 619, 000 African Americans (Quigley et al, 1997). Prevalence of Open Angle Glaucoma (OAG) Prevalence refers to the number of patients with a disease as a percentage of a specified population. Good data on the prevalence of glaucoma are currently available although incidence data on POAG are not (Tielsch, 1996). The Beaver Dam Eye study was conducted in Beaver Dam, Wisconsin (n = 4, 926) (Klein et al, 1992) where the sample was predominantly Caucasian. Open Angle Glaucoma (OAG) was defined by identifying any of the following three clinical parameters: high IOP, abnormal visual field, or a cup to disc ratio that was either large or asymmetric. The overall prevalence of OAG was 2. 1 %.
Prevalence increased with age: 0. 9 % in participants 43 to 54 years old, and, 4. 7 % in participants 75 years of age or older. Gender was not influential. Of the 104 participants with definite OAG, about one third had Iop's less than 22 mm Hg, i. e. low-tension glaucoma, also known as normal tension glaucoma. The authors conclude that the prevalence of OAG in Beaver Dam was comparable to other Caucasian populations (Klein et al, ...
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