- Open Access
A prospective cross-sectional study on quality of life and treatment satisfaction in type 2 diabetic patients with retinopathy without other major late diabetic complications
© Alcubierre et al.; licensee BioMed Central Ltd. 2014
- Received: 14 April 2014
- Accepted: 12 August 2014
- Published: 20 August 2014
To assess quality of life and treatment satisfaction in patients with type 2 diabetes mellitus with diabetic retinopathy (DR) using validated instruments, with comparison to patients without DR.
A prospective cross-sectional study was designed to assess the influence of retinopathy on quality of life and treatment satisfaction in patients with type 2 diabetes mellitus who do not have any other advanced late complications that could interfere with these outcomes. We included 148 patients with DR and 149 without DR, all without other advanced diabetic complications. Quality of life was assessed using the Audit of Diabetes Dependent Quality of Life (ADDQoL) questionnaire, and treatment satisfaction was assessed using the Diabetes Treatment Satisfaction Questionnaire (DTSQ). Clinical and treatment variables related to diabetes were also collected. The degree of DR was classified according to the International Clinical Classification System. Multivariate linear regression models were used to model the ADDQoL and DTSQ scores according to sociodemographical and clinical characteristics, and to model the adjusted relationship of DTSQ with ADDQoL. In DR patients, a subanalysis assessed the relationship of these scores with the degree of retinopathy, severity of macular edema, and previous photocoagulation treatment.
DR was associated with significantly lower quality of life (p < 0.001), when examining the two general quality of life items and most of the specific domains. Concerning DTSQ, no difference was found in the total score, and only two domains that assess the perception of glycemic control (hyper- and hypoglycemia) showed a worse score in DR (p < 0.001 and p = 0.008, respectively). Quality of life was significantly affected by the severity of DR, and treatment satisfaction was significantly affected by the severity of macular edema. In the multivariate analysis, a significant effect of the interaction between diabetes duration, insulin therapy, and the presence of DR was found for both, ADDQoL and DTSQ.
In the absence of other major complications, DR has a negative impact on quality of life in patients with type 2 diabetes. Further, treatment satisfaction was not affected by the presence of DR.
- Diabetic retinopathy
- Quality of life
- Treatment satisfaction
- Specific questionnaires
- Type 2 diabetes mellitus
Diabetic retinopathy (DR) is a diabetes-specific ophthalmic complication that is still very common and often severe. It is the leading cause of preventable blindness in working-age adults ,. In Spain, 15.6% of patients with type 2 diabetes mellitus are affected by the disease in its different stages, with a 4% prevalence of proliferative DR ,.
Improving quality of life is a primary goal when treating diabetic patients with DR. Diabetic visual impairment places the individual in a situation that can profoundly affect their quality of life –. Photocoagulation, the first-line and most frequently used treatment for diabetic retinopathy, has an adverse effect on health-related quality of life and treatment satisfaction in these patients .
We understand treatment satisfaction to be the “confirmation of expectations” for a patient, that is, the agreement between what the patients expects from the treatment and the results obtained . Although new treatment standards advise reconciling traditional measures of vision assessment with the use of patient-reported outcome measures, choosing the most appropriate instrument to measure quality of life can be difficult . The primary reason for using specific measures of diabetes-related quality of life is to provide an accurate, comprehensive, and personal assessment of this complication, analyzing its role in the patient’s life and maximizing the variability in the responses of patients with the same pathology or in certain groups .
In a recent review, Fenwick et al. established that DR is a threat to the quality of life of patients with type 1 or type 2 diabetes, especially in later stages, and illustrated the way in which different psychometric properties of the most frequently used scales can lead to very different outcomes . However, the presence of other diabetic late complications is the very frequent in participants included in studies assessing quality of life in diabetic retinopathy ,. For instance, in the study by Davidov et al., complications like coronary heart disease, nephropathy, peripheral vascular disease or cerebrovascular disease have been shown to be frequent in patients with retinopathy; in that study, patients had a mean of 2.4 associated co-morbidities and only 11% of them were free of any of this major health conditions . In a very large study, the Andhra Pradesh Eye Disease Study , the authors showed the specific adverse impact in terms of quality of life of different eye diseases i.e. cataract, corneal diseases, retinal diseases, glaucoma and uncorrected refractive deffects. Specifically, in that study diseases of the retina with a very similar impact on visual health, like macular degeneration, showed an unfavourable impact on quality of life. Therefore, the specific impact of retinopathy on quality of life in type 2 diabetes deserves further research.
Few studies have assessed the impact of DR on the quality of life of type 2 diabetic patients. In addition, none of the instruments used in those studies, such as generic health status questionnaires or visual function scales, although they analyze patient-reported outcomes, can be considered sufficiently accurate to assess quality of life outcomes in diabetic patients ,. Only one study examined satisfaction with photocoagulation treatment in patients with diabetic maculopathy or proliferative retinopathy, using the Diabetes Treatment Satisfaction Questionnaire (DTSQ), and it reported high levels of satisfaction despite not seeing improvements in visual acuity . However, the results described in the scientific literature regarding the specific impact of DR in patients with type 2 diabetes mellitus should be treated with caution. The coexistence of other advanced diabetic complications, the small sizes of the samples, the heterogeneous distribution of the variables, and the joint analysis of results for type 1 and 2 diabetic patients all limit the utility of previous studies ,,–. We have found no studies in the literature that investigate the specific impact of retinopathy on quality of life and treatment satisfaction in type 2 diabetic patients without other advanced diabetic complications using instruments specifically designed to assess these outcomes in diabetic patients. Thus, we think that further research is needed to explain the impact of retinopathy on these measures, specifically in type 2 diabetic patients in the absence of other associated complications.
This study hypothesizes that patients with DR have poorer self-perceived health-related quality of life and a lower degree of treatment satisfaction, regardless of the contribution of other late complications of diabetes (i.e., diabetic foot disease, cardiovascular disease, and diabetic nephropathy). We therefore present the first study, to our knowledge, specifically designed to assess the impact of DR in terms of quality of life and treatment satisfaction assessments in type 2 diabetic patients without other complications that might have confounding effects during the assessment. In addition, as a secondary objective, we set out to analyze the clinical and sociodemographic variables that may be associated with both assessments.
A prospective, observational, cross-sectional study was designed. Patients were identified from a unpublished prospective study on cerebral microcirculation conducted by our research team in patients with and without retinopathy. From a total sample of 314 patients and based on the sample size calculation (see below), a total of a 299 were offered participation in the current study. All initially contacted patients fulfilled the predefined inclusion criteria and accepted the participation in the study; however, finally 2 subjects did not show up for the study visit even after additional efforts were made to include them. It should be noted that the study visits were scheduled independently of the retinopathy status at the best patient convenience to allow maximum participation. The group with DR (n = 148) consisted of patients between 40 and 75 years of age with type 2 diabetes mellitus who did not have macrovascular complications, a history of diabetic foot disease, macroalbuminuria, or renal failure. The group without DR (n = 149) consisted of patients in the same age range with type 2 diabetes mellitus without DR who also did not have the previously mentioned complications. The group of patients with DR included those who had any degree of DR, with or without microalbuminuria (albumin/creatinine ratio up to 300 mcg/g), but without macroalbuminuria or a history of diabetic foot disease. The group without retinopathy included participants without evidence of retinopathy on ophthalmologic evaluation. All patients had normal renal function (glomerular filtration rate > 60 ml/min). None of the study groups included patients with cardiovascular diabetic complications, which was confirmed by anamnesis and a review of patients’ medical history to verify the lack of heart failure, cerebrovascular disease, ischemic heart disease, or peripheral arterial disease. The recruitment of all the patients was primarily performed through the Department of Ophthalmology of the hospital and the enrollment of the patients was intended to include a similar number of subjects in terms of age and sex groups. This department is the main public referral center for our health care district and is responsible for conducting the screening, assessment and treatment of all DR cases. The study was discussed with all patients, and their written informed consent was obtained. The study was approved by the Ethics Committee of Hospital Arnau de Vilanova.
Demographic and clinical characteristics of the study groups
No retinopathy (n = 149)
Retinopathy (n = 148)
Not even primary
Secondary high cycle
Graduate or higher
Diabetes duration (years)
Serum creatinine (mg/dl)
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
OAD + insulin
< = 0.2
More than 25 minutes/day
Less than 25 minutes/day
All the questionnaires were administered individually by personal interview by a single trained interviewer (N.A.), after the diagnostic assessment at the Department of Ophthalmology. The response rate was 99.3%.
Quality of life
Summary of Audit of Diabetes Dependent Quality of Life (ADDQoL) measures
1 [ 0,1]
Diabetes specific QoL
Freedom to eat
Freedom to drink
Average weighted impact score
The Diabetes Treatment Satisfaction Questionnaire (DTSQ), designed to assess the degree of treatment satisfaction, was used . This instrument has been validated for the Spanish population . It consists of eight questions, two of which are scored separately (frequency of hyper- and hypoglycemia). All items have seven possible responses, and the score ranges between 0 and 6. Overall satisfaction is expressed with an overall score of 0 to 36, with higher values indicating higher treatment satisfaction. This questionnaire has been recommended by the World Health Organization and the International Diabetes Federation as a valid instrument that enables the accurate measurement of treatment satisfaction for type 1 or 2 diabetic patients .
Assessment of diabetic retinopathy
DR and macular edema were classified according to the International Clinical Classification System . This classification is widely used and determines the degree of retinopathy, including macular edema, by objective criteria. The classification categories are as follows: 1) no diabetic retinopathy, 2) mild non-proliferative diabetic retinopathy, 3) moderate non-proliferative diabetic retinopathy, 4) severe diabetic retinopathy, and 5) proliferative diabetic retinopathy. For the diagnosis of macular edema, the Early Treatment Diabetic Retinopathy Study Research Group criteria were used as reference, and the concept of macular edema was applied in those cases where it was clinically significant . If the eyes were not equivalent, the participant was classified according to the eye with more severe stage.
To determine the sample size, an estimation of the standard deviation for the ADDQoL domains was obtained from previous studies . We used the highest reported SD (value 3.37) and predefined a statistical power of 80% and a significance level of 5%. In order to detect a predefined mean difference of at least 1.2 in the ADDQoL score between the study groups and expecting no more than 15% of individuals being lost to follow-up, a minimum sample size of 146 per group was required.
Comparative analyses between groups of diabetic patients with and without retinopathy were performed using the Mann–Whitney U test for quantitative variables and the chi-squared test or Fisher test, as appropriate, for qualitative variables. Graphical analyses of smoothed trends (using a span of 0.95) were performed to explore the possible interactions between the groups and treatment with insulin and diabetes duration, as well as the non-linear relationship of diabetes duration with the ADDQoL and DTSQ scores. Afterwards, two multivariate linear regression models were fit in order to assess whether retinopathy remained a significant contributor to the differences in ADDQoL and DTSQ scores after accounting for treatment with insulin, diabetes duration, and all other variables that had a significant contribution, according to the likelihood ratio test (LR test), to explain changes in each score. Each of the demographical and clinical variables were tested for contribution to the main outcome measures, starting from a model only with the DR identifier adding the variable with the most significant contribution (lower LR test p-value) to the previous model, and so on by refitting the significance of the contribution of each of the remaining variables to the model until no statistical contribution was obtained. A final multivariate linear regression model was fit to assess the association of the reported satisfaction with diabetes treatment and the perceived quality of life, using the same methodology. Additionally, a subanalysis in the group with retinopathy was performed to assess the association of the level of retinopathy, the severity of macular edema, and previous photocoagulation treatment with the ADDQoL and DTSQ scores using a Kruskal-Wallis test and a quantile regression model for median trend for the first two variables and the Mann–Whitney test for the photocoagulation treatment. A significance level of 0.05 was used. The analyses were performed using R statistical software.
The primary clinical and sociodemographic characteristics and their comparison between the two groups are shown in Table 1. Patients with retinopathy had a slightly higher average age because fewer patients with DR were identified between 40 and 50 years of age. Patients with DR had less schooling, a longer duration of diabetes, greater glycosylated hemoglobin levels, and greater frequency of arterial hypertension. As expected, patients with DR had higher urinary albumin concentrations and higher systolic blood pressure. Although body mass was not different, patients with retinopathy had a higher waist circumference. Patients with DR also received more complex treatment which is related to the longer duration of diabetes.
The distribution of each degree of retinopathy was as follows: 40.7% with mild nonproliferative DR, 35.9% with moderate nonproliferative DR, and 23.4% with severe proliferative DR. Diabetic macular edema was present in 52 patients (35.9% of those with DR). Of this percentage, edema was clinically significant in 21.4% and not clinically significant in 14.5%. For the DR group, a significant association between the degree of DR and the presence of clinically significant macular edema was observed (p < 0.0001). A significant association was also observed between the degree of DR and previous photocoagulation treatment (p < 0.0001).
Health-related quality of life using ADDQoL scores
Scores representing diabetes-related quality of life were significantly lower in patients with DR in the following specific domains: leisure, work, freedom to travel, physical ability, family and social life, emotional and sexual relationships, self-confidence, personal finances, motivation, future, and dependence (Table 2). The average weighted impact score showed a median value of −0.35 (95% CI: 0.78-0.06) in the group without DR and −0.88 (95% CI: 1.76-0.38) in the group with DR (p < 0.001). This indicates a negative impact of diabetes on quality of life in both groups, with a greater negative impact in the group with DR. The first two items that assess the current quality of life and overall impact of diabetes on quality of life also had significantly lower outcomes in patients with DR (p < 0.001; Table 2).
In patients with DR, the observed median quality of life scores were −0.65, −0.94, and −1.03 for mild, moderate, and severe DR grades, respectively, and quality of life decreased significantly in relation to the degree of DR (the estimated trend for the median was −0.22 [−0.36, −0.03]), but not in relation to the severity of macular edema (estimated trend for the median of −0.09 [−0.23, 0.02]).
Multivariate linear regression for the audit of diabetes dependent quality of life
Diabetes duration (years)
Diabetes duration-squared (years2)
Diabetes duration* DR
Diabetes duration-squared * DR
Diabetes duration * insulin
Diabetes duration-squared* insulin
DR * insulin
Diabetes duration * DR * insulin
Diabetes duration-squared* DR * Insulin
Treatment satisfaction using DTSQ
Summary of the Diabetes Treatment Satisfaction Questionaries (DTSQ) measures
Hyperglycemias frequency perception
Hypoglycemias frequency perception
Recommend to others
Multivariate linear regression for the diabetes treatment satisfaction questionaries
< 2e −16
Diabetes duration (years)
Physical activity > 20 minutes
Diabetes duration * DR
Relationship between quality of life and treatment satisfaction
Relationship between treatment satisfaction and quality of life
Treatment satisfaction (DTSQ) total score
Diabetes duration (years)
Diabetes duration-squared (years2)
Insulin * DR
DR * Diabetes duration
DR * Diabetes duration-squared
Insulin * Diabetes duration
Insulin * Diabetes duration-squared
DR * Insulin * Diabetes duration
DR * Insulin * Diabetes duration-squared
DTSQ total score * insulin
We have shown that patients with type 2 diabetes with DR and no other advanced late complications report a lower quality of life. The inclusion of only patients without other complications that may have a significant clinical impact on quality of life is a particularly noteworthy element of this study. To our knowledge, this is the first study designed with this specific objective. The results revealed lower ADDQoL scores in the group of patients with DR. Quality of life was affected by the presence and degree of DR, insulin therapy and the duration of the disease. Although the DTSQ showed no statistically significant difference in the final score between study groups, the two specific items that assess perceived glycemic control showed significantly worse scores in patients with DR. Treatment satisfaction was affected over time by the presence of DR, insulin therapy and the severity of macular edema.
The results show the clearly negative impact of DR on quality of life in a large sample with enough statistical power that comprised only subjects with type 2 diabetes mellitus who did not have any other advanced diabetic complications that could exert important confounding or modifying effects on the main study outcome variables. Additionally, the assessment of quality of life and treatment satisfaction using instruments specifically designed and validated for this purpose strengthens these results ,,.
The first approaches to health-related quality of life in the field of diabetes were made through the assessment of health status. However, it is important to note that even if health status is an area of health-related quality of life, there are other domains to consider (e.g., emotional well-being, personal care, physical, social, and cognitive functioning). Quality of life is a recent construct that is conceptually complex and composed of objective and subjective domains. Assessing only health status is unlikely to convey a precise picture of health-related quality of life . With this approach, an optimal health outcome may not be considered an excellent result in terms of quality of life or perceived health status of the patient.
Tung et al. analyzed the impact of the different stages of DR in type 2 diabetic patients with associated nephropathy in Taiwan using utility values . This approach allows the quantification of the level of impairment of the person and the level of functioning in everyday life that is affected by the disease. It allows for an assessment of quality of life by determining health status and is useful for obtaining quality-adjusted life years (QALYs). The results illustrated the influence of the severity of DR and age on utility values. Older age and different degrees of DR had a strong impact on the QALYs after adjusting for other possible non-ophthalmologic health-related factors. Such instruments have demonstrated their validity in cost-utility or economic evaluation studies; however, we do not consider an index that was developed to measure health status suitable for the assessment of quality of life. Assessing DR using a patient’s health status would explain the differences between this and our study regarding age. Furthermore, the presence of diabetic nephropathy in a significant proportion of patients, as in the study by Tung et al. , can exert a confounding effect on the results. In another study, the Los Angeles Latino Eye Study , a large sample of Hispanic patients with type 2 diabetes mellitus and a high burden of comorbidities was studied. The impact of DR and its severity on quality of life was studied using a generic health questionnaire and a vision-specific functioning and quality of life questionnaire designed for people with visual disabilities. The results of the study showed that patients with DR had lower scores on both the Medical Outcomes study 12-Item Short Form Health Survey and the National Eye Institute Visual Function Questionnaire . This association was influenced by both the severity and the laterality of DR. However, the presence of other comorbidities may have had an additive effect on the outcome variables. Chung et al. explored the factors associated with quality of life in a large cohort of Korean patients with type 2 diabetes using the ADDQoL without cardiovascular disease or end-stage renal disease, although patients may have had peripheral neuropathy, retinopathy, and/or diabetic nephropathy . They found that insulin therapy, depressive symptoms, and family history of diabetes were associated with lower quality of life, especially in younger patients. We also found lower ADDQoL scores in younger patients receiving insulin therapy. However, in contrast to our results, the Korean study did not show a significant impact of microvascular complications on quality of life.
Fenwick et al. investigated the impact of DR and macular edema on quality of life in type 1 and 2 diabetic patients using the EuroQoL-5D as a generic utility measure and demonstrated the inadequacy of the instrument and its low sensitivity for the assessment of vision-related quality of life . Moreover, the same authors also assessed the impact of DR with the Vision and Quality of Life Index as a specific instrument for vision and established its validity for measuring the impact that this complication can have on the quality of life of type 1 and 2 diabetic patients. This index, however, did not appear sufficiently sensitive for assessing the impact of the severity of diabetic macular edema, the severity of DR, or the level of visual acuity . However, the coexistence of other diabetic complications and the use of data from patients with either type 1 or type 2 diabetes does not allow for the comparison of these results with our results.
Our results also illustrate the impact of insulin therapy on quality of life and treatment satisfaction. We could not identify any studies specifically designed to assess the issue of treatment satisfaction in patients with type 2 diabetes and retinopathy. Mozaffarieh et al. observed an influence of age on treatment satisfaction in a mixed sample of type 1 and 2 diabetic patients with retinopathy who were treated with photocoagulation . Younger patients had lower DTSQ scores. Using the same instrument, Redekop et al. investigated the clinical and sociodemographic characteristics associated with treatment satisfaction in a sample of Dutch patients with type 2 diabetes mellitus . Lower levels of satisfaction were observed in univariate analyses of patients with diabetic complications, but this association was not maintained after adjustment for age, insulin, and glycated haemoglobin levels. In our study, treatment satisfaction was significantly affected by the patient’s perceived glycemic control, the duration of the disease, the degree of physical activity and smoking.
Regarding the limitations of this study, the study design inherently allows us to study only associations and not causality. Additionally, the fact that diabetes duration is a major factor in the development of DR caused a discrete bias in age distribution, with a lower proportion of younger patients in the retinopathy group. While other major complications that could affect quality of life and treatment satisfaction have been ruled out, potential symptoms of peripheral neuropathy that might influence these aspects were not assessed. However, none of the patients had advanced neuropathy leading to serious complications such as diabetic foot disease. The representativeness of the study groups is partially limited and the conclusions may not be generalized to all the population of patients with type 2 diabetes. The results may be applicable to patients with or without retinopathy in the absence of other advanced late diabetic complications that is an important proportion of patients in the Spanish population according to recent reports .
In conclusion, in type 2 diabetic patients, the presence of DR is associated with poorer quality of life. Although satisfaction with the overall treatment is not different between the two groups of patients, it is influenced by other clinical variables. The results of this study are relevant because they demonstrate for the first time the negative influence of DR, regardless of the presence of other complications, on the quality of life of type 2 diabetic patients in a study specifically designed for that purpose. Clinicians should be aware that quality of life is one of the primary objectives of diabetes treatment. In addition, these findings should be taken into account in clinical practice when treating patients with DR and type 2 diabetes mellitus. Apart from the benefits in terms of visual outcomes, early identification and treatment of patients with DR would have a positive impact on the different dimensions of the patient’s quality of life. However, the potential impact of the early diagnosis and treatment of DR on quality of life deserves the performance of specific intervention studies to address this issue. We also believe that there is a need for additional studies to conduct a linguistic and psychometric validation of new measures of quality of life and treatment satisfaction and to develop measurement tools that would allow the assessment of the impact of DR treatments on the patient.
This study was supported by grant PS09/01035 from Instituto de Salud Carlos III. N.A holds a predoctoral fellowship (FI11/0008) from Instituto de Salud Carlos III, Spain.
- Lecaire TJ, Palma M, Klein R, Klein BE, Cruikshanks KJ: Assessing progress in retinopathy outcomes in type 1 Diabetes: comparing findings from the Wisconsin Diabetes Registry Study and the Wisconsin Epidemiologic Study of Diabetic Retinopathy. Diabetes Care 2013, 36(3):631–637. 10.2337/dc12-0863PubMed CentralView ArticlePubMedGoogle Scholar
- Cheung N, Mitchell P, Wong TY: Diabetic retinopathy. Lancet 2010, 376(9735):124–136. 10.1016/S0140-6736(09)62124-3View ArticlePubMedGoogle Scholar
- Franch J, Artola S, Diez J, Mata M: The evolution of quality care indicators of patients with type 2 diabetes in the Spanish primary care (1996–2007). The RedGEDAPS quality of care program. Med Clin 2010, 135(13):600–607. 10.1016/j.medcli.2009.06.033View ArticleGoogle Scholar
- Romero-Aroca P, Fernández-Alart J, Baget-Bernaldiz M, Méndez-Marín I, Salvat-Serra M: Diabetic retinopathy epidemiology in type II diabetic patients. Effect of the changes in the diagnostic criteria and stricter control of the diabetes between 1993 and 2005 on the incidence of diabetic retinopathy. Arch Soc Esp Oftalmol 2007, 82(4):209–218. 10.4321/S0365-66912007000400005View ArticlePubMedGoogle Scholar
- Coyne KS, Margolis MK, Kennedy-Martin T, Barker TM, Klein R, Paul MD, Revicki DA: The impact of diabetic retinopathy: perspective from patient-focus groups. Fam Pract 2004, 21(4):447–453. 10.1093/fampra/cmh417View ArticlePubMedGoogle Scholar
- Fenwick EK, Pesudovs K, Khadka J, Dirani M, Rees G, Wong TY, Lamoureux EL: The impact of diabetic retinopathy on quality of life: qualitative findings from an item bank development project. Qual Life Res 2012, 21(10):1771–1782. 10.1007/s11136-012-0110-1View ArticlePubMedGoogle Scholar
- Rubin RR, Peyrot M: Quality of life and diabetes. Diabetes Metab Res Rev 1999, 15(3):205–218. 10.1002/(SICI)1520-7560(199905/06)15:3<205::AID-DMRR29>3.0.CO;2-OView ArticlePubMedGoogle Scholar
- Fong DS, Girach A, Boney A: Visual side effects of successful scatter laser photocoagulation surgery for proliferative diabetic retinopathy: a literature review. Retina 2007, 27(7):816–824. 10.1097/IAE.0b013e318042d32cView ArticlePubMedGoogle Scholar
- Mira JJ, Aranaz J: Patient satisfaction as an outcome measure in healthcare. Med Clin (Barc) 2010, 114(3):26–33.Google Scholar
- Hariprasad SM, Mieler WF, Grassi M, Green JL, Jager RD: Vision-related quality of life in patients with diabetic macular oedema. Br J Ophthalmol 2008, 92(1):89–92. 10.1136/bjo.2007.122416View ArticlePubMedGoogle Scholar
- Valderas JM, Alonso J: Patient reported outcome measures: a model-based classification system for research and clinical practice. Qual Life Res 2008, 17(9):1125–1135. 10.1007/s11136-008-9396-4View ArticlePubMedGoogle Scholar
- Fenwick EK, Pesudovs K, Rees G, Dirani M, Kawasaki R, Wong TY, Lamoureux EL: The impact of diabetic retinopathy: understanding the patient’s perspective. Br J Ophthalmol 2011, 95(6):774–782. 10.1136/bjo.2010.191312View ArticlePubMedGoogle Scholar
- Davidov E, Breitscheidel L, Clouth J, Reips M, Happich M: Diabetic retinopathy and health-related quality of life. Graefes Arch Clin Exp Ophthalmol 2009, 247(2):267–272. 10.1007/s00417-008-0960-yView ArticlePubMedGoogle Scholar
- Chung JO, Cho DH, Chung DJ, Chung MY: Assessment of factors associated with the quality of life in Korean type 2 diabetic patients. Intern Med 2013, 52(2):179–185. 10.2169/internalmedicine.52.7513View ArticlePubMedGoogle Scholar
- Nutheti R, Keeffe JE, Shamanna BR, Nirmalan PK, Krishnaiah S, Thomas R: Impact of impaired vision and eye disease on quality of life in Andhra Pradesh. Invest Ophthalmol Vis Sci 2006, 47(11):4742–4748. 10.1167/iovs.06-0020View ArticlePubMedGoogle Scholar
- Mazhar K, Varma R, Choudhury F, Mckean-Cowdin R, Shtir CJ, Azen SP: Severity of diabetic retinopathy and health-related quality of life: the Los Angels Latino Eye Study. Ophthalmology 2011, 118(4):649–655. 10.1016/j.ophtha.2010.08.003PubMed CentralView ArticlePubMedGoogle Scholar
- Mozaffarieh M, Benesch T, Sacu S, Krepler K, Biowski R, Wedrich A: Photocoagulation for diabetic retinopathy: determinants of patient satisfaction and patient-provider relationship. Acta Opthalmol Scand 2005, 83(3):316–321. 10.1111/j.1600-0420.2005.00455.xView ArticleGoogle Scholar
- Tung TH, Chen SJ, Lee FL, Liu JH, Lin CH, Chou P: A community-based study for the utility values associated with diabetic retinopathy among type 2 diabetics in Kinmen, Taiwan. Diabetes Res Clin Pract 2005, 68(3):265–273. 10.1016/j.diabres.2004.10.003View ArticlePubMedGoogle Scholar
- Fenwick EK, Xie J, Ratcliffe J, Pesudovs K, Finger RP, Wong TY, Lamoureux EL: The impact of diabetic retinopathy and diabetic macular edema on health-related quality of life in type 1 and type 2 diabetes. Invest Opthalmol Vis Sci 2012, 53(2):677–684. 10.1167/iovs.11-8992View ArticleGoogle Scholar
- Bernstein S, Moravia A, Sloutskis D: Definition and prevalence of sedentarism in an urban population. Am J Public Health 1999, 89(6):862–867. 10.2105/AJPH.89.6.862PubMed CentralView ArticlePubMedGoogle Scholar
- World Health Organization: , [http://www.who.int/dietphysicalactivity/physical_activity_intensity/en]
- Kaiser PK: Prospective evaluation of visual acuity assessment: a comparison of Snellen versus ETDRS charts in clinical practice [An AOS Thesis]. Trans Am Ophthalmol Soc 2009, 107: 311–324.PubMed CentralPubMedGoogle Scholar
- Bradley C, Todd C, Gorton T, Symonds E, Martin A, Plowright R: The development of an individualised questionnaire measure of perceived impact of diabetes on quality of life: the ADDQoL. Qual Life Res 1999, 8(1–2):79–91. 10.1023/A:1026485130100View ArticlePubMedGoogle Scholar
- Bradley C, de Pablos-Velasco P, Parhofer KG, Eschwège E, Gönder-Frederick L, Simon D: PANORAMA: A European study to evaluate quality of life and treatment satisfaction in patients with type 2 diabetes mellitus-study design. Prim Care Diabetes 2011, 5(4):231–239. 10.1016/j.pcd.2011.04.004View ArticlePubMedGoogle Scholar
- De Pablos-Velasco P, Salguero-Chaves E, Maya-Poyo J, Derivas-Otero B, García-Sánchez R, Viguera-Esther P: Quality of life and satisfaction with treatment in subjects with type 2 diabetes: Results in Spain of the PANORAMA study. Endocrinol Nutr 2014, 61(1):18–26. 10.1016/j.endonu.2013.05.005View ArticleGoogle Scholar
- Botija MP, Lizán L, Gosalbes V, Bonet A, Fornos A: How does intensive therapy to control cardiovascular risk factors affect health-related quality of life in diabetic patients? Aten Primaria 2007, 39(5):227–233. 10.1157/13101795View ArticleGoogle Scholar
- Bradley C: Diabetes Treatment Satisfaction Questionnaire (DTSQ). In Handbook of Psychology and Diabetes: A Guide to Psychological Measurement in Diabetes Research and Practice. Edited by: Bradley C. Harwood Academic Publishers, New York; 1994:111–112.Google Scholar
- Gomis R, Herrera-Pombo J, Calderón A, Rubio-Terrés C, Sarasa P: Validación del cuestionario “Diabetes treatment satisfaction questionnaire” (DTSQ) en la población española. Pharmacoeconomics Spanish Res Articles 2006, 3(1):7–18. 10.1007/BF03320906View ArticleGoogle Scholar
- Bradley C, Gamsu DS: Guidelines for encouraging psychological well-being: Report of a working group of the World Health Organization Regional Office for Europe and International Diabetes Federation European Region St. Vincent Declaration Action Programme for Diabetes. Diabet Med 1994, 11(5):510–516. 10.1111/j.1464-5491.1994.tb00316.xView ArticlePubMedGoogle Scholar
- Wilkinson CP, Ferris FL 3rd, Klein RE, Lee PP, Agarch CD, Davis M, Dills K, Kampik A, Pararajasegaram R, Verdaguer JT: Proposed internacional clinical diabetic retinopathy and diabetic macular edema disease severety scales. Ophthalmology 2003, 110(9):1677–1682. 10.1016/S0161-6420(03)00475-5View ArticlePubMedGoogle Scholar
- Early photocoagulation for diabetic macular retinopathy. ETDRS report number 9 Ophthalmology 1991, 98: 766–785. 10.1016/S0161-6420(13)38011-7Google Scholar
- Hwee W: Health-related Quality of Life in People with Diabetes Mellitus: Perspective from a Multi-ethnic Asian Population. In PhD Thesis. National University of Singapore, Singapore; 2005.Google Scholar
- Speight J, Reaney MD, Barnard KD: Not all roads lead to Rome-a review of quality of life measurement in adults with diabetes. Diabet Med 2009, 26(4):315–327. 10.1111/j.1464-5491.2009.02682.xView ArticlePubMedGoogle Scholar
- Fenwick EK, Xie J, Pesudovs K, Chiang PP, Finger RP, Lamoureux EL: Assessing disutility associated with diabetic retinopathy, diabetic macular aedema and associated visual impairment using the Vision and Quality of Life Index. Clin Exp Optom 2012, 95(3):362–370. 10.1111/j.1444-0938.2012.00742.xView ArticlePubMedGoogle Scholar
- Redekop WK, Koopmanschap MA, Stolk RP: Health-related quality of life and treatment satisfaction in Dutch patients with type 2 diabetes. Diabetes Care 2002, 25(3):458–463. 10.2337/diacare.25.3.458View ArticlePubMedGoogle Scholar
- Vinagre J, Mata-Cases M, Hermosilla E, Morros R, Fina F, Rosell M, Castell C, Franch J, Bolíbar B, Mauricio D: Control of glycemia and cardiovascular risk factors in patients with type 2 diabetes primary care in Catalonia (Spain). Diabetes Care 2012, 35(4):774–779. 10.2337/dc11-1679PubMed CentralView ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.