Retinal venular caliber predicts visual outcome after intravitreal ranibizumab injection treatments for neovascular AMD

Purpose

Relationship between Clinical Macular Changes and Retinal Function in Age-Related Macular Degeneration

Purpose

Retinal nerve fibre layer thinning associated with diabetic peripheral neuropathy

Aims
To investigate the relationship between retinal nerve fibre layer thickness and peripheral neuropathy in patients with Type 2 diabetes, particularly in those who are at higher risk of foot ulceration.

Methods
Global and sectoral retinal nerve fibre layer thicknesses were measured at 3.45 mm diameter around the optic nerve head using optical coherence tomography (OCT). The level of neuropathy was assessed in 106 participants (82 with Type 2 diabetes and 24 healthy controls) using the 0–10 neuropathy disability score. Participants were stratified into four neuropathy groups: none (0–2), mild (3–5), moderate (6–8), and severe (9–10). A neuropathy disability score ‡ 6 was used to define those at higher risk of foot ulceration. Multivariable regression analysis was performed to assess the effect of neuropathy disability scores, age, disease duration and retinopathy on RNFL thickness.

Results
Inferior (but not global or other sectoral) retinal nerve fibre layer thinning was associated with higher neuropathy disability scores (P = 0.03). The retinal nerve fibre layer was significantly thinner for the group with neuropathy disability scores ‡ 6 in the inferior quadrant (P < 0.005). Age, duration of disease and retinopathy levels did not significantly influence retinal nerve fibre layer thickness. Control participants did not show any significant differences in thickness measurements from the group with diabetes and no neuropathy (P > 0.24 for global and all sectors).

Conclusions
Inferior quadrant retinal nerve fibre layer thinning is associated with peripheral neuropathy in patients with Type 2 diabetes, and is more pronounced in those at higher risk of foot ulceration.

Exploring retinal and functional markers of diabetic neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most debilitating complications of diabetes. DPN is a major cause of foot ulceration and lower limb amputation. Early diagnosis and management are key factors in reducing morbidity and mortality. Current techniques for clinical assessment of DPN are relatively insensitive for detecting early disease or involve invasive procedures such as skin biopsies. There is a need for less painful, non-invasive, safe evaluation methods. Eye-care professionals already play an important role in the management of diabetic retinopathy but recent studies have indicated that the eye may also be an important site for the diagnosis and monitoring of neuropathy. Corneal nerve morphology is a promising marker of diabetic neuropathy occurring elsewhere in the body. Emerging evidence tentatively suggests that retinal anatomical markers and a range of functional visual indicators could similarly provide useful information regarding neural damage in diabetes, although this line of research is less well established. This review outlines the growing body of evidence supporting a potential diagnostic role for retinal structure and visual functional markers in the diagnosis and monitoring of peripheral neuropathy in diabetes.

A new design concept for knitted external vein-graft support mesh

Autologous vein-graft failure significantly limits the long-term efficacy of coronary artery bypass procedures. The major cause behind this complication is biomechanical mismatch between the vein and coronary artery. The implanted vein experiences a sudden increase (10-12 fold) in luminal pressures. The resulting vein over-distension or 'ballooning' initiates wall thickening phenomenon and ultimate occlusion. Therefore, a primary goal in improving the longevity of a coronary bypass procedure is to inhibit vein over-distension using mechanical constriction. The idea of using an external vein-graft support mesh has demonstrated sustained benefits and wide acceptance in experimental studies. Nitinol based knitted structures have offered more promising mechanical features than other mesh designs owing to their unique loosely looped construction. However, the conventional plain knit construction still exhibits limitations (radial compliance, deployment ease, flexibility, and bending stresses) which limit this design from proving its real clinical advantage. The new knitted mesh design presented in this study is based on the concept of composite knitting utilising high modulus (nitinol and polyester) and low modulus (polyurethane) material components. The experimental comparison of the new design with a plain knit design demonstrated significant improvement in biomechanical (compliance, flexibility, extensibility, viscoelasticity) and procedural (deployment limit) parameters. The results are indicative of the promising role of new mesh in restoring the lost compliance and pulsatility of vein-graft at high arterial pressures. This way it can assist in controlled vein-graft remodelling and stepwise restoration of vein mechanical homoeostasis. Also, improvement in deployment limit parameter offers more flexibility for a surgeon to use a wide range of vein diameters, which may otherwise be rendered unusable for a plain knit mesh.

Effect of retinal image defocus on the thickness of the human choroid

PURPOSE: To describe the time-course and amplitude of changes to sub-foveal choroidal thickness (SFCT) induced by imposed hyperopic and myopic retinal defocus and to compare the responses in emmetropic and myopic subjects. METHODS: Twelve East Asian subjects (age: 18-34 years; six were emmetropic and six had myopia between -2.00 and -5.00 dioptres (D)) viewed a distant target (video movie at 6 m) for 60 min on two separate occasions while optical coherence tomography (OCT) images of the choroid were taken in both eyes every 5 min to monitor SFCT. On each occasion, one eye was optimally corrected for distance with a contact lens while the other eye wore a contact lens imposing either 2.00 D hyperopic or 2.00 D myopic retinal defocus. RESULTS: Baseline SFCT in myopic eyes (mean ± S.D.): 256 ± 42 μm was significantly less than in emmetropic eyes (423 ± 62 μm; p < 0.01) and was correlated with magnitude of myopia (-39 μm per dioptre of myopia, R(2) = 0.67: p < 0.01). Repeated measures anova (General Linear Model) analysis revealed that in both subject groups, 2.00 D of myopic defocus caused a rapid increase in SFCT in the defocussed eye (significant by 10 min, increasing to approximately 20 μm within 60 min: p < 0.01), with little change in the control eye. In contrast, 2.00 D of hyperopic defocus caused a decrease in SFCT in the experimental eye (significant by 20-35 min. SFCT decreased by approximately 20 μm within 60 min: p < 0.01) with little change in the control eye. CONCLUSIONS: Small but significant changes in SFCT (5-8%) were caused by retinal defocus. SFCT increased within 10 min of exposure to 2.00 D of monocular myopic defocus, but decreased more slowly in response to 2.00 D of monocular hyperopic defocus. In our relatively small sample we could detect no difference in the magnitude of changes to SFCT caused by defocus in myopic eyes compared to emmetropic eyes.

Screening for diabetic retinopathy using a non-mydriatic retinal camera in rural Victoria

PURPOSE: To develop a screening programme for the early detection of diabetic retinopathy using non-mydriatic retinal photography. METHODS: A community based screening service was offered to all people with known diabetes mellitus in selected townships in the LaTrobe and Goulburn Valleys in Victoria. At the local examination centre, basic sociodemographic information was collected as well as details of previous use of eye care services for the early detection of diabetic retinopathy. The examination included visual acuity (VA), glycosylated haemoglobin level and Polaroid photographs of each fundus using a Canon CR5-45NM non-mydriatic retinal camera (Canon, Tochigiken, Japan). Dilating drops were not used. Photographs were subsequently reviewed and letters were sent to all participants (with copies to their general practitioners) with recommendations for appropriate follow up. RESULTS: A total of 1177 people with diabetes attended the screening service, which is estimated to be 40% of the total population with known diabetes in the study area. The mean age was 65 years (range 20-94 years); 559 (48%) people reported not having a dilated fundus examination within the past 2 years; 345 (29%) people had never had a dilated fundus examination. Of the 2354 eyes, 2126 (90%) of the photographs were gradable. A total of 704 people (60%) had normal VA and no evidence of diabetic retinopathy, 209 people (18%) had diabetic retinopathy, 101 people (9%) had evidence of other fundus pathology, 42 people (3%) had reduced acuity (< 6/18) in one or both eyes (with no fundus pathology evident) and 121 people (10%) had ungradable photographs in one or both eyes. CONCLUSIONS: The present study demonstrates the usefulness of a screening programme with non-mydriatic retinal photography as an adjunct to current eye care services for the early detection of diabetic retinopathy.

Retinal tissue thickness is reduced in diabetic peripheral neuropathy

AIM: To investigate the relationship between diabetic peripheral neuropathy (DPN) and retinal tissue thickness.

METHODS: Full retinal thickness in the central retinal, parafoveal, and perifoveal zones and thickness of the ganglion cell complex and retinal nerve fiber layer (RNFL) were assessed in 193 individuals (84 with type 1 diabetes, 67 with type 2 diabetes, and 42 healthy controls) using spectral domain optical coherence tomography. Among those with diabetes, 44 had neuropathy defined using a modified neuropathy disability score recorded on a 0-10 scale. Multiple regression analysis was performed to investigate the relationship between diabetic neuropathy and retinal tissue thickness, adjusted for the presence of diabetic retinopathy (DR), age, sex, duration of diabetes, and HbA1c levels.

RESULTS: In individuals with diabetes, perifoveal thickness was inversely related to the severity of neuropathy (p < 0.05), when adjusted for age, sex, duration of diabetes, and HbA1c levels. DR was associated with reduced thickness in parafovea (p < 0.01). The RNFL was thinner in individuals with greater degrees of neuropathy (p < 0.04).

CONCLUSIONS: DPN is associated with structural compromise involving several retinal layers. This compromise may represent a threat to visual integrity and therefore warrants examination of functional correlates.

Retinal tissue thickness in type 1 and type 2 diabetes

BACKGROUND: The objective was to investigate full retinal and inner retinal thickness in individuals with type 1 and type 2 diabetes. METHODS: Eighty-four individuals with type 1 diabetes (T1DM), 67 individuals with type 2 diabetes (T2DM) and 42 non-diabetic individuals (control group) were enrolled. Participants underwent full retinal thickness evaluation in the central retinal, parafoveal and perifoveal zones and in the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC), using spectral domain optical coherence tomography. As a preliminary step, the key variables of interest - age, sex, diabetic retinopathy (DR), duration of diabetes and HbA1c levels - were analysed and compared between the three groups. Full retinal thickness, RNFL and GCC thicknesses were also compared between the groups. The relationship between the type of diabetes and retinal tissue thickness was explored, adjusting for the five potential confounders. RESULTS: Compared to individuals with T1DM, individuals with T2DM had significantly reduced full retinal thickness in the parafovea and perifovea and reduced RNFL and GCC thickness. The mean differences were six (p = 0.020), seven (p = 0.008), six (p = 0.021) and four micrometres (p = 0.013) for the parafovea, perifovea, RNFL and GCC thicknesses, respectively. Thicknesses within the central zone (p = 0.018) and at the parafovea (p = 0.007) were significantly reduced in T2DM when compared to the control group. After adjusting for age, sex, diabetic retinopathy, duration of diabetes and HbA1c levels, the relationship between type of diabetes and retinal tissue thickness was not statistically significant (p > 0.056). CONCLUSION: Retinal tissue thickness is not significantly different between type 1 and type 2 diabetes, when adjusted for age, sex, diabetic retinopathy, duration of diabetes and HbA1c levels.

Retinal thickness profile of individuals with diabetes

PURPOSE: To examine the retinal thickness profiles of individuals with and without diabetic retinopathy (DR).

METHODS: Full retinal thickness in the central zone, overall and hemisphere thicknesses of the parafovea and perifovea, ganglion cell complex (GCC) thickness and retinal nerve fibre layer (RNFL) thickness were assessed in 185 individuals using spectral domain optical coherence tomography (88 individuals with diabetes but no DR, 55 with DR, and 42 non-diabetic controls). The DR group comprised of 60% of participants with very mild non-proliferative diabetic retinopathy (NPDR) (representing microaneurysms only) and 40% with mild NPDR (hard exudates, cotton-wool spots, and/or mild retinal haemorrhages). Regression analysis was performed to determine the factors associated with retinal tissue thickness, taking into account, age, sex, presence of DR, duration of diabetes, HbA1c levels and type of diabetes.

RESULTS: The mean (S.D.) of the overall parafoveal thickness was 306 (16) in the DR group and 314 (14) in the control group (p = 0.02). The mean (S.D.) of the superior hemisphere parafoveal thickness was 309 (16) in the DR group and 318 (14) in the control group (p = 0.02). The mean (S.D.) of the inferior hemisphere parafoveal thickness was 303 (17) in the DR group and 311 (15) in the control group (p = 0.02). There were no significant differences in retinal thickness between groups in the central zone (p = 0.27) or perifovea (p > 0.41). Neither the overall nor the hemisphere RNFL (p > 0.75) and GCC thickness (p > 0.37) were significantly different between the groups. Regression analysis revealed that parafoveal thickness in diabetic individuals was reduced in association with presence of DR (B = -5.9 μm, p = 0.02) and with advancing age (B = -4.5 μm, p = 0.004, for every 10 year increase in age) when adjusted for sex, duration of diabetes, HbA1c levels and type of diabetes.

CONCLUSION: The inner macula is thinner in the presence of clinical signs of diabetic retinopathy and is compounded by advancing age. The influence of any macular oedema or that by cotton-wool spots could not be ruled out and may still confound these results.