extra-ocular muscles and their innervations
superior rectus = oculomotor inferior rectus = oculomotor lateral rectus = abducens medial rectus = oculomotor superior oblique = trochlear inferior oblique = oculomotor
what muscle closes the eyelid and whats its innervation
orbicularis oculi
- innervated by facial nerve
what muscle opens the eyelid and whats its innervation
levator palpebrae superioris
- innervated by oculomotor nerve
keratoconus
- cornea thins and moves forward
- rugby ball shape
- may be associated with eye rubbing
- responsible for half of corneal transplants
tear film
10 uL
oil from tarsal glands = prevents evaporation
aqueous from lacrimal gland
mucins from goblet cells of conjuctiva
cornea
2/3 refraction of eye
- determined by curvature & refractive indices
examined using slit lamp
avascular
endothelial pump moves water out of cornea stroma
crystalline lens
1/3 refraction of eye - can alter focusing properties
- fine focusing
- most common disease = cataracts
ciliary body
- holds lens in place (connected by zonules)
- within body = ciliary muscle
ciliary epithelium produces aqueous humour
(through pupil -> ant. chamber -> angle of ant. chamber -> trabecular meshwork
when the ciliary muscles relax
biggest diameter
lens pulled outwards = thinner
when the ciliary muscles contract
smaller diameter
= lens anterior/posterior pole distance increases
cells of the retina
ganglion cells --> bipolar cells --> photoreceptor cells (rods & cones) --> retinal pigment epithelium (nutrient/waste exchange)
function of retina
- absorb photons of light
- traslate light into a biochemical message
- translate biochemical message into electrical impulse
- transmit electrical impulse to the brain via ganglion cells
fovea
centre of visual acuity
what are cones responsible for
visual acuity and colour vision
= central vision
absorb different wavelengths of light
- blue, green and red cones
what are rods responsible for
detecting movement and night vision
= peripheral vision
glaucoma
- optic neuropathy
- pattern of axonal loss
- associated with intra-ocular pressure
- common in old age
- sight loss in peripheral first
- optic nerve “cups” = gets bigger, deeper
