This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
Why is the blind spot on the retina not usually perceived? 
Select and explain. 
A. It is very small, below the ability of the sensory cells to detect, B. It is present only in very young children, C. Its location in the visual field is different in each eye, D. Constant eye motion prevents the spot from remaining still
C: Its location in the visual field is different in each eye
Answer: C: Its location in the visual field is different in each eye 
Explanation: Ans. C. Its location in the visual field is different in each eyeRods and cones are absent from the area of the retina where the optic nerve exits. The blind spot is of appreciable size, but because its location is off-center and the eyeballs are mirror images, each eye fills in the information missing from the other, even when the gaze is fixed at a point. There are no connections from lateral cells to the blind spot because nerves are exiting there and do not make synapses.