Lens, vitreous

Question 1

Appreciate the events in embryogenesis that result in the formation of a spherical lens

Answer 1

Originates from surface ectoderm and becomes a sphere of cells with its BM along outside
Developing lens fibers form bow region within the outer lens cortex (defines outer cortex) where completion of their development occurs with complete organelle degeneration—long, thin, tubular shaped cells—flexuous under normal conditions
originate at equator; extend to anterior andposterior sutures at poles on lens, which continue to expand with age—suture line typically
Y-shaped in biconvex lens & linear in round lens—only grow to a certain length

Question 2

Understand the function of the lens and the vitreous

Answer 2

lens- fine focus of light onto the retina, biconvex shape, avascular, cellular makeup, supported by zonules attached by ciliary bodies
vitreous- some focusing ability, largest structure in the eye, hydrogel of hyaluronic acid; 98-99% water; holds components of the eye in place

Question 3

Differentiate between primary, secondary and tertiary vitreous

Answer 3

Primary- hyaloid vascular system (embryo/ BV regresses later)
Secondary- intermediate stage in embryonic development
Tertiary- BV regresses, canal still remains

Question 4

lens

Answer 4

fine focus of light onto the retina, biconvex shape, avascular, cellular makeup, supported by zonules attached by ciliary bodies

Question 5

vitreous; vitreous body

Answer 5

Largest structure in the eye
Hydrogel of hyaluronic acid and 98-99% water
holds components of the eye in place

Question 6

cataract

Answer 6

clouding of the lens which leads to blindness; fibers of the lens become more opaque

Question 7

nuclear sclerosis

Answer 7

lens becomes more densely packed with age; affects color vision and focus but does not cause blinding

Question 8

presbyopia

Answer 8

gradual thickening and loss of flexibility of the natural lens inside your eye.

Question 9

emmetropia

Answer 9

describes the state of vision where an object at infinity is in sharp focus with the eye lens in a neutral or relaxed state. This condition of the normal eye is achieved when the refractive power of the cornea and the axial length of the eye balance out, which focuses rays exactly on the retina, resulting in perfect vision.

Question 10

refraction

Answer 10

change in direction of a wave (light) due to a change in its transmission medium

Question 11

accommodation

Answer 11

lenticular accommodation is dependent on the ability of the lens to change shape; bird lens is softer and more flexible than that of mammalians

Question 12

zonules

Answer 12

ligaments that suspend the lens

attach lens at equator to ciliary musculature

Question 13

focus

Answer 13

cornea is the large focus, lens provides fine focusing ability; need to focus light to the retina; changes in lens/cornea affect vision

Question 14

opacity

Answer 14

cataract- opacity of the lens

nuclear sclerosis-

Question 15

luxation

Answer 15

movement of the lens out of alignment

Question 16

sutures

Answer 16

fibers are cells w/out organelles and are interconnected, grow from the equator and meet at sutures