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A suggested model for early detection of open-angle glaucoma
PREVENTIVE
6, 167- 171(1977)
MEDICINE
STUDENT A Suggested
COMPETITION
Model for Early Detection Glaucoma1,2
PAPER of Open-Angle
JOANNE F. MCVAY~ Department
of Epidemiology, Pittsburgh,
Graduate School of Public Health, Pittsburgh, Pennsylvania 15213
University
of
Primary open-angle (simple) glaucoma is an ocular disease characterized by elevations of intraocular pressure in one or both eyes. This elevated pressure in the susceptible host may lead to damage of the optic nerve with resultant visual-field defects and, if untreated, irreversible blindness. Recognition of this disease in the early stages and arresting its development and the prevention of resultant blindness are the major goals of the proposed prevention program. Effective treatment with normalization of intraocular pressure by medical and surgical means can prevent loss of vision and blindness. Thus, early detection is very important in glaucoma. The proposed model for primary open-angle glaucoma detection would play an instrumental role in the secondary prevention of open-angle glaucoma and in the primary prevention of blindness due to this disease.
I.
THE DISEASE AND ITS MAGNITUDE
Primary open-angle (simple) glaucoma is a disease distinguished by an increase in intraocular pressure in one or both eyes sufficient to produce damage to the optic nerve in a susceptible individual. It is characterized by three abnormalities: (1) elevated intraocular pressure greater than 23 -25 mm Hg by applanation tonometry or greater than 25-27 mm Hg by Schiotz tonometry; (2) typical visual-field defects; and (3) optic atrophy with excavation of the optic disk (5). This increased intraocular pressure is produced by interference with the drainage of the aqueous fluid in the anterior chamber of the eye. The increased intraocular pressure gradually destroys the function of the retina and optic nerve. When distinctive changes in the retina and optic nerve occur, there is loss of vision at the sides of the visual fields and enlargement of the blind spot. Glaucoma is a chronic, slow-developing disease insidious in onset, progressing without symptomatology until late in the disease, when field-vision loss occurs. The disease may proceed to blindness without pain or other symptoms (4). Many of the factors responsible for the visual damage are unknown and, as a result, our knowledge of the natural history of the disease is incomplete. The natural history of untreated glaucoma may span a period from 50 to 70 years. Total blindness is the end stage of the disease and the final step in its natural history (4). 1 Runner-up prize winning paper in the 1st Annual Preventive Medicine Student Competition. 2 This paper was submitted in partial fulfillment of the course requirements for Epidemiology 226, Epidemiological Basis For Disease Control, Dr. Lewis H. Kuller, Professor of Epidemiology and Chairman of the Department. 3 Candidate in the Master of Public Health Program. 167 Copyright All
rights
0
1977 by Academic
of reproduction
in any
Press, form
Inc. reserved.
ISSN
0091-7435
168
JOANNE
II.
DESCRIPTIVE
F. MCVAY
EPIDEMIOLOGY
There are few estimates of incidence. Most studies report prevalence rates from various screenings. The prevalence rates vary with different population surveys. Estimates are as high as 15 to 16%, but the average prevalence quoted lies between 0.5 to 2% of the population over 40 years of age. Higher prevalence rates are reported in diabetics, high myopes, older age groups, and glaucoma families (1,3,4,6,7). The estimated number of glaucoma cases in the United States in persons 35 years of age and over in 1971 was 1,724,300 (9). This estimate is higher than the 1965 estimate of 1,392,OOO cases. One can theorize that the prevalence is increasing. Glaucoma is considered one of the leading causes of blindness in the United States. It is estimated to be responsible for 13.5% of all blindness (9). In addition, countless numbers of persons are blind in one eye or partially sighted in one or both eyes due to this disease. In the 1971 United States population, there were an estimated 441,300 cases of blindness (a rate of 2.14 per 1,000) and 34,650 new cases (rate of 16.8 per 100,000) (9).
If 13.5% of these cases of blindness are caused by glaucoma, then one can estimate that glaucoma was the cause of 59,576 total blind cases and 4,678 new blind cases. The high risk groups are those who are 40 years of age and older, have a history of diabetes mellitus, have a family history of glaucoma, and are in the elevated intraocular tension group. The Negro is at equal risk with the White in incidence, but it is a more devastating disease in the former group. More Negroes with glaucoma go blind than do Whites. III.
PREVENTIVE
PROGRAM
Since the exact etiology of glaucoma is unknown, a primary prevention program is not possible now. The present situation is one of monitoring and controlling the process in order to prevent blindness. Blindness from glaucoma can be prevented and is amenable to primary preventive measures. If glaucoma is diagnosed early and treated, progress of the disease can be checked. Any loss in vision cannot, however, be restored. It has been recognized that our only hope for the control of blindness due to glaucoma is in early detection and treatment. Therefore, secondary preventive programs for glaucoma are practical and feasible. Organized measures in all communities will have to be taken to acquaint the public and the entire medical profession to the early symptoms and dangers of the disease. Screening programs for early detection would have to be established in all communities. The difficulty with screening is that it reaches only a small proportion of the most susceptible population. If diagnosis is made early and the disease treated properly, further loss of vision may be prevented. Late detection will not be able to reverse the pathological changes and their consequences. A.
Diagnostic
Criteria
The measurement of intraocular pressure is one of the most important means of glaucoma detection. Three factors must be present for definitive diagnosis: (i) in-
EARLY
DETECTION
OF GLAUCOMA
169
creased intraocular pressure; (ii) optic nerve atrophy and excavation; and (iii) typical visual-field defects (5). Clinically, it is desirable to diagnose and treat the disease before development of optic nerve atrophy. Increased intraocular pressure is measured by tonometry and impairment in the outflow mechanism is evaluated by tonography. Changes in the optic disk are evaluated by ophthalmoscopy (direct or indirect), and visual field changes are measured by perimetry. The efficacy of specific screening tests for glaucoma is found in the sensitivity-specificity pattern. If high intraocular pressure is selected for screening sensitivity, the number of positives is low and specificity is high. If the screening level is lowered, the sensitivity increases but the specificity is lowered (many false positives) (8). In one study, by lowering the screening level from 26 mm Hg to 22 mm Hg, the sensitivity increased from 58.8 to 75.4%, while the specificity fell from 98.3 to 81.3% (6). The sensitivity-specificity pattern may be quite different for dissimilar age distributions, suggesting the need for screening levels that are characteristic for each age range (2). Rescreening on a continued basis will have an increased sensitivity associated with it and a drop in specificity. The sensitivity can be increased by combining tonometry with ophthalmoscopy and visual fields. Sensitivity will be enhanced by the combination of tests, but each test contributes independently to the combined total of false positives, thus reducing specificity. What is needed is an increase in the sensitivity of the screening program with a minimum loss in specificity (8). The present preventive approach in many communities revolves around individuals seeking eye care from ophthalmologists and eye clinics on their own. These groups have the major responsibility for detecting this disease in the population. Some optometrists may do tonometry with their routine refractions and larger industries may check for glaucoma in the annual physical,examinations of their employees. Many community health agencies carry out periodic screening for other diseases with glaucoma screening incorporated into the program. The present approach does not adequately cover the whole population at risk. B.
Proposed Secondary Prevention
Program for the Community
Glaucoma detection is a community responsibility, and a major part of that responsibility should be assumed by the medical community both in sponsorship and cooperation. The lay public, through public health education, should be informed of this disease, its dangers and consequences, and urged to seek regular medical eye care, particularly after the age of 35. Preventive eye care should be stressed as of utmost importance.
1. The first component in the Preventive Program is Preventive Eye Care Education for those individuals over 35 years of age. (a) All medical personnel, particularly general practitioners and internists, should be educated to the need of doing routine tonometry, ophthalmoscopy and visual fields.
170
JOANNE
F. MCVAY
(b) Optometrists should be encouraged to do routine tonometry and ophthalmoscopy and refer those who have abnormal findings for definitive diagnosis and treatment. (c) The lay public should be educated to recognize the need to seek regular eye care, particularly after age 35. (d) Training of nurses and technicians in tonometry, tonography, and visual fields should be implemented in order to reduce cost and relieve the physician work load in diagnosing and continued monitoring of glaucoma patients. 2. The second component is the performance of routine tonography, ophthalmoscopy, and visual fields by all medical practitioners in their medical examinations and care of those individuals over 35 years of age. This would facilitate early detection of suspect glaucoma in the part of the population which seeks routine medical care. These patients can then be referred to the proper practitioner or facility for diagnosis and treatment. Trained nurses, technicians, and paramedical personnel in these procedures would be of aid to the practitioner in reducing the time and work load incurred because of these extra procedures in examinations. These procedures should be incorporated into the following areas for those individuals over 35 years of age: (a) Industry, with routine physical examinations. (b) All general practitioners and internists, as part of every general physical examination. (c) All medical students and residents in the outpatient department and by the house staff on all hospital admissions. (d) All medical clinics, whether hospital based or community based. (e) Medical or nursing facilities and nursing homes for the disabled and elderly. (0 In all Public Health Clinics, where they provide other screening and diagnostic services. (g) All Ophthalmologists and eye clinics, who should be doing this routinely now. (h) Optometrists, in their routine refractions. 3. The third component is the institution of permanent screening programs in those areas where the population has no access to, or has difficulty in seeking, regular medical and eye care. Here the support and cooperation of public and private health agencies and community groups will be necessary. Glaucoma screening should be incorporated into all community screening programs. This will necessitate the institution of a permanent facility to diagnose, treat, and follow those individuals identified by screening as suspect glaucoma. If this is not possible, then methods for transporting these individuals to a medical eye-care facility must be devised. If a medical clinic does exist in these areas, glaucoma screening and medical eye care can be incorporated into its present structure. The services of trained nurses, technicians, volunteers, resident physicians, and ophthalmologists should be sought. The aid of the local Department of Public Health should be enlisted. This program can be successfully carried out in a Public Health Clinic. If permanent
EARLY
DETECTION
OF GLAUCOMA
171
facilities cannot be had, mobile units both for screening and medical eye care could service many areas. The important aspect of screening is that those detected as suspect glaucoma cases should have confirmatory diagnosis and therapy. The aid of volunteers, social workers, and nurses will have to be enlisted to help the diagnosed glaucoma patient acquire the needed care and to continue monitoring and surveillance of their follow-up care. IV.
CONCLUSIONS
Recognition of glaucoma in the early stages, arresting its development, and preventing blindness are the major goals of the proposed secondary prevention program. Effective treatment with normalization of intraocular pressure by medical and surgical means can preserve the vision of the glaucoma patient. It is only when the public recognizes the disease of glaucoma, its dangers, its prevention, and its control, and is motivated to seek early detection and diagnosis, that resultant blindness will be prevented. Standardized questionnaires, formats, screening procedures, clinical methodology, data collection, and record keeping in all of the component parts of the proposed preventive program would provide valuable information for epidemiological research into the early stages and natural history of the disease, and perhaps its etiology. Only then will primary prevention, the prevention of the disease itself, become a possibility. REFERENCES 1. Armaly, M. F. Glaucoma. Arch. Ophthalmol. 93, 148-149 (1975). 2. Armaly, M. F. The DesMoines population study of glaucoma. Invest. Ophth. 1, 618 (1962). 3. Graham, P. A. Epidemiology of simple glaucoma and ocular hypertension. Brit. J. Ophthalmol. 56, 223-229 (1972). Diagnosis and Therapy of the 4. Kolker, A. E., and Hetherington, J. “Becker-Shaffer’s Glaucomas,” Third Edition. C. V. Mosby Co., St. Louis, 1970. 5. Newell, F. W. “Ophthalmology: Principles and Concepts,” Third Edition. C. V. Mosby Co., St. Louis, 1974. 6. Packer, H., Deutsch, A. R., Deweese, M. W., Kashganian, M., and Lewis, P. M. Frequency of glaucoma in three population groups. JAMA 188, 123-127 (1964). 7. Perkins, E. S. Glaucoma screening from a public health clinic. Brit. Med. J. 1, 417-419 (1965). 8. Pollack, I. P. The challenge of glaucoma screening. Survey Ophthalmol. 13, (1968/1969). 9. “Statistics on Blindness and Vision Problems,” National Society for the Prevention of Blindness, Inc., New York, New York 10016.
6, 167- 171(1977)
MEDICINE
STUDENT A Suggested
COMPETITION
Model for Early Detection Glaucoma1,2
PAPER of Open-Angle
JOANNE F. MCVAY~ Department
of Epidemiology, Pittsburgh,
Graduate School of Public Health, Pittsburgh, Pennsylvania 15213
University
of
Primary open-angle (simple) glaucoma is an ocular disease characterized by elevations of intraocular pressure in one or both eyes. This elevated pressure in the susceptible host may lead to damage of the optic nerve with resultant visual-field defects and, if untreated, irreversible blindness. Recognition of this disease in the early stages and arresting its development and the prevention of resultant blindness are the major goals of the proposed prevention program. Effective treatment with normalization of intraocular pressure by medical and surgical means can prevent loss of vision and blindness. Thus, early detection is very important in glaucoma. The proposed model for primary open-angle glaucoma detection would play an instrumental role in the secondary prevention of open-angle glaucoma and in the primary prevention of blindness due to this disease.
I.
THE DISEASE AND ITS MAGNITUDE
Primary open-angle (simple) glaucoma is a disease distinguished by an increase in intraocular pressure in one or both eyes sufficient to produce damage to the optic nerve in a susceptible individual. It is characterized by three abnormalities: (1) elevated intraocular pressure greater than 23 -25 mm Hg by applanation tonometry or greater than 25-27 mm Hg by Schiotz tonometry; (2) typical visual-field defects; and (3) optic atrophy with excavation of the optic disk (5). This increased intraocular pressure is produced by interference with the drainage of the aqueous fluid in the anterior chamber of the eye. The increased intraocular pressure gradually destroys the function of the retina and optic nerve. When distinctive changes in the retina and optic nerve occur, there is loss of vision at the sides of the visual fields and enlargement of the blind spot. Glaucoma is a chronic, slow-developing disease insidious in onset, progressing without symptomatology until late in the disease, when field-vision loss occurs. The disease may proceed to blindness without pain or other symptoms (4). Many of the factors responsible for the visual damage are unknown and, as a result, our knowledge of the natural history of the disease is incomplete. The natural history of untreated glaucoma may span a period from 50 to 70 years. Total blindness is the end stage of the disease and the final step in its natural history (4). 1 Runner-up prize winning paper in the 1st Annual Preventive Medicine Student Competition. 2 This paper was submitted in partial fulfillment of the course requirements for Epidemiology 226, Epidemiological Basis For Disease Control, Dr. Lewis H. Kuller, Professor of Epidemiology and Chairman of the Department. 3 Candidate in the Master of Public Health Program. 167 Copyright All
rights
0
1977 by Academic
of reproduction
in any
Press, form
Inc. reserved.
ISSN
0091-7435
168
JOANNE
II.
DESCRIPTIVE
F. MCVAY
EPIDEMIOLOGY
There are few estimates of incidence. Most studies report prevalence rates from various screenings. The prevalence rates vary with different population surveys. Estimates are as high as 15 to 16%, but the average prevalence quoted lies between 0.5 to 2% of the population over 40 years of age. Higher prevalence rates are reported in diabetics, high myopes, older age groups, and glaucoma families (1,3,4,6,7). The estimated number of glaucoma cases in the United States in persons 35 years of age and over in 1971 was 1,724,300 (9). This estimate is higher than the 1965 estimate of 1,392,OOO cases. One can theorize that the prevalence is increasing. Glaucoma is considered one of the leading causes of blindness in the United States. It is estimated to be responsible for 13.5% of all blindness (9). In addition, countless numbers of persons are blind in one eye or partially sighted in one or both eyes due to this disease. In the 1971 United States population, there were an estimated 441,300 cases of blindness (a rate of 2.14 per 1,000) and 34,650 new cases (rate of 16.8 per 100,000) (9).
If 13.5% of these cases of blindness are caused by glaucoma, then one can estimate that glaucoma was the cause of 59,576 total blind cases and 4,678 new blind cases. The high risk groups are those who are 40 years of age and older, have a history of diabetes mellitus, have a family history of glaucoma, and are in the elevated intraocular tension group. The Negro is at equal risk with the White in incidence, but it is a more devastating disease in the former group. More Negroes with glaucoma go blind than do Whites. III.
PREVENTIVE
PROGRAM
Since the exact etiology of glaucoma is unknown, a primary prevention program is not possible now. The present situation is one of monitoring and controlling the process in order to prevent blindness. Blindness from glaucoma can be prevented and is amenable to primary preventive measures. If glaucoma is diagnosed early and treated, progress of the disease can be checked. Any loss in vision cannot, however, be restored. It has been recognized that our only hope for the control of blindness due to glaucoma is in early detection and treatment. Therefore, secondary preventive programs for glaucoma are practical and feasible. Organized measures in all communities will have to be taken to acquaint the public and the entire medical profession to the early symptoms and dangers of the disease. Screening programs for early detection would have to be established in all communities. The difficulty with screening is that it reaches only a small proportion of the most susceptible population. If diagnosis is made early and the disease treated properly, further loss of vision may be prevented. Late detection will not be able to reverse the pathological changes and their consequences. A.
Diagnostic
Criteria
The measurement of intraocular pressure is one of the most important means of glaucoma detection. Three factors must be present for definitive diagnosis: (i) in-
EARLY
DETECTION
OF GLAUCOMA
169
creased intraocular pressure; (ii) optic nerve atrophy and excavation; and (iii) typical visual-field defects (5). Clinically, it is desirable to diagnose and treat the disease before development of optic nerve atrophy. Increased intraocular pressure is measured by tonometry and impairment in the outflow mechanism is evaluated by tonography. Changes in the optic disk are evaluated by ophthalmoscopy (direct or indirect), and visual field changes are measured by perimetry. The efficacy of specific screening tests for glaucoma is found in the sensitivity-specificity pattern. If high intraocular pressure is selected for screening sensitivity, the number of positives is low and specificity is high. If the screening level is lowered, the sensitivity increases but the specificity is lowered (many false positives) (8). In one study, by lowering the screening level from 26 mm Hg to 22 mm Hg, the sensitivity increased from 58.8 to 75.4%, while the specificity fell from 98.3 to 81.3% (6). The sensitivity-specificity pattern may be quite different for dissimilar age distributions, suggesting the need for screening levels that are characteristic for each age range (2). Rescreening on a continued basis will have an increased sensitivity associated with it and a drop in specificity. The sensitivity can be increased by combining tonometry with ophthalmoscopy and visual fields. Sensitivity will be enhanced by the combination of tests, but each test contributes independently to the combined total of false positives, thus reducing specificity. What is needed is an increase in the sensitivity of the screening program with a minimum loss in specificity (8). The present preventive approach in many communities revolves around individuals seeking eye care from ophthalmologists and eye clinics on their own. These groups have the major responsibility for detecting this disease in the population. Some optometrists may do tonometry with their routine refractions and larger industries may check for glaucoma in the annual physical,examinations of their employees. Many community health agencies carry out periodic screening for other diseases with glaucoma screening incorporated into the program. The present approach does not adequately cover the whole population at risk. B.
Proposed Secondary Prevention
Program for the Community
Glaucoma detection is a community responsibility, and a major part of that responsibility should be assumed by the medical community both in sponsorship and cooperation. The lay public, through public health education, should be informed of this disease, its dangers and consequences, and urged to seek regular medical eye care, particularly after the age of 35. Preventive eye care should be stressed as of utmost importance.
1. The first component in the Preventive Program is Preventive Eye Care Education for those individuals over 35 years of age. (a) All medical personnel, particularly general practitioners and internists, should be educated to the need of doing routine tonometry, ophthalmoscopy and visual fields.
170
JOANNE
F. MCVAY
(b) Optometrists should be encouraged to do routine tonometry and ophthalmoscopy and refer those who have abnormal findings for definitive diagnosis and treatment. (c) The lay public should be educated to recognize the need to seek regular eye care, particularly after age 35. (d) Training of nurses and technicians in tonometry, tonography, and visual fields should be implemented in order to reduce cost and relieve the physician work load in diagnosing and continued monitoring of glaucoma patients. 2. The second component is the performance of routine tonography, ophthalmoscopy, and visual fields by all medical practitioners in their medical examinations and care of those individuals over 35 years of age. This would facilitate early detection of suspect glaucoma in the part of the population which seeks routine medical care. These patients can then be referred to the proper practitioner or facility for diagnosis and treatment. Trained nurses, technicians, and paramedical personnel in these procedures would be of aid to the practitioner in reducing the time and work load incurred because of these extra procedures in examinations. These procedures should be incorporated into the following areas for those individuals over 35 years of age: (a) Industry, with routine physical examinations. (b) All general practitioners and internists, as part of every general physical examination. (c) All medical students and residents in the outpatient department and by the house staff on all hospital admissions. (d) All medical clinics, whether hospital based or community based. (e) Medical or nursing facilities and nursing homes for the disabled and elderly. (0 In all Public Health Clinics, where they provide other screening and diagnostic services. (g) All Ophthalmologists and eye clinics, who should be doing this routinely now. (h) Optometrists, in their routine refractions. 3. The third component is the institution of permanent screening programs in those areas where the population has no access to, or has difficulty in seeking, regular medical and eye care. Here the support and cooperation of public and private health agencies and community groups will be necessary. Glaucoma screening should be incorporated into all community screening programs. This will necessitate the institution of a permanent facility to diagnose, treat, and follow those individuals identified by screening as suspect glaucoma. If this is not possible, then methods for transporting these individuals to a medical eye-care facility must be devised. If a medical clinic does exist in these areas, glaucoma screening and medical eye care can be incorporated into its present structure. The services of trained nurses, technicians, volunteers, resident physicians, and ophthalmologists should be sought. The aid of the local Department of Public Health should be enlisted. This program can be successfully carried out in a Public Health Clinic. If permanent
EARLY
DETECTION
OF GLAUCOMA
171
facilities cannot be had, mobile units both for screening and medical eye care could service many areas. The important aspect of screening is that those detected as suspect glaucoma cases should have confirmatory diagnosis and therapy. The aid of volunteers, social workers, and nurses will have to be enlisted to help the diagnosed glaucoma patient acquire the needed care and to continue monitoring and surveillance of their follow-up care. IV.
CONCLUSIONS
Recognition of glaucoma in the early stages, arresting its development, and preventing blindness are the major goals of the proposed secondary prevention program. Effective treatment with normalization of intraocular pressure by medical and surgical means can preserve the vision of the glaucoma patient. It is only when the public recognizes the disease of glaucoma, its dangers, its prevention, and its control, and is motivated to seek early detection and diagnosis, that resultant blindness will be prevented. Standardized questionnaires, formats, screening procedures, clinical methodology, data collection, and record keeping in all of the component parts of the proposed preventive program would provide valuable information for epidemiological research into the early stages and natural history of the disease, and perhaps its etiology. Only then will primary prevention, the prevention of the disease itself, become a possibility. REFERENCES 1. Armaly, M. F. Glaucoma. Arch. Ophthalmol. 93, 148-149 (1975). 2. Armaly, M. F. The DesMoines population study of glaucoma. Invest. Ophth. 1, 618 (1962). 3. Graham, P. A. Epidemiology of simple glaucoma and ocular hypertension. Brit. J. Ophthalmol. 56, 223-229 (1972). Diagnosis and Therapy of the 4. Kolker, A. E., and Hetherington, J. “Becker-Shaffer’s Glaucomas,” Third Edition. C. V. Mosby Co., St. Louis, 1970. 5. Newell, F. W. “Ophthalmology: Principles and Concepts,” Third Edition. C. V. Mosby Co., St. Louis, 1974. 6. Packer, H., Deutsch, A. R., Deweese, M. W., Kashganian, M., and Lewis, P. M. Frequency of glaucoma in three population groups. JAMA 188, 123-127 (1964). 7. Perkins, E. S. Glaucoma screening from a public health clinic. Brit. Med. J. 1, 417-419 (1965). 8. Pollack, I. P. The challenge of glaucoma screening. Survey Ophthalmol. 13, (1968/1969). 9. “Statistics on Blindness and Vision Problems,” National Society for the Prevention of Blindness, Inc., New York, New York 10016.