Prevalence Factors Associated With Vision Impairment and Blindness Among Individuals 85 Years and Older in Russia

IMPORTANCE Visual performance is important for quality of life. However, vision impairment among adults 85 years and older has not been intensively examined. OBJECTIVE To assess the prevalence of mild vision impairment (VI), moderate to severe vision impairment, and blindness and the factors associated with these conditions among a population 85 years and older. DESIGN, SETTING, AND PARTICIPANTS The Ural Very Old Study was a population-based cohort study conducted in rural and urban areas in Bashkortostan, Russia from 2017 to 2020. Among 1882 eligible individuals 85 years and older, 1526 participants (81.1%) were enrolled. EXPOSURES Ophthalmologic, physical, and mental examinations. MAIN OUTCOMES AND MEASURES Prevalence of vision impairment and blindness based on best-corrected visual acuity (BCVA; measured using modified Early Treatment of Diabetic Retinopathy Study charts) in the better eye or both eyes. Mild vision impairment was defined as BCVA worse than 6/12 to 6/18, and moderate to severe VI was defined as BCVA worse than 6/18 but equal to or better than 3/60. Blindness was defined as BCVA worse than 3/60. RESULTS Among 1526 participants, 1149 individuals (75.3%; 846 women [73.6%]; mean [SD] age, 88.2 [2.8 years]) had available BCVA Abstract(continued) 0.2%-1.1%]), myopic maculopathy (3 individuals [4.4% of those with blindness and 0.3% of total population; 95% CI, 0%-0.6%]), and corneal opacifications (2 individuals [2.9% of those with blindness and 0.2% of total population; 95% CI, 0%-0.4%]). Higher moderate to severe VI prevalence was associated with older age (odds ratio [OR], 1.19; 95% CI, 1.11-1.28; P < .001), higher blood pressure (OR, 1.01; 95% CI, 1.00-1.02; P = .03), lower hand grip force (OR, 0.88; 95% CI, 0.83-0.95; P < .001), lower score on the Mini-Mental State Examination (OR, 0.95; 95% CI, 0.92-0.98; P < .001), lower prothrombin index (OR, 0.93; 95% CI, 0.89-0.97; P < .001), lower refractive error (OR, 0.91; 95% CI, 0.85-0.97; P = .006), and lower prevalence of previous cataract surgery (OR, 0.48; 95% CI, 0.33-0.68; P < .001). CONCLUSIONS AND RELEVANCE In this cohort study of individuals 85 years and older, the prevalence of moderate to severe VI and blindness was relatively high. Cataracts were the main reversible condition associated with vision loss, and age-related macular degeneration, glaucoma, and myopic maculopathy were the main irreversible conditions. Because a higher prevalence of moderate to severe VI was associated with lower cognitive function and physical strength, improvement of vision through increases in cataract surgery and measures to prevent and treat irreversible conditions may help to improve cognitive function and physical strength. static perimetry; anterior segment imaging using a Scheimflug camera (Pentacam HR, Typ 70900; OCULUS); sonographic measurement of axial length; 23 The prevalence of myopic maculopathy as a factor associated with blindness (0.3% in our study vs 0.03% in the UEMS) and moderate to severe VI (1.1% in our study vs 0.2% in the UEMS) was thus higher in our older population compared with the younger population of the UEMS. Even if one assumes a further age-related increase in the prevalence of myopic maculopathy, the 5- to 10-fold higher prevalence of myopic maculopathy as a factor associated with blindness or moderate to severe VI in our older study population compared middle-aged the UEMS suggests that, 30 The importance of in Asia, 27-29 such 27 visual disabilities in our study. Hand grip strength has been regarded as a biomarker of concurrent overall strength, upper limb function, bone mineral density, depression, multimorbidity, and quality of life. 32


Introduction
Visual performance is important for an individual's quality of life and public health in general. 1,2 Recent meta-analyses 3,4 estimated that 43.3 million individuals were blind, and 295 million individuals had moderate to severe vision impairment (VI) in 2020. The most common factors associated with blindness in individuals 85 years and older were cataracts, glaucoma, undercorrected refractive error, age-related macular degeneration (AMD), and diabetic retinopathy. 4 These and other meta-analyses were limited by a scarcity of population-based studies focusing on adults 85 years and older. Most available studies had an age-related inclusion criterion of 40 years and older, with fewer than 5% of study participants 85 years and older. Our hypothesis was that the prevalence of vision impairment and blindness and their associated factors may differ in a population of individuals 85 years and older compared with younger populations. Therefore, we conducted the Ural Very Old Study (UVOS) to examine the prevalence of vision impairment and blindness and the factors associated with these conditions in a population 85 years and older, to explore the association of vision impairment and blindness with other demographic and clinical variables, and to compare these data with findings obtained among a younger population in the same study regions.

Methods
The UVOS was a population-based study performed in Kirovskii, a rural region that is 65 km from the capital of Ufa, and the Republic of Bashkortostan, Russia, an urban region of Ufa that is approximately 1300 km east of Moscow. The study was conducted between November 2017 and December 2020 and was approved by the ethics committee of the Academic Council of the Ufa Eye Research Institute. Written informed consent was obtained from all participants. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline for cohort studies and the Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER). 5,6 Individuals who were 85 years or older and living in the study regions were eligible for inclusion.
Among 1882 eligible individuals, 1526 participants (81.1%) were enrolled in the study. Participants in the urban study region included the inhabitants of 3 small private retirement homes; there were no retirement homes in the rural study region. The participation rate did not substantially vary between the urban group (1238 of 1523 individuals [81.3%]) and the rural group (288 of 359 individuals [80.2%]). According to the 2010 Russian census, the sex and age composition of the study population was consistent with that of the Russian population who were 85 years and older, with a preponderance of women. 7,8 All participants received a standardized interview conducted by trained social workers; this interview comprised almost 300 questions on socioeconomic background, self-reported ethnic background, diet, smoking, physical activity, quality of life, quality of vision, history of any type of injury or injury associated with interpersonal violence, health assessment, medical history, previous neurologic events, cognitive function, and hearing loss. [9][10][11][12][13][14] Physical and clinical examinations included measurement of anthropomorphic parameters, arterial blood pressure and pulse rate, dynamometric assessment of handgrip strength, and biochemical examination of blood samples obtained under fasting conditions. Arterial hypertension was defined based on recommendations from the American College of Cardiology and the American Heart Association in 2017. 15 Diabetes was characterized as a fasting glucose concentration of Ն126 mg/dL (to convert to mmol/L, multiply by 0.0555) or a self-reported history of physician diagnosis of diabetes or drug treatment for diabetes.
Cognitive function was assessed using the Mini-Mental State Examination (MMSE), 11 anxiety was measured using the State-Trait Anxiety Inventory, 16 and depression was assessed using the Center for Epidemiologic Studies-Depression scale. 9 The estimated glomerular filtration rate was calculated using the equation developed by the Chronic Kidney Disease Epidemiology Collaboration. 17 The design of the UVOS was similar to that of the Ural Eye and Medical Study (UEMS), which has been described in detail previously. 18,19 The ophthalmologic examinations comprised the measurement of presenting, uncorrected, and best-corrected visual acuity (BCVA) using modified Early Treatment of Diabetic Retinopathy Study charts; automated refractometry; static perimetry; anterior segment imaging using a Scheimflug camera (Pentacam HR, Typ 70900; OCULUS); sonographic biometric measurement of axial length; slit lamp biomicroscopy of the anterior and posterior ocular segment; noncontact tonometry; photography of the cornea and lens (slit lamp and camera; Topcon Corp); photography of the optic disc (VISUCAM 500; Carl Zeiss Meditec) and macula (Smartscope EY4; Optomed); and spectraldomain optical coherence tomography of the optic nerve head (RS-3000 Advance; NIDEK) and and late AMD defined as the presence of lesions associated with neovascular AMD or geographic atrophy). Glaucoma was defined using morphological criteria described by Foster et al. 21 Based on criteria from the World Health Organization, 22 we defined mild vision impairment as BCVA worse than 6/12 to 6/18 in the better eye or both eyes, moderate to severe VI as BCVA worse than 6/18 but equal to or better than 3/60 in the better eye or both eyes, and blindness as BCVA worse than 3/60 in the better eye or both eyes. the univariate analyses. We then removed, in a step-by-step manner, those factors from the list of independent variables that had collinearity with other factors and that were no longer significantly associated with the prevalence of moderate to severe VI or blindness. We calculated the odds ratios (ORs) and their 95% CIs. The significance threshold was 2-sided P < .05.  .7%) met the criteria for having mild VI, 562 individuals (48.9%; 95% CI, 46.0%-51.8%) met the criteria for having moderate to severe VI in the better eye or both eyes, and 68 individuals (5.9%; 95% CI, 4.6%-7.3%) met the criteria for having blindness in the better eye or both eyes ( Table 1).

Male Female
A, Moderate to severe vision impairment was defined as visual acuity worse than 6/18 but equal to or better than 3/60 in the better eye or both eyes. B, Blindness was defined as visual acuity worse than 3/60 in the better eye or both eyes. Circles represent prevalence, and error bars represent 95% CIs. and blindness was associated with older age (OR, 1.20; 95% CI, 1.

Discussion
In this cohort study of an ethnically mixed population 85 years and older from Bashkortostan, Russia, the prevalence of blindness, moderate to severe VI, and mild VI was 5.9%, 48.9%, and 9.9%, 7.0% (95% CI, 6.3%-7.8%), respectively. 26 In the latter study, the prevalence of moderate to severe VI and blindness increased to 39.0% and 5.4%, respectively, among individuals 80 years and older. 26 In our study, as in other previous investigations, 4,23,25-29 the presence of cataracts was the most common reversible condition associated with moderate to severe VI and blindness, followed by irreversible conditions associated with vision loss, including AMD, glaucoma, myopic maculopathy, and corneal opacifications. None of the individuals with vision impairment or blindness had diabetic retinopathy as the main condition associated with vision loss (Table 4). In a recent meta-analysis of data from the Global Burden of Disease Study conducted by the Vision Loss Expert Group, 4   In the global meta-analysis, 4 myopic maculopathy was not separately assessed regarding its frequency as a factor associated with moderate to severe VI and blindness. In our study, myopic maculopathy was associated with blindness in 4.4% of all participants with blindness (12.0% of participants with irreversible blindness) and with moderate to severe VI in 2.3% of all participants with moderate to severe VI (9.3% of participants with irreversible moderate to severe VI) ( Table 4).
Myopic maculopathy was the third most common factor associated with irreversible blindness and moderate to severe VI. In the UEMS population, which included participants with substantially younger ages, myopic maculopathy was the second most common factor associated with irreversible blindness  23 The prevalence of myopic maculopathy as a factor associated with blindness (0.3% in our study vs 0.03% in the UEMS) and moderate to severe VI (1.1% in our study vs 0.2% in the UEMS) was thus higher in our older population compared with the younger population of the UEMS. Even if one assumes a further age-related increase in the prevalence of myopic maculopathy, the 5-to 10-fold higher prevalence of myopic maculopathy as a factor associated with blindness or moderate to severe VI in our older study population compared with the middle-aged population of the UEMS suggests that, in the UEMS and UVOS study regions, the prevalence of myopic maculopathy as a factor associated with moderate to severe VI or blindness (in the middle-aged population) may not have substantially increased compared with previous periods. 30 The importance of myopic maculopathy as a factor associated with moderate to severe VI and blindness has also been reported in population-based studies conducted in East Asia, [27][28][29] such as the Beijing Eye Study, 27 in which myopic maculopathy was the most common factor associated with irreversible vision impairment and blindness in a population 40 years and older who were examined in 2001.
Factors associated with moderate to severe VI and blindness were older age, lower MMSE score, lower dynamometric hand grip force, lower prothrombin index, lower prevalence of previous cataract surgery, and more substantial cylindrical refractive error (Table 3). Although the associations with older age have also been reported in previous studies, 4,23,25-29 the association between a higher prevalence of moderate to severe VI and blindness and lower cognitive function (as measured by MMSE score) is of interest because another study 31 found an association between the prevalence of Alzheimer disease and hearing loss. This finding suggests that cataract surgery (and the provision of best-correcting glasses), in particular, may be a means of reducing the risk of cognitive dysfunction.
The finding is also consistent with the observation of lower hand grip force among participants with visual disabilities in our study. Hand grip strength has been regarded as a biomarker of concurrent overall strength, upper limb function, bone mineral density, depression, multimorbidity, and quality of life. 32

Strengths and Limitations
This study has strengths. To our knowledge, the study is the first population-based investigation of the prevalence of moderate to severe VI and blindness among individuals 85 years and older to include a relatively large sample and many demographic, clinical, and ocular factors.
This study also has limitations. First, the presenting visual acuity of participants was not assessed, so we could not determine the prevalence of undercorrection of refractive error as a factor associated with vision impairment and blindness. Second, dense cataracts prevented examination of the fundus; thus, any additional disorders of the optic nerve and macula were not detected. This limitation might have produced an underestimation of the prevalence of macular and optic nerve diseases. Third, difficulty with access to medical services may have been the primary factor associated with the relatively high prevalence of moderate to severe VI and blindness in the study population. We did not, however, assess the interval between the participants' last ophthalmologic examinations and the start of the study.

Conclusions
Among a population 85 years and older from Bashkortostan, Russia, the prevalence of moderate to severe VI and blindness was 48.9% and 5.9%, respectively, with 28.2% and 2.9% of the total study population experiencing moderate to severe VI or blindness associated with cataracts. Because cataracts were the main reversible condition associated with vision loss, increases in cataract surgery may be helpful to address blindness and VI among participants in the study region. Age-related macular degeneration was associated with moderate to severe VI and blindness in 3.9% and 0.6% of the population, respectively, and myopic maculopathy was the third most common factor associated with irreversible blindness and moderate to severe VI. Efforts may be intensified for the prevention and treatment of these conditions. Blindness and moderate to severe VI were associated with lower cognitive function and physical strength (as measured by hand grip force); thus, addressing vision impairment through measures such as cataract surgery may also help to improve cognitive function and physical strength.