9. Anatomy of the lens and vitreous. Intraocular spaces and fluids.

Question 1

what is the physical charecteristics of the lens ?

Answer 1

transparent, biconvex structure in the eye

Question 2

what is the function of the lens ?

Answer 2

along with the cornea, helps to refract light to be focused on the retina by changing its shape

change the focal distance of the eye so that it can focus on objects at various distances - accommodation

Question 3

what is the refractive power of the lens ?

Answer 3

in its natural environment is approximately 18 dioptres- 1/3rd of eye total power

Question 4

what is the anatomy of the lens

Answer 4

the lens capsule

the lens epithelium found only on the anterior side of the lens

cortical fibres

cortex

then nucleus with the nuclear fibres

Zonular fibers originate in the basal lamina of the pars plana and pars plicata of the ciliary body and insert on the equatorial region o

Question 5

does the lens have any nerves , blood vessels or connective tissue ?

Answer 5

no

Question 6

what located anterior and posterior to the lens

Answer 6

anterioir to lens - posterioir chamber

posterioir to lens - vitreous humour

Question 7

what are the intra ocular spaces ?

Answer 7

anterioir chamber (between cornea and iris)
posterioir chamber 

filled with aqueous humour , split by the iris

vitreous chamber - splits b the ciliary body

Question 8

what is the function of the aqueous humour?

Answer 8

transparent, watery fluid

intraocular pressure inflates the globe of the eye -> It is this hydrostatic pressure which keeps the eyeball in a roughly spherical shape and keeps the walls of the eyeball taut.

Provides nutrition (e.g. amino acids and glucose) for the avascular ocular tissues; posterior cornea, trabecular meshwork, lens, and anterior vitreous

Question 9

what is the circulation of aqueous humour?

Answer 9

Aqueous humour is secreted into the posterior chamber by the ciliary body

flow through the narrow space between the posterior iris and the anterior lens

flows through the pupil and enters into the anterior chamber

From there, the aqueous humour exits the eye through the trabecular meshwork into Schlemm’s canal - a channel at the limbus

into the episcleral veins

Question 10

Small variations in the production or outflow of aqueous humour will have a large influence on?

Answer 10

massive effect on intraoccqular pressure

Question 11

angle between iris and cornea , this angle can be obstructed if so what happens

Answer 11

fluid cannot reach schlemm’s canal anymore and cannot be drained anymore

Question 12

what space does the vitreous humour occupy ?

Answer 12

area between the lens and the retina

Question 13

what is the vitreous humour characteristically ?

Answer 13

gel like substance

Question 14

where is the vitreous humour derived from

Answer 14

embryonic mesenchyme cells, which degenerate after birth and thus no more synthesis can take place

Question 15

is the vitreous humour drained ?

Answer 15

no - stangant

therefore of blood cells , byproducts of inflammation get into vitreous humour it will remain there unless surgically removed

Question 16

1mm forward shift of lens causes what ?

Answer 16

increase about 1.4D in power

Question 17

what is the Refractive index of aqueous humor

Answer 17

1.336

Question 18

what is the accommodative power of the ;end ?

Answer 18

at birth
14-16d

25 years - 7-8d

50 years
1-2 d

Question 19

OPTICAL CHANGES IN CATARACTOUS LENS?

Answer 19

Visual Acuity reduction.
Myopic shift.
Monocular diplopia.
Glare.
Color shift.

Question 20

what is the refractive index of vitreous humour ?

Answer 20

same as aqueous