Although CCH is usually diagnosed ophthalmoscopically, ultrasonography, FAF, OCT, FA, and ICGA are also used as ancillary tests to verify tumor diagnosis and assess treatment response. In recent years, OCTA has also used in the diagnosis of CCH and in the evaluation of treatment results [3, 6, 7]. In this study, we focused on SS-OCT/SS-OCTA findings in CCHs managed with TTT/ICG-TTT.

On SS-OCT, CCHs demonstrated a dome-shaped (100%) appearance with medium (81.0%) or low (19.0%) reflectivity, choroidal shadowing (100%), SRF (66.7%), intraretinal edema/intraretinal schisis (33.3%), RPE and or outer retinal atrophy (19.0%), hyperreflective dots (19.0%), and epiretinal membrane (4.8%). In addition, there was expansion of medium and large sized choroidal vessels without compression of choriocapillaris (100%).

On OCTA, there were no structural changes in SCP and DCP slabs in most of the eyes with CCH. However, pressure vascular changes were noted in 14.3% of eyes in the SCP and DCP. Flow-void areas from intraretinal schisis/edema were detected in 33.3% of eyes in the DCP. Similar findings in the DCP have been reported before [3]. In a study comparing eyes with CCH and normal fellow eyes by OCTA, there was no difference in the SCP foveal avascular zone (FAZ), DCP FAZ, and SCP vascular density. However, the mean DCP vascular density was decreased in eyes harboring CCH [19]. Subgroup analysis in the same study demonstrated that eyes with previous/current cystoid macular edema/SRF had decreased DCP vascular density, while eyes without previous/current cystoid macular edema/SRF had similar DCP vascular density compared with fellow eyes [19]. The authors also emphasized that the decrease in DCP vascular density from cystoid macular edema/SRF was not likely a result of artifact as all images were individually analyzed for accuracy in segmentation and only with good signal strengths were included [19].

In 44.4% of CCHs, RPE atrophy was detected over the tumor. In these eyes, outer retinal involvement was observed due to unmasking of flow in intratumoral vessels. Cennamo et al. also noted a dense irregular vascular network in the outer retina in 6 eyes with CCH [16].

On SS-OCTA, we detected internal arborizing tumor vessels demonstrating hyperreflectivity in the choroidal slab in all eyes with CCH. Similarly, superficial multiple whitish irregular vessels resembling “bag of worms” and deeper vessels demonstrating “club-like” appearance were demonstrated at varying depths at the choroidal slab in previous studies [14]. Some authors identified whitish, tortuous, bending or curved vessels, interlaced with few intervening signal void areas on SS-OCTA images of CCH and resembled this appearance to a noodle like-pattern [20, 21]. The transition from irregularly shaped tumor vessels to regularly shaped normal vessels at the tumor margin was also demonstrated [14].

In our study, B-scan angiography overlay demonstrated increased flow signals over the tumor in all eyes. Similarly, Toledo et al. reported high vascular flux over CCHs in B-scan overlay [15]. Quiescent tumors with few intratumoral vessels were reported to remain stable [22]. In a case in which intratumoral blood flow was not detected on OCTA, no change was found in VA and SRF at the 6-month follow-up without treatment [22]. This shows that OCTA can also be useful in monitoring CCH cases that are observed.

SS-OCT findings after TTT and ICG-TTT of CCHs included decrease in tumor thickness, partial or total resolution of SRF and intraretinal edema, RPE atrophy, increased posterior light transmission, and retinal atrophy with loss of lamination. SS-OCT provides invaluable information on retinal changes including retinoschisis overlying the tumor and regression of intraretinal edema and SRF following treatment.

We noticed a decrease in intratumoral vessels following TTT/ICG on SS-OCTA. Giudice et al. reported that two days after photodynamic therapy (PDT), large intralesional vascular channels of CCH appeared dark on OCTA [7]. Cennamo et al. noted reduction of the vessel and flow areas between baseline and 1 year follow-up in 7 CCH cases treated with Ruthenium-106 brachytherapy [23]. The authors speculated that this result was due to the vaso-occlusive effects of PDT and brachytherapy which causes thrombosis of angiomatous channels [7, 23]. However, in another study, persistent medium-sized crisscrossing vessels over the tumor following 2–3 sessions of laser photocoagulation have been reported on OCTA [17].

In our study, loss of choriocapillaris and an increase in the fibrous component and flow void areas were observed on SS-OCTA after TTT/ICG-TTT. A study evaluating comparative OCTA findings before and after TTT (3 eyes) or PDT (4 eyes) reported that complete loss of choriocapillaris and absence of deeper choroidal vessels was observed in all TTT-treated eyes. In contrast, patency of choriocapillaris (100%) and persistence of deeper choroidal vessels (50%) were found in PDT-treated eyes [6]. Partial signal void areas were demonstrated in both groups after treatment (100%) [6]. In terms of preserving choroidal vasculature, the authors recommended PDT in CCH, particularly in cases involving the fovea [6]. TTT/ICG-TTT should be used carefully in subfoveal CCHs [24, 25]. A foveal sparing approach is necessary for subfoveal tumors when using TTT for tumors at this location.

In our series, VA improvement by ≥ 2 lines was observed in 52.4% of eyes after treatment with TTT/ICG-TTT. Complete resolution of SRF was seen in 57.1% of eyes. Although statistical analysis could not be performed due to the limited number of eyes in the TTT group, it appears that fewer treatment sessions of ICG-TTT may be required for SRF resolution compared to TTT. Complete disappearance, decrease in tumor thickness ≥ 30%, and decrease in tumor thickness < 30% were noted in 14.3%, 28.6%, and 57.1% of eyes, respectively. Rate of VA improvement by ≥ 2 lines and rate of complete resolution of SRF were higher in ICG-TTT group compared to TTT group, while rate of decrease in tumor thickness ≥ 30% was higher in TTT group compared to ICG-TTT group. However, these differences were not statistically significant. Our detailed comparative results of laser treatment modalities used in CCH have been reported previously [25].

Our study has certain limitations. First, it is retrospective. Second, patient sample was relatively small. Third, the limited number of patients in the TTT group compared to the ICG-TTT group prevented a more reliable statistical evaluation among the treatment groups.

In summary, SS-OCT and SS-OCTA are useful non-invasive methods for evaluating structural and vascular changes in CCH cases before and after treatment. CCHs usually demonstrate a dome-shaped appearance, choroidal shadowing, and expansion of choroidal structures on SS-OCT. On SS-OCTA, CCHs are characterized by well-defined margins, a mixed reflective internal tumor structure featuring intertwined and irregularly organized large-calibre vessels mixed with signal void areas, presumably representing connective tissue components of the tumor. After TTT/ICG-TTT, RPE atrophy, increased light transmission into the choroid, and decrease in tumor thickness were noted on SS-OCT. Decrease in tumor vessels and increase in the fibrous component and flow-void areas of the tumor were detected on SS-OCTA following TTT/ICG-TTT.