The site where the optic nerve exits the eyeball and no photoreceptors are found is the
(A) fovea centralis,
(B) retina,
(C) choroid,
(D) blindspot
The correct answer and explanation is:
The correct answer is (D) blindspot.
The blind spot, also known as the optic disc, is the site where the optic nerve exits the eyeball. At this location, no photoreceptors (rods or cones) are present, which results in a lack of visual information being sent to the brain from that specific region of the retina. The absence of photoreceptors in the optic disc creates a gap in the visual field, but under normal circumstances, the brain fills in this gap based on surrounding visual data, making the blind spot typically imperceptible to the person.
The optic nerve is responsible for transmitting visual information from the retina to the brain. The optic disc is located where the nerve fibers converge to form the optic nerve, and this exit point does not contain any rods or cones, the cells responsible for detecting light and color. Since there are no photoreceptors in this region, it cannot detect light, making it a “blind” area of the visual field.
The fovea centralis, which is part of the retina, is the area responsible for sharp central vision. This area is densely packed with cones, which are photoreceptors that allow for detailed vision. The retina is the light-sensitive layer at the back of the eye that contains photoreceptors and is responsible for capturing light and converting it into electrical signals. The choroid is a layer of blood vessels between the retina and sclera that provides nourishment to the outer layers of the retina. Unlike the blind spot, these areas all contain photoreceptors and contribute to vision.