Vision 1 Flashcards
What are the three layers of the eyeball wall?
1) Sclera and cornea (outer)
2) Uvea
3) Retina (inner)
What are the three parts of the Uvea?
Choroid (posterior)
Ciliary body (middle)
Pupil (anterior)
What are the functions of the sclera?
- protect eye from trauma
- maintains intraocular pressure
- attachment site of extra-ocular muscles
What is the definition of glaucoma?
When intra-ocular pressure is high enough to cause damage
What is the function of the choroid?
- supplies nutrients and O2 to outer retina (highly vascular)
- pigment absorbs light
What is macular degeneration?
- age related condition where macula (centre of retina which is used for central vision) breaks down
- causes blurry vision only in centre
What is the pathophysiology of macula degeneration?
sheet of vascular tissue starts growing upward from the choroid and infringing on the macula part of the retina (which pushes the retina up)
Define myopia and hypermetropia?
Myopia = short sighted hypermetropia = long sighted
What causes myopia and hypermetropia?
Myopia - Light brought to a focus just before it reaches the retina usually due to having longer eyeballs
hypermetropia - light brought to focus just after the retina usually due to having shorter eyeballs
What is astigmatism?
curvature in the cornea is steeper in one axis then the other resulting in distortion
What is the function of the cornea?
focuses light (this is where most light refraction occurs)
What are the five layers of the cornea?
- epithelium (constantly regenerated by stem cells)
- Bowmans capsule
- stroma
- descemets membrane
- endothelial cells (prevent over hydration of stroma)
What is a corneal abrasion?
- scratch on the cornea
- will heal like a cut thanks to stem cell regeneration
- very painful and patient will be photosensitive
How can you check for corneal abrasion?
apply orange fluorescent drop (fluorescein) to the eye then shine blue light
fluorescein will show up green on abrasion
Can cornea be transplanted?
- can transplant all sections of cornea even half or only deeper layer if necessary
- will need topical eyedrops but no immunosuppressants
What is the function of the iris?
constrict and dilate pupil
What are the two muscles of the iris?
Sphincter pupillae (parasympathetic supply) Dilator pupillae (sympathetic supply)
What is Horners syndrome?
problem with sympathetic supply resulting in unopposed parasympathetic supply resulting in contraction only (pupil always small)
What is the pathway of aqueous humour?
- produced in ciliary body
- moves into anterior chamber between iris and cornea
- travels out through trabecular pathway
- eventually into venous system
- Constantly being produced and drained
What is the most common problem associated with aqueous humour?
Glaucoma caused by a blockage in pathway when travelling between lens and iris or increased resistance when entering trabecular pathway
What is the functions of the ciliary body?
- produce aqueous humour
- accommodation (ciliary muscle contracts when focusing on near objects)
What is presbyopia?
age related reduction in ability to accommodate (caused by lens stiffness)
- treated using varifocal glasses
Where would you find vitreous humour?
posterior to the lens, attached to the retina
What is posterior vitreous detachment?
- vitreous collapses in on itself (normal process) causing flashing lights and floaters in vision
- flashing lights will stop eventually but floaters last forever
Why must you check the retina if patient presents with flashes/floaters?
if getting new floaters/flashing lights will need to check retina in case tear which allows for fluid to get through tear and cause retinal detachment
What are the two layers of the retina?
Neural layer
- Rods and cones
Pigmented layer
(both supplied by choroid)
What aspects of vision are gathered by rods and cones and where are they each most concentrated?
Rods - light intensity - fovea (centre of macula) Cones - Colour - periphery of retina
What is the optic disc?
area where axons from ganglion cells merge to form optic nerve
What area of the retina is supplied by blood vessels seen in fundoscopy?
inner part of retina not deeper part (where pigmented and photoreceptors are)
Why do you have a blind spot at your optic nerve?
There are no photoreceptors located there
