Introduction

Background

Blindness and impaired vision are the most severe pathologies with significant economic, social and medical consequences. The prevalence of blindness and visual impairment in the world is uneven (Zhu, et al., 2013; Nano & Silva, 2012; Abdull et al., 2009; Jadoon et al., 2006; Dineen, Bourne, Ali, Huq and Johnson, 2003; Murthy, Gupta, Bachani, Jose and John, 2005), especially in the different age groups (Zhu et al., 2013; Zhao et al., 2010; Liang et al., 2008; Zhang et al., 2009). Any severe pathology of organs of vision can be the reasons of blindness and visual impairment. The role of individual pathologies in the development of blindness varies depending on the place of residence, age and climatic and geographical conditions (Zhu et al., 2013; Gordois et al., 2012; Ramke, Palagyi, Naduvilath, du Toit and Brian, 2007; Varma, Wang, Ying-Lai, Donofrio and Azen, 2008; Ezelum et al., 2011; Bourne, Dineen, Huq, Ali and Johnson, 2004). This problem also exists in the Azerbaijan Republic. The aim of our study was to evaluate the frequency of annual cases of disability due to blindness in Azerbaijan, specify its characteristic and reasons and age-gender relation. In Azerbaijan, from year to year increases disability, among the reasons that a significant place is occupied by diseases of eye. Therefore, the authors to study of the problem, assuming that the results may be of interest to specialists in other countries.

Methods

Work carried out in accordance with the requirements of the Act on the rights of patients. Work approved by the ethics committee of the Azerbaijan Institute of Advanced Medical Legislation of the Republic of Azerbaijan provides social benefits to the citizens who have lost their vision. People with disabilities are under the supervision of the National Health Service and receive social benefits.

Ophthalmological assistance is available to all citizens with abnormalities of vision, and the patients with ocular pathology have to visit oculists of local polyclinics. The country’s ophthalmologic care includes two-stage: polyclinics refer to the first stage, while the republican specialized centers in the capital of the country are the second stage establishments. Patients receive medical assistance in local polyclinics and in hospitals under the supervision of qualified doctors. With the ineffectiveness of medical care and the formation of blindness patients are sent to medical – social expert commissions under the Ministry of Labour and Social Security of the Azerbaijan Republic, which operate in all regions and are based in the largest medical establishments. In the accompanying document the physician specifies the entire history of the disease, the full list of submitted treatment and settle the hopelessness of further treatment and the need for social welfare. In these committees after thorough verification of the patient’s vision by oculists , the following decision may be made:

invalid of the first group – visual acuity in both eyes with a maximum possible correction < 3/60 ( or 20/400) (visual field is narrowed to 10⁰);

• the second group invalid – visual acuity in both eyes with a maximum correction > 20/400 and < 20/250 (visual field is narrowed 10⁰ to 20⁰);
• the third group disability – one eye is either absent or blind (visual acuity < 20/500); and other eye has visual acuity > 20/200
• visually impaired patients who are not disabled (visual acuity in both eyes with a maximum correction > 20/250, but < 20/200 or one eye has visual acuity > 20/500 and other eye has visual acuity > 20/200

The material for our study were the medical records of disable persons (blind).

These documents have been received from the archive of Ministry of Labour and Social Welfare. Gender, age, education, previous employment, detailed diagnosis with the date of its confirmation and the basic parameters of the vision organ state are indicated there. We used the documents for 2001 – 2008. The total number of the blind persons was 16303. All the diagnoses were coded according to the ICD-10.

The source of our data is the official registration documents of medical and social expert commissions at Ministy Labour and Social Security. Information about the gender appears and age of the disabled blind were taken from the registration documents of medical and social expert commissions, which are compulsory to check the passport. Information about the gender appears and age composition of the population is taken from the State Statistical Committee.

Disabled’s were divided into 8 groups of the original cause of eye disease. Each of the eight groups divided into subgroups by age and gender appears.

The initial cause of blindness as “the disease or injury that resulted in the chain of pathological processes leading directly to blindness” was set for each patient. The patients were divided into groups according to the initial cause of blindness, and within each group they were divides by age (15 – 19 y.o., 20 – 24 y.o., 25 – 29 y.o., 30 – 34 y.o., 35 – 39 y.o., 40 – 44 y.o., 45 – 49 y.o., 50 – 54 y.o., 55 – 59 y.o., and over 60 y.o.) by gender, according to the calendar year of blindness admission, according to the degree of disability (I, II or III group).

The initial cause of blindness, a disease or damage to the organs of sight, which causes a chain of pathological processes that directly leads to blindness. Such diseases were grouped according to ICD-10 blocks ( H00-H063; H10-H13; H15-H22; H25-H28; H30-H36; H40-H42; H43-H45 ; H46-H48; H49-H52; H53-H54). To calculate the incidence of blindness necessary information about age – gender composition of the population was obtained from the printed matters of the State Statistical Committee of Azerbaijan Republic (Stenton, 1999).

Statistical evaluation of the material. Methods of descriptive statistics and analysis of qualitative features (Zhang et al., 2009) were used. The proportion of the blind persons by age, reasons of blindness and severity of disability (  ), standard error (S ), Z criterion at the comparison of two shares, Yates correction for continuity were determined. When comparing more than two shares contingency tables (criterion χ²) were used. The frequency of annual incidence of blindness was defined as the ratio of the blind persons to the amount of population. This criterion was established for each group with blindness and for each age – gender group. For this indicator the standard error by analogy with the error proportion, 95% confidence interval (CI ) at t = 1,96 was determined as well.

Results

Distribution of the Azerbaijani population and contingent of blind persons by age is shown in Table 1. An expressed distinction in the proportion of the persons in different age groups in general population and in the blind is noteworthy.

Table 1: Distribution of the population of Azerbaijan and contingent blind by age (%)

The comparison of the age composition of the blind persons to the age composition of the general population allows us to estimate the probability of the high risk in relation to age. The probability of blindness increases significantly depending on age (see Table 2).

Таble 2: 95% confidence interval frequency of new cases of blindness per year (for 100.000 of the persons of corresponding age and gender)

From this it follows that in most age groups (15 – 44, 55 and over ), the probability of blindness is significantly (P < 0,05) higher among men. Only in the age group of 45-54 y.o. zero hypotheses fairness about the same probability of blindness in men and women is confirmed.

The incidence of blindness due to most ocular diseases is significantly higher among men, and only in the cases of blindness due to the diseases of choroid and retina, optic nerve and optic tracts the validity of the null hypothesis (P> 0.05) is confirmed.

Frequency of development of blindness is relatively more at the diseases of the eye muscles, conjugate eye movement disorders, accommodation and refraction in female (95% CI: 3.5 – 5.3 per 100.000) and male population (95% CI: 5.0 – 7.4 per 100.000).

The second place among ocular pathologies on the possibility of forming blindness occupy eye injuries in male population (95% CI: 4.6-6.2 100.000), diseases of retina and choroid in the female population (95% CI: 2.9 – 4.3 100.000).

Diseases of lens are on the third place among causes of blindness in men (95% CI: 4.1-5.7 per 100.000) and women (95% CI: 1.8 – 2.9 per 100.000) .

Almost the same is the incidence of blindness men due to diseases of sclera, cornea, iris and ciliary body (95% CI: 2.2 – 3.0 per 100.000) and glaucoma (95% CI: 2.1 – 3.2 per 100.000). These pathologies divide 4 – 5^th place between causes of blindness in men. In women diseases of optical nerve and optical tracts (95% CI: 1.2 – 2.0 per 100.000) and glaucoma (95% CI: 1.2 – 2.1 per 100.000) divide 4 – 5^th places between causes of blindness.

The burden of blindness depends on the person’s age when this serious illness has formed. Descriptive statistics of the patients’ age at the primary confirmation of blindness is shown in Table 3.

Table 3: Descriptive statistics of the blind persons age

Blindness is formed at all ages. The average age at initial confirmation of blindness in women and men is significantly different ( 95% CI: 43.1 – 43.5 and 44.6 – 45.0 years, correspondingly).

Depending on the cause of blindness, the average age of patients at the primary confirmation of diagnosis varies widely: the minimum value in blindness due to diseases of the eye muscles, conjugate eye movement disorders, accommodation and refraction (95% CI: 31.7 – 34.1 years for men, 30.0 – 32.8 years for women), the maximum value of blindness due to glaucoma (95% CI: 58.5 – 59.9 years for men, 58.7 – 60.3 for women). Thus in Azerbaijan, 95% confidence interval of the annual rate of blindness is 32,3 – 32,9 per 100.000 men and 18,3 – 21,4 per 100.000 women.

Discussion

Blindness as a consequence of severe eye diseases is formed, at least according to two crucial factors: severity of the disease and its danger and non-adequate medical care.

Our observation shows the probability of blindness at the conditions of the country with the remnants of the Soviet healthcare system. The feature of this system is affordability of medical care and poor qualification of doctors. Therefore, the probability of blindness in Azerbaijan may differ from other countries.

Our work demonstrates high risk of blindness among men aged 60 years and more which 1.6 times prevails that of the women. In Boashane probability of blindness is also higher among men, but the degree of relative risk of less than 1.2.

Chance of high risk of blindness among men is confirmed in the works of many authors.

In our paper we show that the probability of blindness due to eye injury in men repeatedly exceeds that of women (95% CI of the relative risk : 7.8 – 15.3) . This coincides with the data of literature (Zhu et al., 2013). The average age of blindness formation ( 44.8 years for men and 43.3 for women ) at the existing level of life expectancy in Azerbaijan (67.7 years for men , 73.3 years for women) indicates this burden’s size and necessitates prevention of this pathology. Prevention of blindness is possible at prevention of eye diseases and their adequate treatment.

Conclusions

1. In Azerbaijan , 95% confidence interval of the annual rate of blindness is 32,3 – 32,9 per 100.000 men and 18,3 – 21,4 per 100.000 women.
2. The frequency of annual cases of blindness increases with the age of the population, the confidence interval which is 17,5 – 26,3 per 100.000 men and 9,5- 16,3 per 100.000 women aged 15-19 ; 54,7 – 72,1 per 100.000 men and 32,0 – 44,0 per 100.000 women aged 60 years and older.
3. The most common causes of blindness are diseases of the eye muscles, conjugate eye movement disorders, accommodation and refraction (95% CI: 5,0 – 7,4 per 100.000 women, 3,5- 5,3 per 100.000 women over 15 years ) disease of the lens (95% CI: 4,1 – 5,7 per 100.000 men 1,8 – 2,9 per 100.000 women), trauma (95% CI: 6,2 – 4,6 100.000 men, 0.3 – 0.8 per 100.000 women).

Ethics

Work carried out in accordance with the requirements of the Act on the rights of patients. Work approved by the ethics committee of the Azerbaijan Institute of Advanced Medical.

Competing Interests

Rustamova N., Rzayeva A., Agayeva K. declare that they have no competing interests.

Authors Contributions

R.N. performed the statistical analysis

R.A conceived of the study, spent gathering information, coding of medical death certificates.

A.K. articipated in the sequence alignment and drafted the manuscript.

The final manuscript has been read and approved by all the authors.

Acknowledgements

The authors wish to thank Dr. F. Agayeva, head of the Department of Health and the organization of social hygiene of Azerbaijan State Advanced Training Institute for doctors, who actively participated and provided their precious time.

Funding

Azerbaijan State Advanced Training Institute for doctors named after A. Aliyev is funding the article.

References

1. Zhu M., Tong X., Zhao R., He X., Zhao H., Liu M. and Zhu J. (2013).Visual impairment and spectacle coverage rate in Baoshan district, China: population-based study. BMC Public Health, 13:311
2. Nano PL, Silva ME (2012) Causes of Blindness and Visual Impairment in Latin America. Surv. Ophthalmol, 57: 149–77.
3. Gordois A, Cutler H, Pezzullo L, Gordon K, Cruess A, Winyard S, Hamilton W, Chua K (2012). An estimation of the worldwide economic and health burden of visual impairment. Glob Public Health, 7: 465–81.
4. Ramke J, Palagyi A, Naduvilath T, du Toit R, Brian G (2007). Prevalence and cause of blindness and low vision in Timor-Leste. Br J Ophthalmol, 91: 1117–21.
5. Zhao J, Ellwein LB, Cui H, Ge J, Guan H, Lv J, Ma X, Yin J, Yin ZQ, Yuan Y, Liu H(2010). Prevalence of vision impairment in older adults in rural China: the China Nine-Province Survey. Ophthalmology, 117: 409–16.
6. Abdull MM, Sivasubramaniam S, Murthy GV, Gilbert C, Abubakar T, Ezelum C, Rabiu MM. (2009). Nigeria National Blindness and Visual Impairment Study Group: Causes of blindness and visual impairment in Nigeria: the Nigeria national blindness and visual impairment survey. Invest Ophthalmol Vis Sci, 50 : 4114–20.
7. Jadoon MZ, Dineen B, Bourne RR, Shah SP, Khan MA, Johnson GJ, Gilbert CE, Khan MD (2006). Prevalence of blindness and visual impairment in Pakistan: The Pakistan National Blindness and Visual Impairment Survey. Invest Ophthalmol Vis Sci, 7 : 4749–55.
8. Dineen BP, Bourne RRA, Ali SM, Huq DMN, Johnson GJ (2003). Prevalence and causes of blindness and visual impairment in Bangladeshi adults: results of the National Blindness and Low Vision Survey of Bangladesh. Br J Ophthalmol, 87: 820–28.
9. Murthy GVS, Gupta SK, Bachani D, Jose R, John N (2005). Current estimates of blindness in India. Br J Ophthalmol, 89 : 257–60.
10. Varma R, Wang MY, Ying-Lai M, Donofrio J, Azen SP (2008). Los Angeles Latino Eye Study Group: The prevalence and risk indicators of uncorrected refractive error and unmet refractive need in Latinos: The Los Angeles Latino Eye Study. Invest Ophthalmol Vis Sci, 49 : 5264–73.
11. Ezelum C, Razavi H, Sivasubramaniam S, Gilbert CE, Murthy GV, Abubakar T. (2011). Nigeria National Blindness and Visual Impairment Study Group: Refractive error in Nigerian adults: prevalence, type, and spectacle coverage Invest Ophthalmol Vis Sci, 52 : 5449–56.
12. Bourne RR, Dineen BP, Huq DM, Ali SM, Johnson GJ (2004). Correction of refractive error in the adult population of Bangladesh: meeting the unmet need. Invest Ophthalmol Vis Sci, 45:410–17.
13. Liang YB, Friedman DS, Wong TY, Zhan SY, Sun LP, Wang JJ, Duan XR, Yang XH, Wang FH, Zhou Q, Wang NL. (2008). Handan Eye Study Group: Prevalence and causes of low vision and blindness in a rural Chinese adult population: the Handan Eye Study. Ophthalmology, 115:1965–72.
14. Zhang MZ, Lv H, Gao Y, Griffiths S, Sharma A, Lam D, Li L, Tse YK, Liu X, Xu D, Lu B, Congdon N. (2009). Visual morbidity due to inaccurate spectacles among school-children in rural China: the See Well to Learn Well Project. Report 1. Invest Ophthalmol Vis Sci, 50:2011–17.
15. Stenton G. Medical-and-Biological Statistics. – Moscow: Practica, 1999. -459 p. (Rus.)
16. Demographic indicators of Azerbaijan official publication. Statistical yearbook. Baku 2012. www.azstat.org.