Functional losses in type 2 diabetes mellitus

Aims: \ud \ud Psychophysical tests such as Letter contrast sensitivity (CS) and flicker perimetry have been used to detect early functional losses in ocular disease such as age-related maculopathy (ARM) and in vascular disorders such as migraine. This study set out to determine the ability of these tests to detect early functional losses in type 2 diabetics with minimal or early diabetic retinopathy (DR).\ud \ud Methods: \ud \ud Subjects consisted of 20 patients with type 2 diabetes (duration, following diagnosis, ranging from 6 months to 18 years) and 24 age-matched normal controls.\ud \ud Letter CS, using the Pelli-Robson cha.ii, visual acuity (VA) using the standard high contrast Bailey-Lovie chart and monocular visual fields (VF) were measured. Static and flicker VF were measured using the Medmont M600 perimeter (MFA) and SIT A-standard fields using the Humphrey Field Analyser (HFA) were tested.\ud \ud Results: \ud \ud Letter CS was able to discriminate those diabetic subjects with none or early DR and those with and without ME from the control group, whereas VA was not able to detect any significant differences in visual function in these diabetic sub-groups compared to the control group.\ud \ud In terms of visual fields, both the pattern defect (PD) index and hill-ofvision profiles were analysed. In those with early onset of diabetes and in those with none/minimal DR, only the PD index obtained with the flicker technique was significantly worse than the control group. The hill-of-vision profiles showed that the PD loss in those with minimal DR when flicker perimetry was used, was due to a central depression close to fixation, whereas the MFA static and HFA profiles consisted of a general depression across the field. This indicated that the flicker technique is a more sensitive test than the static technique in determining central visual field defects in those with minor observable retinal changes.\ud \ud The inability of the HFA to detect changes to the macula region was thought to be due to the large grid spacing of the stimuli, as when the severity of retinopathy increased to a moderate level, the MFA static technique produced central losses which were not evident with the HFA.\ud \ud Conclusion: \ud \ud For diabetic patients who had either, a duration of diabetes of less than five years, or displayed only minimal or no DR or no ME, VF defects were only elicited with the use of the MFA flicker technique. Further functional losses in those with no or early, clinically detectable changes, were revealed by measuring Pelli-Robson Letter CS