A mains electricity (AC-powered) ophthalmic instrument used to test a patient for abnormal red/green colour vision by differentiating the red/green colour vision defects. It typically consists of two different light sources, one that permits the mixing of proportions of red and green and the other is a standard yellow colour which can be brightness adjusted. These are viewed and subsequently matched by the patient and according to the match, red- versus green-blindness, dichromacy versus anomalous trichromacy, and the severity of colour deficiency can be established. This device may be connected to a computer with dedicated application software.