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-Form a sharp image
-Initiate Image Processing
Structure of the Human Eye
-sclera: hard outer shell;
-main function is to maintain the shape of the eyeball.
-choroid: eye gets its blood supply from
-retina: where image is actually formed
Optical Power: combination of cornea and lens
-How much of the optical power comes from these two? Cornea (2/3); Lens (1/3)
-optical power of the lens is adjustable.
Muscles responsible for this is called ciliary muscles.
-when it is relaxed, the lens is relatively thin weak
-when you need greater optical power, then the ciliary muscles contracts, and it changes the
shape of the lens and makes it more condensed increases the optical power of the lens
-depending on distance of the object, the optical power of lens can be adjusted.
-more bending is required when the object is close so you need greater optical power.
(because when the object comes closer, the muscle needs to bend bigger)
Ciliary Muscles relaxed Ciliary muscles contracted
Accommodation: contraction of the ciliary muscle that allows us to look/focus on nearby
objects. (your ciliary muscles are going to be strained)
2 possibilities that both boil down to same condition/idea:
1. Eyeball too short
2. Shape of Eyeball is normal, but Lens are too weak
-Nearby objects are blurred (Rays do not converge enough)
-Correction: Convex lens
-the optic concern both have same net effect NEARBY OBJECTS ARE BLURRED
(distant objects are okay, but nearby objects are blurry because the rays don’t converge enough
because when we look at nearby object, more bending is required and because the lens is
too weak, the light rays are not converging enough). Distant objects require less bending so it’s
-If the lens is too weak, you want to increase the optical power so we need CONVEX LENS
(bulge out) instead of concaved lens.
1. Eyeball too long 2. Lens too “strong”
-Distant objects are going to be blurry because distant object doesn’t need that much bending,