Unilateral exophthalmos in Sebastes spp.: histopathologic lesions

Abstract. A spontaneous unilateral exophthalmos occurring in five species of otherwise healthy rockfish, Sebastes spp., was investigated. All eyes from nine unilaterally exophthalmic and seven non-exophthalmic rockfish were examined grossly and histologically. In all affected fish the exophthalmos was due to enlargement of the globes resulting from the formation of choroidal cysts filled with a clear, watery fluid and surrounded by dense, aberrant connective tissue. Cyst formation led to gross distortion and disorganization of the choroid. Distorted remnants of the choroidal rete mirabile contained markedly fewer erythrocytes, a homogeneous proteinaceous material and a mild inflammatory cell infiltrate. Thickened scleral cartilage with disoriented chondrocytes was also present in exophthalmic eyes. Some of the affected eyes showed pigmentary abnormalities with clumps of heavily pigmented cells present in the retina and choroid. Retinal degeneration and detachment was also evident in some of the affected eyes.