[Pathophysiology of macular diseases--morphology and function].Nippon Ganka Gakkai Zasshi. 2011 Mar; 115(3):238-74; discussion 275.NG
Ophthalmic fundus imaging plays an important role in the advances in the pathophysiology of retinal diseases. Using fundus imaging, we studied morphological changes in the choroid, subretinal pathophysiology and photoreceptor and retinal pigment epithelial (RPE) cell damage, and functional abnormalities of photoreceptor cells in macular diseases. To evaluate the choroidal changes, we performed enhanced depth imaging optical coherence tomography (EDI-OCT) for macular diseases. Choroidal thickness both in the affected eyes and in the fellow eyes with choroidal vascular hyperpermeability was thicker in patients with central serous chorioretinopathy (CSC). Photodynamic therapy (PDT) reduced the hyperpermeability and led to choroidal thinning in eyes with CSC, whereas laser photocoagulation did not result in any change in choroidal thickness, suggesting different mechanism of action for these two forms of treatment. PDT also decreased choroidal thickness in eyes with polypoidal choroidal vasculopathy. These findings will help to elucidate the pathophysiologic features of CSC as well as responses to treatment. Patients with acute Vogt-Koyanagi-Harada (VKH) disease have markedly thickened choroids. Both the choroidal thickness and the retinal detachment in these patients decreased quickly with corticosteroid treatment. EDI-OCT can be used to evaluate the choroidal involvement in VKH disease in acute stages and may prove useful in the diagnosis and management of this disease. Dome-shaped macula is the result of a localized thickening of the sclera under the macula in highly myopic patients, and it cannot be categorized into any known type of staphyloma. EDI-OCT is helpful in monitoring the proposed site of pathophysiologic changes in the choroid and the sclera, and provides noninvasively information not available by other means. To clarify the subretinal changes and the mechanism of cell damage in macular detachment, we studied the clinical characteristics of yellow deposits (multiple dot-like yellow precipitates and subretinal yellow material) seen in CSC using fundus autofluorescence and OCT. The yellow deposits had highly reflective tissue in the intraretinal and subretinal spaces seen on OCT and hyperfluorescence on short-wave autofluorescence (SW-AF) examinations during the follow-up period. These findings may indicate that formations of yellow deposits are associated with the accumulation of the photoreceptor outer segments and metabolism and phagocytosis by macrophages or RPE cells. SW-AF also demonstrated a hypofluorescence corresponding to the accumulated areas of yellow deposits during the long term followup period. Another study using infrared autofluorescence examination demonstrated that the yellow deposits induced a decrease in melanin and the functional decline of RPE cells in CSC. These may indicate that the existence of depositions in eyes with CSC is associated with photoreceptor and RPE cells damage. Similar yellow deposits can also be seen in eyes with macular detachment, e. g. branch retinal vein occlusion. We report a new method of retinal densitometry using SW-AF examination by scanning laser ophthalmoscope. We named the technique autofluorescence densitometry (AFD). This technique can evaluate photopigment density from serial SW-AF images during exposure to excitation light. This new technique can examine a much broader macular area and create a distribution map of optical density of the photopigments. It is also easy to compare the distribution of the photopigment densities with other retinal imaging devices such as OCT. To investigate functional abnormalities in eyes with CSC, we measured the optical density of the photopigments using AFD in both the acute and quiescent phase. The photopigment density decreased at the serous retinal detachment. The density remained decreased immediately after resolution and showed delayed recovery. The photopigments decreased even in eyes with a morphologic recovery of the outer retina. AFD could identify the functional impairment of the outer retina as characterized by changes in the photopigments.