Resume of eye structure in deer.
Light passes through the cornea on through the pupil onto the retina which registers the image. This in turn is transmitted to the brain by electrical impulses for interpretation.
Deer are herbivores and a prey species The eyes are positioned on the sides of the head to the give the widest possible vision.
The cornea is large to pass maximum light. The pupil has its long axis in the horizontal plane so that sight is in a +/- 350 degrees arc when in a grazing position. This leaves a blind spot of 10 degrees. Next time you are stalking note the animals arrange themselves in a random pattern so that each individual's blind spot is covered by another animal. Many eyes. Along the top of the iris there is a projection called the corpora nigra. This acts as a sunshade in bright light along with other unknown functions.
The lens due to shape and supporting musculature appears unable to focus critically beyond a short distance hence so called head bobbing particularly noticeable in fallow although all species do it. Is this to use different parts of the retinal cones?
The retina consists of outer retinal cells which are photoreceptors and inner retinal cells which provide support for the photoreceptor cells passing the signals to the brain. The photoreceptor cells collect the light and produce electrical impulses based on the type of light striking the cell.
There are two types of photoreceptor cells.Rods and cones. Rods are cells for low light and are located throughout the retina the highest concentration being on the periphery.Logical as pupil wides in low light.
Cones function predominantly in bright light. They have special chemicals,photopigments, which allow them to respond to specific wavelengths or colours of light. Deer have two types of cones which are called dichromatics ( ability to sense two colours of light ) These photopigments sense the two colours and mixtures between them. These colours are blue and green. Rods may also help discriminate colours. Various shades of green to identify edible plants,blue for low light conditions.
One last part of the eye is the tapetum lucidum which is the reflective layer behind the retina. This reflects light back onto the retina so increasing visual acuity in low light. Seen at night when eyes reflect light towards you in torch light.
Camouflage patterns are there to catch stalkers as deer function on scent,sound and movement.Big ears abnormal sounds and fast movement Bye bye deer Anything out of place in their normal environment and they run. Deer survive by crypsis ( hide and observe ) and flight. Stalkers occasionally have the experience of nearly falling over deer before they flee.