For each visual term A–E, select the most appropriate option from the following list of descrip-tions

A. Option 4 Contain rhodopsin. Rhodopsin is responsible for vision in poor light. It (Visual Purple) is the most sensitive visual pigment with a peak sensitivity to light at 505 nm.

B. Option 2 The minimum amount of light that elicits light sensation. In dark adaptation the visual threshold falls.

C. Option 1 Contain the least light-sensitive pigments in the retina. The cones contain three colour sensitive pigments and are responsible for colour vision and vision in bright light.

D. Option 5 Can be measured by use of Snellen letter charts. The results are expressed as a fraction – 20/20 (or 6/6) being normal; a fraction less than unity, e.g. 10/20 indicates below normal acuity.

E. Option 3 The rate below which successive images are seen as separate images. Above that rate the images fuse to provide a continuous image.