In persons with long duration of diabetes, change in visual acuity over a 10-year period of follow-up was the most important predictor for decreased scores in most NEI-VFQ-25 domains. Stopping work during the study period and the presence of systemic comorbidities such as nephropathy were also strongly associated with changes in vision-related quality of life scores.
Our findings in the WESDR that decreases in visual acuity are associated with poorer self-perceived quality of life are consistent with data from other studies21–23
. The same association was seen among people with diabetes, especially those with macular edema24
. The importance of vision loss on quality of life was shown by Coyne et al23
in a study which investigated the impact of diabetic retinopathy on quality of life in a group of people with types 1 and 2 diabetes. They observed that the presence of diabetic retinopathy combined with visual loss had a greater impact on quality of life than the impact of mild retinopathy without visual impairment.
In the current analysis, a loss of 3 lines in visual acuity in the better eye was associated with relatively large score changes not only in domains directly related to visual function, such as near and distant activities, but in domains such as mental health, role difficulties, dependency, and driving. Matza et al8
reported a longitudinal analysis investigating changes in visual acuity and quality of life scores in patients with diabetic retinopathy. Similar to our study, mental health, role limitations, dependency, and driving were the domains most affected by visual acuity worsening by more than 10 letters. Coyle et al23
also showed that those with visual impairment reported a negative influence of poor visual acuity on every aspect of their quality of life, including, physical, social, leisure, and daily activities.
Progression or improvement of diabetic retinopathy was not associated with any vision-specific quality of life domain, when analyzed independent of visual acuity changes in our study. Because proliferative diabetic retinopathy (PDR) not affecting vision (due to traction on the macula or vitreous hemorrhage) is often asymptomatic, this was not unexpected. Also participants with severe long-standing PDR may have adapted to the changes in vision due to their retinopathy. Only seven people developed incident macular edema in their better-seeing eye during the 10-year period, limiting our ability to analyze the role of this condition in our population although this may have contributed to the association of vision with change in VFQ score.
Visual acuity was not associated with domains such as overall health, color vision, and peripheral vision in the current study. In a cross-sectional evaluation of the complication of age-related macular degeneration prevention trial (CAPT), visual acuity was the measurement most strongly associated with most VFQ subscales, except for driving and color vision. These two subscales were most strongly associated with contrast sensitivity, suggesting that other measurements of visual function affect quality of life differently than measurement of visual acuity25
Because visual acuity may be influenced by other ocular conditions, we investigated the impact of glaucoma on our findings. After excluding those with glaucoma at both follow-up visits, we did not observe any changes in our findings regarding the associations between visual acuity, diabetic retinopathy, and quality of life (data not shown). Because changes in the severity of cataract between the two visits were not determined, we could not to evaluate the effect of cataract on changes in visual acuity in the current analysis. Approximately 18% of the people in the study population had undergone cataract surgery in either eye at the 2005–07 visit. Because cataract surgery has been available and easily accessible to this relatively young population, we believe that development of a cataract causing visual impairment in the absence of other ocular disease (e.g., severe retinopathy) would have been removed and would be unlikely to have influenced our results.
The NEI-VFQ-25 questionnaire was sensitive in capturing the influence of complications such as cardiovascular disease and nephropathy in domains such as near vision activities, role difficulties, driving, and peripheral vision. The presence of these conditions could indicate a poorer health state limiting the execution of role activities or those requiring the individual to be relatively free of physical limitations such as for driving. However, the relationship between development of cardiovascular disease and changes in near vision activities and peripheral vision was not clear. These findings suggest that the presence of macro- and microvascular complications should be taken into account when investigating vision-related quality of life in people with type 1 diabetes.
The WESDR provided an opportunity to explore the potential influences of factors other than those directly related to diabetes on quality of life. Stopping work was associated with decreases in the vision-specific social functioning, mental health, role difficulties, and peripheral vision NEI-VFQ domains. None of the previous studies have explored the impact of employment on vision-specific quality of life. As we observed in the current analysis, the domains that were most strongly associated with changes in employment status were those related to well-being and distress, to activities requiring interpersonal interactions such as visiting people in their homes or entertaining friends, and limitations in role activities at work or home due to low vision. Unemployment, especially among those of working age, adds a significant psychological burden to these individuals. Studies have shown that the loss of a job can have an important influence on one’s perception of non-vision-specific quality of life26
. This could explain our findings, regardless of the fact that NEI-VFQ-25 questions were focused on function related to the individual’s vision.
This study has some limitations that should be considered. Visual acuity was the only measurement of visual function used in WESDR. There were no objective measurements of contrast sensitivity, glare recovery, and visual field that might have captured other components of visual function not explained by visual acuity alone6, 27
. This is a cohort of survivors with long-term type 1 diabetes. The ones who were excluded from the analysis had lower vision-related quality of life scores than those who participated in both exams and this might have resulted in an underestimation of the associations examined in this analysis. Finally, the availability of data from only two points in time over a 10-year period also limits the ability to perform a more comprehensive longitudinal analysis of more acute changes. Despite its limitations, the strengths of the WESDR should also be considered. The use of standard protocols such as the ETDRS refraction and visual acuity measurements and fundus photographs and standardized classification scheme for diabetic retinopathy allow detailed assessment of this condition decreasing chances of misclassification. The population-based design provides an opportunity to generalize our findings to persons with long-term type 1 diabetes.
In summary, change in visual acuity, independent of other factors such as the presence of comorbidities, was the most important factor associated with changes in vision-related quality of life scores in individuals with long-term type 1 diabetes over a 10-year period. In addition, psychosocial factors such as employment or marital status may influence quality of life and should be considered in future studies. Our findings support the current guidelines about the necessity of timely dilated eye examinations and treatment in people with type 1 diabetes to prevent vision loss and improve quality of life.