- (C) Light   enters  the eye through an  opening in  the iris.   The iris,   the colored part    of  the eye,    is  a
 muscle that controls the size of the pupil, the hole through which light enters the eye. After passing
 through the pupil, the light is refracted by the lens and ultimately lands on the retina at the back of
 the eye. The blind spot is the part of the retina where the axons of the ganglion cells exit the eye en
 route to the brain; it is known as the blind spot because there are no photoreceptors there. The
 fovea is the part of the retina in which you have highest visual acuity due to the lack of summation
 there.
                    
                      marvins-underground-k-12
                      (Marvins-Underground-K-12)
                      
                    
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