Multiple factors in the prediction of risk of proliferative diabetic retinopathy

Tilted disc syndrome (TDS): New hypotheses for posterior segment complications and their implications in other retinal diseases

Tilted disc syndrome (TDS) is considered a congenital anomaly due to a delayed closure of the embryonic fissure. It is characterized by an oblique orientation of the axis of the optic disc, associated with other posterior pole anomalies such as inferior crescent, situs inversus and inferior staphyloma. The aim of this review was to summarize the data supporting the current hypotheses for the pathogenesis of TDS, and its anatomical and functional clinical consequences. Recent imaging techniques, such as magnetic resonance imaging, wide-field fundus imaging, and 2- and 3-D optical coherence tomography have provided a new perspective on TDS and its complications. Different abnormalities have previously been reported, both in the anterior and posterior segments. The focus was on vision-threatening chorioretinal changes or complications, including choroidal neovascularization and serous retinal detachments and their therapeutic options. Based on clinical observations, assumptions were proposed to understand the occurrence of complications such as chorioretinal degenerative changes, choroidal neovascularization and polypoidal choroidal vasculopathy, macular serous retinal detachment, myopic foveoschisis and chorioretinal folds. These hypotheses could be referred to as the curvature "breaking point" hypothesis, the uneven growth "tractional" hypothesis, the "container-content" imbalance hypothesis, and the "choroidal funnel" hypothesis. Because these complications could also occur in other contexts, understanding the pathogenesis of TDS complications could help to understand their pathophysiology.

Temporal bias in case-control design: preventing reliable predictions of the future

One of the primary tools that researchers use to predict risk is the case-control study. We identify a flaw, temporal bias, that is specific to and uniquely associated with these studies that occurs when the study period is not representative of the data that clinicians have during the diagnostic process. Temporal bias acts to undermine the validity of predictions by over-emphasizing features close to the outcome of interest. We examine the impact of temporal bias across the medical literature, and highlight examples of exaggerated effect sizes, false-negative predictions, and replication failure. Given the ubiquity and practical advantages of case-control studies, we discuss strategies for estimating the influence of and preventing temporal bias where it exists.

Unraveling the role of genetics in the pathogenesis of diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular disease of the retina and the leading cause of visual disability in diabetic patients. Genetic factors have shown to play a pivotal role in DR onset, and several candidate genes have been associated with its progression. A literature search was performed to identify the genes known to be associated with DR through linkage analysis, candidate gene association, and genome-wide association studies (GWAS). A further literature search was performed to discover their potential connection with various biological pathways. A total of 65 genes were found and several of these genes belong to major signaling pathways known to play a significant role in DR, including systemic inflammation, angiogenesis, and neurogenesis. A comprehensive analysis presented in this review will be helpful in unraveling the role of genetics in the pathogenesis of DR.

The association of smoking and risk of diabetic retinopathy in patients with type 1 and type 2 diabetes: a meta-analysis

PURPOSE

To clarify the relevance between smoking and diabetic retinopathy in patients with type 1 and type 2 diabetes mellitus.

METHODS

Published evidence were searched in MEDLINE and EMBASE from the databases began until Feb. 2017. Studies evaluating the association between smoking and diabetic retinopathy or evaluating the risk factors of diabetic retinopathy including smoking were included.

RESULTS

Totally 73 studies were identified, among which 19 studies included type 1 diabetes patients and 56 studies included type 2 diabetes patients. In type 1 diabetes, compare with non-smokers, the risk of diabetic retinopathy significantly increased in smokers (risk ratio (RR) = 1.23, 95% CI 1.14, 1.33, P < 0.001), and the risk of proliferative diabetic retinopathy also significantly increased in smokers (RR = 1.48, 95% CI 1.20, 1.81, P < 0.001). In type 2 diabetes, compare with non-smokers, the risk of diabetic retinopathy significantly decreased in smokers (RR = 0.92, 95% CI 0.86, 0.98, P = 0.02) and the risk of proliferative diabetic retinopathy also significantly decreased in smokers (RR = 0.68, 95% CI 0.61, 0.74, P < 0.001).

CONCLUSIONS

Compare with non-smokers, the risk of diabetic retinopathy significantly increased in smokers with type 1 diabetes while significantly decreased in smokers with type 2 diabetes. However, this result did not change the importance of smoking cessation for public health.

HLA-DQB1 Subtypes Predict Diabetic Retinopathy in Patients with Type I Diabetes Mellitus

Purpose

To investigate if diabetic patients without diabetic retinopathy despite long disease duration have different human leukocyte antigen (HLA) status vs those with an early onset of retinopathy.

Methods

Retrospective, nonrandomized, masked comparative study. Type 1 diabetic patients with a disease onset before age 30 were recruited to the study. The study population consisted of two groups of diabetic patients: those with normal retinopathy course (retinopathy developed during the first 20 years of diabetes onset) (23 patients) and those with postponed retinopathy (no obvious retinopathy in spite of passing 20 years of diabetes) (19 patients). These groups were matched with regard to level of glycemic control, blood pressure, and lipid profile. A group of 23 healthy patients served as controls. HLA-DQB1 typing of blood samples was done using a polymerase chain reaction with sequence-specific primer (PCR-SSP) method.

Results

HLA-DQB1*0201/HLA-DQB1*0501 and HLA-DQB1*0201/HLA-DQB1*0504 haplotypes were more common among type 1 diabetic patients with normal retinopathy course than those with postponed retinopathy (26.1% vs 0.0%; p=0.019). HLA-DQB1*0301 and HLA-DQB1*0304 were less common among those diabetic patients with normal retinopathy course than those with a postponed retinopathy (63.2% vs 34.8%; p=0.067).

Conclusions

Some haplotypes seem to predispose diabetic patients to diabetic retinopathy. HLA typing may be beneficial for predicting the prognosis of diabetic retinopathy in younger diabetic patients.

Myopia is Inversely Associated With the Prevalence of Diabetic Retinopathy in the South Korean Population

PURPOSE

Diabetic retinopathy is a major cause of irreversible vision loss. Recent studies have suggested that myopia may be negatively correlated with the prevalence of diabetic retinopathy. We sought to further investigate the association between refractive error and the likelihood of having diabetic retinopathy in a cross-sectional, population-based study of the South Korean population.

DESIGN

Cross-sectional study.

METHODS

Data were included from right eyes of 13 424 participants who were 40 years and older with gradable fundus photographs of the Fourth and the Fifth Korea National Health and Nutrition Examination Survey. Diabetic retinopathy was graded using standard fundus photographs. Autorefraction data were collected to calculate spherical equivalent of refraction in diopters (D) and further classified into 4 groups: hyperopia (≥1.0 D), emmetropia (-0.99 D to 0.99 D), mild myopia (-1.0 D to -2.99 D), and moderate to high myopia (≤-3.0 D). Demographic, comorbidity, and health-related behavior information was obtained via interview. A multivariate model was used to evaluate the association between the diagnosis of any diabetic retinopathy and the refractive status.

RESULTS

Mild myopia and moderate to high myopia groups were negatively associated with development of any diabetic retinopathy (odds ratio [OR] 0.42; 95% confidence interval [CI] 0.18-0.97 and OR 0.14; 95% CI 0.02-0.88, respectively). In addition, for every 1 D increase in spherical equivalent, there was a 30% increase of having diabetic retinopathy (OR 1.30; 95% CI, 1.08-1.58).

CONCLUSIONS

Our results from a population-based study suggest that myopic status is associated with lower odds of having diabetic retinopathy in the South Korean population.

Myopia and/or longer axial length are protective against diabetic retinopathy: a meta-analysis

PURPOSE

To evaluate the current evidence of the relationship between myopia, together with its structural and refractive component, and diabetic retinopathy (DR) risk.

METHODS

A systematic search was performed up to April, 2015. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated employing random-effects models. Three models were used to assess the association between myopia and risk of DR: axial length (AL) (per millimetre increase) and DR; myopia (myopia versus non-myopia) and DR; refractive error (RE) (per D decrease) and DR. Publication bias of the literature was evaluated using Begg's funnel plots and Egger's test.

RESULTS

A total of 11 studies that met the predefined criteria were included in this meta-analysis. Overall, longer AL (per millimetre increase) was associa-ted with a significantly decreased risk of DR (combined OR, 0.75; 95% CI, 0.65-0.86; p < 0.001); myopic eyes (myopia versus non-myopia) showed a lower risk of DR (combined OR, 0.70; 95% CI, 0.58-0.85; p < 0.001). A greater degree of myopic RE (per D decrease) also revealed a significantly decreased risk of DR (combined OR, 0.89; 95% CI, 0.85-0.93; p < 0.001). The sensitivity analyses and cumulative meta-analysis showed similar results. No publication bias was detected in any of the three models.

CONCLUSIONS

This meta-analysis suggests that both myopic refraction and longer AL are associated with a lower risk of DR. Further studies are needed to determine exact mechanisms underpinning the protective effect of myopia against DR.

Biomarkers in Diabetic Retinopathy

There is a global diabetes epidemic correlating with an increase in obesity. This coincidence may lead to a rise in the prevalence of type 2 diabetes. There is also an as yet unexplained increase in the incidence of type 1 diabetes, which is not related to adiposity. Whilst improved diabetes care has substantially improved diabetes outcomes, the disease remains a common cause of working age adult-onset blindness. Diabetic retinopathy is the most frequently occurring complication of diabetes; it is greatly feared by many diabetes patients. There are multiple risk factors and markers for the onset and progression of diabetic retinopathy, yet residual risk remains. Screening for diabetic retinopathy is recommended to facilitate early detection and treatment. Common biomarkers of diabetic retinopathy and its risk in clinical practice today relate to the visualization of the retinal vasculature and measures of glycemia, lipids, blood pressure, body weight, smoking, and pregnancy status. Greater knowledge of novel biomarkers and mediators of diabetic retinopathy, such as those related to inflammation and angiogenesis, has contributed to the development of additional therapeutics, in particular for late-stage retinopathy, including intra-ocular corticosteroids and intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') agents. Unfortunately, in spite of a range of treatments (including laser photocoagulation, intraocular steroids, and anti-VEGF agents, and more recently oral fenofibrate, a PPAR-alpha agonist lipid-lowering drug), many patients with diabetic retinopathy do not respond well to current therapeutics. Therefore, more effective treatments for diabetic retinopathy are necessary. New analytical techniques, in particular those related to molecular markers, are accelerating progress in diabetic retinopathy research. Given the increasing incidence and prevalence of diabetes, and the limited capacity of healthcare systems to screen and treat diabetic retinopathy, there is need to reliably identify and triage people with diabetes. Biomarkers may facilitate a better understanding of diabetic retinopathy, and contribute to the development of novel treatments and new clinical strategies to prevent vision loss in people with diabetes. This article reviews key aspects related to biomarker research, and focuses on some specific biomarkers relevant to diabetic retinopathy.

Diabetic retinopathy and systemic factors

Diabetic retinopathy, an oculardisease, is governed by systemic as well as local ocular factors. These include primarily chronic levels of blood glucose. Individuals with chronically elevated blood glucose levels have substantially more, and more severe, retinopathy than those with lower blood glucose levels. The relationship of blood glucose to retinopathy is continuous, with no threshold although individuals with hemoglobin A1c levels (a measure of chronic glycemia) <6.5%, generally develop little or no retinopathy. Blood pressure levels have been claimed to influence retinopathy development and progression, but multiple controlled clinical trials of antihypertensive agents in diabetic subjects have produced only weak evidence of benefit from blood pressure lowering on the incidence and progression of diabetic retinopathy. Elevated blood lipids seem to play a role in the progression of retinopathy, and two trials of fenofibrate, a lipid-lowering agent that has not proved effective in preventing cardiovascular disease, have shown benefit in preventing retinopathy progression. The mechanism of this effect may not, however, be directly related to the reduction in blood lipids. Finally, there is strong, but only circumstantial, evidence for a genetic or epigenetic influence on the pathogenesis of diabetic retinopathy. Despite the power of large-scale epidemiologic studies and modern molecular biological and computational techniques, the gene or genes, which predispose or protect against the development and progression of diabetic retinopathy remain elusive.

Refractive error and ocular parameters: comparison of two SD-OCT systems

PURPOSE

Spectral domain optical coherence tomography (OCT) was used to examine the influence of refractive error (RE) on foveal retinal and choroidal thicknesses and scleral canal width (SCW). The performance of the Cirrus and Bioptigen spectral domain OCT instruments was compared in the same eyes.

METHODS

Both eyes of 40 healthy human subjects, aged 22 to 38 years, were dilated and imaged, with the Cirrus OCT, using 6-mm five-line rasters collapsed into one line, one centered on the fovea and one bisecting the optic nerve head. Seventy-two of the same eyes were imaged with the Bioptigen OCT, using 6- by 6-mm scans, one centered on the fovea and one on the optic nerve head. Subfoveal retinal and choroidal thicknesses and SCW were measured. Axial lengths (ALs) and REs were obtained using an IOLMaster and a Grand Seiko autorefractor, respectively.

RESULTS

Only right eyes were included in analyses. Spherical equivalent REs ranged from -12.18 to +8.12 diopters (mean [±SD], -3.44 [±4.06] diopters), and ALs ranged from 20.56 to 29.17 mm (mean [±SD], 24.86 [±1.91] mm). Myopia was associated with relatively thin choroids at the fovea (p < 0.05) but normal retinal thickness. Scleral canal width was significantly correlated with AL as measured with the Bioptigen OCT (p < 0.05). Retinal and choroidal thicknesses recorded with the Bioptigen OCT tended to be smaller than values obtained with the Cirrus OCT (mean difference, 5.63 and 24.76 μm, respectively), whereas the converse was true for the SCW (mean difference, 25.45 μm).

CONCLUSIONS

The finding that high myopes tend to have a thinner subfoveal choroid is consistent with previous studies. That high myopia was linked to enlarged scleral canals may help to explain the increased risk of glaucoma in myopia. Observed differences obtained with the Cirrus and Bioptigen instruments urge caution in comparing results collected with different instruments.

Diabetic retinopathy: variations in patient therapeutic outcomes and pharmacogenomics

Diabetes and its microvascular complications in patients poses a significant challenge and constitutes a major health problem. When it comes to manifestations in the eye, each case of diabetic retinopathy (DR) is unique, in terms of the phenotype, genotype, and, more importantly, the therapeutic response. It is therefore important to identify factors that distinguish one patient from another. Personalized therapy in DR is a new trend aimed at achieving maximum therapeutic response in patients by identifying genotypic and phenotypic factors that may result in less than optimal response to conventional therapy, and consequently, lead to poorer outcome. With advances in the identification of these genetic markers, such as gene polymorphisms and human leucocyte antigen associations, as well as development of drugs that can target their effects, the future of personalized medicine in DR is promising. In this comprehensive review, data from various studies have been analyzed to present what has been achieved in the field of pharmacogenomics thus far. An insight into future research is also provided.

Association between myopia and diabetic retinopathy: a review of observational findings and potential mechanisms

A protective, but inconsistent association between myopia and a decreased risk of diabetic retinopathy (DR) has been suggested in several studies. However, it is unclear whether the structural, or the refractive components of myopia; or both, is the main contributor to this protective relationship. This paper provides a comprehensive review of existing evidence on the association between myopia, and its structural (axial length [AL], anterior chamber depth [ACD]) and refractive (lens biometry and corneal curvature [CC]) components, with DR. 11 studies consisting of 7230 subjects from 1960 to April 2012, were reviewed. A longer AL was the only variable associated with a lower risk and severity of DR. Therefore, the available evidence suggests that AL is the main contributor to the protective influence of myopia on DR observed in earlier studies. Further investigations are now needed to determine the mechanisms by which AL protects against DR.

HLA genes, islet autoantibodies and residual C-peptide at the clinical onset of type 1 diabetes mellitus and the risk of retinopathy 15 years later

Aims/Hypothesis

HLA genes, islet autoantibodies and residual C-peptide were studied to determine the independent association of each exposure with diabetic retinopathy (DR), 15 years after the clinical onset of type 1 diabetes in 15–34 year old individuals.

Methods

The cohort was identified in 1992 and 1993 by the Diabetes Incidence Study in Sweden (DISS), which investigates incident cases of diabetes for patients between 15 and 34 years of age. Blood samples at diagnosis were analyzed to determine HLA genotype, islet autoantibodies and serum C-peptide. In 2009, fundus photographs were obtained from patient records. Study measures were supplemented with data from the Swedish National Diabetes Registry.

Results

The prevalence of DR was 60.2% (148/246). Autoantibodies against the 65 kD isoform of glutamate decarboxylase (GADA) at the onset of clinical diabetes increased the risk of DR 15 years later, relative risk 1.12 for each 100 WHO units/ml, [95% CI 1.02 to 1.23]. This equates to risk estimates of 1.27, [95% CI 1.04 to 1.62] and 1.43, [95% CI 1.06 to 1.94] for participants in the highest 25^th (GADA>233 WHO units/ml) and 5^th percentile (GADA>319 WHO units/ml) of GADA, respectively. These were adjusted for duration of diabetes, HbA_1c, treated hypertension, sex, age at diagnosis, HLA and C-peptide. Islet cell autoantibodies, insulinoma-antigen 2 autoantibodies, residual C-peptide and the type 1 diabetes associated haplotypes DQ2, DQ8 and DQ6 were not associated with DR.

Conclusions

Increased levels of GADA at the onset of type 1 diabetes were associated with DR 15 years later. These results, if confirmed, could provide additional insights into the pathogenesis of the most common microvascular complication of diabetes and lead to better risk stratification for both patient screenings and DR treatment trials.

Prevention of diabetic eye disease: the commonest cause of blindness in individuals younger than 65 years

There has been a considerable advancement in the treatment of diabetes and understanding of the biochemical mechanisms underlying diabetic complications in the last 20 years. However, this advancement has not translated into a consistent reduction in diabetic retinopathy, one of the most frightening complications of diabetes mellitus. It is probable that greater attention to preventive intervention will help reduce the damage load in the next future, and that several drugs for the treatment of more advanced stages of diabetic retinopathy will become available. Competent strategies targeting prevention based on screening programs should be proposed to reduce the burden and to improve the clinical outcome of this devastating diabetes complication.

Are myopic eyes less likely to have diabetic retinopathy?

PURPOSE

Eyes with myopia may be less likely to develop diabetic retinopathy (DR). The relationship between refractive error, ocular biometry, and DR therefore was investigated.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Persons with diabetes from the Singapore Malay Eye Study (SiMES).

METHODS

Diabetes mellitus was defined as random glucose of 11.1 mmol/l or more, use of diabetic medication, or a physician diagnosis of diabetes. Spherical equivalent refraction (SE) was assessed using an autokeratorefractometer and subjective refraction. Axial length (AL) and anterior chamber depth (ACD) were measured by IOLMaster (Carl Zeiss Meditec AG, Jena, Germany). Diabetic retinopathy was graded from retinal photographs.

MAIN OUTCOME MEASURES

Any DR was defined by characteristic lesions defined by the Early Treatment Diabetic Retinopathy Study (ETDRS); moderate DR by ETDRS retinopathy severity scores of 43 or higher; and vision-threatening retinopathy by severe nonproliferative retinopathy, proliferative DR, or clinically significant macular edema.

RESULTS

Of 3280 adult Malay participants (78.7% response), 629 persons with diabetes contributed to this analysis. In multivariate analyses adjusting for age, gender, education, height, cataract, hypertension, hemoglobin A1c, and other factors, eyes with myopic SE were less likely to have any DR (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.84-0.96; P = 0.002, per 1-diopter [D] decrease), moderate DR (OR, 0.83; 95% CI, 0.73-0.93; P = 0.001, per 1-D decrease), and vision-threatening DR (OR, 0.77; 95% CI, 0.67-0.88; P<0.001, per 1-D decrease). Eyes with longer AL were less likely to have any DR (OR, 0.86; 95% CI, 0.75-0.99; P = 0.041, per 1-mm increase), moderate DR (OR, 0.80; 95% CI, 0.62-1.05; P = 0.11, per 1-mm increase), and vision-threatening DR (OR, 0.63; 95% CI, 0.40-0.99; P = 0.044, per mm increase). Eyes with deeper ACD were less likely to have moderate DR (OR, 0.32; 95% CI, 0.16-0.64; P = 0.001, per 1-mm increase) and vision-threatening DR (OR, 0.14; 95% CI, 0.06-0.36; P = 0.001, per 1-mm increase).

CONCLUSIONS

Myopic refraction and longer AL are associated with a lower risk of DR, particularly vision-threatening retinopathy, without any evidence of a threshold.

Blood pressure and cardiac autonomic function in relation to risk factors and treatment perspectives in Type 1 diabetes

The cumulative incidence of diabetic nephropathy in Type 1 diabetes mellitus is in the order of 25 30%. The recognition that elevated blood pressure (BP) is a major factor in the progression of these patients to end-stage renal failure has led to the widespread use of antihypertensive therapy in order to preserve glomerular filtration rate and ultimately to reduce mortality. The routine measurement of microalbuminuria allows early identification of the subgroup of patients at increased risk of developing clinical nephropathy. Microalbuminuric Type 1 diabetic patients show a number of characteristic pathological abnormalities. In addition to elevated BP and abnormal circadian rhythm, there are also associated abnormalities of vagal function, lipid profile and endothelial function, as well as an increased prevalence of retinopathy. The first section of this two-part review focusses on the early changes associated with renal involvement in Type 1 diabetes. It addresses the associations between urinary albumin excretion, glycaemic control, smoking, BP, circadian BP variation, QT interval abnormalities and autonomic function in three groups of patients; those with normoalbuminuria, those progressing towards microalbuminuria and those with established low-grade microalbuminuria.

Controlled multicenter study on the effect of computer assistance in intensive insulin therapy of type 1 diabetics

This paper describes the results of a controlled multicenter study on the effect of the computer assistance in the intensive insulin therapy. The patient collective consisted of 50 diabetics, randomly divided in two groups with 25 patients per group. The Multiple Subcutaneous Injection (MSI) group was treated with the usually intensive regimen. The treatment in the Computer Assisted Meal Related Insulin Therapy (CAMIT) group was performed with the aid of a specialized pocket computer. Only in the CAMIT group during the study we observed a significant decrease: in the mean blood glucose (BG) with 1.6+/-0.4 mmol/l (P<0.05), in the BG amplitudes by 1.0+/-0.3 mmol/l (P<0.05), and in the hypoglycemia frequency-from 2.0+/-0.4 to 1.2+/-0.3 (P<0.01) hypoglycemic episodes weekly. The HbA(1) values fell in the MSI group by 3.7+/-3.7% and in the CAMIT group significantly by 15.6+/-2.2% (P<0.05). Consequently, the computer-assisted intensive insulin therapy resulted in an improved metabolic control.

HLA-DR3 and DR4 and their relation to the incidence and progression of diabetic retinopathy

PURPOSE

Cross-sectional data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy indicated that patients with HLA-DR4, but not DR3, were more likely to have prevalent proliferative retinopathy than those without both antigens. We describe the relation of HLA-DR3 and DR4 antigens to the 14-year incidence and progression of diabetic retinopathy and macular edema in this cohort.

DESIGN

A population-based cohort study.

PARTICIPANTS

A probability sample of male and female patients receiving primary care for diabetes in 11 counties of southern Wisconsin.

METHODS

Participants were invited for a baseline examination in 1980 to 1982, with follow-up examinations at 4, 10, and 14 years later. At the 4-year examination, a random sample of participants (n = 428) diagnosed with diabetes before the age of 30 and taking insulin were selected for HLA-DR typing.

MAIN OUTCOME MEASURES

Fourteen-year incidence and progression of diabetic retinopathy and macular edema based on masked stereoscopic fundus photographic grading.

RESULTS

There was no relation between HLA-DR3 and DR4 status with the 14-year incidence and progression of diabetic retinopathy, progression to proliferative retinopathy, and incidence of macular edema. Patients with either HLA-DR3 or DR4 were less likely to progress to proliferative retinopathy compared with those who were negative for both, although these relations were not statistically significant. The associations did not vary after adjusting for hypertension status, baseline retinopathy, and glycosylated hemoglobin levels, or after stratifying by duration of diabetes (less than 10 years vs. 10 years or more) and age at diagnosis of diabetes (less than 15 years vs. 15 years or more). Furthermore, 10-year mortality and 14-year nephropathy rates did not differ by HLA-DR3 or DR4 status, suggesting that selective mortality did not explain the pattern of associations seen.

CONCLUSIONS

In contrast to the initial cross-sectional findings, these data suggest that HLA-DR3 or DR4 status is unrelated to 14-year incidence and progression of diabetic retinopathy. The discrepancy may be related to increasing homogeneity of retinopathy and diminishing power to detect small differences, but it may also reflect the uncertain and inconsistent effects of HLA-DR3 or DR4 on the development and progression of diabetic retinopathy.

Relation of apolipoprotein (a) phenotypes to diabetic retinopathy in elderly type 2 diabetes

The aim of this study was to clarify the relationship between apolipoprotein (a) (apo (a) ) phenotypes and diabetic retinopathy in elderly type 2 diabetes. Serum Lp (a) concentrations and apo (a) phenotypes were analyzed in 250 diabetic patients aged 60 to 88 years old. Apo (a) phenotypes were classified into 7 subtypes (F, B, S1, S2, S3, S4, O (Null) ) by the method SDS electrophoresis with Western blotting. Patients were divided into two groups according to their apo (a) phenotypes:a low molecular weight (LMW) Lp (a) group, and a high molecular weight (HML) Lp (a) group. Patients were classified as having one of 4 types of diabetic retinopathy: no retinopathy (R0), simple retinopathy (R1), pre-proliferative retinopathy (R2), and proliferative retinopathy (R3). There was a significant association between serum Lp (a) levels and severity of diabetic retinopathy (p<0.001). A gradual trend toward increasing serum Lp (a) levels was observed across the groups (from R0 to R3). A significantly greater percentage of LMW Lp (a) was observed in the R1, R2, and R3 groups than in the R0 group (42.9% (p<0.001), 27.0% (p<0.01), and 27.3% (p<0.05) vs. 10.4%). Multiple logistic regression analysis revealed that duration of diabetes and LMW Lp (a) are independent risk factors for diabetic retinopathy. These results provide significant evidence that LMW Lp (a) contributes to an increased risk of diabetic retinopathy in elderly type 2 diabetes.

Tumor necrosis factor allelic polymorphism with diabetic retinopathy in India

The association of tumor necrosis factor (TNF) with diabetic retinopathy (DR) has been described previously. A total of 207 Asian Indian patients of 15-year duration of type 2 diabetes were identified. This group included (i) 100 patients with DR and (ii) 107 patients without retinopathy (DNR). In this study, we correlated the length of the (GT)n microsatellite di-nucleotide repeat upstream to the promoter region of TNF gene with susceptibility for the development of retinopathy. The microsatellite was polymerase chain reaction amplified and electrophoresed on polyacrylamide gel and silver stained. In our study population, there were 18 alleles ranging from 97 to 131 base pairs (bp). Allele 4 (103 bp) had a higher prevalence (9.81%) in the DNR group compared to that (2.5%) in the DR group (P=0.002). Patients with retinopathy and allele 8 (111 bp) had a tendency to develop proliferative diabetic retinopathy (PDR). In this study of Indian subjects, it is suggested that allele 4 is a low risk allele for developing retinopathy and allele 8 (111 bp) shows an association with PDR.

Coagulation pathways and diabetic retinopathy: abnormal modulation in a selected group of insulin dependent diabetic patients

AIMS

To investigate whether diabetic retinopathy (DR), already associated with microvascular alterations, ischaemia, and endothelial dysfunction, was also characterised by abnormal modulation of coagulation pathways.

METHODS

Plasma samples, collected from 67 type 1 diabetics comparable for age, duration of disease (DD), and metabolic control (MC), were processed for prothrombin degradation products (F1+2) and factor VII coagulant activity (FVII:c). 50 normal subjects served as a control group. The ETDRS-Airlie House Classification of DR was used.

RESULTS

A significant correlation between FVII:c and F1+2 plasma concentrations was observed (p <0.05). FVII:c (p <0.005) and F1+2 (p <0.0001) levels were higher in diabetics than in controls, especially in patients with proliferative DR (FVII:c p <0.0001; F1+2 p<0.005). However, cases without retinal lesions and healthy subjects did not differ significantly (FVII:c and F1+2 p >0.05).

CONCLUSIONS

These findings pointed out the presence of a hypercoagulable state associated with endothelial dysfunction in patients with insulin dependent diabetes mellitus (IDDM), demonstrated both by increased FVII:c and F1+2 plasma levels. Moreover, the observation of different DR related degrees of procoagulant activity, despite comparable DD and MC, strengthens the hypothesis of multiple risk factors in the pathogenesis of DR.

Epidemiology of Diabetes Interventions and Complications (EDIC). Design, implementation, and preliminary results of a long-term follow-up of the Diabetes Control and Complications Trial cohort

OBJECTIVE

The Diabetes Control and Complications Trial (DCCT) demonstrated the powerful impact of glycemic control on the early manifestations of microvascular complications. Contemporary prospective data on the evolution of macrovascular and late microvascular complications of type 1 diabetes are limited. The Epidemiology of Diabetes Interventions and Complications (EDIC) study is a multicenter, longitudinal, observational study designed to use the well-characterized DCCT cohort of > 1,400 patients to determine the long-term effects of prior separation of glycemic levels on micro- and macrovascular outcomes.

RESEARCH DESIGN AND METHODS

Using a standardized annual history and physical examination, 28 EDIC clinical centers that were DCCT clinics will follow the EDIC cohort for 10 years. Annual evaluation also includes resting electrocardiogram. Doppler ultrasound measurements of ankle/arm blood pressure, and screening for nephropathy. At regular intervals, a timed 4-h urine is collected, lipid profiles are obtained, and stereoscopic fundus photographs are taken. In addition, dual B-mode Doppler ultrasound scans of the common and internal carotid arteries will be performed at years 1 and 6 and at study end.

RESULTS

Written informed consent was obtained from 96% of the DCCT subjects. The participants, compared with nonparticipants, tended to have better glycemic control at the completion of the DCCT and were more likely to have their diabetes care provided by DCCT personnel. The EDIC baseline measurement stratified by sex delineates multiple cardiovascular disease risk factor differences such as age (older in men), waist-to-hip ratio (higher in men). HDL cholesterol (lower in men), hypertension (more prevalent in men), and maximum intimal-medial thickness of common and internal carotid arteries (thicker in men). Of the original conventional treatment group, 69% have changed to continuous subcutaneous insulin infusion or multiple daily injections. Although the mean HbA1c difference between the intensive and conventional treatment groups narrowed at EDIC years 1 and 2, HbA1c remained significantly lower in the intensive group. Of all expected clinic visits, 95% were completed, and the quality of EDIC data is very similar to that observed in the DCCT.

CONCLUSIONS

Although obvious problems exist in extended follow-up studies of completed clinical trials, these are balanced by the value of continued systematic observation of the DCCT cohort. In contrast to other epidemiologic studies, EDIC will provide 1) definitive data on type 1 as distinct from type 2 diabetes; 2) reliance on prospective rather than on cross-sectional analysis; 3) long-term follow-up in a large population; 4) consistent use of objective, reliable measures of outcomes and glycemia; and 5) observation of patients from before the onset of complications.

Ocular neovascularization: an epidemiologic review

Neovascularization occurs in many eye diseases, and its epidemiologic impact is significant. However, data on the prevalence and incidence of ocular neovascularization have never been compiled to demonstrate its pervasiveness. This overview of ocular angiogenesis provides a review of the epidemiologic literature for neovascularization in various parts of the eye, including the cornea, iris, retina, and choroid. Relevant disease states are reviewed, as are their risk factors, so that their pathogenesis can be better understood. Data on the prevalence and incidence of the major diseases involving angiogenesis are synthesized to provide statistical evidence of the span and magnitude of ocular neovascularization. These prevalence and incidence data on ocular neovascularization are extrapolated to USA population data where possible, and "worst-case" estimates are calculated as well. Information was gathered with a search of the MEDLINE database, published monographs and volumes, and consultation with a number of primary authors. This study attempts to unify much of past and present epidemiologic research, and the information is presented in sections divided according to the anatomy of the eye.

The association between cigarette smoking and ocular diseases

Tobacco smoke is composed of as many as 4,000 active compounds, most of them toxic on either acute or long-term exposure. Many of them are also poisonous to ocular tissues, affecting the eye mainly through ischemic or oxidative mechanisms. The list of ophthalmologic disorders associated with cigarette smoking continues to grow. Most chronic ocular diseases, with the possible exception of diabetic retinopathy and primary open-angle glaucoma, appear to be associated with smoking. Both cataract development and age-related macular degeneration, the leading causes of severe visual impairment and blindness, are directly accelerated by smoking. Other common ocular disorders, such as retinal ischemia, anterior ischemic optic neuropathy, and Graves ophthalmopathy, are also significantly linked to this harmful habit. Tobacco smoking is the direct cause of tobacco-alcohol amblyopia, a once common but now rare disease characterized by severe visual loss, which is probably a result of toxic optic nerve damage. Cigarette smoking is highly irritating to the conjunctival mucosa, also affecting the eyes of nonsmokers by passive exposure (secondhand smoking). The dangerous effects of smoking are transmitted through the placenta, and offspring of smoking mothers are prone to develop strabismus. Efforts should be directed toward augmenting the campaign against tobacco smoking by adding the increased risk of blindness to the better-known arguments against smoking. We should urge our patients to quit smoking, and we must make them keenly aware of the afflictions that can develop when smoke gets in our eyes.

Lipids and lipoproteins in diabetic adolescents and young adults with retinopathy

PURPOSE

To compare serum concentrations of lipoproteins and apolipoproteins in insulin-dependent diabetic patients with and without retinopathy.

METHODS

A cross-sectional study was performed on 42 diabetic adolescents and young adults with different degrees of retinopathy. The mean +/- SD age of the patient was 21.1 years (range 12.8-27.9 years); their mean duration of diabetes was 12.3 years (range 7.1-19.9 years). Their glycosylated haemoglobin (HbA1c) and fructosamine were respectively 10.2% (8.2-15.4%) and 280.8 mumol/l (202.1-458.5 mumol/l). Forty-two diabetics without retinopathy similar to the study population as regards age, sex, duration of disease, HbA1c and microalbuminuria values, and 42 healthy subjects, served as controls.

RESULTS

Serum lipid and lipoprotein concentrations were not different from those of healthy controls in patients either with or without retinopathy. The diabetic patients were subdivided in two groups according to the degree of their retinopathy: background and preproliferative/proliferative retinopathy. Patients with preproliferative/proliferative retinopathy were found to have significantly higher lipoprotein (a) values than the other group (background, 73.3 IU/l; preproliferative/proliferative, 205.9 IU/l; p < 0.001).

CONCLUSION

The increase in lipoprotein (a) levels might play a role in the development of severe retinopathy.

Diabetic retinopathy in Down's syndrome

AIM

To determine the prevalence of diabetic retinopathy in patients with Down's syndrome and diabetes mellitus.

METHODS

Nine patients with Down's syndrome and diabetes mellitus were assessed. Factors recorded included type and duration of diabetes, level of diabetic control, blood pressure, urinalysis, and results of ophthalmological examination.

RESULTS

The duration of diabetes ranged from 8 to 41 years (mean 17.6 years). All had satisfactory glycaemic control and blood pressure measurements on the low side of normal (mean 106.6/70 mm Hg). One patient had early background diabetic retinopathy. The remainder had no evidence of diabetic retinopathy.

CONCLUSION

The low prevalence of diabetic retinopathy in these Down's syndrome patients, despite the long duration, is an interesting finding. It suggests some inherent protective factor against the development of diabetic retinopathy in this patient subgroup.

Inverse relationship between GAD65 antibody levels and severe retinopathy in younger type 1 diabetic patients

Several risk factors for severe non-proliferative and proliferative retinopathy in type 1 diabetes mellitus have been proposed without explaining the rapid progression of retinopathy in some patients. Since GAD65 autoantibodies (GAD65Abs) are detected against glutamic acid decarboxylase (GAD), which is mainly expressed in islets and nervous tissue in type 1 diabetic patients, the aim of the present investigation was to test the hypothesis whether GAD65Abs are associated with rapidly progressing severe retinopathy. Patients with severe non-proliferative or proliferative retinopathy (n = 27) were compared with another group, which in spite of long diabetes duration had no or only mild signs of retinopathy (n = 28). GAD65Abs were analysed in a radioimmunoassay using in vitro translated human GAD65, and the levels were expressed as an index in relation to positive and negative reference samples. Using a cut-off level representing the 99th percentile of normals, 6/27 (22%) with and 9/28 (32%) without severe retinopathy were considered GAD65Ab positive. Although there was no difference in the number of GAD65Ab positive patients, the GAD65Ab levels were lower in patients with (0.30; 0.11-0.64) than without (0.68; 0.34-1.12) severe retinopathy (P = 0.03). The patients were also subjected to HLA-DR and DQ typing by PCR and hybridization with oligospecific probes. DQ2/8 was more common in patients with (56%) than without (29%) severe retinopathy (P = 0.05), but DQ2/8 could not account for the lower GAD65Ab levels in patients with severe retinopathy. It is concluded that GAD65Ab levels are inversely correlated with severe retinopathy in young type 1 diabetic patients.

Genetic markers in early diabetic retinopathy of adolescents with type I diabetes

The aim of this study was to evaluate the role of HLA (human leucocyte antigen) class I (A, B, C) and class II (DR) alleles and familial insulin-dependent diabetes mellitus as possible risk markers for early retinopathy in a population of 103 Finnish adolescents with type I diabetes mellitus for 3.6-16.2 years. Fifty-one of the patients (49.5%) had signs of retinopathy in fundus photographs. HLA DR1 was found in 31% of the subjects with retinopathy, but in only 5% of those without retinopathy (p = 0.02). The corresponding figures for HLA DR1/4 were 17% and 2.6%, respectively (p = 0.22). The frequency of HLA DR3, DR4, or DR3/4 heterozygosity did not differ between the two groups of patients. Signs of early retinopathy showed thus an association with the presence of the HLA DR1 allele, and a mild protective effect of the HLA A9 and B40 alleles was indicated. Other HLA A, B, C, or DR alleles did not have any effect on the risk for early development of retinopathy, neither had a positive family history of type I diabetes.

Long-term influence of insulin dependent diabetes mellitus on refraction and its components: a population based twin study

AIM

To study whether refraction of the eye, or some of its components is influenced by duration of insulin dependent diabetes mellitus.

METHODS

From the young cohort of the population based Danish Twin Register, containing 20,888 twin pairs born between 1953 and 1982, all twin pairs having one or both partners affected with IDDM were searched. Autorefraction, autokeratometry, and ultrasonic biometric measurements were carried out on 45 twin pairs: 16 monozygotic (MZ) twin pairs, 14 dizygotic twin pairs of same sex (DZss), and 15 dizygotic twin pairs of opposite sex (DZos). To obtain an estimate of the influence of duration of diabetes, the intrapair differences in duration of diabetes were correlated with intrapair differences in refraction and each of its components.

RESULTS

Refraction was statistically significantly negatively correlated with duration of diabetes in the DZss group, and axial length correspondingly positively correlated. Surprisingly, refraction and axial length in the MZ group, adjusted for confounding factors, were correlated with diabetes duration in the opposite direction than in the DZss group, although not reaching statistical significance. Lens thickness was statistically significantly positively correlated with duration of diabetes in both MZ and DZ twins. Anterior chamber depth was negatively correlated with duration of diabetes in all the zygosity groups.

CONCLUSIONS

Studies of relations between refraction and duration of diabetes show diverging results. In the MZ group, a tendency to reduced axial length and corresponding hyperopia with increasing duration of diabetes was found. However, in the DZ group of same sex the opposite tendency was found. Increasing lens thickness and decreasing anterior chamber depth with increasing duration of diabetes have been confirmed in this study.

Diabetic eye disease

Diabetic retinopathy accounts for most visual loss in the United States among working-age individuals. With appropriate detection, evaluation, and treatment, the risk for severe visual loss from this condition is dramatically reduced. This article details the natural history, pathophysiology, complications, grading, evaluation, and treatment for patients with diabetic retinopathy and discusses potential novel treatment modalities currently under investigation.

Epidemiology of late diabetic complications. A basis for the development and evaluation of preventive programs

This article examines the relationship between duration and level of glycemia in patients with diabetes and the occurrence of complications in the eyes, kidneys, and heart. Emphasis is placed on those aspects that are relevant to the development and evaluation of preventive and therapeutic programs against these complications. Data on patients with insulin-dependent diabetes mellitus are reviewed, and the similarities and differences with the data on patients with non-insulin-dependent diabetes mellitus are discussed.

An association in non-insulin-dependent diabetes mellitus subjects between susceptibility to retinopathy and tumor necrosis factor polymorphism

In IDDM an association between diabetic retinopathy and polymorphic markers of MHC has been described. However, these associations are complicated by a primary association between the MHC and IDDM. Because the pathogenesis of retinopathy is likely to be the same in IDDM and NIDDM, NIDDM subjects with retinopathy would be the ideal population to study for an association with MHC markers. The following South Indian subjects were therefore studied: unselected NIDDM (n = 76), unselected IDDM (n = 99), non-diabetic controls (n = 96), NIDDM subjects with maculopathy (MAC), n = 55, NIDDM subjects with proliferative retinopathy (PR), n = 53, and without retinopathy (LTD), n = 46. DNA was amplified and studied using a microsatellite polymorphism located 3.5 kb upstream of TNF-beta within the MHC class III region on the short arm of chromosome 6. No differences in allelic distribution were observed between the random NIDDM subjects and controls (p = 0.17). Differences in allelic distribution were found between unselected IDDM and controls (P = 0.016) and between the NIDDM subjects with maculopathy and/or proliferative retinopathy and no retinopathy (P = 0.006). This association could be accounted for by those patients with proliferative retinopathy (MAC vs LTD, p = 0.23; MAC vs PR, p = 0.07; and PR vs LTD, p = 0.002).

The acute effect of smoking on retinal blood flow in subjects with and without diabetes

PURPOSE

This study investigates the effect of smoking on retinal blood flow and autoregulation in smokers with and without diabetes.

METHODS

Eleven patients with diabetes mellitus and ten control subjects were investigated. Laser Doppler velocimetry and retinal photography were used to measure retinal blood flow; vascular autoregulation was assessed with 60% oxygen breathing. These procedures were performed before and after smoking.

RESULTS

Both groups demonstrated a significant increase in heart rate and systolic and diastolic blood pressure (P < 0.01). In both groups, smoking caused a significant decrease in retinal blood flow: 9.6% +/- 12% in the control group (P < 0.05) and 16.4% +/- 13.8% in the diabetic group (P < 0.01). The pre-smoking oxygen reactivity was comparable in both groups (P = 0.5); 27.9% +/- 3.3% and 32.0% +/- 5.0% in the control and diabetic groups, respectively. After smoking, oxygen reactivity was reduced significantly in the control group to 9.6% +/- 4.0% (P = 0.002) and eliminated in the patients with diabetes.

CONCLUSIONS

This study shows that smoking reduces retinal blood flow and the ability of the retinal vessels to autoregulate to hyperoxia; these effects are likely to be due to the vasoconstrictive effect of nicotine, which is mediated through activation of the sympathetic system. Smoking has been shown previously to increase the level of carboxyhemoglobin, thereby reducing the oxygen-carrying capacity of blood, which, when associated with the reduced blood flow shown in the current study, may reduce retinal oxygen delivery. Hypoxia is a major factor in the progression of diabetic retinopathy; therefore, smoking may exert a detrimental influence, which may be compounded further by the additional effect smoking has on autoregulation.

Cigarette smoking and diabetes: an update

The article provides an overview of recent scientific information on the role of cigarette smoking in the prognosis of diabetes. Data sources included an English-language MEDLINE search for 1989 through 6/1993, supplemented by manual search of bibliographies of pertinent articles. Only studies of humans were considered. Cigarette smoking is related to the development and progression of diabetic nephropathy. Therefore, smoking status has to be taken into account in clinical studies on the course of nephropathy. The association between smoking and retinopathy is less consistent. Evidence is accumulating that cigarette smoking influences insulin action. Several large prospective cohort studies have shown that the relative risk for all-cause mortality is about twice as high for smoking compared to non-smoking diabetic patients. Strong associations are consistently found between cigarette-pack years and complications. It has been calculated that the theoretical benefit of stopping smoking is the most (cost-)effective risk factor intervention for diabetic patients. However, available programmes to help diabetic patients to stop smoking are unsuccessful.

Ocular factors in the incidence and progression of diabetic retinopathy

PURPOSE

To investigate the association of intraocular pressure (IOP), ocular perfusion pressure, and myopia with the incidence and progression of diabetic retinopathy.

METHODS

The design is a cohort study of a population-based sample (n = 1210) of persons with younger-onset diabetes (diagnosis was made before 30 years of age, and subjects were taking insulin) and a random sample (n = 1780) of persons with older-onset diabetes (diagnosis made after 30 years of age). Baseline and 4-year follow-up examinations were completed by 891 younger-onset and 987 older-onset persons. Retinopathy was graded from stereoscopic fundus photographs. Endpoints were incidence of retinopathy, progression of retinopathy, and progression to proliferative diabetic retinopathy (PDR). Ocular perfusion pressure was calculated from IOP and blood pressure. Myopia was a refractive error of -2 diopters or less.

RESULTS

In univariate analyses, ocular perfusion pressure was associated with incidence of retinopathy (P < 0.005), progression of retinopathy (P = 0.07), and progression to PDR (P < 0.001) in the younger-onset group but not in older-onset subjects taking or not taking insulin. Intraocular pressure and myopia were not associated with any endpoint in any group. Using logistic regression to control for covariates, ocular perfusion pressure was significantly associated only with incidence of retinopathy in younger-onset persons. The odds ratio for a 10-mmHg increase in ocular perfusion pressure was 2.13 (95% confidence interval, 1.30-3.50). Also, myopia was protective for progression to PDR in younger-onset persons with an odds ratio of 0.40 (95% confidence interval, 0.18-0.86).

CONCLUSIONS

These results suggest that pressure phenomena may be related to the development of retinopathy in younger-onset persons. This would have implications for treatments affecting both IOP and blood pressure.