Colour centre This is more important for perceiving the colour of objects and pictures. The double-opponent cells are receptive to opposite inputs from different cone cells in the retina. This is ideal for identifying contrasting colours, such as red and green. [1] Double-opponent cells are particularly important in computing local cone ratios from visual information from their receptive fields. Single opponent colour-sensitive neurons can be divided into two categories depending on the signals they receive from the cone cells: L-M neurons and S/(L+M) neurons. The three types of cone cells, small (S), medium (M), and long (L), detect different wavelengths across the
Laser safety near-infrared light onto the retina. A laser beam can be focused to an intensity on the retina which may be up to 200,000 times higher than at the point where the laser beam enters the eye. Most of the light is absorbed by melanin pigments in the pigment epithelium just behind the photoreceptors, and causes burns in the retina. Ultraviolet light with wavelengths shorter than 400 nm tends to be absorbed by lens and 300 nm in the cornea, where it can produce injuries at relatively low powers due to photochemical damage. Infrared light mainly causes thermal damage to the