Abstract
Purpose:
Hard exudates are observed in fundus of retinal vascular diseases including diabetic retinopathy. Previous histological studies in autopsy specimen have shown these characteristics. However, the detailed characteristics of hard exudates has not been investigated in vivo patients with retinal vascular diseases.
Methods:
Twenty-one eyes of nineteen patients with hard exudates were examined. We imaged hard exudates using spectral domain OCT (SD-OCT) and prototype adaptive optics scanning light ophthalmoscopy (AO-SLO) systems in all patients. The characteristics (location, size, morphology, and reflection patter) were investigated.
Results:
AO-SLO showed two morphological types of hard exudates which could not be distinguished from the fundus examination. One type is accumulated round particles (28.9±5.4µm) (round type; major axis: 374±236μm, area: 63091±9970μm2, reflective intensity: 134±24). Another type is an irregular shaped hyperreflective deposition (irregular type; major axis: 227±133μm, area: 24659±8076μm2, reflective intensity:132±19). The area as well as the major axis in round type were significantly bigger than of irregular type, whereas there was no significant difference of the reflective intensity and the vertical location. Both types could be observed in all diseases. These types could change into each other.
Conclusions:
High resolution imaging revealed two types of hard exudates. One could consist of phagocytes (round type) and another could be lipid or proteinaceous materials (irregular type). In vivo observation of hard exudates using AO-SLO confirmed to the previous histopathological findings.