Cancer Associated Retinopathy (CAR)
Rapid painless loss of vision (central scotoma) + photopsia + photosensitivity + loss colour vision + nyctalopia.
Retinal examination often normal – sometimes pseudo-RP appearance.
Markedly abnormal ERG
Paraneoplastic retinopathies (PR): antibodies towards retinal proteins with underlying malignancy – eg. CAR or MAR (melanoma associated retinopathy.
Autoimmune reintopathies (AIR): antibodies towards retinal proteins without underlying malignancy
CAR: small cell lung cancer (common); uterine/cervical ca; breast ca – usually female around 65 years old.
CAR vs. MAR findings:
CAR – affects both rods and cones –> ERG has absent cone responses with reduced a and b waves in both photopic and scotopic conditions.
MAR – affects bipolar cells that interfere rod functions –> reduced or absent dark adapted b wave (indicates bipolar and Muller cells dysfunction with preserved photoreceptor function).
SUSPECT in anyone with new onset progressive vision loss with normal fundus appearance.
Check colour vision and visual fields.
ERG (full-field) +/- MERG (to monitor disease progression and correlate with visual field loss).
Antiretinal antibodies (but may not be present in 35% of CAR) – antorecoverin antibodies, antienolase antibodies.
CXR / CT (chest)
CT (abdomen or pelvis) or PET (whole body) or mammography.
Female – pelvic and breast examination.
History of cutaneous melanoma.
Retrobulbar optic neuropathy
Neuro-ophth causes – demyelination, compressive orbital/intracranial lesion, ischaemia, toxicity or hereditary
Inflammatory disease (with antiretinal antibodies) – AZOOR (bilateral, asymmetrical, similar ERG changes), MEWDS (usually unilateral, disc swelling and resolves spontaneously), retinal vasculitis, VKH, Behcet’s dieases, sympathetic ophthalmia or infectious related (all have their typical history and presentation to differentiate)
Prognosis: Poor visual recovery despite treatment of cause. Corticosteroids and immunosuppressive agents may help stabilise vision but not reverse visual loss.