the eyeball

what are the 3 layers of the eyeball?

- fibrous

- vascular

- inner

what is the outermost layer of the eyeball?

fibrous layer

what does the fibrous layer consist of?

sclera + cornea

how are the sclera + cornea associated?

they are continuous with each other

what is the main functions of the sclera + cornea? (2)

- provide shape to the eye

- support the deeper structures

how much of the fibrous layer is composed of the sclera?

85%

what is the sclera visible as?

the white part of the eye

what does the sclera in particular provide?

attachment for the extraocular muscles

what does the cornea look like?

transparent

where is the cornea found?

centrally at the front of the eye

what does the cornea in particular do?

refracts the light entering the eye

what is the middle layer of the eyeball?

vascular layer

what 3 things does the vascular layer consist of?

- choroid

- ciliary body

- iris

what is the choroid?

layer of connective tissue + blood vessels

what does the choroid do?

provides nourishment to the retina

what is the membrane between the choroid and the retina called?

Bruch's membrane

what are the 2 parts of the ciliary body?

- ciliary muscle

- ciliary processes

what is the ciliary muscle?

collection of smooth muscle fibres

what are the ciliary muscle fibres attached to?

lens of the eye

how are the ciliary muscle fibres attached to the lens?

suspensory ligaments

what 2 things are the suspensory ligaments attached to?

ciliary processes + lens

what is the function of the ciliary body? (2)

- controls the shape of the lens

- produces aqueous humour

what is the iris?

circular structure with an aperture in the centre (pupil)

what is the iris made up of?

smooth muscle fibres

what is the function of the iris?

smooth muscle fibres alter the diameter of the pupil

where is the iris located?

between the lens and the cornea

what is the inner layer of the eye made up of?

the retina

what are the 2 layers of the retina?

- pigmented outer layer

- neural inner layer

what is the pigmented outer layer made up of?

single layer of cells

where is the pigmented outer layer of the retina?

attached to the choroid and continues round whole inner surface of the eye

what is the function of the pigmented outer layer of the retina?

supports the choroid in absorbing light - to prevent scattering of light within the eyeball

what is the neural inner layer of the retina composed of?

photoreceptors

where is the neural inner layer of the retina located?

posteriorly and laterally

what section of retina is covered by both the pigmented outer layer and neural inner layer?

posteriorly + laterally

what is the posterolateral portion of the retina called?

the optic retina

what section of retina is only covered by the pigmented outer layer?

anterior section

what is the anterior section of the retina called?

non-visual retina

what is interesting about the layering of the retina?

pigmented epithelium is the deepest part (furthest away from the light)

what is the centre of the retina marked by?

the macula

what are the features of the macula? (2)

- yellow in colour

- highly pigmented

why are some eye pathologies macula-sparing?

because the macula has a dual blood supply

what does the macula contain?

depression called the fovea centralis

what does the fovea centralis contain?

high concentration of photoreceptors

what is the function of the fovea centralis associated with?

high acuity vision

what is the area of the retina called where the optic nerve enters?

the optic disc

what is special about the optic disc?

contains no photoreceptors

what are the 4 structures inside the eyeball?

- vitreous body

- lens

- anterior chamber

- posterior chamber

what is the vitreous body?

transparent gel

where is the vitreous body?

fills posterior segment of the eyeball (all space behind the lens)

what runs in the centre of the vitreous body?

hyaloid canal

where does the hyaloid canal run from and to?

from optic disc to the lens

what is the hyaloid canal?

remnant of hyaloid artery

what are the 3 functions of the vitreous body?

- contributes to magnifying power of eye

- supports the lens

- holds layers of retina in place

where is the lens located?

between vitreous humour and the pupil

how is the shape of the lens altered?

by the ciliary body

where is the anterior chamber?

between cornea and iris

where is the posterior chamber?

between iris + ciliary processes

what are the anterior + posterior chambers filled with?

aqueous humour

what does the aqueous humour do?

nourished + protects the eye

how is aqueous humour produced?

by the capillary networks within the ciliary body

where does the aqueous humour drain?

canal of schlemm

what is another name for the canal of schlemm?

sceral venous sinus

which artery supplies the eyeball?

ophthalmic artery - branch from the internal carotid

which veins drain the eyeball?

superior + inferior ophthalmic veins into the cavernous sinus