Questions: Focusing System of the Eye Three events occur to bring the image into focus on the retina: accommodation, pupil constriction, and convergence. Test your knowledge about these events by selecting 'True' or 'False'. Accommodation is as a result of parasympathetic stimulation from the Optic nerve (l). In accommodation, the lens becomes more convex (spherical) in shape. One reason accommodation becomes more difficult as an object is brought closer to the eye because the lens cannot become any more flattened. When we look at a close-up object, the pupil diameter decreases. When the pupil is constricted, the light entering the eye tends to pass through the center of the lens than through the edges of the lens. The smaller the pupil diameter, the more light enters the eye and is directed toward the retina. Both pupils can pick up the light rays when the eyes are looking forward. Convergence states that eyes are rotated medially as an object moves closer. In convergence, rotation of the eyes is accomplished by the medial oblique muscles.

Let's analyze each statement related to the focusing system of the eye and determine whether they are true or false.

1. Accommodation is as a result of parasympathetic stimulation from the Optic nerve (l).

   • False: Accommodation is controlled by the parasympathetic nervous system, but it is mediated by the oculomotor nerve (cranial nerve III), not the optic nerve (cranial nerve II).

2. In accommodation, the lens becomes more convex (spherical) in shape. One reason accommodation becomes more difficult as an object is brought closer to the eye because the lens cannot become any more flattened.

   • False: In accommodation, the lens indeed becomes more convex (spherical) to focus on close objects. However, the difficulty in accommodation as an object is brought closer is due to the lens's inability to become more convex, not because it cannot become more flattened.

3. When we look at a close-up object, the pupil diameter decreases.

   • True: This is known as the pupillary near response, where the pupil constricts to increase the depth of focus when looking at close objects.

4. When the pupil is constricted, the light entering the eye tends to pass through the center of the lens than through the edges of the lens.

   • True: Constriction of the pupil reduces the amount of peripheral light entering the eye, which helps in reducing optical aberrations and improves the sharpness of the image.

5. The smaller the pupil diameter, the more light enters the eye and is directed toward the retina.

   • False: A smaller pupil diameter actually reduces the amount of light entering the eye. However, it does improve the focus and sharpness of the image by reducing spherical aberrations.

6. Both pupils can pick up the light rays when the eyes are looking forward.

   • False: Each eye has its own field of view, and while there is a significant overlap in the central field of vision, each pupil primarily picks up light rays from its respective field of view.

7. Convergence states that eyes are rotated medially as an object moves closer.

   • True: Convergence is the process where both eyes rotate medially (towards the nose) to maintain single binocular vision as an object moves closer.

8. In convergence, rotation of the eyes is accomplished by the medial oblique muscles.

   • False: The medial rectus muscles, not the medial oblique muscles, are responsible for the medial rotation of the eyes during convergence.

In summary:

• The answer to the first statement is False.
• The answer to the second statement is False.
• The answer to the third statement is True.