Swept Source optical coherence tomography of choroidal nevi

The aim of this article is to report on retinal and choroidal morphology in choroidal nevi documented with Swept Source optical coherence tomography (SS-OCT).

This is a retrospective, observational study.

We included 27 consecutive patients with choroidal nevi. Mean age was 66.3 years (21-95 years).

The SS-OCT scanning protocol consisted of a single line scan through the centre of the nevi with a resolution of 3 µm, built from 1024 A-scans, with a length of 12 mm. We attempted to visualize the outer choroidoscleral boundary and suprachoroidal layer (SCL) below the choroidal nevus and to observe any other defects of retinal or choroidal morphology.

In all cases, we observed that the inner margin of benign tumours was separated from the retinal pigment epithelium with a hyporeflective band. Melanotic nevi cast partial (41%) or complete shadow (41%) on the underlying structures. The outer choroidoscleral boundary was visible under the tumour in 8 eyes (25%). SCL and suprachoroidal space were noted in 40% of eyes in close proximity to the lesion, but in no case were these lines visible directly below the lesion. Thinning of the choriocapillaries was observed in 8 eyes (25%) and thinning of the choroid in 5 eyes (15.6%).

Using SS-OCT, we observed that the inner border of benign choroidal lesions was always situated below a hyporeflective band, possibly corresponding to the choriocapillaries. A new finding was that we observed the SCL in 40% of cases. This was always visible in close proximity to the nevus, never directly below it.