Retinal pigment epithelial trough: a sign of chronicity of choroidal nevi

To describe the clinical features and natural course of choroidal nevi with retinal pigment epithelial (RPE) trough.

Retrospective observational case series.

Of the 90 patients (91 choroidal nevi), 88 (98%) were Caucasian and 59 (66%) were women, with a mean age of 56 years (range 18-79 years) at presentation. The mean largest nevus basal diameter was 7 mm (range 3-12 mm) and the mean thickness was 2.2 mm (range 0.8-3.4 mm). Orange pigment and subretinal fluid were associated with 9 (10%) and 16 (18%) of the nevi, respectively. Overlying RPE alterations included RPE atrophy (93%), RPE hyperplasia (74%), drusen (54%), and RPE fibrous metaplasia (36%). Retinal pigment epithelial trough was present at initial evaluation in 88 eyes and developed during follow-up from a long-standing pocket of shallow subretinal fluid in 3 other eyes. The mean largest dimension of the RPE trough was 4 mm (range 1-16 mm) and most (76%) were located at the inferior margin of the nevus. Of 91 nevi, 82 had subsequent follow-up with a mean follow-up duration of 79 months (range 3-464 mo). Of these, 19 (23%) showed slight growth and only 3 (4%) had presumed transformation into melanoma. None of the patients showed evidence of distant metastasis.

Retinal pigment epithelial trough results from resorption of long-standing serous subretinal fluid and should therefore be considered a sign of chronicity of choroidal nevi. Choroidal nevi associated with RPE trough, despite their greater thickness and larger size, are relatively stable with minimal risk of progression into melanoma.