Spatial visual filtering in diabetes mellitus.
OBJECTIVE
To investigate spatial visual filtering in a group of diabetic patients and compare the results with those of a group of controls.


METHODS
The luminance threshold of a moving 2 degrees achromatic target, viewed against a 17 degrees achromatic background grating, was measured as a function of grating periodicity from 0.21 to 31.4 cpd in 22 diabetic patients and 12 controls, giving a response characteristic of the spatial function of a sustained-response type of visual channel. A previously published model of spatiotemporal filtering, integrating photoreceptor kinetics with difference-of-Gaussian circularly symmetric receptive fields, was used to analyse the data.


METHODS
The model gave a good fit to the data in the control group, with a mean central space constant of 0.046 degrees and centre:surround ratio of 1:5.2 and mean R(2)=0.78 (SD 0.12). The mean central space constant in the diabetic group was 0.051 degrees and the centre:surround ratio 1:4.2, although best fit was significantly worse, at R(2)=0.54 (SD 0.19), P=0.001. The best fit for diabetic subjects with grade 2 maculopathy was significantly worse than for those with no maculopathy ( P=0.03).


CONCLUSIONS
The study demonstrates a disruption of circularly symmetric centre-surround receptive field structure of the sustained-response channel in the diabetic retina to a degree that is consistent with the retinal level of anatomical change in diabetic maculopathy.
Biophysics, Imperial College of Science, Technology and Medicine, South Kensington, SW7 2BZ, London, UK.
Nigel Philip
NP
Davies
Antony Bryan
AB
Morland
D016022:Case-Control Studies; D003920:Diabetes Mellitus / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000503:physiopathology; D005260:Female; D006801:Humans; D008029:Lighting; D008266:Macula Lutea / Q000503:physiopathology; D008954:Models, Biological; D010775:Photic Stimulation / Q000379:methods; D011247:Pregnancy; D012165:Retinal Ganglion Cells / Q000502:physiology; D012684:Sensory Thresholds; D014785:Vision, Ocular; D014794:Visual Fields