Enhanced optical coherence patterns of diabetic macular oedema and their correlation with the pathophysiology

Purpose: To describe different patterns of diabetic macular oedema (DMO) using a computerized alignment and averaging of sequences in optical coherence tomography (OCT) B-scans and to show the correlation of these patterns with the pathophysiology of the condition. Methods: We carried out a prospective, uncontrolled study, including 46 human subjects with untreated DMO. Enhanced OCT images were produced. We correlated different OCT patterns of DMO with ETDRS visual acuity and with the thickness of the central 1-mm of the macula. We also correlated these patterns with theories of the pathophysiology of DMO. Results: Enhanced OCT images enabled us to examine how different layers of the macula were affected. The external limiting membrane (ELM) was clearly seen in all stages, including advanced stages. The sequence of DMO events in different macular layers can be divided into five patterns. Morphologically, DMO starts at the outer nuclear layer/Henle's layer. As the oedema progresses, cysts are seen in the fovea and the DMO spreads further into the inner nuclear layer. The ELM seems to act as a barrier for proteins and plays an important role in the development of DMO. Conclusions: Enhanced OCT revealed new details of DMO pathophysiology. The different morphological patterns of DMO seen in enhanced OCT may represent different levels of severity of the disease.