INTRODUCTION

The mean expected lifespan for humans rose from the 40s at the beginning of the 20^th century to the 80s at the beginning of the 21^stcentury⁽¹⁾. Populations are increasingly aging worldwide, and the high rates of development of chronic health conditions over the aging process increase the rates of morbidity and mortality and are associated with disability^(2-3). The Global Burden of Disease estimated that 190 million individuals had a severe disability in 2010, including conditions such as quadriplegia, severe depression, and blindness⁽⁴⁾. Blindness has socioeconomic consequences in all societies, with the costs of lost productivity, rehabilitation, and education of the blind constituting a significant economic burden for individuals, their families, and societies⁽⁵⁾. Visually impaired and blind elderly people usually face restrictions in their ability to participate in various activities. Decreased participation and activity loss are associated with increased risk of functional and cognitive decline; in addition, these patients are at risk of social isolation and may suffer from loneliness^(6-10). Worldwide, 161-258 million individuals are estimated to be visually impaired, and in 33-39 million of this population, vision is reduced to the level of blindness^(11-13). In Turkey, according to the Turkish Statistical Institute, 85.7% of the disabled do not work, with half of these not able to work due to severe disability. Further, 37.2% of these individuals do not work due to ocular disability. According to the 2011 data from the Social Security Institution of the Republic of Turkey, approximately $2.9 billion was allocated for disabled people, with $2 billion (71.5%) spent on the severely disabled and their relatives. Ophthalmologic disability accounted for 8.4% of the total disabilities^(14,15). Therefore, blindness and visual impairment are amongst the most important public health problems. An international, comprehensive classification system has been developed by the World Health Organization (WHO) to define health and health-related conditions, as well as the functionality and limits of humans, in standard language and settings. This system, called the International Classification of Functioning, Disability, and Health, has been used as a classification system in studies of disabled individuals. In Turkey, a disability rate determined by a regional health board, including physicians specialized in related diseases, is taken into account. In addition to the international standards, these measures are used along with the Balthazar formula when assessing the total disability level of an individual⁽¹⁶⁾. In order to receive disability and nursing care benefits, the disability level of the individual must be at least 50% for them to be evaluated as "severely disabled" by the board. In this study, we aimed to identify the rate of ophthalmologic diseases in patients who had been evaluated as being severely disabled and to identify the specific ophthalmologic conditions leading to visual impairment and blindness among subjects aged 65 years or older.

METHODS

RESULTS

A total of 199 severely disabled patients who were over 64 years old were included in the present study, with 125 women (62.8%) and 74 men (37.2%). In terms of insurance, 89 were in the No-SSI group, and 110 were in the SSI group. Fifty-six individuals applied to the disability board from urban areas, and 143 patients applied from rural areas. The mean age was 79.29 ± 6.92 years (range: 65-97 years). The mean TBDR was 88.75 ± 7.96 (range: 60-100). All the patients had the mean major disability rate (MDR) (Table 1). The most common disabilities according to the medical specialty are shown in table 2. Neurological diseases were the most common, with 94 patients (47.2%), followed by eye diseases, with 34 patients (17.1%). The most common ophthalmologic diseases were cataract, glaucoma, and age-related macular degeneration (AMD). Table 3 shows the ocular diseases, causes of blindness, and visual impairment, as well as their rates for each eye. The mean right and left eye visual acuities were 1.17 ± 1.10 logMAR and 1.13 ± 1.0 logMAR, respectively. Of the 60 patients with ophthalmologic diseases or conditions, 33 were blind and 10 had visual impairment. In total, 90 eyes suffered from blindness (63 eyes) and visual impairment (27 eyes). Cataract was the main cause for blindness, followed by glaucoma. However, seven eyes had neovascular glaucoma, and the cause of neovascularization was unclear from the medical charts.

Cataract was the most common cause for visual impairment. No significant differences were noted in the age, TBDR, ophthalmologic disability rate, visual acuity of the right eye, and visual acuity of the left eye between the sexes. Further, there were no significant differences in TBDR, ophthalmologic disability rate, and the visual acuities of the right and left eyes between the patients who were being followed up at the time of application to the disability board and the ones who were not. Further, the mean age of the patients who were being followed up at the time of application to the disability board was significantly lower than that of the patients who were not being followed up at the time of application (p =0.015) (Table 4).

The mean MDR of the patients with eye disorders was statistically significantly higher than that of the patients with other disorders; the mean MDRs were 92.82 ± 4.50 and 87.92 ± 8.27, respectively (p =0.001). The number of patients without SSI was significantly higher in rural areas than in urban areas (85%, p <0.001). No statistical significance was detected in terms of the other parameters (Table 5). The sociodemographic and economic characteristics of the patients who were blind and visually impaired are shown in table 6. Seventy-nine percent of the blind patients were from rural areas, and 88% of the blind patients had no regular follow-up. Nearly 64% of the blind patients were women.

Of the 199 patients, 60 (30%) had ophthalmologic conditions or diseases. Thirty-four (57%) had applied to the disability board because of eye disease and 22% because of neurological disorders. Forty-three of the 199 patients (22%) were blind or visually impaired. The mean age of the blind or visually impaired patients was 81.4 ± 6.9 years. Among the blind and visually impaired patients, the rate of those with SSI was significantly higher in women (75%; p =0.037) and patients from urban areas (73%; p =0.043). The follow-up rate was significantly lower in women (p =0.025).

Among the 199 severely disabled patients, we compared the characteristics of the 60 patients with visual impairment or blindness with the other severely disabled patients by univariate analysis. There was a significant difference in terms of the follow-up status (Table 7). To assess the associations of the place of residence, SSI status, follow-up status, and gender with visual condition, we performed a multinomial logistic regression analysis. The visually impaired and blind patients were more likely to have a lower follow-up rate than the other severely disabled patients (OR: 0.231, 95% Cl: 0.077-0.688,p =0.009).

DISCUSSION

Aging is a natural process, and the increased rates of age-related diseases due to this increase in life expectancy are currently an important public health issue. Individuals aged 65 years or older now comprise 14.7%, 12.5%, and 13% of the whole population of the Netherlands, Australia, and the USA, respectively⁽¹⁸⁾. While the current population aged 65 years or older is 5.9 million (approximately 8%) in Turkey, it has been extrapolated to reach over 8.5 million (approximately 10%) in 10 years' time⁽¹⁹⁾. According to data released in 2011, there are 30,318 patients aged over 65 years receiving disability benefits who are severely disabled⁽¹⁵⁾. The individuals aged 65 years or older who received care services at home or special care centers constitute 6.6%, 6.0%, and 3.5% of the total population in the Netherlands, Australia, and the USA, respectively⁽¹⁸⁾.

In the present study, we noticed that ophthalmology is among the first three major disciplines related to severe disability. Globally, there are 32 million blind people and 153 million people with visual impairment who are 50 years old or older. In Europe, there are 3000 blind people and 25,500 people with visual impairment per one million people⁽¹²⁾. The burden of visual impairment is greatest amongst those 50 years of age and older. Globally, 84.6% of blind people and 77.5% of visually impaired people are in these age groups⁽¹³⁾. A study from the Netherlands reported prevalence rates in 2008 of 2.4% for blindness and 7.8% for visual impairment in people aged 65 years and over⁽²⁰⁾. The prevalence of blindness in adult individuals has been assessed as varying between 0.5% and 3% in different studies^(21,22).

In our study, we found that the major causes for blindness and visual impairment were cataract, glaucoma, AMD, retinal detachment, and neovascular glaucoma, in descending order. Pascolini and Mariotti reviewed studies on this topic and found that cataract (51%) was the most common cause of blindness⁽¹²⁾.

Moreover, cataract has been found to be the most common cause of blindness in various population-based studies. However, the causes of blindness and its prevalence vary in countries depending on their levels of economic development and even within different regions of the same country^{(13,14,23,24)}. A study on Latin American countries reported that unoperated cataract is the main cause of blindness⁽²²⁾. In the Barbados eye study, the most common causes of blindness were, in descending order, cataract (58.3%), glaucoma (14.3%), diabetic retinopathy (8.7%), optic atrophy (7.1%), and AMD (2.4%)⁽²³⁾. Cataract is also the main cause of blindness in Paraguay⁽²⁴⁾. In several studies performed in European countries and the USA, which are places with high life expectancy, the most common cause of visual impairment has been shown to be AMD^(25,26). In a study conducted in 2008 the Netherlands, the main cause of blindness was macular degeneration, followed by cataract, refractive errors, glaucoma, and diabetic retinopathy⁽¹⁸⁾. In the present study, we studied severely disabled elderly patients, and our study was not population based, as the aforementioned studies were; therefore, we were not able to compare our results with those from the previous studies.

In Turkey, there are more than 400,000 visually impaired individuals according to data from 2002. Of these, 48,500 (11.8%) individuals were blind, while 162,000 (39%) individuals had visual impairment. In Eastern Turkey, of 35,000 visually impaired, 9400 (26.7%) individuals were blind, and 11,000 (31.1%) individuals had visual impairment, whereas in industrialized and developed regions of Western Turkey, 13% were blind, and 34% had visual impairment. Forty-nine percent of the visually impaired in Eastern Turkey and 33% in Western Turkey did not undergo treatment for their visual impairment⁽¹⁴⁾. Our study was performed by retrospective analysis of two years of data from the disability board of a tertiary hospital in Eastern Turkey. Seven percent of the disabled were over 65 years old, and were classed as severely disabled. Thirty percent of these patients had ophthalmologic diseases, and 17% were identified as being severely disabled due to ophthalmologic diseases. In a study that assessed blindness globally, the largest proportion of blind people resided in South Asia, followed by East Asia and Southeast Asia. The prevalence of blindness varied from 0.1% in the high-income North America region to 0.7% in the North Africa and Middle East regions. Moreover, the prevalence of blindness among older adults was greater than 4% in Western Sub-Saharan Africa, Eastern Sub-Saharan Africa, South Asia, North Africa, and the Middle East. The prevalence of blindness was lowest in high-income regions, with percentages of 0.4% or lower^(13,27).

In the Netherlands, an estimated 311,000 people are visually impaired, and the visual loss is thought to be treatable or preventable in 174,000 (56%) of these people⁽¹⁸⁾. The most common preventable and treatable cause of blindness throughout the world is cataract, and this is particularly true in developing countries. When cataracts are left untreated, the relatives of the patients, and eventually, society as a whole, face economic and moral burdens⁽¹³⁾. It has been calculated that blindness and visual impairment constitute a financial burden of 15-73 billion US dollars per year^(28,29).

According to the data from the TSI, 42.4% of all the disabled people in Turkey have a disability rate of 70% or more. The percentages of disabled people living in urban areas, aged 65 years and over, and who are females constitute 62.4%, 15.2%, and 41.4%, respectively, out of all the disabled people in Turkey⁽¹⁴⁾. Apart from the official data of Turkey, in our study, 27% of the individuals who received the severely disabled rating for ophthalmologic reasons came from urban areas, and 73% came from rural areas. Additionally, 79% of the blind patients came from rural areas, and the patients living in rural areas had significantly lower rates of having SSI. Health access and utilization of eye care services may be influenced by various sociodemographic factors such as age, sex, and education level⁽³⁰⁾. In our study, we found that having SSI was associated with patients' place of residence. Patients with no SSI have to pay their own health expenses when they seek medical care in tertiary centers if they are not referred officially by a local physician, which may be an obstacle to health services. Therefore, the place of residence as a sociodemographic factor might have affected health access in our study, particularly in blind patients. In our study, we noted a higher rate of females than males aged over 65 years who were classed as severely disabled due to blindness; further, females had significantly lower rates of follow-up. Thus, gender affects health access. In all regions worldwide, women have a higher age-standardized prevalence of vision impairment and blindness than men⁽¹³⁾. Globally, 4.2% of males and 5.3% of females aged over 70 years are blind, and 18.8% of males and 20.9% of females aged over 70 years are visually impaired,⁽¹³⁾suggesting lower accessibility to health for women compared with that for men. Multivariate analysis showed that patients who were severely disabled due to their ophthalmological conditions were less likely to visit hospitals than the other severely disabled patients. Compatible with this finding, it was shown that elderly people with visual impairment and/or blindness have participation restrictions and activity loss that are associated with functional and cognitive decline^(6-10).

In conclusion, blindness gives rise to severe disability and constitutes a large proportion of the diseases that lead to severe disability. The most common ophthalmologic diseases that cause severe disability are cataract, glaucoma, and AMD. Sociodemographic factors that may affect the accessibility to health services of visually impaired and blind people include their place of residence and gender. Finally, visually impaired and blind people are more likely to have lower follow-up rates than other severely disabled people.