2.92: Understand the Function of the Eye in Focusing Near and Distant Objects, and in Responding to Changes in Light Intensity

*RESPONSE OF EYE TO DISTANCE OF OBJECT:

NEAR OBJECT	DISTANT OBJECT
Diagram showing Response of Eye to Near Object	Diagram showing Response of Eye to Distant Object
When looking at a near object, incoming light is divergent In response, Ciliary Muscles will contract, while Suspensory Ligaments slack As a result, the Lens become thicker and more curved, refracting light rays more strongly to converge on the Retina	When looking at a distant object, incoming light is parallel In response, Ciliary Muscles will relax, while Suspensory Ligaments stretch As a result, the Lens become thinner and less curved, refracting light rays less strongly to converge on the Retina

OBJECT	CILIARY MUSCLES	SUSPENSORY LIGAMENTS	MUSCLE TENSION ON LENS	LENS SHAPE
NEAR	Contract	Slack	Low	Thicker and more curved
DISTANT	Relax	Stretch	High	Thinner and less curved

*RESPONSE OF EYE TO CHANGES IN LIGHT INTENSITY:

DARK	BRIGHT
Diagram showing Response of Eye to Dark Environment	Diagram showing Response of Eye to Bright Environment
When in dark environment, Photoreceptors - Rods and Cones, detect the change in light intensity As a result, reflex occurs involving Muscles in the Iris - Radial Muscles contract and Circular Muscles relax to increase the diameter of the Pupil As Diameter of Pupil increases, Pupil dilates to allow more light to enter the Eye to be refracted onto Retina for vision	When in bright environment, Photoreceptors - Rods and Cones, detect the change in light intensity As a result, reflex occurs involving Muscles in the Iris - Radial Muscles relax and Circular Muscles contract to decrease the diameter of the Pupil As diameter fo Pupil decreases, Pupil contracts to allow less light to enter the Eye to be refracted onto Retina for vision

ENVIRONMENT	RADIAL MUSCLES	CIRCULAR MUSCLES	PUPIL DIAMETER	AMOUNT OF LIGHT ENTERS
DARK	Contract	Relax	Increase	More
BRIGHT	Relax	Contract	Decrease	Less