Trend of Retinal Diseases in Developing Countries

Hussain Nazimul; Khanna Rohit; Hussain Anjli

Expert Rev Ophthalmol.  2008;3(1):43-50.  2008 Future Drugs Ltd.
Posted 03/19/2008

Abstract and Introduction

Abstract

The trend of retinal blindness has changed its pattern over the years in developing countries. A decade ago, hereditary retinal disorders formed the major cause of visual loss due to retinal diseases. With the improvement in health and science, Diabetic retinopathy, age-related macular degeneration (AMD) and retinopathy of prematurity (ROP) have become the important and increasing causes of retinal blindness. It is expected that there would be 57 million diabetics in India by 2025 and 137 million people older than 65 years of age by 2021. By 2030, it is estimated that the number of diabetics greater than 64 years of age will be greater than 82 million in developing countries and greater than 42 million in developed countries. The prevalence of AMD ranges from 0.6 to 1.1% in developing countries with the exception of certain countries such as Pakistan and Bangladesh. By WHO criteria, there are 1.5 million blind children worldwide, of whom 1 million are in Asia, 0.3 million in Africa, 0.1 million in Latin America and 0.1 million in the rest of the world. The incidence of ROP in neonatal intensive care unit (NICU) or referral to tertiary care hospital ranges from approximately 21 to 40%. Proper implementation of measures, such as health education and promotion, accessible eye care services, strengthening of infrastructure and affordable technology can possibly help to tackle this avoidable and treatable retinal cause of blindness.

Introduction

Cataract is the major cause of blindness in developing nations and is responsible for 50% of blindness.[1] In developing nations, mainly India, South America and some Western Pacific countries, causes other than cataract have started assuming significance. This is primarily due to a change in the demographic shift where there is a trend towards increasing prevalence of other noncommunicable eye diseases, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD).[1-9] On the other hand, with improvement in management of neonatal care, there is also an increase in the trend of retinopathy of prematurity (ROP) as seen in the major cities of countries such as Latin America and India. In India in the 1980s, cataract was responsible for 80% of blindness whereas in 2002, it was responsible for approximately 60% of blindness, suggesting a changing trend in causes of blindness.[2,3]

Globally, it is estimated that there will be 244 million people (14.9% of the population) that are 65 years and older by 2050, compared with 42 million (4.5% of the population) in 1995.[4] This shift in demographics is likely to be accompanied by a shift in the prevalence of noncommunicable diseases, including retinal diseases such as DR and AMD in most of the developing nations.

Magnitude of Global Blindness

The first report on the estimate of global blindness (in 1975) estimated 28 million to be blind and was projected to rise to 45 million in the subsequent 20 years.[5] It was projected that without timely and appropriate measures to control blindness, the current level would double by the year 2020,[6] resulting in economic losses of close to US$150-250 billion.[7] This led to launch of Vision 2020: The Right to Sight in the year 1999.[6] Compared with 1995 estimates, a recent report by the WHO in 2002 estimated a decrease in infectious causes of blindness (mainly trachoma and onchocerciasis) and an increasing trend towards noncommunicable causes of blindness (mainly glaucoma, AMD and DR).[1-5] This was more prominent in developed countries like America, Western Europe and Australia; however, there was a changing trend in developing countries as well. This was mainly due to an increase in the aging population. It was found that from 1990 to 2002, the aging population above 50 years in developed countries increased by 16% and in developing countries (excluding China) was 47% (27% in China).[1] With an increase in the availability of proper documentation of the retinal diseases and an increase in the diagnostic skills required for detection of early retinal disease, more information regarding retinal disease and blindness may become available in the literature.

Retinal Blindness in Developing Countries: Changing Trends

The majority of data on retinal blindness come from developed countries and very little from the developing countries. Data from developing countries such as India and China have shown an increasing trend in blindness caused by retinal diseases in adults from DR and AMD and also in children from ROP.[1,9]

Chronic diseases are in pandemic proportion and a major cause of morbidity and mortality worldwide. Long-term predictions suggest that the major burden of this will fall on developing countries. In the 20th Century, in Europe and other developed countries, with a decrease in infectious conditions, there was a parallel increase in the incidence of noncommunicable diseases. Developing countries appear to be facing the same problem; they lie in between the ongoing epidemic of infectious diseases on one hand and emerging problem of noncommunicable diseases on the other. This is primarily due the demographic and socio-economic transition occurring in these countries. It is predicted that, by the year 2020, noncommunicable diseases will cause seven out of ten deaths in developing countries and cardiovascular diseases, diabetes, cancer and pulmonary disease will share the major burden.[8]

Diabetes-Related Burden of Retinal Diseases

Diabetes, which was once considered a disease of the developed world, has become a pandemic with nearly two-thirds of diabetics living in the developing world. Globally, it was estimated that the total number of diabetics was 171 million in year 2000 and is expected to increase to 366 million in 2030: a 114% rise.[9] These projections are based on increased life expectancy with changes in lifestyle and more urbanization. It is estimated that there will be a 42% increase in the prevalence of diabetes in developed countries and nearly a 150-200% rise in developing countries.[9] In Asia, it is estimated to increase by threefold with major burden shared by India and China. It is expected to increase from 31.7 million to 79.4 million in India and from 20.8 to 42.3 million in China in a span of 30 years from 2000 to 2030.[9] Similar changes will be noticed in other developing countries.[9] Furthermore, in developing countries, the majority of diabetes is at a younger age (between 45-64 years), in contrast to the developed world where most are above 64 years of age. By 2030, it is estimated that the number of diabetics older than 64 years of age will be higher than 82 million in developing countries and greater than 42 million in developed countries [Figure 1].[9]

Figure 1. 

Showing the change in diabetic population in developing countries over time (2000-2030). Prevention of blindness from Diabetes Mellitus. A report of WHO consultation in Geneva, Switzerland, November 2005

     

Looking at the changing trends in the prevalence of diabetes in India, as compared with 1971, the prevalence of diabetes has increased ten times in urban areas (1.2 in 1971 vs 12.1% in 2002) whereas the increase in rural India is approximately five times (1.3 in 1979 vs 6.4% in 2004).[10,11] The prevalence between 1989 and 1995, showed a 40% rise in prevalence of diabetes and a further increase of 16.4 in the next 5 years.[12] A similar shift is also observed from other developing Asian nations such as Sri Lanka, where a study on the rural community in 1990 reported a prevalence of 2.5%; in 2005 the prevalence was 14.2% among males and 13.5% among females.[13] Similarly in 2000, in rural communities in Sri Lanka, the prevalence of diabetes was 8.5%. This shift in rural area was mainly due to an increase in monthly income, level of education and BMI.[14] Such shift is seen worldwide in developing countries where prevalence of diabetes has tripled since 1985. Recent data concerning the developing countries are alarming with some areas (North Africa, the Middle East, India, China and Mexico) reporting the prevalence of diabetes larger than in Europe and America. This huge increase is again attributed to poor dietary habits, Westernization, increased BMI, sedentary lifestyle, environmental and genetic factors.[15]

Treatment of diabetes and its complications has huge economic impact. The direct cost of treatment in a study in India showed doubling in a span of 7 years from 1998 to 2005.[16] At the same time, there is evidence of decrease in health-related quality of life in these patients.[17]

The most important ocular complication, which can lead to visual disability due to diabetes, is DR. There are few studies from the developing world reporting prevalence of DR and most of them are from India. Different studies in India have reported the prevalence of DR in known diabetics to be 20-34%[18-22] and for newly diagnosed diabetics, 5.1-7.3%. As duration of diabetes is one of the major risk factor for development of retinopathy[20,22,23] and with an increased life expectancy and early onset of diabetes, incidence of retinopathy is expected to increase. WHO estimates at present suggest that it is responsible for the blindness of 4.8 million people in the world. Projections based on the increased life expectancy, changes in lifestyle, decreased incidence of communicable diseases with superimposed genetic and environmental factors, it is presumed that if there is no timely intervention, a further rise is expected.

AMD-Related Burden of Visual Disability

AMD is the leading cause of blindness in the developed world and is responsible for 50% of blindness.[1] Though there are enough data on blindness data for AMD from industrialized nations,[24-28] there are limited data from the developing world.[29-32] Both studies from the developing and developed world have shown age as one of the strong risk factors. The prevalence of AMD increases with increasing age. Data from developing countries such as China and India show variation in the prevalence. Data from the Beijing Eye study[30] show a very low prevalence of late ARM (0.6%), which is very similar to the Aravind Comprehensive Eye Study (ACES).[29] They are much lower than reported in the Andhra Pradesh Eye Disease Study (APEDS) and from North India.[31,32] This can be explained by the different methods of examination where the ACES did not used fundus photography, which was used in APEDS and in North India study. Similarly, racial difference is noted in the Baltimore Eye Survey,[27] with black people having less prevalence than white people, postulating a racial difference being responsible for prevalence. Overall, present prevalence in the developing world is lower than the developed world (with the exception of Japan), still with increasing life expectancy, changing lifestyle and improvement in control strategies of other causes of blindness, this is expected to rise.[7]

In one of the population-based studies in the southern part of India, increasing age was associated with vitreoretinal disorders.[29] The prevalence of any vitreoretinal disorder was 10.8% (95 confidence interval[CI]: 9.9-11.8%). Among the treatable or avoidable retinal blindness, the prevalence was 0.4% for nonproliferative DR, 0.04% for preproliferative DR, 0.06% for proliferative DR and 0.06% for clinically significant macular edema. The age specific prevalence for AMD was 1.3% for the ages between 40 and 49 years, 3.9% for those aged 50-59 years, 5.0% for those aged 60-69 years and 6.9% for those 70 years and older. The prevalence of early AMD was 2.7% and that of late AMD was 0.6%. The age adjusted prevalence of AMD was 3.1% (95% CI: 2.7-3.6%).

By contrast, national and low-vision surveys of Bangladesh have shown that very high levels of blindness and low vision were due to unoperated cataract and, to lesser extent, uncorrected aphakia among the study subjects.[33] Macular degeneration was found to be the third most common cause of blindness (12.03%). The relative higher incidence of cataract blindness may be attributed to low cataract surgical output in Bangladesh. The incidence of DR was 0.63% in the study population. This may be due to the relatively short life expectancy of Bangladeshi adults and relatively low minimum age (30 years) as the main subject inclusion criteria in the study.

Similarly, in the first national blindness survey of Pakistan it was estimated that cataract is the main cause of blindness (66.7%). In the second national survey (2002-2004), refractive error (36.7%) and cataract (35.9%) were estimated to be the major causes of visual impairment of less than 6/12, while macular degeneration accounted for 2.8% and DR for 0.2%.[34] Even though diabetes-related visual impairment was fairly low in the study, it was commented that it is likely to underestimate the true burden of retinopathy in the population as diabetic patients are more likely to have cataract. It is predicted that with rapid urbanization, Pakistan will be among the five countries with the highest prevalence of diabetes by the year 2025; this is likely to alter the existing pattern of blindness.

The prevalence estimates of AMD in mainland China[30] (1.1% in persons >75 years of age) were lower than estimates from the Chinese population in Taiwan or Singapore where AMD is the third most common cause of visual impairment, accounting for 10.4%. However, there appears to be a discrepancy in the prevalence of AMD between Greater Beijing and Shanghai. In Shanghai, where late AMD was 1.9%[35] and the prevalence rate of AMD above 60 and 80 years were 13.5 and 23.5%, respectively. This major difference in estimates may be due to difference in the definition and grading system used. The other reasons may be ethnic differences between the population living in these areas, climate differences, food habits and environmental parameters. Now that China is developing so rapidly, the burden of AMD will increase enormously in future years.

However, the Beijing eye study, where visual impairment and blindness was assessed from rural and urban regions of greater Beijing showed that cataract is the major cause of low vision followed by degenerative myopia and glaucomatous optic atrophy.[36] Degenerative myopia dominated the younger population whereas cataract dominated the older population.

As treatment for this condition is more expensive and results have not been very satisfactory, the best approach is to modify the risk factors involved (which are chiefly smoking and hypertension). As the demographic shift in next 25 years predicts a major shift of population increase in to the older age group (>65 years) in developing countries,[9] the prevalence of these diseases are going to rise. As the treatment is not very effective and is expensive, focus should be on primary prevention in terms of health education and health promotion.

Burden of Retinopathy of Prematurity

It is estimated that there are 1.4 million blind children in the world, two-thirds of whom live in the developing countries.[37-40] In India, the prevalence is estimated to be 0.81/1000 children in well-developed states to 1.5/1000 in the poorest. Gogate et al. have also shown that there is a changing pattern in retinal blindness during childhood from 13.8 to 11.2% in India.[39] However, literature is not available to comment on the blindness due to ROP. It is possible that ROP may be one of the potential causes of avoidable retinal blindness in childhood in many newly industrialized developing countries.

In total, 5% of worldwide blindness involves children younger than 15 years of age and 50% of these belong to the developing countries.[40] By WHO criteria, there are 1.5 million blind children worldwide, of whom 1 million are in Asia, 0.3 million in Africa, 0.1 million in Latin America and 0.1 million in rest of the world. There are marked differences in the rest causes of pediatric blindness based on the regional differences and socio-economic factors. In this review it was commented that there has been a significant increase in both cortical vision loss and ROP in the past decade. Hence, the suggested need for more complete and uniform data, based on the established WHO reporting format.

The incidence of ROP in neonatal intensive care units (NICUs) or referral to tertiary care hospital in India ranged from approximately 21 to 40%.[41-44] It has also been shown that the changing trends of ROP at the tertiary NICU between 1999-2000 and 1993-94. Even though the overall incidence of ROP was not significantly different between the two periods (32 vs 20%, respectively), a decreasing trend in the proportion of severe ROP (stage III) was noted in the later part of the decade (42-21%).[42] Similarly, in countries such as South Africa, Turkey, Vietnam and China, the incidence of ROP were alike.[45-48]

Surprisingly, more mature infants are developing severe ROP in most of the developing countries compared with highly developed countries. This may suggest that the screening criteria of the developed countries may not hold true and requires adaptation to the to the concerned population. These concerns and revised criteria have already been suggested and practiced in most of these countries.[49,50]

In developing countries with a human development index (HDI) of 31-100, ROP is emerging as a major cause of blindness. It is believed that two-thirds of the 50,000 children who are blind from ROP worldwide live in Latin America.[51] The reasons cited were premature birth rates are higher, secondly, neonatal care may be compromised as a result of a lack of resources, leading to higher rates of severe ROP not only in extremely premature infants but also in larger, more mature infants. Lastly, owing to a lack of awareness, skilled personnel and financial constraints, screening and treatment programs are not in place in the neonatal units. In poorly developed countries (United Nation Development Program[UNDP] ranking <100) blindness from ROP is virtually unknown. This is due to the fact that services for the care of the premature infants are not well developed and the preterm infants do not survive long enough to develop severe ROP. Excellent neonatal care can prevent ROP to a large extent, but babies developing threshold disease need to be identified as treatment at this stage is highly effective at preventing visual loss.[52]

Future Trend

In India, the population older than 65 years is expected to be 137 million by 2021.[53] It is also estimated that there will be a rapid increase in the number of people with diabetes mellitus - approximately 57 million diabetics by 2025.[29] This will create a challenge in the control of diabetes and AMD as the major cause of blindness due to retinal causes in the future.

The shift in the prevalence of treatable retinal diseases is primarily due to development in medical practice, technological advancement and increase in the geriatric population. This has also been contributed to by progressive urbanization of rural areas and marginal accessibility to healthcare. Healthcare facilities for the management of geriatric diseases has also tremendously improved conferring the longevity of the patients. Previously, it has been seen that the major causes of retinal blindness in the developing nations were mostly congenital or hereditary retinal diseases. The national survey of 2001-2002 has shown blindness due to posterior segment disease to be 4.7% in India.[54]

Hence there is a tremendous impact of increasing retinal blindness secondary to DR, ROP and AMD in the developing nations. This entails the necessity for accessible comprehensive eye care services, establishment of human resources, screening and awareness of the disease and affordable eye health policy.

Expert Commentary

Good primary health care and personnel trained in primary eye care are essential for the control of blindness in the developing countries.[55] Primary eye care includes promotion of eye health, action in the community to prevent conditions which cause blindness and recognition and treatment of common eye diseases by trained community level health workers. In order to tackle the diabetic and AMD blindness, instigating a health awareness camp, and education in the rural areas and less developed areas is of utmost importance. Examination of the fundus while evaluating for refractive errors could be an easy way of detecting the aging changes in these eyes to prevent blindness. However, the practical problem of assessing the fundus changes proves to be a dilemma by primary health workers. Taking fundus pictures with portable nonmydriatic camera by an ophthalmic technician can be useful in telemedicine and dispense quality eye care to the rural areas. This can reduce the cost and direct the patients towards proper eye care in a secondary or tertiary eye care facility. The use of telemedicine facilities has already proven to be effective in diabetic screening and treatment in the southern India and in Canada. It has been shown already that telemedicine is effective in periodic screening of DR.[56]

For proper delivery of eye care at the secondary and tertiary level, adequately trained skilled human resource and infrastructure forms an integral part of quality eye care service delivery. Ensuring the goals of VISION 2020, screening and treatment for DR and ROP can achieve the goal to reduce the emerging retinal cause of blindness in the developing nations. Especially in ROP, screening of the premature neonates in the NICUs forms the most important part of early detection, follow-up and management of these babies with lasers that is an absolute necessity. An intensive protocol of evaluating these neonates can successfully prevent progression to blinding ROP.

In order to render high-quality eye care service for DR and AMD, the tertiary and secondary care center should be well equipped with lasers and other pharmacological therapeutic agents. The important critical issue that arises in the management of this treatable retinal blindness in developing nations is the financial economics involved. Treatments can be widely accepted and willingness to undergo is only possible if latest modern therapeutic agents can be accessible within the limits of livelihood of the people in developing nations. Endeavour such as nongovernmental organization contributions, accessible government health policy and improved standard of earning can add to the armamentarium of approaches to tackle the retinal blindness.

Low Vision Services

AMD causes a number of visual impairments including deteriorating visual acuity, central visual field sensitivity and contrast sensitivity. These impairments usually cause significant disability such as difficulties in reading, everyday activities of daily living and watching television; all of which has tremendous impact on quality of life.[57] Hence, there appears a potential role of visual rehabilitation in these patients. This is also applicable to patients with DR anda more challenging task with the growing ROP infants.

It has been shown in a randomized controlled trial that conventional low-vision rehabilitation is as effective as enhanced low vision services. This suggests that conventional services can be delivered easily by any trained low vision delivery personnel , such as an optician or a vision technician.[58] Research has also shown that vision impairment compromises quality of life and limits social interaction and independence. This interferes with the person's ability to care for themself and others, indicating the need for community and vision-related support.[59] Hassel et al. have demonstrated when the association of duration of vision loss was tested with the impact on quality of life, there was no significant relation.[57] However, those with more severe vision loss reported a greater impact on the quality of life. Hence, needs for intervention with low vision services to assess and improve the quality of life and safe mobility should be considered in these patients.

In one of the reviews of patients with AMD in southern India, both near and distance vision improved statistically in a significant number of individuals with the use of spectacles (low vision devices) available at low cost.[60] Counseling of patients regarding their limitations and loss of independence also formed an important part of management. However, reports have also shown that substantial differences exist in the use of such services across all levels of presumed visual impairment.[61]

Evidence indicates that poor psychological well-being and depression are more prevalent in people with AMD than in population at large. This has been associated with loss of valued activities.[62] Hence the use of quality of life, well-being and vision-function measures are important to assess the value of services offered to people with AMD to ensure that the management of these patients is effective. Therefore, measures need to be taken in terms of:[63]

  • Increasing public awareness;

  • Improving training for health professionals in communication skills and use and interpretation of patient reported outcome measures;

  • Increasing the provision for support, rehabilitation and low vision services;

  • Funding for research and implementation of research findings with continued evaluation of impact of diagnosis and service provision on visual function, well-being, satisfaction and quality of life.

Five-Year View

In spite of the potential burden, measures that can be implemented to face the increasing blindness due to retinal cause can be the following:[64,65]

  • Health education and promotion related to diabetes, AMD and ROP that can alter the behavior and barriers to uptake the health care services;

  • Promotion of health by advocacy. To design activities that can raise the awareness and importance of blindness prevention with the policy makers and local community;

  • To make secondary and tertiary eye care services especially related to retinal diagnostics and treatment accessible and affordable, acceptable and effective;

  • Training of adequate human resources is the key factor to achieve the goal;

  • Capacity building of existing eye care infrastructure with adequate training of personnel's in retinal diseases to provide proper treatment;

  • Use of appropriate and affordable technology.

In most of the developing nations there is a low priority of retinal diseases, with the belief that treatment is not effective as well as inaccessible.[66] It is also true that using digital fundus cameras can substantially reduce the running cost of film and maintenance. Use of newer solid-state diode lasers can also reduce the running cost and will appear to be cost effective in the long term. Yorstan has also remarked that if 400 treatments are carried out each year then the cost-per-treatment is $20 as the key to cost-effectiveness is volume of burden of the disease.[65] Owing to advances in technology as well as indigenously made machines in some of the developing nations, it will be suitable for treatment in all clinics in these countries. Tailor-made training, both short- and long-term advanced training, in tertiary care hospitals can progressively build enough personnel for treatment of avoidable and treatable blindness due to retinal diseases.

If these measures are followed, it is possible that major retinal blindness can be detected but issues remain regarding the affordability of treatment, primarily for wet AMD which, at the moment is too expensive for many individuals. This is more so because most of the developing nations do not have a national health policy to bear the expenditure of treatment.

As far as ROP and DR are concerned, they have the potential to achieve the targets of treatment detection to treat and detect if measures are uniformly and selectively implemented in the major inhabited areas of the nation. However, these are all influenced by the changing government policy, economic status of the nation, political instability and freedom of nongovernment organizations participation.

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Papers of special note have been highlighted as:
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Sidebar: Key Issues

  • An increasing global geriatric population (>65 years), expected to be 137 million by 2021 in India alone.

  • An increasing global diabetic population, expected to be 57 million diabetics by 2025.

  • An increasing incidence of retinopathy of prematurity as seen in Latin America.

  • An increasing urbanization.

  • A lack of proper health policy.

  • A lack of uniform accessible comprehensive and adequate eye care services.

  • A lack of eye health awareness especially related to retinal diseases and the possible level of treatment available.

  • An insufficient human resource development.

Disclaimer

No writing assistance was utilized in the production of this manuscript.

Reprint Address

Hussain Nazimul, DNBSmt. Kanuri Santhamma Retina Vitreous Centre, LV Prasad Eye Institute, LV Prasad Marg, Banjara Hills, Hyderabad 500034, Andhra Pradesh, India. Email: nazimul@rediffmail.com


Hussain Nazimul, DNBSmt. Kanuri Santhamma Retina Vitreous Centre, LV Prasad Eye Institute, LV Prasad Marg, Banjara Hills, Hyderabad 500034, Andhra Pradesh, India
Author's email: nazimul@rediffmail.com

Khanna Rohit, International Centre for Advancement of Rural Eye care, LV Prasad Eye Institute, LV Prasad Marg, Banjara Hills, Hyderabad, Andhra Pradesh, India
Author's email: rohit@lvpei.org

Hussain Anjli, Medical Retina and ROP Specialist, Swarup Eye Centre, Dwarkapuri Colony, Panjagutta, Hyderabad, Andhra Pradesh, India
Author's email:
anjli_hussain@rediffmail.com

Disclosure: The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.