Comparing retinal function and structure in diabetic maculopathy and retinal detachment with ff-ERG and a combination of mfERG and OCT
Abstract: Diabetic maculopathy and retinal detachment, especially involving macula, are potentially sight-threatening conditions. Previous evaluations of retinal function, and treatment of these conditions have been subjective methods depending on the examiner or the collaboration with the examined patient. Retinal structure has been based on the subjective evaluation of the ophthalmologist. Development of ff-ERG, multifocal ERG (mfERG), which reflects central retinal function, and optical coherence tomography (OCT) which analyzes central retinal structure has enhanced our possibility to evaluate the retinal disorders in a more objective way. The aim of this thesis was to correlate central retinal function (mfERG) to central retinal structure (OCT) in diabetic macular edema and in retinal detachment before and after surgery. Where appropriate total retinal function (ffERG) was evaluated. A standardized combination of OCT and mfERG was developed. Retinal function correlated negatively to retinal thickness, the presence of hard exudates and the nasal part of macula, in patients with diabetes. Reduced amplitude and prolonged implicit time correlated to macular central thickness. When the central macular thickness exceeded 300 µm the reduced amplitude and prolonged implicit time seemed to be more pronounced. Eyes with hard exudates had prolonged implicit time compared to eyes without hard exudates, despite no differences in macular thickness. Hard exudates prolong the implicit time, even at a distance from the fovea center. The nasal macular area showed lower amplitude and prolonged implicit time compared to the temporal. Evaluation of laser treatment showed increased mfERG amplitude, reduced macular thickness and resolved hard exudates. In retinal detachment electroretinographic deterioration occurs both in short-term and long-term detachment. In long-term detachment the deterioration of retinal function is pronounced with no detectable macular function. After the scleral buckling procedure, in short-term detachment mfERG amplitude and rod function improves postoperatively. After vitrectomy including retinectomy in long-term detachment retinal function can improve. A combination of mfERG and OCT, and where appropriate, ffERG, are suitable tools for further studies regarding retinal and macular function and structure in diabetic maculopathy and retinal detachment, and evaluation of treatment.
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