There are currently 3 established techniques employed routinely to determine the risk of foot ulceration in the patient with diabetes mellitus. These are the assessment of circulation, neuropathy, and foot pressure. These assessments are widely used clinically as well as in the research domain with an aim to prevent the onset of foot ulceration. Routine neuropathic evaluation includes the assessment of sensory loss in the plantar skin of the foot using both the Semmes Weinstein monofilament and the biothesiometer. Thermological measurements of the foot to assess responses to thermal stimuli and cutaneous thermal discrimination threshold are relatively uncommon. Indeed, there remains uncertainty regarding the importance of thermal changes in the development of foot ulcers. Applications of thermography and thermometry in lower extremity wounds, vascular complications, and neuropathic complications have progressed as a result of improved imaging software and transducer technology. However, the uncertainty associated with the specific thermal modality, the costs, and processing times render its adaptation to the clinic. Therefore, wider adoption of thermological measurements has been limited. This article reviews thermal measurement techniques specific to diabetic foot such as electrical contact thermometry, cutaneous thermal discrimination thresholds, infrared thermography, and liquid crystal thermography.

Patients with diabetes require annual screening for effective timing of sight-saving treatment. However, the lack of screening and the shortage of ophthalmologists limit the ocular health care available. This is stimulating research into automated analysis of the reflectance images of the ocular fundus. Publications applicable to the automated screening of diabetic retinopathy are summarised. The review has been structured to mimic some of the processes that an ophthalmologist performs when examining the retina. Thus image processing tasks, such as vessel and lesion location, are reviewed before any intelligent or automated systems. Most research has been undertaken in identification of the retinal vasculature and analysis of early pathological changes. Progress has been made in the identification of the retinal vasculature and the more common pathological features, such as small aneurysms and exudates. Ancillary research into image preprocessing has also been identified. In summary, the advent of digital data sets has made image analysis more accessible, although questions regarding the assessment of individual algorithms and whole systems are only just being addressed.

Summary. Miniature, amperometric glucose sensors were constructed using entrapped 1,1'-dimethylferrocene to mediate electron transfer between immobilised glucose oxidase and a carbon base electrode. Electrodes were calibrated in buffered glucose solutions and then implanted in the subcutaneous tissue of anaesthetised, non-diabetic pigs. Subcutaneous tissue glucose concentrations, as measured by the sensor, were about 20% of blood glucose values, measured by a conventional glucose oxidase assay. After an intravenous 0.07 mol bolus glucose injection, electrode responses increased with almost no time lag, but the subsequent rates of rise and fall of electrodemeasured tissue glucose concentrations were slower than that of the blood values. After an intravenous 0.2 U/Kg bolus short-acting insulin injection the electrode response was also rapid, but decreased at a slower rate than the blood glucose concentrations. We conclude that this is a feasible technology for future development as an implantable glucose sensor for use in diabetic man.

Miniature, amperometric glucose sensors were constructed for implantation in the subcutaneous tissue of normal and insulin-dependent diabetic subjects. To minimise dependence on fluctuating tissue oxygen tension, we employed the technology of mediated electron transfer, with 1,1'-dimethylferrocene acting as the redox shuttle between immobilized glucose oxidase and a platinum base electrode. In 6 normal subjects, the subcutaneous sensor responses mirrored the simultaneously-measured changes in blood glucose concentration after a 75 g oral glucose load and after intravenous injection of 0.15 U/kg short-acting insulin, though increases and decreases in the sensor output were slower than the glycaemic changes. The mean peak delay in sensor response after the oral glucose was 40 min (range 0-45 min) and the delay in the hypoglycaemic nadir was 4 min (range 0-15 min). In 5 insulin-dependent diabetic subjects, spontaneous and induced hypoglycaemia was detectable by the implanted sensor. In addition, marked and frequent oscillations in the sensor current occurred in several normal and diabetic individuals as the blood glucose fell below about 1.9 mmol/l. These oscillations were present in a diabetic subject who had lost adrenergic warning symptoms to hypoglycaemia. Continuous metabolic monitoring in diabetes, particularly the detection of hypoglycaemia, may be possible with implanted sensors based on this technology.

Recent advances in the development of transducers for the measurement of vertical and shear forces acting on the plantar surface of the foot are reviewed. Barefoot and in-shoe discrete and matrix transducers are reviewed in terms of structure, operation, performance and limitations. Examples of capacitive, piezo-electric, optical, conductive and resistive types of transducer are presented. Where available, the current clinical status is specified.