Cancer-associated retinopathy

This is a paraneoplastic phenomenon whereby a systemic malignancy such as lung cancer causes blindness. The exact mechanism is unknown is believed to be related to an autimmune disturbance.

The symptoms are bilateral loss of vision, night blindness and flashing lights (i.e., 'photopsia').

Usually, the visual symptoms precede the diagnosis of the underlying cancer. However, with skin melanoma, the ocular disease tends to occur years after treatment of the skin tumour, usually when systemic metastases develop.

The back of the eye may look surprisingly normal. Diagnosis is based on the symptoms, electrical tests of retinal function (ERG), and blood tests showing particular antibodies.