LONGITUDINAL ANALYSIS OF DIABETIC CHOROIDOPATHY IN PROLIFERATIVE DIABETIC RETINOPATHY TREATED WITH PANRETINAL PHOTOCOAGULATION USING WIDEFIELD SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY

Abstract

Purpose: Widefield swept-source optical coherence tomography (OCT) imaging was used to characterize choroidal thickness and vascularity at baseline in proliferative diabetic retinopathy (PDR) and longitudinally after panretinal photocoagulation (PRP).

Methods: Patients with treatment-naive PDR were imaged at baseline and at 1 week, 1 month, and 3 months after PRP. Previously validated algorithms were used to calculate the mean choroidal thickness (MCT) and choroidal vascularity index (CVI) in 5 regions of 12 mm × 12 mm scans.

Results: Fourteen PDR eyes were included. Baseline MCT in PDR eyes did not differ significantly from normal eyes, but CVI measurements in PDR eyes were lower in all regions (P < 0.001-0.008). After PRP, MCT measurements in PDR eyes were significantly lower at 1 month and 3 months in all regions (P < 0.001-0.005) except the fovea (P = 0.074). However, CVI measurements did not change over time in any region after PRP.

Conclusion: The choroid in PDR eyes has a smaller CVI than that in normal eyes. After PRP, the choroidal thickness decreases outside the fovea, but the CVI remains constant, which suggests that a relative decrease in choroidal vascularity persists. These widefield swept-source OCT results are consistent with choroidal alterations found in histopathological reports of diabetic choroidopathy.

Figure 1.. Widefield (WF) color, fluorescein angiography, and swept source (SS) OCT imaging of representative proliferative diabetic retinopathy (PDR) eye with choroidal thickness and vascularity maps.

(A) The baseline widefield (WF) color fundus image shows few intraretinal hemorrhages and a superonasal cotton-wool spot. (B) The WF fluorescein angiogram (FA) highlights areas of ischemia and multifocal preretinal neovascularization. Neither of the conventional WF imaging modalities depict choroidal details. On the same visit, WF SS-OCT imaging was performed with a 12×12mm field of view (corresponding to the red square in A). (C) Choroidal thickness maps, (D) choroidal vascularity maps, and (E) choroidal vascularity index maps were generated throughout the 12×12mm field of view using previously-validated algorithms (see Methods). Areas with a thicker choroid or larger CVI measurements are depicted with warmer colors in the respective topographic heat maps (C, E). Scale bars are shown to the right of C and E.

Figure 2.. Mean choroidal thickness and choroidal vascularity index measurements in eyes with proliferative diabetic retinopathy (PDR).

Baseline values for mean choroidal thickness (MCT) and (B) choroidal vascularity index (CVI) measurements (see Methods) are plotted against age for 20 eyes with PDR (blue dots) and 144 normal eyes (red dots). These values were determined by analyzing 12×12mm widefield (WF) swept source (SS) OCT choroidal slabs with automated algorithms as described in the Methods. The values shown are averages throughout the entire 12×12mm scan, excluding the optic nerve.

Figure 3.. Longitudinal widefield (WF) swept source (SS) OCT imaging of choroidal thickness and vascularity after panretinal photocoagulation (PRP) in a representative eye with proliferative diabetic retinopathy (PDR).

(A-D) Topographic heat maps of choroidal thickness measurements throughout the 12×12mm WF SS-OCT scans for the baseline visit (left column), 1 week visit (second to left column), 1 month visit (second to right column), and 3 month visit (right column). PRP was performed immediately after baseline imaging. In this eye, there was a modest increase in choroidal thickness at 1 week followed by choroidal thinning. (E-H) Choroidal vasculature throughout 12×12mm WF SS-OCT scans arrayed for the 4 visits as in A-D. (I-L) Topographic heat maps of the choroidal vascularity index (CVI; see Methods) arrayed for the 4 visits as above. There were no significant changes in CVI throughout all 4 visits. Scale bars for choroidal thickness and CVI are shown to the right.

Figure 4.. Longitudinal widefield (WF) swept source (SS) OCT imaging of choroidal thickness and vascularity after panretinal photocoagulation (PRP) in a second representative eye with proliferative diabetic retinopathy (PDR).

(A-D) Topographic heat maps of choroidal thickness measurements throughout the 12×12mm WF SS-OCT scans for the baseline visit (left column), 1 week visit (second to left column), 1 month visit (second to right column), and 3 month visit (right column). PRP was performed immediately after baseline imaging. In this eye, there was a modest increase in choroidal thickness at 1 week followed by choroidal thinning. (E-H) Choroidal vasculature throughout 12×12mm WF SS-OCT scans arrayed for the 4 visits as in A-D. (I-L) Topographic heat maps of the choroidal vascularity index (CVI; see Methods) arrayed for the 4 visits as above. There were no significant changes in CVI throughout all 4 visits. Scale bars for choroidal thickness and CVI are shown to the right.