Topographical relationship between the choroidal watershed zone and submacular idiopathic choroidal neovascularisation.

AIMS To investigate the relationship between idiopathic choroidal neovascularisation (CNV) and choroidal watershed zones (CWZs) using indocyanine green angiography (ICGA). DESIGN Multicentre, retrospective, interventional case series. METHODS The medical records and ICGA findings of 44 patients (44 eyes) diagnosed with idiopathic CNV were reviewed. CWZs, defined as hypofluorescence that disappeared during the early phase of ICGA, were classified, and the findings were compared with those of a control group of 30 eyes. The topographical relationship between CWZs and CNV was evaluated. Visual acuity and recurrence were analysed according to the CWZ classification. RESULTS The CNV lesion was subfoveal in 16 eyes, juxtafoveal in 12 eyes and extrafoveal in 16 eyes. The most common types of CWZs were stellate (23 eyes, 52.3%) and vertical (19 eyes, 43.2%). CWZs involving the fovea were seen in more patients with idiopathic CNV (37 eyes, 84.1%) than in the control group (11 eyes, 36.7%, p<0.001). The topographical relationship between CWZs and CNV was determined in 42 eyes (95.5%), with the CNV located within the CWZ in 39 eyes and at the margin in 3 eyes. Extrafoveal CNV was within the CWZ in all 16 affected eyes. At 6 months, visual acuity was significantly worse in patients with subfoveal CNV (p=0.028) or stellate CWZs (p=0.039). CONCLUSIONS The findings of a CWZ were related to the location and functional outcome of idiopathic CNV. Our results suggest that choroidal circulation is a predisposing factor for the development of CNV in young patients.