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Public health and prevention of blindness in diabetes
International Journal of Diabetes Mellitus (2015) 3, 1–3
Diabetes Science International
International Journal of Diabetes Mellitus www.elsevier.com/locate/ijdm www.sciencedirect.com
EDITORIAL
Public health and prevention of blindness in diabetes The world is facing an epidemic of diabetes mellitus [1]. Currently, more than 250 million people in the world have diabetes and it is predicted that this number will double in a little over 20 years [2–3]. The epidemic is not evenly distributed around the world. While the world-wide prevalence of diabetes is 3–4%, several countries and regions experience a prevalence rate of diabetes of well over 10%. This includes some countries in the Middle East, where in some cases, the prevalence of diabetes among middle aged adults exceed 16% [4]. Diabetic retinopathy is a relatively new disease. Before the discovery of insulin, less than 100 years ago, it was virtually unknown. Diabetic retinopathy entered the medical literature towards the middle of the twentieth century as more diabetics survived long enough to develop the disease. In the latter part of twentieth century, diabetic eye disease rapidly became an important cause of blindness. Epidemiological studies have shown that about 1/3rd of type 2 diabetics and every other type 1 diabetic patient is likely to develop sight threatening retinopathy within their life time. Sight threatening retinopathy, i.e. diabetic macular edema and/or proliferative diabetic retinopathy represents a significant threat to vision, and requires medical intervention to reduce risk of the vision loss and blindness [5]. Blindness from diabetes soared in the latter part of the 20th century. In Sweden, in the 1980s, it was reported that 4.4% of type 1 and 1.4% of type 2 diabetic patients were legally blind, with an additional 4.9% and 7.2% respectively with reduced vision [6]. These studies may represent a peak in blindness risk for diabetics. This is before systematic screening and preventive laser treatment was instituted in Scandinavian countries. From Wisconsin USA, it has been also reported a 10 year incidence of diabetic blindness of about 2% in type 1 and 4–5% in
1877-5934 Ó 2015 International Journal of Diabetes Mellitus. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijdm.2011.01.011 Production and hosting by Elsevier
type 2, with an additional 9% and 24–37% having visual impairment [7]. Let us take as an example a hypothetical country with 2 million diabetic patients, mostly with type 2 diabetes. About 1/3rd of this group would be expected to develop sight threatening retinopathy within their lifetime, and in the absence of early diagnosis and optimal treatment, 50% of these are likely to suffer vision loss. This worst case scenario would indicate between 3 and 400,000 current diabetic patients having reduced vision or blindness. If we look at the American epidemiology [7], we might expect about 100,000 people to become legally blind, and 5–700,000 to suffer from milder visual impairment, whereas the Scandinavian statistics would predict slightly lower rates. While the actual outcome also depends on the overall quality of diabetes care, the availability of ophthalmic care for those with eye symptoms and tertiary eye care, this gives an idea of the overall scope of the problem. Such a rate of blindness is not only a tragedy for the individuals involved and a major problem for the health system, but an economic burden on society, which needs to support a large number of people who are unable to work because of reduced vision. Retinal photocoagulation has proved to be effective in reducing the risk of vision loss and blindness, particularly in proliferative diabetic retinopathy (DRS) and also in clinically significant diabetic macular edema [8]. Recently, intravitreal VEGF antibodies have been reported to be a valuable treatment modality for diabetic macular edema [9,10]. Careful control of blood pressure, glucose and other metabolic parameters also plays a significant role in the treatment of diabetic eye disease. The key to successful photocoagulation in diabetic retinopathy is the timing of the treatment. Optimally, patients receive retinal photocoagulation in the early stages of proliferative diabetic retinopathy or diabetic macular edema. At this point in time, treatment is much more likely to succeed than if the retinopathy were to be more advanced. Since patients have no or minimal symptoms of early sight threatening retinopathy, the only way to diagnose sight threatening retinopathy in its early stages, and ensure the optimal timing of treatment, is to systematically look for this disease through screening examinations. This approach started in the 1980s,
2 and has enjoyed enormous success [5,11,12]. Diabetic patients were scheduled for an annual screening for retinopathy, either through a standard eye examination with dilated pupils by an ophthalmologist, or through fundus photography, where the images were read by expert ophthalmologists. In both cases, those diabetic patients who were diagnosed with sight threatening retinopathy were referred to laser treatment. It was felt at that time that annual screening examinations were adequate for the diabetic group and experience has shown that this approach resulted in an enormous reduction in the prevalence of diabetic blindness [5]. Reports from the Nordic countries now indicate the prevalence of blindness, which is considerably lower than reported in the 1980s. Zoega reported a 0.3% blindness prevalence in diabetic patients in Iceland [13]. Olafsdottir et al. reported about the same in a Swedish population [14], and Jeppesen and Bek report 0.6 and 1.5% prevalence of legal blindness in a type 1 and 2 diabetic population in Denmark [15]. Backlund et al. reported a one third reduction in diabetic blindness with screening in Stockholm [16], while Henricsson et al. reported that the yearly incidence of new blindness was 1 per 1000 in a Swedish diabetic population in a public health screening program [17]. The public health approach, with regular eye screening, has significantly reduced diabetic blindness in Nordic countries. At the same time, diabetic eye disease remains a leading cause of blindness in the 20–60 year age-group, and one of the most common causes of blindness overall in many countries around the world, including the United States [18]. Diabetic retinopathy usually develops 5–15 years after the onset of disease [19]. In countries where the prevalence of diabetes mellitus is rising rapidly, many individuals, relatively speaking, will have a short duration of diabetes and may not yet have developed serious retinopathy. The rise in sight threatening retinopathy and vision loss follows diabetes epidemic with a lag time of approximately 10 years. This delay is a double edged sword. On the one hand, it may lull health authorities into thinking that the situation is not as bad as feared, and may thus ignore the need for a public health approach. On the other hand, the delay provides time to set up screening services and organize the public health approach, the better to prevent the onslaught of sight threatening retinopathy and to make use of the calm before the storm. The World Health Organization and all major professional societies in ophthalmology and diabetology recognize that regular eye screening and preventive laser treatment are essential to prevent the diabetes epidemic from becoming an enormous world-wide epidemic of blindness. The WHO recommends that every diabetic patient be screened for diabetic retinopathy once a year, and those diagnosed with sight threatening retinopathy receive the appropriate treatment. This recommendation is based, in part, on the experience and success of the Nordic countries, where 30 years of experience has proved the value of this approach. The success of retinal screening for diabetic eye disease is proved by experience, and amply reported in the medical literature [5,13]. Historically, diabetic eye screening started as annual screening examinations and this has proved to be adequate for the successful prevention of blindness. However, this ‘‘one size fits all’’ approach is clearly simplistic [20]. Diabetic patients are at variable risk for the development of sight threatening retinopathy. This risk is influenced by the duration and type of diabetes mellitus, blood glucose levels,
Editorial blood pressure, the presence of retinopathy and a few other minor risk factors [21,22]. These risk factors create a spectrum of risk, with some individuals at high risk and many at low risk, including those with a short duration of diabetes mellitus. It would clearly make more sense to adjust the screening intervals to the risk profile of the individual patient, so that those at high risk frequently come for screening examinations and those at low risk less frequently [23]. We have developed a mathematical algorithm, which calculates the individual risk for sight threatening retinopathy based on duration of diabetes, hemoglobin A1C levels, blood pressure and presence of retinopathy and recommends an appropriate screening interval for each individual [24]. This algorithm is available on the internet on www.risk.is and was tested in a database of diabetic screening for 20 years in Denmark. With this algorithm, the number of screening visits for the population could be reduced by more than 50%, whilst maintaining safety. This is mostly due to less frequent screening visits for diabetic patients with short duration of diabetes, as well as those in very good medical control. This use of information technology means that for a given amount of medical resources, twice the number of diabetic patients may be served, compared with fixed annual examinations. In a country with a rising diabetes epidemic and relatively many individuals with a short duration of diabetes, the use of information technology may be even more important and increase the efficacy of the public health approach even more. A public health approach and screening for diabetic retinopathy is a proven method to dramatically reduce the diabetic blindness [25–26]. This is the only way to prevent the world-wide diabetes epidemic from becoming an epidemic of blindness with enormous implications for health and the economy. Information technology makes screening more effective and feasible on a global scale. References [1] Matthews DR, Matthews PC. Banting Memorial Lecture 2010^. Type 2 diabetes as an ‘infectious’ disease: is this the Black Death of the 21st century? Diabet Med 2011;28:2–9. [2] Zimmet P, Alberti KG, Shaw J. Global and societal implications of the diabetes epidemic. Nature 2001;414:782–7. [3] Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care 2004;27:1047–53. [4] Al Rubeaan Khalid. Type 2 diabetes mellitus red zone. Int J Diabetes Mellitus 2010;1:1–2. [5] Stefansson E, Bek T, Porta M, Larsen N, Kristinsson JK, Agardh E. Screening and prevention of diabetic blindness. Acta Ophthalmol Scand 2000;78:374–85. [6] Jerneld B, Algvere P. Visual acuity in a diabetic population. Acta Ophthalmol (Copenh) 1987;65:170–7. [7] Moss SE, Klein R, Klein BE. Ten-year incidence of visual loss in a diabetic population. Ophthalmology 1994;101:1061–70. [8] Group ETDRSr: Photocoagulation for diabetic macular edema. Early Treatment Diabetic Retinopathy Study report number 1. Early Treatment Diabetic Retinopathy Study research group. Arch Ophthalmol 1985;103:1796–806. [9] Iacono P, Battaglia Parodi M, Bandello F. Antivascular endothelial growth factor in diabetic retinopathy. Dev Ophthalmol 2010;46:39–53. [10] Nicholson BP, Schachat AP. A review of clinical trials of antiVEGF agents for diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2010;248:915–30.
Editorial [11] Mayon-White VA, Jenkins LM, Knight AH. A district screening and treatment service for diabetic retinopathy. Diabet Med 1986;3:253–6. [12] Danielsen R, Helgason T, Jonasson F. Prognostic factors and retinopathy in type 1 diabetics in Iceland. Acta Med Scand 1983;213:323–6. [13] Zoega GM, Gunnarsdottir T, Bjornsdottir S, Hreietharsson AB, Viggosson G, Stefansson E. Screening compliance and visual outcome in diabetes. Acta Ophthalmol Scand 2005;83:687–90. [14] Olafsdottir E, Andersson DK, Stefansson E. Visual acuity in a population with regular screening for type 2 diabetes mellitus and eye disease. Acta Ophthalmol Scand 2007;85:40–5. [15] Jeppesen P, Bek T. The occurrence and causes of registered blindness in diabetes patients in Arhus County, Denmark. Acta Ophthalmol Scand 2004;82:526–30. [16] Backlund LB, Algvere PV, Rosenqvist U. New blindness in diabetes reduced by more than one-third in Stockholm County. Diabet Med 1997;14:732–40. [17] Henricsson M, Tyrberg M, Heijl A, Janzon L. Incidence of blindness and visual impairment in diabetic patients participating in an ophthalmological control and screening programme. Acta Ophthalmol Scand 1996;74:533–8. [18] Cotter SA, Varma R, Ying-Lai M, Azen SP, Klein R. Causes of low vision and blindness in adult Latinos: the Los Angeles Latino Eye Study. Ophthalmology 2006;113:1574–82. [19] Kristinsson JK. Diabetic retinopathy. Screening and prevention of blindness [A doctoral thesis]. Acta Ophthalmol Scand Suppl; 1997. p. 1–76. [20] Olafsdottir E, Stefansson E. Biennial eye screening in patients with diabetes without retinopathy: 10-year experience. Br J Ophthalmol 2007;91:1599–601. [21] Mehlsen J, Erlandsen M, Poulsen PL, Bek T. Identification of independent risk factors for the development of diabetic retinopathy requiring treatment. Acta Ophthalmol 2009.
3 [22] Vesteinsdottir E, Bjornsdottir S, Hreidarsson AB, Stefansson E. Risk of retinal neovascularization in the second eye in patients with proliferative diabetic retinopathy. Acta Ophthalmol 2009. [23] Mehlsen J, Erlandsen M, Poulsen PL, Bek T. Individualized optimization of the screening interval for diabetic retinopathy: a new model. Acta Ophthalmol 2010. [24] Stefansson E, Olafsdottir E, Gudmundsdottir A, Bek T, Mehlsen J, Palsson O, Thorisdottir O, Einarsson S, Einarsdottir A, Aspelund T. Information technology to control screening for diabetic retinopathy. ARVO; 2010 [abstract #2092/A132. www.arvo.org]. [25] Einarsdottir AB, Stefansson E. Prevention of diabetic retinopathy. Lancet 2009;373:1316–8. [26] Stefansson E. Prevention of diabetic blindness. Br J Ophthalmol 2006;90:2–3.
a
Einar Stefa´nsson a,b,* Anna Bryndı´ s Einarsdo´ttir a University of Iceland, Landspitali University Hospital, Reykjavik, Iceland b
King Saud University, Riyadh, Saudi Arabia Corresponding author at: Acta Ophthalmologica, University of Iceland, National University Hospital, 101 Reykjavı´k, Iceland. Tel.: +354 543 7217 (O), +354 824 5962 (cell); fax: +354 543 4831. E-mail address: [email protected] (E. Stefa´nsson) *
Diabetes Science International
International Journal of Diabetes Mellitus www.elsevier.com/locate/ijdm www.sciencedirect.com
EDITORIAL
Public health and prevention of blindness in diabetes The world is facing an epidemic of diabetes mellitus [1]. Currently, more than 250 million people in the world have diabetes and it is predicted that this number will double in a little over 20 years [2–3]. The epidemic is not evenly distributed around the world. While the world-wide prevalence of diabetes is 3–4%, several countries and regions experience a prevalence rate of diabetes of well over 10%. This includes some countries in the Middle East, where in some cases, the prevalence of diabetes among middle aged adults exceed 16% [4]. Diabetic retinopathy is a relatively new disease. Before the discovery of insulin, less than 100 years ago, it was virtually unknown. Diabetic retinopathy entered the medical literature towards the middle of the twentieth century as more diabetics survived long enough to develop the disease. In the latter part of twentieth century, diabetic eye disease rapidly became an important cause of blindness. Epidemiological studies have shown that about 1/3rd of type 2 diabetics and every other type 1 diabetic patient is likely to develop sight threatening retinopathy within their life time. Sight threatening retinopathy, i.e. diabetic macular edema and/or proliferative diabetic retinopathy represents a significant threat to vision, and requires medical intervention to reduce risk of the vision loss and blindness [5]. Blindness from diabetes soared in the latter part of the 20th century. In Sweden, in the 1980s, it was reported that 4.4% of type 1 and 1.4% of type 2 diabetic patients were legally blind, with an additional 4.9% and 7.2% respectively with reduced vision [6]. These studies may represent a peak in blindness risk for diabetics. This is before systematic screening and preventive laser treatment was instituted in Scandinavian countries. From Wisconsin USA, it has been also reported a 10 year incidence of diabetic blindness of about 2% in type 1 and 4–5% in
1877-5934 Ó 2015 International Journal of Diabetes Mellitus. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijdm.2011.01.011 Production and hosting by Elsevier
type 2, with an additional 9% and 24–37% having visual impairment [7]. Let us take as an example a hypothetical country with 2 million diabetic patients, mostly with type 2 diabetes. About 1/3rd of this group would be expected to develop sight threatening retinopathy within their lifetime, and in the absence of early diagnosis and optimal treatment, 50% of these are likely to suffer vision loss. This worst case scenario would indicate between 3 and 400,000 current diabetic patients having reduced vision or blindness. If we look at the American epidemiology [7], we might expect about 100,000 people to become legally blind, and 5–700,000 to suffer from milder visual impairment, whereas the Scandinavian statistics would predict slightly lower rates. While the actual outcome also depends on the overall quality of diabetes care, the availability of ophthalmic care for those with eye symptoms and tertiary eye care, this gives an idea of the overall scope of the problem. Such a rate of blindness is not only a tragedy for the individuals involved and a major problem for the health system, but an economic burden on society, which needs to support a large number of people who are unable to work because of reduced vision. Retinal photocoagulation has proved to be effective in reducing the risk of vision loss and blindness, particularly in proliferative diabetic retinopathy (DRS) and also in clinically significant diabetic macular edema [8]. Recently, intravitreal VEGF antibodies have been reported to be a valuable treatment modality for diabetic macular edema [9,10]. Careful control of blood pressure, glucose and other metabolic parameters also plays a significant role in the treatment of diabetic eye disease. The key to successful photocoagulation in diabetic retinopathy is the timing of the treatment. Optimally, patients receive retinal photocoagulation in the early stages of proliferative diabetic retinopathy or diabetic macular edema. At this point in time, treatment is much more likely to succeed than if the retinopathy were to be more advanced. Since patients have no or minimal symptoms of early sight threatening retinopathy, the only way to diagnose sight threatening retinopathy in its early stages, and ensure the optimal timing of treatment, is to systematically look for this disease through screening examinations. This approach started in the 1980s,
2 and has enjoyed enormous success [5,11,12]. Diabetic patients were scheduled for an annual screening for retinopathy, either through a standard eye examination with dilated pupils by an ophthalmologist, or through fundus photography, where the images were read by expert ophthalmologists. In both cases, those diabetic patients who were diagnosed with sight threatening retinopathy were referred to laser treatment. It was felt at that time that annual screening examinations were adequate for the diabetic group and experience has shown that this approach resulted in an enormous reduction in the prevalence of diabetic blindness [5]. Reports from the Nordic countries now indicate the prevalence of blindness, which is considerably lower than reported in the 1980s. Zoega reported a 0.3% blindness prevalence in diabetic patients in Iceland [13]. Olafsdottir et al. reported about the same in a Swedish population [14], and Jeppesen and Bek report 0.6 and 1.5% prevalence of legal blindness in a type 1 and 2 diabetic population in Denmark [15]. Backlund et al. reported a one third reduction in diabetic blindness with screening in Stockholm [16], while Henricsson et al. reported that the yearly incidence of new blindness was 1 per 1000 in a Swedish diabetic population in a public health screening program [17]. The public health approach, with regular eye screening, has significantly reduced diabetic blindness in Nordic countries. At the same time, diabetic eye disease remains a leading cause of blindness in the 20–60 year age-group, and one of the most common causes of blindness overall in many countries around the world, including the United States [18]. Diabetic retinopathy usually develops 5–15 years after the onset of disease [19]. In countries where the prevalence of diabetes mellitus is rising rapidly, many individuals, relatively speaking, will have a short duration of diabetes and may not yet have developed serious retinopathy. The rise in sight threatening retinopathy and vision loss follows diabetes epidemic with a lag time of approximately 10 years. This delay is a double edged sword. On the one hand, it may lull health authorities into thinking that the situation is not as bad as feared, and may thus ignore the need for a public health approach. On the other hand, the delay provides time to set up screening services and organize the public health approach, the better to prevent the onslaught of sight threatening retinopathy and to make use of the calm before the storm. The World Health Organization and all major professional societies in ophthalmology and diabetology recognize that regular eye screening and preventive laser treatment are essential to prevent the diabetes epidemic from becoming an enormous world-wide epidemic of blindness. The WHO recommends that every diabetic patient be screened for diabetic retinopathy once a year, and those diagnosed with sight threatening retinopathy receive the appropriate treatment. This recommendation is based, in part, on the experience and success of the Nordic countries, where 30 years of experience has proved the value of this approach. The success of retinal screening for diabetic eye disease is proved by experience, and amply reported in the medical literature [5,13]. Historically, diabetic eye screening started as annual screening examinations and this has proved to be adequate for the successful prevention of blindness. However, this ‘‘one size fits all’’ approach is clearly simplistic [20]. Diabetic patients are at variable risk for the development of sight threatening retinopathy. This risk is influenced by the duration and type of diabetes mellitus, blood glucose levels,
Editorial blood pressure, the presence of retinopathy and a few other minor risk factors [21,22]. These risk factors create a spectrum of risk, with some individuals at high risk and many at low risk, including those with a short duration of diabetes mellitus. It would clearly make more sense to adjust the screening intervals to the risk profile of the individual patient, so that those at high risk frequently come for screening examinations and those at low risk less frequently [23]. We have developed a mathematical algorithm, which calculates the individual risk for sight threatening retinopathy based on duration of diabetes, hemoglobin A1C levels, blood pressure and presence of retinopathy and recommends an appropriate screening interval for each individual [24]. This algorithm is available on the internet on www.risk.is and was tested in a database of diabetic screening for 20 years in Denmark. With this algorithm, the number of screening visits for the population could be reduced by more than 50%, whilst maintaining safety. This is mostly due to less frequent screening visits for diabetic patients with short duration of diabetes, as well as those in very good medical control. This use of information technology means that for a given amount of medical resources, twice the number of diabetic patients may be served, compared with fixed annual examinations. In a country with a rising diabetes epidemic and relatively many individuals with a short duration of diabetes, the use of information technology may be even more important and increase the efficacy of the public health approach even more. A public health approach and screening for diabetic retinopathy is a proven method to dramatically reduce the diabetic blindness [25–26]. This is the only way to prevent the world-wide diabetes epidemic from becoming an epidemic of blindness with enormous implications for health and the economy. Information technology makes screening more effective and feasible on a global scale. References [1] Matthews DR, Matthews PC. Banting Memorial Lecture 2010^. Type 2 diabetes as an ‘infectious’ disease: is this the Black Death of the 21st century? Diabet Med 2011;28:2–9. [2] Zimmet P, Alberti KG, Shaw J. Global and societal implications of the diabetes epidemic. Nature 2001;414:782–7. [3] Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care 2004;27:1047–53. [4] Al Rubeaan Khalid. Type 2 diabetes mellitus red zone. Int J Diabetes Mellitus 2010;1:1–2. [5] Stefansson E, Bek T, Porta M, Larsen N, Kristinsson JK, Agardh E. Screening and prevention of diabetic blindness. Acta Ophthalmol Scand 2000;78:374–85. [6] Jerneld B, Algvere P. Visual acuity in a diabetic population. Acta Ophthalmol (Copenh) 1987;65:170–7. [7] Moss SE, Klein R, Klein BE. Ten-year incidence of visual loss in a diabetic population. Ophthalmology 1994;101:1061–70. [8] Group ETDRSr: Photocoagulation for diabetic macular edema. Early Treatment Diabetic Retinopathy Study report number 1. Early Treatment Diabetic Retinopathy Study research group. Arch Ophthalmol 1985;103:1796–806. [9] Iacono P, Battaglia Parodi M, Bandello F. Antivascular endothelial growth factor in diabetic retinopathy. Dev Ophthalmol 2010;46:39–53. [10] Nicholson BP, Schachat AP. A review of clinical trials of antiVEGF agents for diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2010;248:915–30.
Editorial [11] Mayon-White VA, Jenkins LM, Knight AH. A district screening and treatment service for diabetic retinopathy. Diabet Med 1986;3:253–6. [12] Danielsen R, Helgason T, Jonasson F. Prognostic factors and retinopathy in type 1 diabetics in Iceland. Acta Med Scand 1983;213:323–6. [13] Zoega GM, Gunnarsdottir T, Bjornsdottir S, Hreietharsson AB, Viggosson G, Stefansson E. Screening compliance and visual outcome in diabetes. Acta Ophthalmol Scand 2005;83:687–90. [14] Olafsdottir E, Andersson DK, Stefansson E. Visual acuity in a population with regular screening for type 2 diabetes mellitus and eye disease. Acta Ophthalmol Scand 2007;85:40–5. [15] Jeppesen P, Bek T. The occurrence and causes of registered blindness in diabetes patients in Arhus County, Denmark. Acta Ophthalmol Scand 2004;82:526–30. [16] Backlund LB, Algvere PV, Rosenqvist U. New blindness in diabetes reduced by more than one-third in Stockholm County. Diabet Med 1997;14:732–40. [17] Henricsson M, Tyrberg M, Heijl A, Janzon L. Incidence of blindness and visual impairment in diabetic patients participating in an ophthalmological control and screening programme. Acta Ophthalmol Scand 1996;74:533–8. [18] Cotter SA, Varma R, Ying-Lai M, Azen SP, Klein R. Causes of low vision and blindness in adult Latinos: the Los Angeles Latino Eye Study. Ophthalmology 2006;113:1574–82. [19] Kristinsson JK. Diabetic retinopathy. Screening and prevention of blindness [A doctoral thesis]. Acta Ophthalmol Scand Suppl; 1997. p. 1–76. [20] Olafsdottir E, Stefansson E. Biennial eye screening in patients with diabetes without retinopathy: 10-year experience. Br J Ophthalmol 2007;91:1599–601. [21] Mehlsen J, Erlandsen M, Poulsen PL, Bek T. Identification of independent risk factors for the development of diabetic retinopathy requiring treatment. Acta Ophthalmol 2009.
3 [22] Vesteinsdottir E, Bjornsdottir S, Hreidarsson AB, Stefansson E. Risk of retinal neovascularization in the second eye in patients with proliferative diabetic retinopathy. Acta Ophthalmol 2009. [23] Mehlsen J, Erlandsen M, Poulsen PL, Bek T. Individualized optimization of the screening interval for diabetic retinopathy: a new model. Acta Ophthalmol 2010. [24] Stefansson E, Olafsdottir E, Gudmundsdottir A, Bek T, Mehlsen J, Palsson O, Thorisdottir O, Einarsson S, Einarsdottir A, Aspelund T. Information technology to control screening for diabetic retinopathy. ARVO; 2010 [abstract #2092/A132. www.arvo.org]. [25] Einarsdottir AB, Stefansson E. Prevention of diabetic retinopathy. Lancet 2009;373:1316–8. [26] Stefansson E. Prevention of diabetic blindness. Br J Ophthalmol 2006;90:2–3.
a
Einar Stefa´nsson a,b,* Anna Bryndı´ s Einarsdo´ttir a University of Iceland, Landspitali University Hospital, Reykjavik, Iceland b
King Saud University, Riyadh, Saudi Arabia Corresponding author at: Acta Ophthalmologica, University of Iceland, National University Hospital, 101 Reykjavı´k, Iceland. Tel.: +354 543 7217 (O), +354 824 5962 (cell); fax: +354 543 4831. E-mail address: [email protected] (E. Stefa´nsson) *