both vogt - koyanagi - harada ( vkh ) disease and central serous chorioretinopathy ( csc ) develop serous retinal detachment , and since recently , it has been well known that in both diseases , the thick choroid can be seen on optical coherence tomography ( oct ) . however , the pathogenesis of each disease is totally different ; vkh is an inflammatory disease affecting melanocytes , while csc is a disorder of choroidal circulation . steroids treat vkh but worsen csc ; therefore , it is important to distinguish these diseases . we report a case of vkh disease in which recurred serous retinal detachment was treated successfully with steroids , but the last recurrence did not respond to the steroids and angiographic findings suggested csc . here , we show the multimodal images of this case including en face oct images during the course of vkh disease . in this study , we use swept - source oct ( dri oct-1 , topcon , tokyo , japan ) , which allows superior visualization of the choroid thanks to a 1,050-nm wavelength light source and a scanning speed of 100,000 a scans / second . the axial and transverse resolution of the system was 8 and 20 m , respectively . the oct scan protocol was 3d scan covering an area of 12  9 mm horizontal and vertical b scans . the software enabled us to reconstruct a series of en face images from 3d volume scan , where 992 consecutive en face images were created with a depth interval of 2.6 m . when observing choroidal vessels , we referred to the en face images around the depth of the upper one third of haller 's layer , where the choroidal vessels were seen clearly at each visit . a 50-year - old man was referred to the sumitomo hospital with blurring of vision in his right eye from 2 weeks prior . his best - corrected decimal visual acuity ( bcva ) on presentation was 0.8 in the right eye and 1.2 in the left eye . intraocular pressure was normal and no remarkable inflammation was observed in either the anterior or posterior chamber in both eyes . fundus and oct examination showed bilateral optic disc swelling and exudative subretinal fluid ( srf ) in his right eye . choroid was significantly thick in both eyes : much thicker in the right eye than in the left eye ( 593 and 393 m , respectively ; fig . en face oct images showed blurry choroidal vessels and retinal pigment epithelium ( rpe ) folds associated with the disc swelling bilaterally ( fig . fluorescein angiography ( fa ) and indocyanine green angiography ( icga ) was performed using spectral - domain oct ( spectralis , heidelberg engineering , heidelberg , germany ) . fa showed the leakage from the optic disc bilaterally and pooling of the dye in the subretinal space at the macula in the right eye ( fig . 1e , f ) and icga depicted patchy hyperfluorescent areas from the early phase and hypofluorescent dots in the late phase ( fig . this patient was diagnosed with vkh disease and started to receive high - dose steroid pulse treatment . methylprednisolone ( 1,000 mg / day ) was intravenously administered for 3 days , followed by oral prednisolone for 16 weeks tapering off from 30 mg / day . soon after the initiation of steroid treatment , the patient recognized a clearer visual field . the choroid became thinner ( 238 m in the right eye and 212 m in the left eye ) and en face oct showed the clearer visualization of choroidal vessels bilaterally . however , 4 weeks after the cessation of steroids , bilateral disc swelling , thickened choroid ( 490 m in the right eye and 464 m in the left eye ) and srf in the right eye recurred . systemic steroids were started again and 4 weeks later , bilateral disc swelling resolved completely with the reduction of the choroidal thickness and srf . two weeks later , however , srf in the right eye recurred under the oral steroid medication without disc swelling . no leakage was apparent on fa and no hypofluorescent dots were seen on icga . the choroidal thickness was unchanged with normal appearance on en face images ; however , after sub - tenon 's capsule triamcinolone acetonide ( stta ) injection ( 20 mg ) , srf resolved . four weeks later , srf recurred again and to avoid the excessive use of steroids , bevacizumab was injected intravitreally ; however , there were no remarkable changes . the additional stta and the oral steroids were effective and complete resolution of srf was obtained with improved vision of 1.0 . four weeks later , however , srf recurred with pigment epithelial detachment ( ped ; fig . 2a ) with a decreased bcva of 0.4 despite the continuation of the oral steroids and the stta , which were ineffective to resolve it . at this time , the choroid was not thick and en face oct depicted the choroidal vessels clearly ( fig . fa showed several leakages near the fovea and icga also depicted the leakage at the corresponding regions on fa with surrounding mixed hyper and hypofluorescence ( fig . 2c , then , the eye was diagnosed with prednisolone - induced csc , and the intake of oral steroids was tapered . one month after the stopping of oral steroids , bilateral inflammation in the anterior chamber occurred with bilateral disc swelling . oct showed thickened choroid ( 412 m in the right eye and 396 m in the left eye ) with blurred choroidal vessels bilaterally , and then steroid therapy was restarted . over 6 months under the low - dose oral steroids , this patient was initially diagnosed with vkh because of the bilateral disc swelling and characteristic hyporeflective dots on icga with thick choroid on oct . his symptoms were quite responsive to the systemic steroids . during the course , the srf in his right eye recurred several times without disc swelling , and it had been treated with steroids including stta , but gradually became refractory . finally , the discontinuation of steroids was effective to resolve the fluid . from the fa and icga , the origin of the srf was considered to be choroidal vascular hyperpermeability such as csc which developed secondary to the steroids . , longer administration of steroids or stta may cause the development or worsening of csc . if steroids are continued even after the development of csc , they may worsen csc . irreversible visual deterioration due to the damage of the rpe has been reported in the eyes with csc secondary to steroids . therefore , we should know the early signs of the csc in eyes with vkh treated with steroids . so far , only two cases have been reported from japan in whom secondary csc occurred during the treatment for vkh . in each case , srf had relapsed during steroid tapering ( prednisolone 15 and 5 mg , respectively ) , and diagnosed with csc using fa by the findings of dye leakages from the punctate hyperfluorescent spots seen at early phase . with the tapering of the steroids , srf promptly disappeared . both reports concluded that angiography was the definitive tool to diagnose secondary csc . in vkh , the characteristic fa leakage is multifocal in the early stage followed by pooling of dye in the subretinal space . otherwise in csc , univocal leakage from the level of rpe in the early stage is typical , but in eyes with csc associated with steroids , the intense leakage from multiple regions is often seen ; therefore , in addition to fa , the evaluation of multimodal imaging including icga is essential to differentiate both diseases . on conventional oct b scans , retinal detachment is easily detected , but it occurs in both vkh and csc and sometimes it is difficult to distinguish them . the following are the differential points on oct : vkh accompanies the folds of rpe , fluctuation of inner limiting membrane and subretinal septa , while ped is more common in csc . the choroid is significantly thicker in vkh than that in csc . when diagnosing vkh and csc based on choroidal thickness , attention is required because the choroid is usually thicker in active vkh than in csc , but choroidal thickness changes during the course of vkh and at the cicatricial stage of vkh , the choroid becomes thin . in our case , the noninvasive en face oct scans of the choroid could suggest the different condition from active vkh as the cause of the recurrent srf . every time showing the active vkh , the choroid was bilaterally thick and the choroidal vessels were blurred on en face oct images . on the contrary , when srf recurred without disc swelling , the choroidal thickness did not significantly increase and vessels were clearly traced , and such condition was considered to be associated with secondary csc . through the course of this patient , en face choroidal imaging is helpful to understand the disease condition . since the en face image is the same two - dimensional image as a conventional fundus photograph and angiography , it is easy to compare them . as histologically reported , the choroidal thickening in vkh is caused by the diffuse infiltration of lymphocytes , macrophages and epithelioid cells . macrophages and polymorphonuclear neutrophils infiltrate into the choroid accompanied by interstitial edema and vascular dilatation . such cellular infiltration may cause the blurry choroid on en face images . in csc , the choroid becomes thick due to the hyperpermeable choroidal vessels with an enlarged diameter but not blurry . the en face oct images of the choroid reflect those differences well and increase the accuracy of the diagnosis . careful follow - up is warranted in vkh patients since secondary csc may develop during steroid treatment . en face oct observation of the choroid written informed consent to publish was obtained from the patient for publication of this case report and any accompanying images . a copy of the written consent is available for review by the editor of this journal .
vogt - koyanagi - harada ( vkh ) disease and central serous chorioretinopathy ( csc ) develop serous retinal detachment ; however , the treatment of each disease is totally different . 
 steroids treat vkh but worsen csc ; therefore , it is important to distinguish these diseases . here , we report a case with csc which was diagnosed by en face optical coherence tomography ( oct ) imaging during the course of vkh disease . a 50-year - old man was referred with blurring of vision in his right eye . 
 fundus examination showed bilateral optic disc swelling and macular fluid in the right eye . 
 oct showed thick choroid , and en face oct images depicted blurry choroid without clear delineation of choroidal vessels . 
 combined with angiography findings , this patient was diagnosed with vkh disease and treated with steroids . 
 promptly , fundus abnormalities resolved with the reduction of the choroidal thickness and the choroidal vessels became visible on the en face images . during the tapering of the steroid , serous macular detachment in the right eye recurred several times . 
 steroid treatment was effective at first ; however , at the fourth appearance of submacular fluid , the patient did not respond . at that time , the choroidal vessels on the en face oct images were clear , which significantly differed from the images at the time of recurrence of vkh . 
 angiography also suggested csc - like leakage . 
 the tapering of the steroids was effective in resolving the fluid . 
 secondary csc may develop in the eye with vkh after steroid treatment . 
 en face oct observation of the choroid may be helpful to distinguish each condition .