Correlation between macular structure and function with multifocal pupillographic objective perimetry in early-stage type 2 diabetic macular oedema

Purpose. To correlate regional macular thickness, with per-region macular sensitivities and delays as measured by multifocal pupillographic objective perimetry (mfPOP), commercially known as ObjectiveField Analyser (OFA), in Type-2 diabetes (T2D) patients without and with off-centre mild diabetic macular oedema (DMO).Methods. We recruited 33 T2D patients (59.2 ± 10.5 y, 17 males). Mean OFA values within inner and outer macular regions were sorted according to retinal thickness. This allowed structure-function correlations to be computed relative to the degree of DMO, wherever it was. A generalised linear mixed-effects model determined which variables contribute to clinical diagnosis of DMO. Results. The mean sensitivity difference compared to normal in T2D patients was negative and the mean delay difference positive indicating declining sensitivity and prolonged delay relative to normal. Peripheral OFA hypersensitivity and shorter delays than normal were seen with shorter diabetes duration. For DMO patients outer macular thickness was correlated significantly with inner- and outer-macular OFA sensitivity and delay, all p<0.0012, but inner thickness was not correlated. The same was true for diabetic patients without DMO (median p-value was 0.001). A Mixed-effects logistic regression model determined outer thickness and OFA sensitivity (p=0.043), male gender (p=0.313) and time in the study (p=0.001), contributed independently to the odds of a clinical diagnosis of DMO. Conclusions. The mean sensitivity difference decreased, and mean delay difference increased in diabetic patients compared to normal in later-stage disease. Outer macular thickness correlated significantly with inner and outer OFA sensitivity and delay, while the inner macular thickness did not. As a clinical end-point outer thickness and functional measures may be a better indication of eye health in diabetic eye disease than is provided by visual acuity or other central functional measures.