Multimodal Imaging and the Effect of Half-fluence PDT on Choroidal Volume in Central Serous Chorioretinopathy

Abstract

 

Purpose

 

To evaluate the effect of half-fluence photodynamic therapy (PDT) on choroidal thickness maps obtained by enhanced depth imaging (EDI) spectral domain optical coherence tomography (SD-OCT) in central serous chorioretinopathy (CSC) patients. The goal was to identify association between choroidal thickness and overlying subretinal fluid (SRF) and changes seen on SD-OCT scan that correspond to hyperfluorescent lesions on fluorescein (FA) and indocyanine green (ICG) angiography.

 

Methods

 

Retrospective study of patients who underwent half-fluence PDT for CSC at Northwestern University between March 2010 and August 2013. Late FA and ICG images were superimposed on SD-OCT choroidal thickness maps, using free online software, the GNU Image Manipulation Program (GIMP). Morphologic alterations in SD-OCT were correlated with the hyperfluorescent areas in FA and ICG. In seven eyes that underwent EDI-OCT, total choroidal volume was evaluated before and after PDT. Changes in choroidal thickness in relation to the location of SRF, treatment location and angiographic leakage were investigated.

 

Results

 

20 eyes were included in this study. All eyes showed RPE irregularities in proximity of FA and ICG hyperfluorescent areas, including pigment epithelial detachment (75%), retinal pigment epithelium loss (RPE) loss (35%), RPE-microrip (20%) and an RPE double layer sign (30%). In 85% of eyes, RPE changes and angiographic hyperfluorescence were found within the area of SRF. The choroidal volume decreased from 9.35 ± 1.99 mm³ to 8.52 ± 1.92 mm³ and 8.04 ± 1.7 mm³ at 1 and 3 months post PDT respectively (p≤0.001). There was no significant difference between the choroidal thickness change after PDT in subgrids where PDT was applied compared to the untreated subgrids (p=0.1). There was no statistical difference in average choroidal thickness in subgrids with overlying SRF compared to subgrids without overlying SRF (p=0.148).

 

Conclusions

 

RPE changes on SD-OCT consistently correlated to underlying angiographic leakage. Therefore, SD-OCT may be a valuable additional tool to localize active lesions and serve as an adjunct to guide PDT treatment in chronic CSC patients. Choroidal thickening showed no correlation to the locus of SRF or leakage on FA and ICG angiography. The effect of PDT is not confined to the treated areas but may extend to adjacent choroidal tissue, causing a decrease in total average volume.

 

Keywords: 550 imaging/image analysis: clinical • 647 photodynamic therapy