When assessing a client’s vision, the nurse should keep which fact in mind?
Answers:
a. The right half of each retina receives input from the right visual field. b. The left optic tract contains nerve fibers from the right half of each retina. c. The right optic tract contains nerve fibers from the left half of each retina. d. The left half of each retina receives input from the right visual field.
The correct answer and explanation is:
The correct answer is b. The left optic tract contains nerve fibers from the right half of each retina.
The visual pathways in the brain are arranged in a way that each optic tract carries information from the opposite visual field. This means that the right visual field is processed by the left hemisphere of the brain, and vice versa for the left visual field. The key points to understand this are:
- The retina is divided into two halves: the nasal half (near the nose) and the temporal half (toward the ear). Each half of the retina captures a different part of the visual field. The right visual field is detected by the left half of both retinas, and the left visual field is detected by the right half of both retinas.
- After the image is captured by the retina, the nerve fibers from each half of the retina travel along the optic nerve toward the brain. However, at the optic chiasm, the fibers from the nasal half of each retina cross over to the opposite side, while the fibers from the temporal half do not cross.
- Therefore, the right visual field (which is processed by the left half of both retinas) is carried to the left optic tract, and the left visual field (processed by the right half of both retinas) is carried to the right optic tract.
- This crossing of fibers allows the brain to combine visual input from both eyes to create a single, coherent image. Damage to any part of the optic pathway can lead to visual deficits, depending on the area affected. For instance, damage to the optic tract would affect vision from the opposite visual field.
By understanding these pathways, a nurse can interpret the client’s vision more effectively and recognize signs of neurological problems that could impact vision.