Ординатура / Офтальмология / Английские материалы / Age-Related Changes of the Human Eye_Cavallotti, Cerulli_2008

2

Fig. 1.1 Prevalence of Blindness

The major causes of blindness and reduced vision are related to cataracts, glaucoma, age-related macular degeneration, and diabetic retinopathy—all of which recognize aging as the major risk factor. The burden of visual impairment is not distributed uniformly through the world. The least developed regions carry the largest share. Visual impairment is also unequally distributed across age groups, with incidence largely confined to adults 50 years of age and older (83%). A distribution imbalance is also found with regard to the gender throughout the world—females have a significantly higher risk of developing visual impairment than males because their life expectancy is higher and their economic possibilities may be less.

Notwithstanding the progress in surgical intervention that has been made in many countries over the last several decades, cataracts remains the leading cause of visual impairment in all regions of the world, except in the most developed countries. Other major causes of blindness are (in order of frequency): glaucoma, ARMD, diabetic retinopathy, and trachoma.1 More specifically, Table 1.1 provides the available data on the estimated prevalence of eye diseases as causes of blindness and reduced vision. These diseases do recognize that aging is the major risk factor.

WHO has examined and forecast the distribution of the world population at the year 2000, 2025 and 2050, as displayed in Table 1.2.

Table 1.1 Estimated prevalence of the eye diseases

Table 1.2 Distribution of world population at the years 2000, 2025, 2050

The dramatic increase in the number and percentages of the world’s population is clearly noted as definitively more evident in less-developed countries, while the financial allocation of resources and health services availability and health technology are weaker in those same countries.

Without proper interventions, the increase in the number and percentage of people over the age of 50 will lead in the near future to a significant increase in the number and percentage of eye diseases that recognize age as the major risk factor. It has been estimated that without extra interventions, the total number of blind individuals worldwide would increase from 44 million in the year 2000 to 76 million in 2020 Table 1.3.

A successful intervention by the VISION 2020 initiative could result in only 24 million people suffering from blindness by 2020 and lead to a reduction of 429 million cases of blindness per year. A conservative estimate of the economic gain is 103 billion dollars.2 A proper approach in the treatment of these clinical pictures will lead to a reduction in numbers and percentage of the blind but also to an increase of reduced vision patients with a dramatic need for rehabilitation activities.

How many glaucoma patients are currently affected, how many of them are blind or severely impaired by this disease, what are the geographical and temporal distributions, and what are the main risk factors? These are questions without real scientific answers.3

As we have seen, the WHO estimates that this pathology represents the second cause of blindness and reduced vision worldwide after cataracts. It is estimated that in the year 2000, 66.8 million people are affected by open angle glaucoma. Of these, 6.7 million were affected by a bilateral blindness secondary to this disease, according to Quigley and Vitale.4 In the same year, 2.47 million patients were affected by this pathology just in the United States—1.84 million were Caucasians and 619,000 were people of color.

Numerous considerations can be made from the results of this study. Taking into account the person’s age at the beginning of the illness, together with the death rate, the illness lasts longer by 27% in colored people in comparison to patients of the Caucasian race.

In industrialized countries, less than 50 percent of the population with glaucoma realize that they are affected. This percentage is much lower in developing countries.

As for other disease, epidemiological studies have considered several risk factors, such as age, sex, race, social and economical factors, working activities, climate, the use of tobacco or alcohol, genetic, and ocular factors. Undoubtedly, the Intraocular Pressure (IOP) represents the major risk factor for the development of

the disease, but together with other factors, we should consider that the prevalence of glaucoma increases with age, with higher baseline IOP values in the elderly.5 This can be explained by the physiological reduction in time of the retinal ganglion cells, associated with a prolonged exposure to nontolerated high values of IOP, together with the action of other risk factors.6 The lack of, or a delay in, a diagnosis may lead to an irreversible blindness. Given the number of patients affected, the social-economical implications related to this pathology are very onerous.

In a recent study, for example, it has been calculated that in Germany, 800,000 patients are affected by glaucoma. Every year, Social Security spends more than 1,000 Euro per patient. On the other hand, if we consider the number of patients who are certified blind in connection with this illness, we must consider that the German government spends 150 million Euro in national Social Security and health expenses. These costs are destined to rise due to the fact that the average life span has increased and will continue to increase in the future.

In a multicentric study carried out in France, Germany, Italy, and Great Britain, the average cost per person for glaucoma each year was 726 Euro.7 As we have already seen, diabetic retinopathy contributes to 4.8% of blindness and reduced vision worldwide. We must remember that in the United States it is understood that 14 million are affected by diabetes, and of these, 43 percent present a related retinopathy. This complication creates 8,000 new cases of blindness each year.

For this pathology—together with other risk factors such as the type of diabetes, race, sex, controlling blood sugar levels and blood pressure, dislipidemia, nephropathy, pregnancy, and the duration of the illness (both for diabetes type 1 and type 2)—aging represents one of the most important risk factors to be considered. It has been estimated that after 20 years, almost all diabetic type 1 patients, and 60 percent of diabetic type 2 patients are affected by this retinal complication. Furthermore, if we consider that cataract surgery—a pathology typical of old age—worsens the course of diabetic retinopathy, we realize that aging represents an important element to be considered for diabetic patients.

Taking into account the higher life expectancy for diabetic patients and the aging of the world population, especially in the Southern hemisphere (and thus a major risk to be affected by type 2 diabetes), we can easily understand what sort of dimension this problem can assume in the near future. Aging is not only a risk factor for the previously mentioned diseases (Fig. 1.3).

The social changes in our time often leave the elderly in a condition of loneliness and eventually with economical and cultural barriers toward the access to health services. This may lead to a delay in early diagnosis, a delay in the beginning of an appropriate treatment, difficulties in following the medical prescriptions, and the related rehabilitation with a subsequently more significant handicap. This is not only true for eye diseases, but also for uncorrected changes in refraction. WHO has estimated that 153 million people are visually impaired due to uncorrected refractive errors (URE), with 95 percent of them being over 50 years of age.

Although this book has been divided into different sections, an effort should be made to understand that the eye represent a functional unit and any modification of any one of its structures will lead necessarily to changes and/or dysfunction of the whole globe.

Fig. 1.3 Age-related eye diseases as causes of blindness and low vision

In addition, I would like to stress that visual function is not only related to the eye, but is a complex activity that is strongly and intimately connected with the brain. Any anomaly, dysfunction, or disease of the globe can be associated with relevant changes in the structure, and thus the function, of the brain. Our hope is that this book will give an exhaustive panorama of what happens when the eye ages, thus contributing to the understanding of the physiology and physiopathology of eye diseases.

References

1.Resnikoff S and Co. Policy and Practice “Global data on visual impairment in the year 2002”

2.Frick K, et al. (2003) The magnitude and cost of global blindness: An increasing problem that can be alleviated. Am. J. Ophth. April 471-476

3.Quigley HA (1996) Number of people with glaucoma worldwide Br. J. Ophthalmol. May 80(5):389-393

4.Quigley HA, Vitale S (1997) Models of open-angle glaucoma prevalence and incidence in the United States. Invest. Ophthalmol Vis Sci Jan 38:83-91

5.Friedman DS et al. (2006) The prevalence of open angle glaucoma among blacks and whites 73 years old: the Salisbury Eye Evaluation Glaucoma Study. Arch. Ophthalmol. 124:1625-30

6.Sommer A et al. (1991) A population-based evaluation of glaucoma screening: the Baltimore Eye Survey. Am. J. of Epidemiol. 134:1102-1110

7.Traverso CE et al. (2005) Direct costs of glaucoma and severity of the disease. Br. J. Ophthalmol 89:1245-9

Recommended Bibliographic Resources

Recent Books on Vision Disorders in Old Age (www.amazon.com)

1.The Aging Eye by Sandra Gordon, Harvard Medical School, 2001.

2.Communication Technologies for the Elderly: Vision, Hearing & Speech by Rosemary Lubinski, D. Jeffery Higginbotham, 1997.

3.The effects of aging and environment on vision by Donald A. Armstrong, et al., 1991.

4.Treating vision problems in the older adult (Mosby’s optometric problem-solving series) by Gerald G. Melore, 2001.

5.Vision and Aging by Alfred A. Rosenbloom, Meredith W. Morgan, 1993.

6.Age-Related Macular Degeneration by Jennifer I. Lim, 2002.

7.The Impact of Vision Loss in the Elderly (Garland Studies on the Elderly in America) by Julia J. Kleinschmidt, 1995.

8.Vision in Alzheimer’s Disease (Interdisciplinary Topics in Gerontology) by Alice Croningolomb, et al., 2004.

9.The Senescence of Human Vision (Oxford Medical Publications) by R.A. Weale, 2001.

10.Issues in Aging and Vision: A Curriculum for University programs and In-service Training by Alberta L. Orr, 1998.

11.Aging with developmental disabilities changes in vision by Marshall E. Flax, 1996.

12.Trends in vision and hearing among older Americans by U.S. Dept of Health and Human Services, 2000.

13.Optometric gerontology: A resource manual by Sherrell J. Aston, 2003.