The eye Flashcards
What fills the space between the cornea and the lens of the eye?
fluid filled aqueous humor
What is the function of the conjunctiva?
Lines inner surface of eyelids lubricates & protects the eye, protects cornea, enables independent movement of eyelids
What is the function of the sclera?
- Tough, dense connective tissue
- protective layer from injury, provides attachment for extra ocular muscles
- carries vasculature
- Covering of dura mayor as eye is outgrowth of diencephalon
What is the nerve supply to:
- Sphincter pupillae muscle (circular muscles)
- Dilator pupillae muscle (radial muscles)
- Ciliary muscles within the ciliary body
- SP= parasympathetic from oculomotor
- DP= sympathetic from superior cervical ganglion
- CM= parasympathetic from oculomotor
What are cataracts?
Lens of the eye becomes opaque, leads to increasing visual impairment
What does the pressure of aqueous humor control?
Maintains the shape of the cornea and thus the refractive properties of the eye
Where is aqueous humor made and reabsorbed?
Made= ciliary body Absorbed= sclera venous sinus (canal of schlemm)
What is glaucoma?
- Problems with drainage of aqueous humor
- Inc intraocular pressure can lead to blindness by compression of the retina & its blood supply
What are the functions of the choroid layer of the eyeball?
- Vascular layer-nourishes retina
- Assists with absorption of light to prevent scattering
What is the retina made up of?
- Outer pigment cell layer: single cuboidal epithelial layer with melanin filled microvilli extending from inner surface
- A multi layered neural retina
What does the retina line?
Most of posterior compartment of the eye, posterior to the lens & ciliary body
What does the retina contain?
- Photoreceptors
- First & second order neurons of the visual pathway
What are the functional differences between rod & cone cells?
R= Vision at low light levels, No colour, Low spatial acuity C= Active at high light levels, colour, high spatial acuity
Where are there no photoreceptors in the eye? What does this form?
- Optic papilla
- Forms a blind spot on the retina
What is the pathway taken by the axons of the retinal ganglion cells?
- Run over inner surface of the retina
- Converge on the optic disc or optic papilla
- 2nd order ganglions turn outwards to form optic nerve
What is papilloedema and How does papilloedema occur?
Optic disc swelling caused by inc intracranial pressure
- Subarachnoid space continuous with optic nerve sheath
- CSF pressure inc transmits to optic nerve sheath
- Acts as tourniquet impeding axoplasmic transport
- Halo around optic disc due to retinal lifting
What lies just lateral to the optic disc?
- Yellow pigmented zone- Macula lutea
- Centre is a specialised region called the fovea
What is the fovea and how is it specialised?
- Point on the retina at which the image of the object at the centre of the visual axis falls
- Consists of closely packed cone cells giving sharpest image & colour
Where do blood vessels supplying the retina cells lie?
Central retinal artery traverses optic nerve & enters at optic disc
What is the Ophthalmic artery a branch of?
- Internal carotid
- Carried with optic nerve
What are the interneuron layers of the retina and their function
- Horizontal
- Amacrine
- Modulate information/improve quality
Where are auditory & visual fibres projected to in the brainstem?
A= Medial geniculate nucleus V= Lateral geniculate nucleus
Where specifically does light hit on the retina? Where does this pass to?
- Temporal retina= ipsilateral geniculate nucleus
- Nasal retina= Contralateral geniculate nucleus
Where do the upper & lower visual fields project to?
- U= Pass to lower bank (striate) calcimine sulcus
- L= Pass to upper bank of calcarine sulcus
How would a pituitary lesion affect vision?
- Compress optic chiasma
- Heteronymous hemianopia
Where does light hitting the Macula Lutea project to?
Occipital pole (most posterior)
Where do pre-ganglionc fibres pass to?
Pass in occulomotor nerve to ciliary ganglion
What is the Edinger-Westphal nucleus?
Parasympathetic cortex of oculomotor fibres pass to both L&R nuclei
Where do optic radiation fibres pass to?
Calcarine sulcus of occipital lobe
