Incidence and Progression of Diabetic Retinopathy in American Indian and Alaska Native Individuals Served by the Indian Health Service, 2015-2019

Importance

Estimates of diabetic retinopathy (DR) incidence and progression in American Indian and Alaska Native individuals are based on data from before 1992 and may not be informative for strategizing resources and practice patterns.

Objective

To examine incidence and progression of DR in American Indian and Alaska Native individuals.

Design, Setting, and Participants

This was a retrospective cohort study conducted from January 1, 2015, to December 31, 2019, and included adults with diabetes and no evidence of DR or mild nonproliferative DR (NPDR) in 2015 who were reexamined at least 1 time during the 2016 to 2019 period. The study setting was the Indian Health Service (IHS) teleophthalmology program for diabetic eye disease.

Exposure

Development of new DR or worsening of mild NPDR in American Indian and Alaska Native individuals with diabetes.

Main Outcomes and Measures

Outcomes were any increase in DR, 2 or more (2+) step increases, and overall change in DR severity. Patients were evaluated with nonmydriatic ultra-widefield imaging (UWFI) or nonmydriatic fundus photography (NMFP). Standard risk factors were included.

Results

The total cohort of 8374 individuals had a mean (SD) age of 53.2 (12.2) years and a mean (SD) hemoglobin A1c level of 8.3% (2.2%) in 2015, and 4775 were female (57.0%). Of patients with no DR in 2015, 18.0% (1280 of 7097) had mild NPDR or worse in 2016 to 2019, and 0.1% (10 of 7097) had PDR. The incidence rate from no DR to any DR was 69.6 cases per 1000 person-years at risk. A total of 6.2% of participants (441 of 7097) progressed from no DR to moderate NPDR or worse (ie, 2+ step increase; 24.0 cases per 1000 person-years at risk). Of patients with mild NPDR in 2015, 27.2% (347 of 1277) progressed to moderate NPDR or worse in 2016 to 2019, and 2.3% (30 of 1277) progressed to severe NPDR or worse (ie, 2+ step progression). Incidence and progression were associated with expected risk factors and evaluation with UWFI.

Conclusions and Relevance

In this cohort study, the estimates of DR incidence and progression were lower than those previously reported for American Indian and Alaska Native individuals. The results suggest extending the time between DR re-evaluations for certain patients in this population, if follow-up compliance and visual acuity outcomes are not jeopardized.

Prevalence of Diabetic Eye Diseases in American Indians and Alaska Natives (AI/AN) as Identified by the Indian Health Service's National Teleophthalmology Program Using Ultrawide Field Imaging (UWFI)

PURPOSE

Estimates of diabetic eye disease in American Indian and Alaska Natives (AI/AN) vary over time, region, and methods. This article reports recent prevalence of diabetic retinopathy (DR) and diabetic macular edema (DME) in AI/AN served by the Indian Health Services' (IHS) teleophthalmology program, as identified using ultrawide field imaging (UWFI).

METHODS

This was a retrospective analysis of 2016-2019 clinical data (n = 53,900). UWF images were acquired by certified imagers using a validated protocol, and graded by licensed, certified optometrists supervised by an ophthalmologist. Graders evaluated the extent/severity of retinal lesions in comparison to standard photographs. DR lesions predominantly in any peripheral field were considered "predominantly peripheral lesions" (PPL). The analyses calculated prevalence of any DR, any DME, DR and DME severity, sight-threatening disease, and PPL.

RESULTS

Patients averaged 56 years of age with a 68 mmol/mol A1c and 55% had had diabetes for 5+ years. Prevalence of any DR, any DME, and sight-threatening disease was 28.6%, 3.0%, and 3.0%. In patients with mild nonproliferative DR, PPL was seen in 25.3%. PPL suggested a more severe level of DR in 8.7% of patients. DR increased with age. DME decreased with age. Males and patients in the Nashville IHS area had more diabetic eye disease.

CONCLUSION

AI/AN have a high burden of diabetes and its complications. The IHS is resource-constrained, making accurate disease estimates necessary for resource allocation and budget justifications to Congress. These data update the estimates of diabetic eye disease in Indian Country and suggest that UWFI identifies early DR.

Associations with sight-threatening diabetic macular oedema among Indigenous adults with type 2 diabetes attending an Indigenous primary care clinic in remote Australia: a Centre of Research Excellence in Diabetic Retinopathy and Telehealth Eye and Associated Medical Services Network study

Objective

To identify factors associated with sight-threatening diabetic macular oedema (STDM) in Indigenous Australians attending an Indigenous primary care clinic in remote Australia.

Methods and analysis

A cross-sectional study design of retinopathy screening data and routinely-collected clinical data among 236 adult Indigenous participants with type 2 diabetes (35.6% men) set in one Indigenous primary care clinic in remote Australia. The primary outcome variable was STDM assessed from retinal images.

Results

Age (median (range)) was 48 (21–86) years, and known diabetes duration (median (range)) was 8.0 (0–24) years. Prevalence of STDM was high (14.8%) and similar in men and women. STDM was associated with longer diabetes duration (11.7 vs 7.9 years, respectively; p<0.001) and markers of renal impairment: abnormal estimated Glomerular Filtration Rate (eGFR) (62.9 vs 38.3%, respectively; p=0.007), severe macroalbuminuria (>300 mg/mmol) (20.6 vs 5.7%, respectively; p=0.014) and chronic kidney disease (25.7 vs 12.2%, respectively; p=0.035). Some clinical factors differed by sex: anaemia was more prevalent in women. A higher proportion of men were smokers, prescribed statins and had increased albuminuria. Men had higher blood pressure, but lower glycated Haemoglobin A1c (HbA1c) levels and body mass index, than women.

Conclusion

STDM prevalence was high and similar in men and women. Markers of renal impairment and longer diabetes duration were associated with STDM in this Indigenous primary care population. Embedded teleretinal screening, known diabetes duration-based risk stratification and targeted interventions may lower the prevalence of STDM in remote Indigenous primary care services.

Trial registration number

Australia and New Zealand Clinical Trials Register: ACTRN 12616000370404.

The Indian Health Service Primary Care-Based Teleophthalmology Program for Diabetic Eye Disease Surveillance and Management

Background: Historically, fewer than half of American Indians and Alaska Natives (AI/AN) with diabetes received the annual diabetic retinopathy (DR) examination that is considered the minimum standard of care; this rate is similar to that of the general United States (U.S.) population with diabetes. Solution: The Indian Health Service-Joslin Vision Network (IHS-JVN) Teleophthalmology Program in 2000 to increase compliance with DR standards of care among AI/AN through validated, primary care-based telemedicine. The IHS-JVN provides remote diagnosis of DR severity, with a report including management recommendations that is returned to the patient's primary care provider. The program conforms with the American Telemedicine Association (ATA) Practice Guidelines for Ocular Telehealth-Diabetic Retinopathy. Outcomes: The IHS-JVN has been expanding incrementally since the first patients were recruited in 2000; this expansion coincides with large improvements in the annual DR examination rates reported as part of local, regional, and national regulatory compliance under the Government Performance and Results Act (GPRA). Currently, with 99 clinical implementations in 23 states, IHS-JVN is the largest primary care-based ATA validation category three telemedicine program in the U.S. Summary: This article describes the program's workflow, imaging and reading technologies, diagnostic protocols, reports to providers, training, quality assurance processes, and geographical distribution. In addition to its clinical use, the program has been utilized in research on utilization of diabetic eye care, cost-effectiveness, technology development, and DR epidemiology of the AI/AN population. Potential next steps for this program are discussed.

Screening for diabetic retinopathy and reduced vision among Indigenous Australians in Top End primary care health services: a TEAMSnet sub-study

BACKGROUND

Diabetic retinopathy (DR) prevalence is higher in Indigenous Australians than in other Australians and is a major cause of vision loss. Consequently, timely screening and treatment is paramount, and annual eye screening is recommended for Indigenous Australians.

AIMS

To assess the prevalence of DR, reduced vision and DR treatment coverage among Indigenous Australian adults with diabetes attending Top End indigenous primary care health services.

METHODS

A cross-sectional DR screening study conducted from November 2013 to December 2015 in two very remote Northern Territory Aboriginal primary healthcare services.

RESULTS

In 287 subjects, the prevalence of non-proliferative DR, proliferative DR and clinically significant diabetic macular oedema was 37.3%, 5.4% and 9.0% respectively. Treatment coverage for PDR was 60% (of 10 patients) and for CSMO was 17% (of 23 patients). Vision data were available from 122 participants at one site. The proportion with normal vision, reduced vision, impaired vision and blindness was 31.1%, 52.5%, 15.6% and 0.8% respectively. Overall, ungradable monocular image sets (46%) were associated with poorer quality images and missing protocol images (both P < 0.001). Ungradable images for DR were associated with presence of small pupils/media opacities (P < 0.001). Ungradable images for diabetic macular oedema were associated with poorer image quality (P < 0.001), cataracts (P < 0.001) and small pupils (P = 0.04).

CONCLUSIONS

A high prevalence of DR, CSMO and impaired vision was noted in Indigenous Australians with diabetes. Screening in primary care is feasible, but more effective screening methods are needed.

Health-related behaviours in a remote Indigenous population with Type 2 diabetes: a Central Australian primary care survey in the Telehealth Eye and Associated Medical Services Network [TEAMSnet] project

AIM

There is a wealth of data concerning the health behaviours of Indigenous Australians, but the health behaviours of Indigenous Australians with diabetes are not systematically documented. At the clinical level, understanding a person's health behaviours can help identify and address barriers to diabetes care and promote good clinical outcomes.

METHODS

We used a novel survey tool to systematically collect health behaviour data on Smoking, Nutrition, Alcohol consumption, Physical activity and Emotional well-being (SNAPE) from Indigenous Australians with Type 2 diabetes in a remote primary care setting in Alice Springs.

RESULTS

At least one of the five surveys in the SNAPE tool was completed by 210 participants: 30% male, mean age 52.6 years (range 22.9 - 87.4). Fifty per cent of men and 23% of women were current smokers (P < 0.001). None of the participants reported an adequate intake of vegetables. Only 9.6% reported an adequate fruit intake. Some 49% of men and 32% of women consumed alcohol in the past year (P = 0.022), and 46% of drinkers were considered high-risk or likely-dependent drinkers. On average, participants walked 10 min or more at a time 6.0 days a week and spent 4.8 h sitting on a weekday. Mean adapted Patient Health Questionnaire 9 score was 4.61, with 34% of participants having mild depressive symptoms and 11% having moderate-severe depressive symptoms.

CONCLUSIONS

Our SNAPE survey tool results present a high-risk, disadvantaged Indigenous population with Type 2 diabetes. More resources will be needed to sustainably implement interventions with the goal of improving health behaviours and subsequent long-term health.

Prevalence of diabetic retinopathy and diabetic macular edema in a primary care-based teleophthalmology program for American Indians and Alaskan Natives

BACKGROUND

Diabetes and its complications are more common in American Indians and Alaska Natives (AI/AN) than other US racial/ethnic populations. Prior reports of diabetic retinopathy (DR) prevalence in AI/AN are dated, and research on diabetic macular edema (DME) is limited. This study characterizes the recent prevalence of DR and DME in AI/AN using primary care-based teleophthalmology surveillance.

METHODS

This is a multi-site, clinic-based, cross-sectional study of DR and DME. The sample is composed of AI /AN patients with diabetes (n = 53,998), served by the nationally distributed Indian Health Service-Joslin Vision Network Teleophthalmology Program (IHS-JVN) in primary care clinics of US Indian Health Service (IHS), Tribal, and Urban Indian health care facilities (I/T/U) from 1 November 2011 to 31 October 2016. Patients were recruited opportunistically for a retinal examination using the IHS-JVN during their regular diabetes care. The IHS-JVN used clinically validated, non-mydriatic, retinal imaging and retinopathy assessment protocols to identify the severity levels of non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), DME, and sight threatening retinopathy (STR; a composite measure). Key social-demographic (age, gender, IHS area), diabetes-related health (diabetes therapy, duration of diabetes, A1c), and imaging technology variables were examined. The analysis calculated frequencies and percentages of severity levels of disease.

RESULTS

Prevalence of any NPDR, PDR, DME, and STR among AI/AN patients undergoing DR teleophthalmology surveillance by IHS-JVN was 17.7%, 2.3%, 2.3%, and 4.2%, respectively. Prevalence was lowest in Alaska and highest among patients with A1c >/ = 8%, duration of diabetes > 10 years, or using insulin.

CONCLUSIONS

Prevalence of DR in this cohort was approximately half that in previous reports for AI/AN, and prevalence of DME was less than that reported in non-AI/AN populations. A similar reduction in diabetes related end-stage renal disease in the same population and time period has been reported by other researchers. Since these two diabetic complications share a common microvasculopathic mechanism, this coincident change in prevalence may also share a common basis, possibly related to improved diabetes management.

An evaluation of the telehealth facilitation of diabetes and cardiovascular care in remote Australian Indigenous communities: - protocol for the telehealth eye and associated medical services network [TEAMSnet] project, a pre-post study design

Background

Despite substantial investment in detection, early intervention and evidence-based treatments, current management strategies for diabetes-associated retinopathy and cardiovascular disease are largely based on real-time and face-to-face approaches. There are limited data re telehealth facilitation in type 2 diabetes management. Therefore, we aim to investigate efficacy of telehealth facilitation of diabetes and cardiovascular disease care in high-risk vulnerable Aboriginal and Torres Strait Islanders in remote/very remote Australia.

Methods

Using a pre-post intervention design, 600 Indigenous Australians with type 2 diabetes will be recruited from three primary-care health-services in the Northern Territory. Diabetes status will be based on clinical records. There will be four technological interventions: 1. Baseline retinal imaging [as a real-time patient education/engagement tool and telehealth screening strategy]. 2. A lifestyle survey tool administered at ≈ 6-months. 3. At ≈ 6— and 18-months, an electronic cardiovascular disease and diabetes decision-support tool based on current guidelines in the Standard Treatment Manual of the Central Australian Rural Practitioner’s Association to generate clinical recommendations. 4. Mobile tablet technology developed to enhance participant engagement in self-management. Data will include: Pre-intervention clinical and encounter-history data, baseline retinopathy status, decision-support and survey data/opportunistic mobile tablet encounter data. The primary outcome is increased participant adherence to clinical appointments, a marker of engagement and self-management. A cost-benefit analysis will be performed.

Discussion

Remoteness is a major barrier to provision and uptake of best-practice chronic disease management. Telehealth, beyond videoconferencing of consultations, could facilitate evidence-based management of diabetes and cardiovascular disease in Indigenous Australians and serve as a model for other conditions.

Trial registration

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN 12616000370404 was retrospectively registered on 22/03/2016

An internet-based diabetes management platform improves team care and outcomes in an urban Latino population

OBJECTIVE

To compare usual diabetes care (UDC) to a comprehensive diabetes care intervention condition (IC) involving an Internet-based "diabetes dashboard" management tool used by clinicians.

RESEARCH DESIGN AND METHODS

We used a parallel-group randomized design. Diabetes nurses, diabetes dietitians, and providers used the diabetes dashboard as a clinical decision support system to deliver a five-visit, 6-month intervention to 199 poorly controlled (HbA1c >7.5% [58 mmol/mol]) Latino type 2 diabetic (T2D) patients (mean age 55 years, 60% female) at urban community health centers. We compared this intervention to an established, in-house UDC program (n = 200) for its impact on blood glucose control and psychosocial outcomes.

RESULTS

Recruitment and retention rates were 79.0 and 88.5%, respectively. Compared with UDC, more IC patients reached HbA1c targets of <7% (53 mmol/mol; 15.8 vs. 7.0%, respectively, P < 0.01) and <8% (64 mmol/mol; 45.2 vs. 25.3%, respectively, P < 0.001). In multiple linear regression adjusting for baseline HbA1c, adjusted mean ± SE HbA1c at follow-up was significantly lower in the IC compared with the UDC group (P < 0.001; IC 8.4 ± 0.10%; UDC 9.2 ± 0.10%). The results showed lower diabetes distress at follow-up for IC patients (40.4 ± 2.1) as compared with UDC patients (48.3 ± 2.0) (P < 0.01), and also lower social distress (32.2 ± 1.3 vs. 27.2 ± 1.4, P < 0.01). There was a similar, statistically significant (P < 0.01) improvement for both groups in the proportion of patients moving from depressed status at baseline to nondepressed at follow-up (41.8 vs. 40%; no significance between groups).

CONCLUSIONS

The diabetes dashboard intervention significantly improved diabetes-related outcomes among Latinos with poorly controlled T2D compared with a similar diabetes team condition without access to the diabetes dashboard.

Telemedicine and ocular health in diabetes mellitus

Teleretinal/teleophthalmological programs that use existing health information technology infrastructure solutions for people with diabetes increase access to and adherence to appropriate eye care. Teleophthalmological studies indicate that the single act of patients viewing their own retinal images improves self-management behaviour and clinical outcomes. In some settings this can be done at lower cost and with improved visual outcomes compared with standard eye care. Cost-effective and sustainable teleretinal surveillance for detection of diabetic retinopathy requires a combination of an inexpensive portable device for taking low light-level retinal images without the use of pharmacological dilation of the pupil and a computer-assisted methodology for rapidly detecting and diagnosing diabetic retinopathy. A more holistic telehealth-care paradigm augmented with the use of health information technology, medical devices, mobile phone and mobile health applications and software applications to improve health-care co-ordination, self-care management and education can significantly impact a broad range of health outcomes, including prevention of diabetes-associated visual loss. This approach will require a collaborative, transformational, patient-centred health-care program that integrates data from medical record systems with remote monitoring of data and a longitudinal health record. This includes data associated with social media applications and personal mobile health technology and should support continuous interactions between the patient, health-care team and the patient's social environment. Taken together, this system will deliver contextually and temporally relevant decision support to patients to facilitate their well-being and to reduce the risk of diabetic complications.

Comparison of low-light nonmydriatic digital imaging with 35-mm ETDRS seven-standard field stereo color fundus photographs and clinical examination

PURPOSE

To compare agreement between diagnosis of clinical level of diabetic retinopathy (DR) and diabetic macular edema (DME) derived from nonmydriatic fundus images using a digital camera back optimized for low-flash image capture (MegaVision) compared with standard seven-field Early Treatment Diabetic Retinopathy Study (ETDRS) photographs and dilated clinical examination. Subject comfort and image acquisition time were also evaluated.

SUBJECTS AND METHODS

In total, 126 eyes from 67 subjects with diabetes underwent Joslin Vision Network nonmydriatic retinal imaging. ETDRS photographs were obtained after pupillary dilation, and fundus examination was performed by a retina specialist.

RESULTS

There was near-perfect agreement between MegaVision and ETDRS photographs (κ=0.81, 95% confidence interval [CI] 0.73-0.89) for clinical DR severity levels. Substantial agreement was observed with clinical examination (κ=0.71, 95% CI 0.62-0.80). For DME severity level there was near-perfect agreement with ETDRS photographs (κ=0.92, 95% CI 0.87-0.98) and moderate agreement with clinical examination (κ=0.58, 95% CI 0.46-0.71). The wider MegaVision 45° field led to identification of nonproliferative changes in areas not imaged by the 30° field of ETDRS photos. Field area unique to ETDRS photographs identified proliferative changes not visualized with MegaVision. Mean MegaVision acquisition time was 9:52 min. After imaging, 60% of subjects preferred the MegaVision lower flash settings.

CONCLUSIONS

When evaluated using a rigorous protocol, images captured using a low-light digital camera compared favorably with ETDRS photography and clinical examination for grading level of DR and DME. Furthermore, these data suggest the importance of more extensive peripheral images and suggest that utilization of wide-field retinal imaging may further improve accuracy of DR assessment.

Automated Retinal Imaging System (ARIS) compared with ETDRS protocol color stereoscopic retinal photography to assess level of diabetic retinopathy

BACKGROUND

Early Treatment Diabetic Retinopathy Study (ETDRS) seven-standard-field color stereoscopic retinal photography (ETDRS photos) has been a gold standard for determining diabetic retinopathy (DR) severity. The Automated Retinal Imaging System (ARIS™, model 110, Visual Pathways, Inc., Prescott, AZ) acquires seven-sequential color stereoscopic digital images (ARIS images) by a semiautomated technician-run process generally corresponding to ETDRS photos. We assessed the correlation between a single semiautomated ARIS imaging session without any re-imaging and ETDRS photos performed by a certified photographer for the determination of DR severity.

METHODS

Two independent masked readers graded mydriatic ARIS images and ETDRS photos. A third masked retinal specialist adjudicated discrepancies. Correlation between the two modalities was compared using weighted-κ statistics.

RESULTS

We evaluated 211 eyes of 106 patients with varying levels of DR. Partially ungradable images were present in 3.4% of ETDRS photos versus 31.8% of ARIS images. Exact agreement and agreement within one level between ETDRS photos and ARIS images using only completely gradable image sets occurred in 69% (κ=0.81) and 90% of cases, respectively. Exact agreement for clinically significant macular edema was 92.1% (κ=0.59). There was 100% agreement for eyes with high-risk proliferative DR. Within one level of DR severity, 100% agreement occurred for the following: questionable nonproliferative DR (NPDR), moderate NPDR, and severe NPDR.

CONCLUSIONS

Results suggest that semiautomated ARIS images compare favorably with ETDRS photos when full image sets can be obtained; however, partially ungradable image sets occurred almost 10 times more frequently with ARIS images than with ETDRS photos. In the two-thirds of cases where ARIS images can be utilized, ARIS can obtain retinal images comparable to ETDRS photos while requiring less highly trained personnel than generally needed for standard ETDRS photos.

Comprehensive diabetes management program for poorly controlled Hispanic type 2 patients at a community health center

Technology and improved care coordination models can help diabetes educators and providers meet national care standards and provide culturally sensitive diabetes education that may improve diabetes outcomes. The purpose of the study was to evaluate the clinical usefulness of a nurse-led diabetes care program (Comprehensive Diabetes Management Program, CDMP) for poorly controlled Hispanic type 2 diabetes (T2DM) patients in an urban community health center setting. Patients were randomized to the intervention condition (IC; n = 21) or an attention control condition (AC; n = 18). IC and AC conditions were compared on rates of adherence to national clinical practice guidelines (blood glucose, blood pressure, foot exam, eye exam), and levels of diabetes distress, depression, and treatment satisfaction. IC patients had a significant improvement in A1C from baseline to 12-month follow-up compared with AC (-1.6% ± 1.4% versus -0.6% ± 1.1%; P = .01). The proportion of IC patients meeting clinical goals at follow-up tended to be higher than AC for A1c (IC = 45%; AC = 28%), systolic blood pressure (IC = 55%; AC = 28%), eye screening (IC = 91%; AC = 78%), and foot screening, (IC = 86%; AC = 72%). Diabetes distress and treatment satisfaction also showed greater improvement for IC than AC (P = .05 and P = .06, respectively), with no differences for depression. The CDMP intervention was more effective than an attention control condition in helping patients meet evidence-based guidelines for diabetes care.

Telehealth practice recommendations for diabetic retinopathy, second edition

Ocular telemedicine and telehealth have the potential to decrease vision loss from DR. Planning, execution, and follow-up are key factors for success. Telemedicine is complex, requiring the services of expert teams working collaboratively to provide care matching the quality of conventional clinical settings. Improving access and outcomes, however, makes telemedicine a valuable tool for our diabetic patients. Programs that focus on patient needs, consider available resources, define clear goals, promote informed expectations, appropriately train personnel, and adhere to regulatory and statutory requirements have the highest chance of achieving success.

Evolution of a web-based, prototype Personal Health Application for diabetes self-management

Behaviors carried out by the person with diabetes (e.g., healthy eating, physical activity, judicious use of medication, glucose monitoring, coping and problem-solving, regular clinic visits, etc.) are of central importance in diabetes management. To assist with these behaviors, we developed a prototype PHA for diabetes self-management that was based on User-Centered Design principles and congruent with the anticipatory vision of Project Health Design (PHD). This article presents aspects of the prototype PHA's functionality as conceived under PHD and describes modifications to the PHA now being undertaken under new sponsorship, in response to user feedback and timing tests we have performed. In brief, the prototype Personal Health Application (PHA) receives data on the major diabetes management domains from a Personal Health Record (PHR) and analyzes and provides feedback based on clinically vetted educational content. The information is presented within "gadgets" within a portal-based website. The PHR used for the first implementation was the Common Platform developed by PHD. Key changes include a re-conceptualization of the gadgets by topic areas originally defined by the American Association of Diabetes Educators, a refocusing on low-cost approaches to diabetes monitoring and data entry, and synchronization with a new PHR, Microsoft® HealthVault™.

Combining iGoogle and personal health records to create a prototype personal health application for diabetes self-management

OBJECTIVE

The aim of this project is to create a prototype for a personal health application (PHA) for patients (i.e., consumers) with diabetes by employing a user-centered design process. This article describes the design process for and resulting architecture, workflow, and functionality of such a PHA.

MATERIALS AND METHODS

For the design process, we conducted focus groups with people who have diabetes (n = 21) to ascertain their needs for a PHA. We then developed a prototype in response to these needs, and through additional focus groups and step-by-step demonstrations for people with diabetes as well as healthcare providers, we obtained feedback about the prototype. The feedback led to changes in the PHA's presentation and function.

RESULTS

Focus group participants said they wanted a tool that could give them timely, readily available information on how diabetes-related domains interact, how their behaviors affect them, and what to do next. Thus, the prototype PHA is Internet-based, retrieves data for diabetes self-management from a personal health record, displays those data using gadgets in the consumer's iGoogle page, and makes the data available to a decision-support component that provides lifestyle-oriented advice. Manipulation of the data enables consumers to anticipate the results of future actions and to see interrelationships.

CONCLUSIONS

A user-centered design process resulted in a PHA that uses technology that is publicly available, employs a personal health record, and is Internet based. This PHA can provide the backbone for a decision support system that can bring together the cornerstones of diabetes self-management and integrate them into the life of the person with diabetes.

Plasma kallikrein mediates angiotensin II type 1 receptor-stimulated retinal vascular permeability

Hypertension is a leading risk factor for the development and progression of diabetic retinopathy and contributes to a variety of other retinal diseases in the absence of diabetes mellitus. Inhibition of the renin-angiotensin system has been shown to provide beneficial effects against diabetic retinopathy, both in the absence and presence of hypertension, suggesting that angiotensin II (Ang II) and the Ang II type 1 receptor may contribute to retinal vascular dysfunction. We investigated the effects of the Ang II type 1 receptor antagonist candesartan on retinal vascular permeability (RVP) in normotensive rats with streptozotocin-induced diabetes mellitus and in rats with Ang II-induced hypertension. We showed that candesartan treatment decreased diabetes mellitus- and Ang II-stimulated RVP by 58% (P<0.05) and 79% (P<0.05), respectively, compared with untreated controls, suggesting that activation of the Ang II type 1 receptor contributes to blood-retinal barrier dysfunction. We found that plasma kallikrein levels are increased in the retina of rats with Ang II-stimulated hypertension and that intravitreal injection of either plasma kallikrein or bradykinin is sufficient to increase RVP. We showed that a novel small molecule inhibitor of plasma kallikrein, 1-benzyl-1H-pyrazole-4-carboxylic acid 4-carbamimidoyl-benzylamide, delivered systemically via a subcutaneous pump, decreased Ang II-stimulated RVP by 70% (P<0.05) and ameliorates Ang II-induced hypertension, measured from the carotid artery by telemetry, but did not reduce Ang II-induced retinal leukostasis. These findings demonstrate that activation of the Ang II type 1 receptor increases RVP and suggest that systemic plasma kallikrein inhibition may provide a new therapeutic approach for ameliorating blood-retinal barrier dysfunction induced by hypertension.

Usability test of an internet-based informatics tool for diabetes care providers: the comprehensive diabetes management program

BACKGROUND

Research suggests Internet-based care management tools are associated with improvements in care and patient outcomes. However, although such tools change workflow, rarely is their usability addressed and reported. This article presents a usability study of an Internet-based informatics application called the Comprehensive Diabetes Management Program (CDMP), developed by content experts and technologists. Our aim is to demonstrate a process for conducting a usability study of such a tool and to report results.

METHODS

We conducted the usability test with six diabetes care providers under controlled conditions. Each provider worked with the CDMP in a single session using a "think aloud" process. Providers performed standardized tasks with fictitious patient data, and we observed how they approached these tasks, documenting verbalizations and subjective ratings. The providers then completed a usability questionnaire and interviews.

RESULTS

Overall, the scores on the usability questionnaire were neutral to favorable. For specific subdomains of the questionnaire, the providers' reported problems with the application's ease of use, performance, and support features, but were satisfied with its visual appeal and content. The results from the observational and interview data indicated areas for improvement, particularly in navigation and terminology.

CONCLUSIONS

The usability study identified several issues for improvement, confirming the need for usability testing of Internet-based informatics applications, even those developed by experts. To our knowledge, there have been no other usability studies of an Internet-based informatics application with the functionality of the CDMP. Such studies can form the foundation for translation of Internet-based medical informatics tools into clinical practice.

Retinal blood flow in diabetes

OBJECTIVE

This is a review of work focused on characterizing retinal blood flow in diabetes. The review describes results on validation of the methodology for retinal blood flow measurements, the mechanisms of action of various factors that contribute to abnormalities in retinal blood flow in diabetic rodent models, and the translation of these results to clinical studies demonstrating the effectiveness of different therapeutic agents in normalizing retinal blood flow abnormalities in patients with diabetes.

METHODS

Retinal blood flow measurements were performed using video fluorescein angiography, a methodology that is based on the measurement of fluorescein dye circulation times through the retinal circulation.

RESULTS

The results of a number of experiments are summarized, detailing the effects of hyperglycemia and the roles of factors such as protein kinase C activation, endothelin-1 and endothelin-3, angiotensin-II, and nitric oxide in the development of retinal blood flow abnormalities in diabetes.

CONCLUSION

The measurement of retinal blood flow both in animals and in clinical trials using the same retinal blood flow measurement methodology can provide a valuable method of quantitation allowing characterization of physiological effects and their association with metabolic alterations in diabetes and their effects on the development and incidence of microvascular complications.

Noninvasive volumetric imaging and morphometry of the rodent retina with high-speed, ultrahigh-resolution optical coherence tomography

PURPOSE

To demonstrate high-speed, ultrahigh-resolution optical coherence tomography (OCT) for noninvasive, in vivo, three-dimensional imaging of the retina in rat and mouse models.

METHODS

A high-speed, ultrahigh-resolution OCT system using spectral, or Fourier domain, detection has been developed for small animal retinal imaging. Imaging is performed with a contact lens and postobjective scanning. An axial image resolution of 2.8 mum is achieved with a spectrally broadband superluminescent diode light source with a bandwidth of approximately 150 nm at approximately 900-nm center wavelength. Imaging can be performed at 24,000 axial scans per second, which is approximately 100 times faster than previous ultrahigh-resolution OCT systems. High-definition and three-dimensional retinal imaging is performed in vivo in mouse and rat models.

RESULTS

High-speed, ultrahigh-resolution OCT enabled high-definition, high transverse pixel density imaging of the murine retina and visualization of all major intraretinal layers. Raster scan protocols enabled three-dimensional volumetric imagingand comprehensive retinal segmentation algorithms allowed measurement of retinal layers. An OCT fundus image, akin to a fundus photograph was generated by axial summation of three-dimensional OCT data, thus enabling precise registration of OCT measurements to retinal fundus features.

CONCLUSIONS

High-speed, ultrahigh-resolution OCT enables imaging of retinal architectural morphology in small animal models. OCT fundus images allow precise registration of OCT images and repeated measurements with respect to retinal fundus features. Three-dimensional OCT imaging enables visualization and quantification of retinal structure, which promises to allow repeated, noninvasive measurements to track disease progression, thereby reducing the need for killing the animal for histology. This capability can accelerate basic research studies in rats and mice and their translation into clinical patient care.

Extracellular carbonic anhydrase mediates hemorrhagic retinal and cerebral vascular permeability through prekallikrein activation

Excessive retinal vascular permeability contributes to the pathogenesis of proliferative diabetic retinopathy and diabetic macular edema, leading causes of vision loss in working-age adults. Using mass spectroscopy-based proteomics, we detected 117 proteins in human vitreous and elevated levels of extracellular carbonic anhydrase-I (CA-I) in vitreous from individuals with diabetic retinopathy, suggesting that retinal hemorrhage and erythrocyte lysis contribute to the diabetic vitreous proteome. Intravitreous injection of CA-I in rats increased retinal vessel leakage and caused intraretinal edema. CA-I-induced alkalinization of vitreous increased kallikrein activity and its generation of factor XIIa, revealing a new pathway for contact system activation. CA-I-induced retinal edema was decreased by complement 1 inhibitor, neutralizing antibody to prekallikrein and bradykinin receptor antagonism. Subdural infusion of CA-I in rats induced cerebral vascular permeability, suggesting that extracellular CA-I could have broad relevance to neurovascular edema. Inhibition of extracellular CA-I and kallikrein-mediated innate inflammation could provide new therapeutic opportunities for the treatment of hemorrhage-induced retinal and cerebral edema.

Comparison of nonmydriatic digital retinal imaging versus dilated ophthalmic examination for nondiabetic eye disease in persons with diabetes

OBJECTIVE

To evaluate the ability of stereoscopic nonmydriatic digital retinal imaging to detect ocular pathologic features other than diabetic retinopathy (DR) in patients with diabetes mellitus (DM) compared with dilated retinal examination by retinal specialist ophthalmologists.

DESIGN

Clinic-based comparative instrument study and retrospective chart review.

PARTICIPANTS

Two hundred eighty Joslin Diabetes Center outpatients (560 eyes) with type 1 or type 2 DM.

METHODS

Nonsimultaneous stereoscopic nonmydriatic digital retinal images (640 x 480 pixels) of three 45 degrees retinal fields were acquired and graded for clinical level of DR and other ocular pathologic features by certified readers according to Joslin Vision Network (JVN) protocol. Retrospective chart review compared findings from JVN digital images with findings from dilated retinal examination by retinal specialists performed within an average of 39.6 days of digital imaging. An independent senior retinal specialist adjudicated disagreements by review of 7 standard field 35-mm Early Treatment Diabetic Retinopathy Study protocol fundus photographs and JVN images.

MAIN OUTCOME MEASURES

Detection of non-DR ocular pathologic features by digital imaging as compared with clinical examination.

RESULTS

Nonmydriatic digital evaluation identified at least 1 non-DR ocular finding in 40.7% of patients (114/280). Non-diabetes mellitus ocular pathologic features identified by digital images, clinical examination, or both included cataract (n = 100); age-related maculopathy (n = 52); suspicion of glaucoma (n = 18); choroidal lesions (n = 18); evidence of systemic disorder (e.g., hypertension or renal disease; n = 15); epiretinal membrane (n = 11); chorioretinal atrophy, scar, or both (n = 6); retinal emboli (n = 3); retinitis pigmentosa (n = 1); and asteroid hyalosis (n = 1). Agreement of nonmydriatic imaging with clinical examination for presence and absence of these findings was 95.4%, 91.3%, 98.2%, 98.6%, 98.2%, 99.6%, 100%, 100%, 100%, and 100%, respectively. Kappa values for all non-DR lesions demonstrated near perfect agreement (kappa> or =0.80) except for age-related maculopathy (kappa = 0.71) and choroidal lesions (kappa = 0.73), where agreement was substantial. Overall, only 55 eyes (9.8%) were ungradable for level of DR and 85 eyes (15.2%) were ungradable for macular edema.

CONCLUSIONS

Joslin Vision Network nonmydriatic digital imaging demonstrated excellent agreement with dilated ophthalmic examination by retinal specialists in the detection of ocular disease other than DR, suggesting a potential role for this technology in evaluating non-DR disorders and highlighting the extent of findings other than retinopathy in patients with diabetes.

Role of the angiotensin II type 1 receptor in the pathogenesis of diabetic retinopathy: effects of blood pressure control and beyond

Diabetic retinopathy is characterized by both functional and morphological changes in the retinal microvessels that can lead to macular edema, neovascularization, and vision loss. Hypertension has been identified as a major risk factor for diabetic retinopathy and randomized clinical trials have shown that reduction of blood pressure using angiotensin converting enzyme (ACE) inhibitors reduces the progression of diabetic retinopathy. The major components of the renin-angiotensin system have been identified in ocular tissues. Activation of angiotensin II type 1 (AT1) receptors expressed on retinal endothelial cells and pericytes has been implicated in contributing to the microvascular abnormalities in diabetic retinopathy. We have examined the experimental and clinical evidence for the role of the renin-angiotensin system in the pathogenesis of diabetic retinopathy, including the effects of ACE inhibition and AT1-receptor antagonism on diabetes-induced abnormalities in retinal hemodynamics, vascular permeability, and leukostasis; retinal neovascularization in rodent models of oxygen-induced retinopathy; and results from randomized clinical trials that have investigated the effects of ACE inhibitors on the progression of diabetic retinopathy in diabetic patients in the absence or presence of hypertension. The effects of AT1-receptor antagonism on the retina have been attributed to decreases in systemic blood pressure and the concomitant reduction in mechanical vascular stretch, in addition to the intraocular effects blocking AT1-receptor stimulation of retinal endothelial cells and pericytes. Results from the current DIabetic REtinopathy Candesartan Trials program will evaluate the potential of the AT1-receptor as a therapeutic target for diabetic retinopathy.

Nonmydriatic teleretinal imaging improves adherence to annual eye examinations in patients with diabetes

We studied whether nonmydriatic digital retinal imaging with remote interpretation (teleretinal imaging) in the ambulatory care setting affected adherence to annual dilated eye examinations among patients with diabetes. We randomly assigned 448 patients to a teleretinal imaging group or a control group. We measured the number of patients who had dilated eye examinations within 12 months of group assignment and the agreement for level of diabetic retinopathy between teleretinal imaging and the eye examinations. The teleretinal imaging group (n = 223) had significantly more dilated eye examinations than the control group (n = 225). Teleretinal imaging and eye examination results showed significant correlation and moderate agreement. Cataract and smaller pupil size were significantly associated with ungradable retinal images. Two-thirds of patients with ungradable images had other ocular findings. Patients reported high satisfaction with nonmydriatic teleretinal imaging. Nonmydriatic teleretinal imaging improves diabetic retinopathy assessment rates.

A Modeled Economic Analysis of a Digital Teleophthalmology System As Used by Three Federal Healthcare Agencies for Detecting Proliferative Diabetic Retinopathy

The objective of this study was to compare, using a 12-month time frame, the cost-effectiveness of a non-mydriatic digital tele-ophthalmology system (Joslin Vision Network) versus traditional clinic-based ophthalmoscopy examinations with pupil dilation to detect proliferative diabetic retinopathy and its consequences. Decision analysis techniques, including Monte Carlo simulation, were used to model the use of the Joslin Vision Network versus conventional clinic-based ophthalmoscopy among the entire diabetic populations served by the Indian Health Service, the Department of Veterans Affairs, and the active duty Department of Defense. The economic perspective analyzed was that of each federal agency. Data sources for costs and outcomes included the published literature, epidemiologic data, administrative data, market prices, and expert opinion. Outcome measures included the number of true positive cases of proliferative diabetic retinopathy detected, the number of patients treated with panretinal laser photocoagulation, and the number of cases of severe vision loss averted. In the base-case analyses, the Joslin Vision Network was the dominant strategy in all but two of the nine modeled scenarios, meaning that it was both less costly and more effective. In the active duty Department of Defense population, the Joslin Vision Network would be more effective but cost an extra 1,618 dollars per additional patient treated with panretinal laser photo-coagulation and an additional 13,748 dollars per severe vision loss event averted. Based on our economic model, the Joslin Vision Network has the potential to be more effective than clinic-based ophthalmoscopy for detecting proliferative diabetic retinopathy and averting cases of severe vision loss, and may do so at lower cost.

The effect of vitamin E on endothelial function of micro- and macrocirculation and left ventricular function in type 1 and type 2 diabetic patients

We examined the effects of high-dosage vitamin E treatment over a 12-month period on the vascular reactivity of micro- and macrocirculation and left ventricular function in diabetic patients. Subjects (n = 89) were randomized to vitamin E (1,800 IU daily) or placebo and were followed for 12 months. High-resolution ultrasound images were used to measure the flow-mediated dilation (FMD; endothelium dependent) and nitroglycerin-induced dilation (NID; endothelium independent) of the brachial artery. Laser Doppler perfusion imaging was used to measure vascular reactivity in the forearm skin. Left ventricular function was evaluated using transthoracic echocardiogram. At the end of the 6-month period, a worsening in endothelium-dependent skin vasodilation (P = 0.02) and rise in endothelin levels (P = 0.01) were found in the vitamin E compared with the placebo group. At the end of the 12-month period, a worsening was observed in NID (P = 0.02) and a marginal worsening was seen in systolic blood pressure (P = 0.04) and FMD (P = 0.04) in the vitamin E compared with the placebo group. In addition C-reactive protein levels decreased marginally in the vitamin E compared with the placebo group (P = 0.05). No changes were observed in left ventricular function. We concluded that long-term treatment with 1,800 IU of vitamin E has no beneficial effects on endothelial or left ventricular function in diabetic patients. Because vitamin E-treated patients had a worsening in some vascular reactivity measurements when compared with control subjects, the use of high dosages of vitamin E cannot be recommended.

Characterization of retinal leukostasis and hemodynamics in insulin resistance and diabetes: role of oxidants and protein kinase-C activation

Increases in leukostasis/monocyte adhesion to the capillary endothelium (leukostasis) and decreases in retinal blood flow may be causally associated and are implicated in the pathogenesis of diabetic retinopathy. In this study, we demonstrate that increases in leukostasis are observed in insulin-resistant states without diabetes, whereas decreases in retinal blood flow require diabetes and hyperglycemia. Microimpaction studies using beads mimicking retinal capillary obstruction by leukocytes did not affect retinal blood flow. In diabetic rats, treatment with the antioxidant alpha-lipoic acid normalized the amount of leukostasis but not retinal blood flow. In contrast, treatment with D-alpha-tocopherol and protein kinase-C beta-isoform inhibition (LY333531) prevented the increases in leukostasis and decreases in retinal blood flow in diabetic rats. Serum hydroxyperoxide, a marker of oxidative stress, was increased in diabetic rats, but normalized by treatment with antioxidants alpha-lipoic acid and D-alpha-tocopherol and, surprisingly, PKC beta-isoform inhibition. These findings suggest that leukostasis is associated with endothelial dysfunction, insulin resistance, and oxidative stress but is not related to retinal blood flow and is not sufficient to cause diabetic-like retinopathy. Moreover, treatment with PKC beta inhibition is effective to normalize diabetes or hyperglycemia-induced PKC beta-isoform activation and oxidative stress.

Stereo nonmydriatic digital-video color retinal imaging compared with Early Treatment Diabetic Retinopathy Study seven standard field 35-mm stereo color photos for determining level of diabetic retinopathy

OBJECTIVE

To evaluate the ability to determine clinical levels of diabetic retinopathy, timing of next appropriate retinal evaluation, and necessity of referral to ophthalmology specialists using stereoscopic nonmydriatic digital-video color retinal images as compared with Early Treatment Diabetic Retinopathy Study (ETDRS) seven standard field 35-mm stereoscopic color fundus photographs.

DESIGN

Prospective, clinic-based, comparative instrument validation study.

PARTICIPANTS

Fifty-four patients (108 eyes) with type 1 or type 2 diabetes mellitus selected after chart review from a single center to include the full spectrum of diabetic retinopathy.

METHODS

Nonsimultaneous 45 degrees -field stereoscopic digital-video color images (JVN images) were obtained from three fields with the Joslin Vision Network (JVN) system before pupil dilation. Following pupil dilation, ETDRS seven standard field 35-mm stereoscopic color 30 degrees fundus photographs (ETDRS photos) were obtained. Joslin Vision Network images and ETDRS photos were graded on a lesion-by-lesion basis by two independent, masked readers to assess ETDRS clinical level of diabetic retinopathy. An independent ophthalmology retina specialist adjudicated interreader disagreements in a masked fashion.

MAIN OUTCOME MEASURES

Determination of ETDRS clinical level of diabetic retinopathy, timing of next ophthalmic evaluation of diabetic retinopathy, and need for prompt referral to ophthalmology specialist.

RESULTS

There was substantial agreement (kappa = 0.65) between the clinical level of diabetic retinopathy assessed from the undilated JVN images and the dilated ETDRS photos. Agreement was excellent (kappa = 0.87) for suggested referral to ophthalmology specialists for eye examinations. Comparison of individual lesions between the JVN images and the ETDRS photos and for interreader comparisons were comparable to the prior ETDRS study.

CONCLUSIONS

Undilated digital-video images using the JVN system were comparable photographs for the determination of diabetic retinopathy level. The results validate the agreement between nonmydriatic JVN images and dilated ETDRS photographs and suggest that this digital technique may be an effective telemedicine tool for remotely determining the level of diabetic retinopathy, suggesting timing of next retinal evaluation and identifying the need for prompt referral to ophthalmology specialists. Thus, the JVN system would be an appropriate tool for facilitating increased access of diabetic patients into recommended eye evaluations, but should not be construed as a paradigm that would replace the need for comprehensive eye examinations.

Leukocyte-mediated endothelial cell injury and death in the diabetic retina

Endothelial cell death is a hallmark of diabetic retinopathy. Its occurrence is required for the formation of acellular (devitalized) capillaries, lesions that produce irreversible retinal ischemia through their inability to support blood flow. The mechanisms underlying diabetic retinal endothelial cell injury and death remain largely unknown. The current study demonstrates that adherent leukocytes are temporally and spatially associated with retinal endothelial cell injury and death within 1 week of streptozotocin-induced experimental diabetes in rats. Moreover, the antibody-based neutralization of intercellular adhesion molecule-1 and CD18 is shown to prevent both leukocyte adhesion and retinal endothelial cell injury and death. These data highlight the central and causal role of adherent leukocytes in the pathogenesis of diabetic retinopathy. They also underscore the potential utility of anti-intercellular adhesion molecule1- and anti-CD18-based therapies in the treatment of diabetic retinopathy, a newly recognized inflammatory disease.

Endothelin-3 regulation of retinal hemodynamics in nondiabetic and diabetic rats

PURPOSE

To investigate the mechanisms of action of endothelin (ET)-3 on the regulation of retinal hemodynamics in diabetic and nondiabetic rats.

METHODS

Retinal blood flow changes were measured using video fluorescein angiography. Measurements were made before and after intravitreal injections of different ET-3 concentrations in nondiabetic rats and rats with streptozotocin (STZ)-induced diabetes. The effect of ET-3 on retinal blood flow was also investigated in nondiabetic rats after pretreatment with N:(G)-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (NOS) inhibitor; BQ-788, an ET receptor B (ETB) antagonist; and BQ-123, an ET receptor A (ETA) antagonist. Control animals were injected intravitreally with vehicle alone.

RESULTS

In nondiabetic rats, ET-3 induced a dose-dependent rapid increase in retinal blood flow 2 minutes after intravitreal injection (maximal at 10(-)(8) M, P < 0. 01) followed 15 and 30 minutes after ET-3 injection by dose-dependent decreases in retinal blood flow (maximal effect at 10(-)(6) M, P < 0.05). The ET-3-stimulated retinal blood flow increase was inhibited by 10(-)(4) M BQ-788 (P < 0.01) and 10(-)(3) M L-NMMA (P < 0.05). The ET-3-stimulated decrease in retinal blood flow at later times (15 minutes) was inhibited (P < 0.03) by 10(-4) M BQ-123. In diabetic rats, baseline retinal blood flows were decreased compared with nondiabetic rats (P < 0.01), showed dose-dependent increases 2 minutes after ET-3 injection (P < 0.03), and at later times remained significantly increased (P < 0.05) in contrast to flows in nondiabetic rats.

CONCLUSIONS

The ET-3-induced initial rapid retinal blood flow increase in nondiabetic rats is mediated by the ET-3/ETB and NOS action. The subsequent retinal blood flow decrease is mediated by ET-3/ETA action. Diabetic rats showed comparable ET-3-induced retinal blood flow increases indicating normal ET-3/ETB action. However, at later times, retinal blood flow remained increased, suggesting an abnormal ET-3/ETA action.

von Willebrand factor and retinal circulation in early-stage retinopathy of type 1 diabetes

OBJECTIVE

Although retinopathy is a common microvascular complication of type 1 diabetes, the mechanism for this complication is still unknown. Changes in retinal circulation have been noted before the development of overt retinal pathology. Because von Willebrand factor (vWF) is a marker for endothelial dysfunction and mediates platelet adhesion, we determined if there was an association between vWF and retinal circulation in the early stages of diabetic retinopathy.

RESEARCH DESIGN AND METHODS

Twenty subjects (aged 32.4 +/- 7.8 years) with type 1 diabetes and minimal or no retinopathy were studied. The mean duration of diabetes was 4.7 +/- 2.6 years. Data were collected at baseline and after 4 months of 1,800 IU vitamin E therapy or placebo. Retinal circulation was evaluated by video fluorescein angiography. Plasma vWF antigen levels were measured by enzyme-linked immunosorbent assay and fibrinogen by the Clauss method.

RESULTS

Retinal blood flow was negatively correlated with vWF levels (r = -0.44, P = 0.008), whereas retinal circulation time was positively correlated with vWF levels (r = 0.33, P = 0.048). Fibrinogen levels were not significantly associated with either retinal index. However, fibrinogen levels were positively associated with HbA1c levels (r = 0.34, P = 0.01), indicating an association between poor glycemic control and higher fibrinogen levels.

CONCLUSIONS

Increased vWF was associated with a prolonged retinal circulation time and reduced retinal blood flow in early-stage retinopathy of type 1 diabetes. Reduced blood flow associated with increased vWF levels may promote stasis in the retinal circulation and lead to local hypoxemia. These changes might contribute to the microvascular complications of diabetes. Whether the vWF levels predict retinal complications deserves further investigation.

Retinal expression, regulation, and functional bioactivity of prostacyclin-stimulating factor

Prostacyclin-stimulating factor (PSF) acts on vascular endothelial cells to stimulate the synthesis of the vasodilatory molecule prostacyclin (PGI2). We have examined the expression, regulation, and hemodynamic bioactivity of PSF both in whole retina and in cultured cells derived from this tissue. PSF was expressed in all retinal cell types examined in vitro, but immunohistochemical analysis revealed PSF mainly associated with retinal vessels. PSF expression was constitutive in retinal pericytes (RPCs) but could be modulated in bovine retinal capillary endothelial cells (RECs) by cell confluency, hypoxia, serum starvation, high glucose concentrations, or inversely by soluble factors present in early vs. late retinopathy, such as TGF-beta, VEGF, or bFGF. In addition, RPC-conditioned media dramatically increased REC PGI2 production, a response inhibited by blocking PSF with a specific antisense oligodeoxynucleotide (ODN). In vivo, PGI2 increased retinal blood flow (RBF) in control and diabetic animals. Furthermore, the early drop in RBF during the initial weeks after inducing diabetes in rats, as well as the later increase in RBF, both correlated with levels of retinal PSF. RBF also responded to treatment with RPC-conditioned media, and this effect could be partially blocked using the antisense PSF ODN. We conclude that PSF expressed by ocular cells can induce PGI2, retinal vascular dilation, and increased retinal blood flow, and that alterations in retinal PSF expression may explain the biphasic changes in RBF observed in diabetes.

Vascular endothelial growth factor (VEGF)-induced retinal vascular permeability is mediated by intercellular adhesion molecule-1 (ICAM-1)

Two prominent vascular endothelial growth factor (VEGF)-induced retinal effects are vascular permeability and capillary nonperfusion. The mechanisms by which these effects occur are not completely known. Using a rat model, we show that intravitreous injections of VEGF precipitate an extensive retinal leukocyte stasis (leukostasis) that coincides with enhanced vascular permeability and capillary nonperfusion. The leukostasis is accompanied by the up-regulation of intercellular adhesion molecule-1 expression in the retina. The inhibition of intercellular adhesion molecule-1 bioactivity with a neutralizing antibody prevents the permeability and leukostasis increases by 79% and 54%, respectively. These data are the first to demonstrate that a nonendothelial cell type contributes to VEGF-induced vascular permeability. Additionally, they identify a potential mechanism for VEGF-induced retinal capillary nonperfusion.

Integrin-mediated neutrophil adhesion and retinal leukostasis in diabetes

PURPOSE

A critical early event in the pathogenesis of diabetic retinopathy is leukocyte adhesion to the diabetic retinal vasculature. The process is mediated, in part, by intercellular adhesion molecule-1 (ICAM-1) and results in blood-retinal barrier breakdown and capillary nonperfusion. This study evaluated the expression and function of the corresponding ICAM-1-binding leukocyte beta2-integrins in experimental diabetes.

METHODS

Diabetes was induced in Long Evans rats with streptozotocin. The expression of the surface integrin subunits CD11a, CD11b, and CD18 on rat neutrophils isolated from peripheral blood was quantitated with flow cytometry. In vitro neutrophil adhesion was studied using quantitative endothelial cell-neutrophil adhesion assays. The adhesive role of the integrin subunits CD11a, CD11b, and CD18 was tested using specific neutralizing monoclonal antibodies. CD18 bioactivity was blocked in vivo with anti-CD18 F(ab')2 fragments, and the effect on retinal leukocyte adhesion was quantitated with acridine orange leukocyte fluorography.

RESULTS

Neutrophil CD11a, CD11b, and CD18 surface integrin levels were 62% (n = 5, P = 0.006), 54% (n = 5, P = 0.045), and 38% (n = 5, P = 0.009) greater in diabetic versus nondiabetic animals, respectively. Seventy-five percent more neutrophils from diabetic versus nondiabetic animals adhered to rat endothelial cell monolayers (n = 6, P = 0.02). Pretreatment of leukocytes with either anti-CD11b or anti-CD18 antibodies lowered the proportion of adherent diabetic neutrophils by 41% (n = 6, P = 0.01 for each treatment), whereas anti-CD11a antibodies had no significant effect (n = 6, P = 0.5). In vivo, systemic administration of anti-CD18 F(ab')2 fragments decreased diabetic retinal leukostasis by 62% (n = 5, P = 0.001).

CONCLUSIONS

Neutrophils from diabetic animals exhibit higher levels of surface integrin expression and integrin-mediated adhesion. In vivo, CD18 blockade significantly decreases leukostasis in the diabetic retinal microvasculature. Integrin adhesion molecules may serve as therapeutic targets for the treatment and/or prevention of early diabetic retinopathy.

Prevention of leukostasis and vascular leakage in streptozotocin-induced diabetic retinopathy via intercellular adhesion molecule-1 inhibition

Diabetic retinopathy is a leading cause of adult vision loss and blindness. Much of the retinal damage that characterizes the disease results from retinal vascular leakage and nonperfusion. This study shows that diabetic retinal vascular leakage and nonperfusion are temporally and spatially associated with retinal leukocyte stasis (leukostasis) in the rat model of streptozotocin-induced diabetes. Retinal leukostasis increases within days of developing diabetes and correlates with the increased expression of retinal intercellular adhesion molecule-1 (ICAM-1). ICAM-1 blockade with a mAb prevents diabetic retinal leukostasis and vascular leakage by 48.5% and 85.6%, respectively. These data identify the causal role of leukocytes in the pathogenesis of diabetic retinopathy and establish the potential utility of ICAM-1 inhibition as a therapeutic strategy for the prevention of diabetic retinopathy.

Can protein kinase C inhibition and vitamin E prevent the development of diabetic vascular complications?

Hyperglycemia causes vascular complications of diabetes possible by the activation of protein kinase C (PKC). We have provided substantial evidence that activation of PKC can lead to a whole host of vascular dysfunction in diabetes. The activation of PKC induced by hyperglycemia appears to be due to an increase in diacylglycerol (DAG) levels, a physiological activator of PKC. Studies involving cultural cells, animal models of diabetes and patients have shown that inhibition of PKC by specific PKC inhibitor was able to reverse many of the vascular dysfunctions in the retina, kidney and cardiovascular systems induced by either hyperglycemia or diabetes. In addition high doses of vitamin E were shown to decrease the level of DAG and PKC induced by diabetes or hyperglycemia. Thus animal and clinical studies have shown that high doses of vitamin E treatment can apparently reverse some of the changes in the retinal and renal vessels.

High-dose vitamin E supplementation normalizes retinal blood flow and creatinine clearance in patients with type 1 diabetes

OBJECTIVE

To determine the effectiveness of vitamin E treatment in normalizing retinal blood flow and renal function in patients with <10 years of type 1 diabetes.

RESEARCH DESIGN AND METHODS

An 8-month randomized double-masked placebo-controlled crossover trial evaluated 36 type 1 diabetic and 9 nondiabetic subjects. Subjects were randomly assigned to either 1,800 IU vitamin E/day or placebo for 4 months and followed, after treatment crossover, for a further 4 months. Retinal blood flow was measured using video fluorescein angiography, and renal function was assessed using normalized creatinine clearance from timed urine collections.

RESULTS

After vitamin E treatment, serum levels of vitamin E were significantly elevated (P<0.01) in both type 1 diabetic and control patients. Hemoglobin A1c was not affected by vitamin E treatment. Diabetic patient baseline retinal blood flow (29.1+/-7.5 pixel2/s) was significantly (P = 0.030) decreased compared with that of nondiabetic subjects (35.2+/-7.2 pixel2/s). After vitamin E treatment, diabetic patient retinal blood flow (34.5+/-7.8 pixel2/s) was significantly increased (P<0.001) and was comparable with that of nondiabetic subjects. Additionally, vitamin E treatment significantly (P = 0.039) normalized elevated baseline creatinine clearance in diabetic patients.

CONCLUSIONS

Oral vitamin E treatment appears to be effective in normalizing retinal hemodynamic abnormalities and improving renal function in type 1 diabetic patients of short disease duration without inducing a significant change in glycemic control. This suggests that vitamin E supplementation may provide an additional benefit in reducing the risks for developing diabetic retinopathy or nephropathy.

Joslin Vision Network Validation Study: pilot image stabilization phase

PURPOSE

This preliminary study is designed to evaluate the quality of initial images obtained using the Joslin Vision Network (JVN) image capture and retrieval system.

METHODS

Digitized images of 18 patients (36 eyes) were obtained using Topcon Non-mydriatic Fundus Camera and various imaging protocols as described for each series of images. Level of retinopathy ranged from no diabetic retinopathy to proliferative diabetic retinopathy. Images were reviewed and evaluated in comparison to medical record notes and Early Treatment Diabetic Retinopathy Study (ETDRS) seven-standard field stereoscopic 35-mm retinal fundus photographs--when available--to determine the ability of JVN digitized images to allow appropriate diagnosis and clinical management. JVN images were also evaluated for presence of photographic artifacts and stereoscopic presentation. The various displays and relative value of each JVN display were also evaluated.

RESULTS

Using combinations of JVN image displays, JVN images were shown to match diagnosed level of diabetic retinopathy as determined from record notes and/or ETDRS seven-standard field stereoscopic 35-mm retinal fundus photography. Viewing images with various combinations of JVN image displays delineates possible sources of artifacts in JVN images. Areas to guide future image capture and image reading are identified.

CONCLUSIONS

The JVN image capture system and reading of images by certified readers should allow appropriate photodiagnostic information to support the JVN, the diabetes mellitus disease management telemedicine initiative of the Joslin Diabetes Center. A rigid, full-scale, masked study to compare the Joslin Vision Network to seven-standard field stereoscopic 35-mm retinal fundus photography should be pursued to validate the image-gathering and image-reading strategy to support the Joslin Vision Network.

Reversibility of retinal flow abnormalities is disease-duration dependent in diabetic rats

Decreased retinal blood flow has been measured in streptozotocin (STZ)-induced diabetes of 1 week's duration, and primary insulin intervention was effective in maintaining normal retinal blood flow in diabetic rats. Retinal blood-flow abnormalities precede clinical diabetic retinopathy in both diabetic animals and patients. An important characteristic of diabetic retinopathy is the difficulty of reversibility once it has been established. Because altered retinal hemodynamics is a possible marker of early diabetic retinopathy, we investigated in this study whether retinal blood-flow changes in rats can be normalized by secondary insulin intervention following short and chronic periods of untreated STZ-induced diabetes. Subcutaneous insulin pumps were placed into diabetic rats for 1 week after 1 week of diabetes (2-week group) and after 3 weeks of diabetes (4-week group). Retinal circulatory parameters were determined using image analysis of video fluorescein angiogram recordings. For the 2-week group, retinal blood flow was significantly (P < 0.05) reduced in the untreated diabetic rats compared with nondiabetic and insulin-treated diabetic rats (80.6+/-29.2, 131.9+/-50.1, and 151.3+/-54.0 pixels2/s respectively). Retinal blood flow was also significantly (P < 0.05) reduced in the 4-week untreated diabetic rats compared with nondiabetic rats (95.7+/-22.2 vs. 125.7+/-29.5 pixels2/s). In contrast to the shorter-duration group, insulin treatment for 1 week after 3 weeks of diabetes did not totally normalize retinal blood flow (117.5+/-32.4 pixels2/s). These results suggest that vascular abnormalities could become more resistant to normalization following short-term (1 week) insulin treatment after longer periods of untreated diabetes.

Prevention of diabetes-induced abnormal retinal blood flow by treatment with d-alpha-tocopherol

Hyperglycemia in diabetes mellitus has been shown to activate diacylglycerol (DAG)-protein kinase C (PKC) pathway in the vascular tissues, possibly altering vascular function. We have characterized the effects of vitamin E (d-alpha-tocopherol) on activation of PKC and DAG levels in retinal tissues of diabetic rats, and correlated its effects to retinal hemodynamics using video-based fluorescein angiography (VFA). Comparing streptozotocin-induced diabetic rats to controls, membranous PKC specific activities were increased by 71% (p < 0.05). Western blot analysis showed that the membranous PKC beta II isoform was significantly increased by 133 +/- 45% (p < 0.05). Intraperitoneal injection of d-alpha-tocopherol (40 mg/kg) every other day prevented the increases in membranous PKC specific activity and PKC beta II protein shown by immunoblots. Similar to PKC activities, total DAG levels were increased in the retina and were normalized by d-alpha-tocopherol treatment. Physiologically, abnormalities of retinal blood hemodynamics, as measured using VFA, which previously have been reported to be associated with increases of DAG and PKC levels in the diabetic rats, were prevented by d-alpha-tocopherol treatment in diabetic rats. The direct effect of d-alpha-tocopherol on total DAG and [3H]-palmitate incorporation into DAG were also examined using cultured bovine retinal endothelial cells (REC). Exposure of REC to 22 mM glucose for three days increased total DAG and [3H]-palmitate labeled DAG levels by 35 +/- 8% and 50 +/- 8%, respectively (p < 0.05). The presence of d-alpha-tocopherol (50 micrograms/ml) prevented the increase of both total DAG and [3H]-palmitate labeled DAG levels in cells exposed to 22 mM glucose. These findings suggested that the mechanism of the d-alpha-tocopherol's effect appears to be mediated by the normalization of the hyperglycemia-induced activation of the DAG-PKC pathway which leads to the normalization of abnormal retinal blood flow seen in diabetes mellitus.

Specific retinal diacylglycerol and protein kinase C beta isoform modulation mimics abnormal retinal hemodynamics in diabetic rats

PURPOSE

Elevation of diacylglycerol (DAG) and protein kinase C (PKC) levels in diabetic vascular tissue is associated with abnormalities of retinal and renal hemodynamics. The object of this study was to determine whether direct elevation of retinal DAG levels, in the absence of diabetes or hyperglycemia, can mimic the hemodynamic abnormalities normally observed in diabetic rats. Retinal DAG levels were elevated using an inhibitor of DAG kinase that converts DAG to phosphatidic acid. The effectiveness of a specific PKC-beta isoform inhibitor introduced directly into the retinas of diabetic rats in reversing diabetes-related abnormal retinal hemodynamics was also investigated.

METHODS

For retinal blood flow studies, diacylglycerol kinase (DGK) inhibitor R59949, at various concentrations, was injected into the vitreous of nondiabetic Sprague-Dawley rats (n = 33), and a PKC-beta isoform-selective inhibitor LY333531 was injected into the vitreous of rats with streptozotocin (STZ)-induced diabetes of 2 weeks' duration (n = 21). Retinal hemodynamic changes were quantitated using video-based fluorescein angiography. Total DAG levels were assayed from five nondiabetic rat retinas after DGK inhibition and retinal PKC activities were assayed from six diabetic rat retinas after PKC-beta inhibition.

RESULTS

DGK inhibitor R59949 injected into the vitreous dose dependently increased the mean circulation time (MCT) and decreased retinal blood flow (EC50 = 10(-8) M). After 30 minutes, 10(-5) M R59949 induced a 1.7-fold increase in total retinal DAG levels, compared with the levels in vehicle-injected eyes, an increase in MCT from 0.87 +/- 0.05 seconds to 1.44 +/- 0.12 seconds (P < 0.01) and a decrease in retinal blood flow from 105.3 +/- 6.5 pixel2/second to 64.1 +/- 5 pixel2/second (P < 0.01). The effect of R59949 was sustained for 60 minutes after injection. These retinal hemodynamic parameters after DGK inhibition were comparable to those measured at baseline in rats with STZ-induced diabetes of 2 weeks' duration (MCT = 1.38 +/- 0.20 seconds; retinal blood flow = 68 +/- 11.2 pixel2/second). Intravitreal injection of the PKC-beta inhibitor (LY333531) at 10(-5) M in diabetic rats decreased by a factor of 1.6 the diabetes-related increased PKC activation, decreased the prolonged MCT (0.98 +/- 0.13 seconds; P < 0.01) and increased retinal blood flow (93.4 +/- 14.2 pixel2/second; P < 0.01). The measured retinal circulatory parameters after PKC inhibition in the retina were comparable to those measured at baseline in the nondiabetic rats.

CONCLUSIONS

These results provide direct evidence that DAG elevation and subsequent PKC-beta isoform activation are the primary biochemical sequelae responsible for the development of the abnormal retinal hemodynamics observed in diabetic rats.

Vascular endothelial growth factor and severity of nonproliferative diabetic retinopathy mediate retinal hemodynamics in vivo: a potential role for vascular endothelial growth factor in the progression of nonproliferative diabetic retinopathy

PURPOSE

To determine the effect of vascular endothelial growth factor and retinopathy level on retinal hemodynamics in nondiabetic and diabetic rats and to evaluate retinal hemodynamics in nondiabetic and diabetic patients.

METHODS

Forty-eight diabetic and 22 nondiabetic patients had their diabetic retinopathy levels determined from fundus photographs according to Early Treatment Diabetic Retinopathy Study (ETDRS). Fluorescein angiograms were recorded from the left eye by video fluorescein angiography. Retinal blood flow was calculated from the digitized angiograms. Human recombinant vascular endothelial growth factor or vehicle alone was injected intravitreally into 13 nondiabetic and 11 diabetic rats.

RESULTS

Retinal blood flow decreased 33% in patients with ETDRS retinopathy level 10 compared with control patients (P = .001) and increased sequentially in more advanced stages of retinopathy, with a strong correlation between retinal blood flow and retinopathy level (r2 = 0.434, P = .001). In the diabetic rats, retinal blood flow was decreased 35.6% (P = .01). Vascular endothelial growth factor maximally increased retinal blood flow by 36.1% in nondiabetic rats after 25 minutes (P = .001) and by 73.7% in diabetic rats after only 5 minutes (P = .01) and caused a greater response in diabetic than in nondiabetic rats.

CONCLUSIONS

Retinal blood flow increases with advancing nonproliferative diabetic retinopathy in humans, and diabetes accentuates the vascular endothelial growth factor-induced increase in retinal blood flow and venous dilation in rats. Vascular endothelial growth factor may contribute to the changes in retinal hemodynamics and morphology observed in early diabetic retinopathy.

Vascular endothelial growth factor-induced retinal permeability is mediated by protein kinase C in vivo and suppressed by an orally effective beta-isoform-selective inhibitor

Increased vascular permeability and excessive neovascularization are the hallmarks of endothelial dysfunction, which can lead to diabetic macular edema and proliferative diabetic retinopathy in the eye. Vascular endothelial growth factor (VEGF) is an important mediator of ocular neovascularization and a known vasopermeability factor in nonocular tissues. In these studies, we demonstrate that intravitreal injection of VEGF rapidly activates protein kinase C (PKC) in the retina at concentrations observed clinically, inducing membrane translocation of PKC isoforms alpha, betaII, and delta and >threefold increases in retinal vasopermeability in vivo. The effect of VEGF on retinal vascular permeability appears to be mediated predominantly by the beta-isoform of PKC with >95% inhibition of VEGF-induced permeability by intravitreal or oral administration of a PKC beta-isoform-selective inhibitor that did not inhibit histamine-mediated effects. These studies represent the first direct demonstration that VEGF can increase intraocular vascular permeability through activation of PKC in vivo and suggest that oral pharmacological therapies involving PKC beta-isoform-selective inhibitors may prove efficacious for the treatment of VEGF-associated ocular disorders such as diabetic retinopathy.

Regulation of retinal hemodynamics in diabetic rats by increased expression and action of endothelin-1

PURPOSE

To investigate the role of endogenous endothelin-1 (ET-1) expression and its interaction with the ETA receptor in the physiologic regulation of vascular tone as well as in the development of abnormal retinal hemodynamics in diabetes.

METHODS

Retinal blood flow, using digitized video fluorescein angiography recordings, was quantitated after intravitreous injections of ET-1; BQ-123, an ETA receptor antagonist; and phosporamindon, an endothelin converting enzyme inhibitor in the eyes of diabetic and nondiabetic rats. A total of 154 rats were used for these experiments. Message levels of preproendothelin-1 (preproET-1) were measured from the retina of diabetic and nondiabetic rats using competitive polymerase chain reaction (PCR) techniques.

RESULTS

Retinal blood flow was reduced (33%, P < 0.001) in diabetic rats compared to nondiabetic rats. BQ-123, an ETA receptor antagonist, but not saralasin, an angiotensin receptor antagonist, increased retinal blood flow in a dose-dependent manner in diabetic (EC50 of 8 x 10(-7) M) and in nondiabetic rats (EC50 of 8 x 10(-8) M). Besides being resistant to BQ-123, the maximal response in diabetic animals occurred 20 minutes later than in nondiabetic animals. Decreasing ET-1 levels by inhibiting endothelin-converting enzyme with phosphoramidon normalized retinal blood flow in diabetic rats. In nondiabetic rats, the intravitreous injection of exogenous ET-1 (10(-8) M) resulted in retinal blood flow decreases comparable to those measured in diabetic animals, and the subsequent injection of 10(-4) M BQ-123 produced retinal blood flow changes comparable to those measured in BQ-123 injected diabetic rats. Comparison of preproET-1 messenger RNA expression in the retina, brain and lung of control and diabetic rats using quantitative PCR and Northern blot analysis showed 2.0- and 1.7-fold increases in the retina and the brain, respectively, without changes in the lung.

CONCLUSIONS

These data suggest that ET-1 is involved in the regulation of retinal blood flow in normal physiologic outcome, and an increase in the endogenous expression of ET-1 contributes to the reduction of retinal blood flow reported in the early stages of diabetes mellitus.

Endothelin-1 action via endothelin receptors is a primary mechanism modulating retinal circulatory response to hyperoxia

PURPOSE

To determine the role of endothelin (ET)-ETA receptor mediation and endogenous production of endothelin-1 (ET-1) in the retinal response to hyperoxia.

METHODS

Brown-Norway rats (n = 30) were injected intravitreally with an ETA receptor-selective antagonist, BQ-123, and an inhibitor of ET-converting enzyme (ECE), phosphoramidon, and were exposed to a 100% oxygen breathing mixture. Control rats underwent intravitreal injection of vehicle alone (2.5% Emulphor in phosphate-buffered saline). The retinal hemodynamic responses were analyzed using video-based fluorescein angiography (VFA) methodology. Baseline measurements were made with the animals breathing room air, and this was followed by intravitreal injections of the above agents. Subsequent VFA measurements were made after 5, 10, and 15 minutes of breathing 100% oxygen.

RESULTS

The 10 rats injected with vehicle alone demonstrated the expected retinal response to hyperoxia, with significant (P < 0.001) vessel constriction (18% +/- 5%), an increase in retinal mean circulation time (0.84 +/- 0.13 seconds in room air and 1.59 +/- 0.27 seconds in 100% oxygen), and a decrease in blood flow (110.7 +/- 19.2 pixel2/second in room air and 41.9 +/- 9.0 pixel2/second in 100% oxygen), compared to values measured during room air breathing. The hyperoxic response in rats (n = 9) injected with 10(-4) M BQ-123 was significantly (P < 0.001) blunted compared to the group injected with vehicle alone. In contrast, intravitreal injection of saralasin, a specific angiotensin II receptor antagonist, had no significant effect on the retinal response to hyperoxia (n = 5). Intravitreal phosphoramidon (10(-3) M, n = 6) injection also resulted in a significantly (P < 0.001) blunted circulatory response to hyperoxia compared to rats injected with vehicle alone. This blunted response after ECE inhibition was comparable to that measured after ETA receptor antagonism with BQ-123 injection.

CONCLUSIONS

These results demonstrate that the enhancement of ET-1 action, possibly caused by the activation of ECE, plays a primary role in regulating the retinal hemodynamic response to hyperoxia.