Increased blood viscosity in diabetic proliferative retinopathy.

Blood rheology and haemostasis were assessed in 18 diabetics with proliferative retinopathy and in 18 diabetics without proliferative retinopathy, matched for age, sex, smoking habit and type, duration and treatment of diabetes. Proliferative retinopathy was associated with significantly higher levels of blood viscosity at high and low shear rates, which were related to higher levels of plasma viscosity and fibrinogen. Blood urea, glucose, glycosylated haemoglobin and white cell count were also significantly higher, whereas haematocrit, red cell deformability and several other haematological and biochemical variables did not differ significantly in the 2 groups. In view of these findings, and of our recent demonstration that increased blood viscosity also exists in those patients with retinal vein occlusion who develop a similar proliferative retinopathy, we suggest that hyperviscosity may contribute to retinal ischaemia and hence proliferative retinopathy.

Colour vision of diabetics.

The Farnsworth-Munsell 100-hue test has been assessed as a screening test for the detection of diabetic retinopathy likely to benefit from laser photocoagulation therapy. Two hundred and thirty-two diabetic eyes of 126 patients were tested. The results were assessed both for total error score relative to age and for the presence of polarity. Although the incidence of abnormal colour discrimination was found to correlate with the severity of retinopathy, the test was not sufficiently selective to be of value as a screening test in the detection of retinopathy requiring treatment.

Short-term effect of slit-lamp illumination and argon laser light on visual function of diabetic and non-diabetic subjects.

Visual acuity, colour vision, and contrast sensitivity of diabetic and non-diabetic subjects were measured before, 20 minutes after, and 24 hours after exposure to slit-lamp illumination either alone or during argon laser photocoagulation. In some instances a significant deterioration of these visual functions was noted when the tests were repeated 20 minutes after light exposure, but by 24 hours after light exposure visual function of all groups had returned to pre-exposure levels. The visual acuity was the most systematically affected by the procedure; there were wide interindividual differences in the changes observed in the other tests.

Common causes of blindness and visual handicap in the west of Scotland.

An analysis of blind registration forms was made to determine the commonest causes of blindness in the west of Scotland. It was found that the leading causes of blindness in order of frequency of incidence were senile macular degeneration, glaucoma, cataract, diabetic retinopathy, and myopic degeneration. Diabetic retinopathy was the leading cause of blindness among persons of working age.

Blood viscosity in proliferative diabetic retinopathy and complicated retinal vein thrombosis.

Forty-two patients with longstanding retinal vein thrombosis and 36 patients with diabetes had their blood viscosity levels measured. In both conditions blood viscosity, plasma viscosity, and plasma fibrinogen levels were significantly higher in those patients with capillary non-perfusion and/or new vessels on fluorescein angiography, compared to those patients without these complications. The possible role of abnormal blood viscosity in producing capillary non-perfusion and its sequelae in both conditions is discussed.