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.

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.

Gaze behavior among experts and trainees during optic disc examination : does how we look affect what we see?

Purpose. The authors compared the visual gaze behaviors of glaucoma subspecialists with those of ophthalmology trainees during optic disc and retinal nerve fiber layer (RNFL) examination.

Methods. Seven glaucoma subspecialists and 23 ophthalmology trainees participated in the project. Participants were shown eight glaucomatous optic disc images with varied morphology. Eye movements during examination of the optic disc photographs were tracked. For each disc image, graders were asked to assign a presumptive diagnosis for probability of glaucoma. There was no time restriction.

Results. Overall, trainees spent more time looking at disc images than glaucoma subspecialists (21.3 [13.9–37.7] vs. 16.6 [12.7–19.7]) seconds; median [interquartile range (IQR)], respectively; P < 0.01) and had no systematic patterns of gaze behavior, and gaze behavior was unaltered by disc morphology or topographic cues of pathology. Experienced viewers demonstrated more systematic and ordered gaze behavior patterns and spent longer times observing areas with the greatest likelihood of pathology (superior and inferior poles of the optic nerve head and adjacent RNFL) compared with the trainees. For discs with focal pathology, the proportion of total time spent examining definite areas of pathology was 28.9% (22.4%–33.6%) for glaucoma subspecialists and 13.5% (12.2%–19.2%) for trainees (median [IQR]; P < 0.05). Furthermore, experts adapted their viewing habits according to disc morphology.

Conclusions. Glaucoma subspecialists adopt systematic gaze behavior when examining the optic nerve and RNFL, whereas trainees do not. It remains to be elucidated whether incorporating systematic viewing behavior of the optic disc and RNFL into teaching programs for trainees may expedite their acquisition of accurate and efficient glaucoma diagnosis skills.

Evaluation of segmentation algorithms for extraction of RNFL in OCT images

The thickness of the retinal nerve fiber layer (RFNL) has become a diagnose measure for glaucoma assessment. To measure this thickness, accurate segmentation of the RFNL in optical coherence tomography (OCT) images is essential. Identification of a suitable segmentation algorithm will facilitate the enhancement of the RNFL thickness measurement accuracy. This paper investigates the performance of six algorithms in the segmentation of RNFL in OCT images. The algorithms are: normalised cuts, region growing, k-means clustering, active contour, level sets segmentation: Piecewise Gaussian Method (PGM) and Kernelized Method (KM). The performance of the six algorithms are determined through a set of experiments on OCT retinal images. An experimental procedure is used to measure the performance of the tested algorithms. The measured segmentation precision-recall results of the six algorithms are compared and discussed.

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.

Pneumatic vehicle

A pneumatic vehicle is provided with a first sub-assembly with a chassis, part of the vehicle body, a pair of B-pillars, a pair of rear rails, wheels, an elongate aluminum compressed load bearing air tank oriented longitudinally in the chassis, side panels connected to the tank and the wheels, a heat exchanger to heat the compressed air, and an air motor driven by the heated, compressed air and connected to a wheel. A ventilation system has a restrictive solenoid valve for directing air to the heat exchanger. The air tank is provided with a carbon filament reinforced plastic layer, and a fiberglass and aramid-fiber layer. A second sub-assembly includes part of the vehicle body bonded to the first-sub-assembly using a structural adhesive, a pair of A-pillars, and a pair of roof rails. Seating includes inflatable components for adjustment.

CHASSIS FOR PNEUMATIC VEHICLE

A pneumatic vehicle is provided with a first sub-assembly with a chassis, part of the vehicle body, a pair of B-pillars, a pair of rear rails, wheels, an elongate aluminum compressed load bearing air tank oriented longitudinally in the chassis, side panels connected to the tank and the wheels, a heat exchanger to heat the compressed air, and an air motor driven by the heated, compressed air and connected to a wheel. A ventilation system has a restrictive solenoid valve for directing air to the heat exchanger. The air tank is provided with a carbon filament reinforced plastic layer, and a fiberglass and aramid-fiber layer. A second sub-assembly includes part of the vehicle body bonded to the first-sub-assembly using a structural adhesive, a pair of A-pillars, and a pair of roof rails. Seating includes inflatable components for adjustment.

PNEUMATIC POWERTRAIN FOR AN AUTOMOTIVE VEHICLE

A pneumatic vehicle is provided with a chassis, wheels, a compressed air tank, a heat exchanger to heat the compressed air, and an air motor driven by the heated air and connected to at least one wheel. A pneumatic vehicle is provided with a chassis, wheels, a compressed air tank, and an air motor driven by the compressed air and connected to a wheel. The vehicle also has a ventilation system for the passenger compartment, a heat exchanger, and a restrictive solenoid valve for directing ventilation system air to the heat exchanger. A pneumatic vehicle is provided with a chassis, wheels, an aluminum compressed air tank, a carbon filament reinforced plastic layer over the tank, a fiberglass and aramid-fiber layer over the carbon filament reinforced plastic layer, and an air motor driven by the compressed air and connected to at least one wheel.

PNEUMATIC VEHICLE

A pneumatic vehicle is provided with a first sub- assembly with a chassis, part of the vehicle body, a pair of B-pillars, a pair of rear rails, wheels, an elongate aluminum compressed load bearing air tank oriented longitudinally in the chassis, side panels connected to the tank and the wheels, a heat exchanger to heat the compressed air, and an air motor driven by the heated, compressed air and connected to a wheel. A ventilation system has a restrictive solenoid valve for directing air to the heat exchanger. The air tank is provided with a carbon filament reinforced plastic layer, and a fiberglass and aramid-fiber layer. A second sub-assembly includes part of the vehicle body bonded to the first-sub-assembly using a structural adhesive, a pair of A-pillars, and a pair of roof rails. Seating includes inflatable components for adjustment.

Chassis for pneumatic vehicle

A pneumatic vehicle is provided with a first sub-assembly with a chassis, part of the vehicle body, a pair of B-pillars, a pair of rear rails, wheels, an elongate aluminum compressed load bearing air tank oriented longitudinally in the chassis, side panels connected to the tank and the wheels, a heat exchanger to heat the compressed air, and an air motor driven by the heated, compressed air and connected to a wheel. A ventilation system has a restrictive solenoid valve for directing air to the heat exchanger. The air tank is provided with a carbon filament reinforced plastic layer, and a fiberglass and aramid-fiber layer. A second sub-assembly includes part of the vehicle body bonded to the first-sub-assembly using a structural adhesive, a pair of A-pillars, and a pair of roof rails. Seating includes inflatable components for adjustment.

Pneumatic powertrain for an automotive vehicle

A pneumatic vehicle is provided with a chassis, wheels, a compressed air tank, a heat exchanger to heat the compressed air, and an air motor driven by the heated air and connected to at least one wheel. A pneumatic vehicle is provided with a chassis, wheels, a compressed air tank, and an air motor driven by the compressed air and connected to a wheel. The vehicle also has a ventilation system for the passenger compartment, a heat exchanger, and a restrictive solenoid valve for directing ventilation system air to the heat exchanger. A pneumatic vehicle is provided with a chassis, wheels, an aluminum compressed air tank, a carbon filament reinforced plastic layer over the tank, a fiberglass and aramid-fiber layer over the carbon filament reinforced plastic layer, and an air motor driven by the compressed air and connected to at least one wheel.

Chassis for pneumatic vehicle

A pneumatic vehicle is provided with a first sub-assembly with a chassis, part of the vehicle body, a pair of B-pillars, a pair of rear rails, wheels, an elongate aluminum compressed load bearing air tank oriented longitudinally in the chassis, side panels connected to the tank and the wheels, a heat exchanger to heat the compressed air, and an air motor driven by the heated, compressed air and connected to a wheel. A ventilation system has a restrictive solenoid valve for directing air to the heat exchanger. The air tank is provided with a carbon filament reinforced plastic layer, and a fiberglass and aramid-fiber layer. A second sub-assembly includes part of the vehicle body bonded to the first-sub-assembly using a structural adhesive, a pair of A-pillars, and a pair of roof rails. Seating includes inflatable components for adjustment.

Nerve guidance conduits from aligned nanofibers: improvement of nerve regeneration through longitudinal nanogrooves on a fiber surface

A novel fibrous conduit consisting of well-aligned nanofibers with longitudinal nanogrooves on the fiber surface was prepared by electrospinning and was subjected to an in vivo nerve regeneration study on rats using a sciatic nerve injury model. For comparison, a fibrous conduit having a similar fiber alignment structure without surface groove and an autograft were also conducted in the same test. The electrophysiological, walking track, gastrocnemius muscle, triple-immunofluorescence, and immunohistological analyses indicated that grooved fibers effectively improved sciatic nerve regeneration. This is mainly attributed to the highly ordered secondary structure formed by surface grooves and an increase in the specific surface area. Fibrous conduits made of longitudinally aligned nanofibers with longitudinal nanogrooves on the fiber surface may offer a new nerve guidance conduit for peripheral nerve repair and regeneration.