Retinal pigment epithelium disorder in Vogt-Koyanagi-Harada disease revealed by hyperosmolarity response of ocular standing potential.

The hyperosmolarity response of the ocular standing potential was examined in 14 eyes of 7 cases of Harada's disease between 8 and 1,341 days after the onset of the disease. The hyperosmolarity response remained normal at the initial stage of the disease when choroiditis, retinal detachment and iridocyclitis were the main manifestations. The hyperosmolarity response was suppressed when depigmentation of the fundus progressed to the stage of the "sunset glow" appearance. The present study suggests that a sensitivity reduction to osmotic stress takes place in the retinal pigment epithelium concomitantly with the transition from the stage of depigmentation to the stage of "sunset glow". This dysfunction can be disclosed by the hyperosmolarity response, but not by the conventional examination of the light peak/dark trough ratio of the ocular standing potential.