Frequency and risk factors of non-retinopathy ocular conditions in people with diabetes: the Singapore Malay Eye Study

AIM

To investigate the frequency and risk factors of non-retinopathy ocular conditions in persons with diabetes.

METHODS

A population-based cross-sectional study of 3176 Malay persons aged between 40 and 79 years in Singapore was conducted. Cataract, glaucoma, refractive errors, age-related macular degeneration, dry eye, epiretinal membrane, ocular hypertension and retinal conditions were assessed based on standardized interviews, clinical examinations and laboratory investigations.

RESULTS

A total of 768 participants (24.2%) had diabetes. People with diabetes were more likely to have cortical cataract (52.1 vs. 37.3%, P < 0.001), ocular hypertension (10.9 vs. 7.4%, P = 0.002) and epiretinal membrane (17.2 vs. 10.1%, P < 0.001) compared with those without diabetes. The odds of having cortical cataract (odds ratio 1.63, 95% CI 1.20-2.20) and epiretinal membrane (among those with previous cataract surgery: odds ratio 1.63, 95% CI 1.20-2.20) were significantly higher in people with diabetes compared with those without. The population attributable risks for cortical cataract and epiretinal membrane because of diabetes were 8.7 and 9.0%, respectively. In persons with diabetes, hypertension and high cholesterol were the major risk factors associated with non-retinopathy eye complications such as ocular hypertension (odds ratio 1.18, 95% CI 1.04-1.33) and retinal emboli (odds ratio 1.99, 95% CI 1.05-3.80).

CONCLUSION

Our results allow clinicians to better inform patients with diabetes that they are more likely to have cortical cataract and epiretinal membranes (those with previous cataract surgery) in addition to diabetic retinopathy. Two modifiable risk factors-blood pressure and cholesterol associated with ocular hypertension and retinal emboli, respectively-are also risk factors for non-retinopathy ocular conditions in persons with diabetes.

PP112. Prediction of preeclampsia based on clinical risk factors: A prospective high-risk cohort study

INTRODUCTION

Early recognition of preeclampsia (PE) is crucial for better obstetric care. Clinical risk factors are easier to identify than biochemical markers and may be useful in the prediction of PE.

OBJECTIVES

To evaluate which risk factors provide the best prediction for PE in a group at high-risk for developing PE.

METHODS

A prospective cohort study of 100 pregnant women was performed. During the first trimester we included pregnant women who had at least one of the following risk factors for PE: previous history of PE, previous history of HELLP, pre-existing hypertension, diabetes mellitus, multiple pregnancy, obesity or autoimmune diseases. These women were monitored during their pregnancy and their medical data were used to set up a database. We focused on baseline characteristics (parity, maternal age, maternal smoking, ethnic origin, blood pressure at booking, risk factors mentioned above and medication use). Differences between groups were analysed using the Student's t test or the Mann-Whitney U test as applicable. Categorical data were analysed with χ(2) statistics. Subsequently, multivariable logistic regression analysis with a stepwise backward selection procedure of predictors was performed to identify independent risk factors for PE.

RESULTS

Of the 100 women 22 (22.0%) developed PE and 13 (13.0%) developed gestational hypertension (GH). More women in the group with progression to PE had a history of PE (50.0% versus 26.2%, p=0.039), while less women had a multiple pregnancy (4.5% versus 27.7%, p=0.023) as compared with the group not progressing to either PE or GH. In the group of GH, no women were using antihypertensive medication while in the group of women not progressing to either PE or GH 32.3% were using antihypertensive medication (p=0.017). Multivariable logistic regression revealed that singleton pregnancy was the only independent predictor of PE (OR 8.04, 95% CI 1.01 - 64.3, p=0.045).

CONCLUSION

In this prospective cohort study we evaluated clinical risk factors for the development of PE in pregnant high-risk women based on obstetric history and comorbidity. We found that a singleton pregnancy was the only independent predictor for PE in this group of high-risk women. The other risk factors for which the women were included were not strong enough to act as a predictor for PE in this relatively small cohort. Nonetheless, it is important to be alert for PE in this group of pregnant women with high-risk for PE, especially because most of them have more than one risk factor.

Retinal vascular changes following intravitreal ranibizumab injections for neovascular AMD over a 1-year period

PURPOSE

To assess retinal vascular calibre changes in eyes with neovascular age-related macular degeneration (AMD), treated with intravitreal anti-vascular endothelial growth factor agents, over a 1-year period and compare any such changes to untreated fellow eyes.

METHODS

Treatment naïve patients with neovascular AMD received three consecutive intravitreal injections of ranibizumab, followed by a pro re nata dosing regimen up to 1 year, with the aim of maintaining a 'fluid-free' macula. Retinal arteriolar and venular calibre was measured from digital fundus photographs at baseline and at three monthly intervals to 1 year, and summarised as central retinal artery equivalent (CRAE) and central retinal venular equivalent (CRVE), respectively.

RESULTS

A total of 53 injected eyes and 41 fellow, non-injected eyes were analysed. At baseline, there were no differences in retinal vascular calibre between injected and non-injected eyes (mean CRAE (SD) 144.93 (14.07) vs 145.74 (13.10) μm, P=0.80 and mean CRVE (SD) 216.23 (25.93) vs 219.91 (22.82) μm, P=0.53). Over a 12-month period, retinal venular calibre dilatation occurred in injected eyes (mean CRVE change +5.71 (14.71) μm, P=0.007), with no change in retinal arterioles, +0.69 (14.71) μm, P=0.68. In non-injected eyes, arteriolar narrowing occurred as a whole, mean CRAE change -4.20 (7.00) μm, P=0.001, over 12 months, with a trend for narrowing in venules, -2.16 (11.56) μm, P=0.28. In injected eyes, after controlling for covariates, the changes in CRVE over 12 months mirrored improvements in macular thickness, -0.06 (-0.005, -0.11) μm, P=0.04, and visual acuity, +9.66 (-0.30, +19.32) μm, P=0.06.

CONCLUSION

Intravitreal ranibizumab significantly dilated retinal venules after a 1-year period.

Automatic glaucoma diagnosis from fundus image

Glaucoma is currently diagnosed by glaucoma specialists using specialized imaging devices like HRT and OCT. Fundus imaging is a modality widely used in primary healthcare. An automatic glaucoma diagnosis system based on fundus image can be deployed to primary healthcare clinics and has potential for early disease diagnosis. A mass glaucoma screening program can also be facilitated using such a system. We present an automatic fundus image based cup-to-disc ratio measurement system; and demonstrate its potential for automatic objective glaucoma diagnosis and screening. It provides strong support to use fundus image as the modality for automatic glaucoma diagnosis.

Novel versus traditional risk markers for diabetic retinopathy

AIMS/HYPOTHESIS

To explore the relative contribution of novel and traditional risk markers for diabetic retinopathy (DR).

METHODS

A clinic-based study of 224 diabetic patients (85 type 1, 139 type 2) from a diabetes clinic was performed. DR was graded from fundus photographs according to the Airlie House Classification system and classified as absent or present (at least ETDRS level 14). Novel risk markers assessed included serum apolipoprotein (Apo) AI and B, skin microvascular responses to acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) iontophoresis, flicker-light-induced retinal vasodilation and retinal vascular tortuosity. Relative contribution was determined by semi-partial correlation coefficient generated from a logistic regression model containing all traditional and novel risk markers simultaneously.

RESULTS

There were 144 (64.3%) participants with DR. Of the novel markers, ApoAI, flicker-light-induced vasodilation and retinal arteriolar tortuosity were significantly associated with DR, independently of traditional measures (all p < 0.03). Diabetes duration contributed most (51%) to the risk of DR, followed by ApoAI (16%), systolic blood pressure (13%), retinal arteriolar tortuosity (8%) and flicker-light-induced venular and arteriolar dilation (3% and 0.5%, respectively).

CONCLUSIONS/INTERPRETATION

ApoAI and retinal arteriolar tortuosity made considerable contributions to DR risk, independently of traditional risk markers. Findings from this study suggest that serum ApoAI and retinal arteriolar tortuosity may be novel and independent risk markers of DR.

Republished article: The impact of diabetic retinopathy: understanding the patient's perspective

Understanding the impact of a condition from the patient's perspective is important, and different types of patient-reported outcomes or instruments are available to help with this. This review article summarises the current evidence on the impact of diabetic retinopathy (DR) and its associated vision impairment on patient-reported outcomes. We have included research that has used a range of outcome measures to assess the impact of DR on generic health-related quality of life, utility, vision-functioning and vision-specific quality of life. This review also offers clarification on frequently misused psychometric terminologies to help clinicians and researchers better understand the literature associated with patient-reported outcome research. Overall, the evidence suggests that DR, particularly in its vision-threatening stages, has a substantial, negative impact on the patient. However, our understanding of the impact of DR is currently restricted due to limitations inherent in currently available patient-reported outcome measures. We conclude by discussing potential directions for future research in this area, such as item banking and computer adaptive testing.

Review of key findings from the Singapore Malay Eye Study (SiMES-1)

INTRODUCTION

This study highlights the key epidemiological findings from the Singapore Malay Eye Study (SiMES-1).

METHODS

SiMES-1 was a cross-sectional, population-based epidemiological study on eye diseases. It was performed on 3,280 randomly selected Malay adults living in the south-western part of Singapore. All study participants underwent various validated questionnaires and detailed eye examinations. A review of all papers published from SiMES-1 was performed.

RESULTS

A total of 24.6% of the study population had myopia, while 35.3% had hyperopia and 39.4% had astigmatism. 20.4% of the population had under-corrected refractive error. 1,338 (45.7%) participants were diagnosed to have cataracts in at least one eye. 8.6% of the study population had undergone cataract surgery in either eye, while 4.7% had bilateral cataract surgery. 150 (4.6%) participants were diagnosed to have glaucoma, of which primary open angle glaucoma was the most common type (3.2% of the study population), followed by secondary glaucoma (0.8%) and primary angle closure glaucoma (0.2%). Pterygium was diagnosed in 508 out of 3,266 study participants, giving a prevalence rate of 15.6%. The presence of diabetic retinopathy was observed in 421 (12.9%) out of 3,265 study participants. 183 (5.6%) study participants had some degree of age-related macular degeneration (AMD), of which 23 (0.7%) were classified as having late AMD.

CONCLUSION

This paper provides a summary of the prevalence of common eye diseases among the Singaporean adult Malay population and provides data useful for public health education and disease prevention.

The relationship between aortic stiffness and changes in retinal microvessels among Asian ischemic stroke patients

Large-artery stiffness is a risk factor for stroke, including cerebral small-vessel disease. Retinal microvascular changes are thought to mirror those in cerebral microvessels. We investigated the relationship between aortic stiffness and retinal microvascular changes in Asian ischemic stroke patients. We studied 145 acute ischemic stroke patients in Singapore who had aortic stiffness measurements using carotid-femoral pulse wave velocity (cPWV). Retinal photographs were assessed for retinal microvessel caliber and qualitative signs of focal arteriolar narrowing, arteriovenous nicking and enhanced arteriolar light reflex. Aortic stiffening was associated with retinal arteriolar changes. Retinal arteriolar caliber decreased with increasing cPWV (r=-0.207, P=0.014). After adjusting for age, gender, hypertension, diabetes, mean arterial pressure and small-vessel stroke subtype, patients within the highest cPWV quartile were more likely to have generalized retinal arteriolar narrowing defined as lowest caliber tertile (odds ratio (OR) 6.84, 95% confidence interval (CI) 1.45-32.30), focal arteriolar narrowing (OR 13.85, CI 1.82-105.67), arteriovenous nicking (OR 5.08, CI 1.12-23.00) and enhanced arteriolar light reflex (OR 3.83, CI 0.89-16.48), compared with those within the lowest quartile. In ischemic stroke patients, aortic stiffening is associated with retinal arteriolar luminal narrowing as well as features of retinal arteriolosclerosis.

Retinal vascular tortuosity in persons with diabetes and diabetic retinopathy

AIM/HYPOTHESIS

The aim of this hypothesis was to examine the association of retinal vessel tortuosity with diabetes and diabetic retinopathy (DR).

METHODS

A clinic-based study of 327 participants (224 with diabetes and 103 non-diabetic controls) aged ≥ 18 years. DR was graded from fundus photographs according to the modified Airlie House Classification system and categorised into mild non-proliferative DR (NPDR), moderate NPDR and vision-threatening DR (VTDR). Retinal vessel tortuosity was measured from disc-centred retinal photographs. Measurements were taken, using a semi-automated computer program by a single grader, of arterioles and venules within 0.5 to 2 disc diameters away from the optic disc.

RESULTS

There were 114 (44%) participants with DR. In the multivariate analysis, retinal arteriolar and venular tortuosity were increased in participants with diabetes without DR (mean difference 12.4 × 10(-5) and 13.3 × 10(-5), respectively; both p < 0.05) and in those with DR (mean difference 15.4 × 10(-5) and 15.0 × 10(-5), respectively; both p < 0.01) compared with non-diabetic participants. Among participants with diabetes, increased arteriolar tortuosity was significantly associated with mild NPDR (OR 1.53, 95% CI 1.03-2.05, per SD increase in arteriolar tortuosity) and moderate NPDR (OR 1.67, 95% CI 1.10-2.55) but not VTDR (OR 0.91, 95% CI 0.54-1.54). No association with DR was found for venular tortuosity.

CONCLUSIONS/INTERPRETATION

Persons with diabetes had more tortuous retinal vasculature than persons without diabetes. In persons with diabetes, increased arteriolar tortuosity was associated with mild and moderate stages of DR. This suggests that retinal vascular tortuosity might be an early indicator of microvascular damage in diabetes; thus, further investigation is indicated.

Association of retinal arteriolar dilatation with lower verbal memory: the Edinburgh Type 2 Diabetes Study

AIMS/HYPOTHESIS

Retinal vascular calibre changes may reflect early subclinical microvascular disease in diabetes. Because of the considerable homology between retinal and cerebral microcirculation, we examined whether retinal vascular calibre, as a proxy of cerebral microvascular disease, was associated with cognitive function in older people with type 2 diabetes.

METHODS

A cross-sectional analysis of 954 people aged 60-75 years with type 2 diabetes from the population-based Edinburgh Type 2 Diabetes Study was performed. Participants underwent standard seven-field binocular digital retinal photography and a battery of seven cognitive function tests. The Mill Hill Vocabulary Scale was used to estimate pre-morbid cognitive ability. Retinal vascular calibre was measured from an image field with the optic disc in the centre using a validated computer-based program.

RESULTS

After age and sex adjustment, larger retinal arteriolar and venular calibres were significantly associated with lower scores for the Wechsler Logical Memory test, with standardised regression coefficients -0.119 and -0.084, respectively (p < 0.01), but not with other cognitive tests. There was a significant interaction between sex and retinal vascular calibre for logical memory. In male participants, the association of increased retinal arteriolar calibre with logical memory persisted (p < 0.05) when further adjusted for vocabulary, venular calibre, depression, cardiovascular risk factors and macrovascular disease. In female participants, this association was weaker and not significant.

CONCLUSIONS/INTERPRETATION

Retinal arteriolar dilatation was associated with poorer memory, independent of estimated prior cognitive ability in older men with type 2 diabetes. The sex interaction with stronger findings in men requires confirmation. Nevertheless, these data suggest that impaired cerebral arteriolar autoregulation in smooth muscle cells, leading to arteriolar dilatation, may be a possible pathogenic mechanism in verbal declarative memory decrements in people with diabetes.

Relationship between a range of sedentary behaviours and blood pressure during early adolescence

Very few studies have explored links between physical activity, sedentary behaviours and blood pressure (BP) in early adolescence. We aimed to assess the association between a range of sedentary activities (screen time, television (TV) viewing, computer usage, video game usage and time spent in homework or reading) and BP in schoolchildren. Eligible year-7 students (2353/3144, mean age 12.7 years) from a random cluster sample of 21 Sydney schools were examined during 2003-2005. Parents and children completed detailed questionnaires of activity. BP was measured using a standard protocol and high BP was defined using published guidelines. Height and weight were measured, and body mass index (BMI) calculated. After adjusting for age, sex, ethnicity, parental education, height, BMI and time spent in physical activity, each hour per day spent in screen time, watching TV and playing video games was associated with a significant increase in diastolic BP of 0.44 (P=0.0001), 0.99 (P<0.0001) and 0.64 mm Hg (P=0.04), respectively. In contrast, each hour per day spent reading was associated with a decrease of 0.91 (P=0.01) and 0.69 mm Hg (P=0.02) in systolic and diastolic BP, respectively. Our results indicate that addressing different types of sedentary activities could be a potentially important strategy to reduce the prevalence of elevated BP in children.

How does hypertension affect your eyes?

Hypertension has profound effects on various parts of the eye. Classically, elevated blood pressure results in a series of retinal microvascular changes called hypertensive retinopathy, comprising of generalized and focal retinal arteriolar narrowing, arteriovenous nicking, retinal hemorrhages, microaneurysms and, in severe cases, optic disc and macular edema. Studies have shown that mild hypertensive retinopathy signs are common and seen in nearly 10% of the general adult non-diabetic population. Hypertensive retinopathy signs are associated with other indicators of end-organ damage (for example, left ventricular hypertrophy, renal impairment) and may be a risk marker of future clinical events, such as stroke, congestive heart failure and cardiovascular mortality. Furthermore, hypertension is one of the major risk factors for development and progression of diabetic retinopathy, and control of blood pressure has been shown in large clinical trials to prevent visual loss from diabetic retinopathy. In addition, several retinal diseases such as retinal vascular occlusion (artery and vein occlusion), retinal arteriolar emboli, macroaneurysm, ischemic optic neuropathy and age-related macular degeneration may also be related to hypertension; however, there is as yet no evidence that treatment of hypertension prevents vision loss from these conditions. In management of patients with hypertension, physicians should be aware of the full spectrum of the relationship of blood pressure and the eye.

Serum C-reactive protein level and prediabetes in two Asian populations

AIMS/HYPOTHESIS

Prediabetes, an early stage in the hyperglycaemic continuum, increases the future risk of developing diabetes and cardiovascular disease (CVD). C-reactive protein (CRP), a marker of inflammation, is associated with diabetes and CVD. However, studies examining the association between CRP and prediabetes among participants without diabetes are limited.

METHODS

We analysed data from two large population-based studies in Singapore: the Singapore Prospective Study Programme (SP2, n = 4,252 Chinese, Malay and Indians aged ≥ 24 years) and the Singapore Malay Eye Study (SiMES, n = 2,337 Malays aged 40-80 years), participants of which were free of diabetes mellitus. Prediabetes was defined as glycated haemoglobin of 5.7-6.4% in SiMES (n = 1,231); fasting plasma glucose of 5.6-6.9 mmol/l in SP2 (n = 386).

RESULTS

Elevated high sensitivity CRP (hsCRP) levels were found to be associated with prediabetes after adjusting for age, sex, race-ethnicity, education, smoking, alcohol consumption, hypertension, BMI and total cholesterol. Comparing those with hsCRP <1 mg/l (referent), the OR (95% confidence interval) of prediabetes in persons with hsCRP 1-3 mg/l and >3 mg/l was 1.31 (0.99-1.74) and 2.17 (1.61-2.92), p (trend) < 0.0001 in SP2; 1.23 (1.00-1.52) and 1.31 (1.06-1.64), p (trend) = 0.02 in SiMES. In subgroup analysis, the association was stronger in women, Chinese and Malays, and participants with BMI < 25 kg/m(2).

CONCLUSIONS

Data from two population-based Asian cohorts suggest that elevated serum hsCRP levels are associated with prediabetes.

Mixture model-based approach for optic cup segmentation

Glaucoma is a leading cause of blindness with permanent damage to optic nerve head. ARGALI is an automated computer-aided diagnosis system designed for glaucoma detection via optic cup-to-disc ratio assessment. It employs several methods to determine the optic cup and disc from retinal images.

Fusion of multiscale wavelet-based fractal analysis on retina image for stroke prediction

In this paper, we present a novel method of analyzing retinal vasculature using Fourier Fractal Dimension to extract the complexity of the retinal vasculature enhanced at different wavelet scales. Logistic regression was used as a fusion method to model the classifier for 5-year stroke prediction. The efficacy of this technique has been tested using standard pattern recognition performance evaluation, Receivers Operating Characteristics (ROC) analysis and medical prediction statistics, odds ratio. Stroke prediction model was developed using the proposed system.

Robust methodology for fractal analysis of the retinal vasculature

We have developed a robust method to perform retinal vascular fractal analysis from digital retina images. The technique preprocesses the green channel retina images with Gabor wavelet transforms to enhance the retinal images. Fourier Fractal dimension is computed on these preprocessed images and does not require any segmentation of the vessels. This novel technique requires human input only at a single step; the allocation of the optic disk center. We have tested this technique on 380 retina images from healthy individuals aged 50+ years, randomly selected from the Blue Mountains Eye Study population. To assess its reliability in assessing retinal vascular fractals from different allocation of optic center, we performed pair-wise Pearson correlation between the fractal dimension estimates with 100 simulated region of interest for each of the 380 images. There was Gaussian distribution variation in the optic center allocation in each simulation. The resulting mean correlation coefficient (standard deviation) was 0.93 (0.005). The repeatability of this method was found to be better than the earlier box-counting method. Using this method to assess retinal vascular fractals, we have also confirmed a reduction in the retinal vasculature complexity with aging, consistent with observations from other human organ systems.

Learning-based approach for the automatic detection of the optic disc in digital retinal fundus photographs

The optic disc is an important feature in the retina. We propose a method for the detection of the optic disc based on a supervised learning scheme. The method employs pixel and local neighbourhood features extracted from the ROI of a digital retinal fundus photograph. A support vector machine based classification mechanism is used to classify each image point as belonging to the cup and retina. The proposed method is evaluated on a sample image set of 68 retinal fundus images. The results show a high correlation (r>0.9) with the ground truth segmentation, with an overlap error of 6.02%, and found to be comparable to the inter-observer variability based on an independent second observer segmentation of the same data set.