The portion of the middle tunic that regulates the amount of light passing to the visual receptors of the eye is the
A) aqueous humor
B) cornea
C) iris
D) lens
E) choroid

Question

Quizplus · Accepted Answer

The portion of the middle tunic that regulates the amount of light passing to the visual receptors is the iris. The iris is responsible for controlling the diameter of the pupil, and thus the amount of light that enters the eye. Choice A (aqueous humor) is a fluid that fills the space between the cornea and the lens, but it does not regulate the amount of light. Choice B (cornea) is the clear, outermost layer of the eye that helps to focus light, but it does not regulate the amount of light. Choice D (lens) helps to focus light onto the retina, but it does not regulate the amount of light. Choice E (choroid) is a layer of tissue that supplies blood to the retina, but it does not regulate the amount of light.

The Portion of the Middle Tunic That Regulates the Amount