The subject views pairs of small coloured lights, reflected from a standard mirror which is supplied with each instrument; the mirror is at 3 metres and the task is to name the colours.
Typically, the names white, red and green are allowed, with yellow in clinical mode.
Note: There are two different reds, each called red, and two different greens, each called green.
THE NEED FOR LANTERN COLOUR TESTS
Lanterns are established and practical means for detecting colour vision defects, for clinical, aviation and marine purposes and instil confidence by resembling real tasks.
Naming small coloured lights is required in transport and danger warnings.
- Ensuring safety for aircraft pilots, mariners, drivers, railway staff and others.
- Detecting inherited anomalies of colour perception. Up to 8% of males have these.
- Detecting and monitoring perceptual anomalies in pathological conditions.(Diabetes, cataract and varied retinal degenerations are typical examples.)
UK STANDARDS are set for Navy, Merchant Marine, RAF, and Civil Aviation use. Those set by Holmes-Wright lanterns for Air and Marine use are closely matched and used in the CAM, since the H/W lanterns are now not made. In addition, the CAM lantern provides an extra Clinical Mode in the same instrument.
Care is taken over matching colours, brightness and aperture sizes. Each CAM is issued with a spare lamp unit, easily replaced after 2,500 hours, for recycling, although lamp life is estimated at 4000 hours.
The Cam was developed from the 2002 prototype, with which Prof. R. Fletcher won a competition organised by the College and Association of Optometrists.