Opthamology Flashcards
What is refraction?
The bending of light from one optical medium to another
What’re the refractive media in the eye?
Cornea
Aqueous humour
Lens
Vitreous humour
What makes accommodation happen?
Cilliaris
What is accommodation?
The capacity to change focus from distance objects to close objects
What 3 things happen simultaneously in accommodation?
Lens thickens
Pupils constrict
Eyes converge
What muscle causes the lens to thicken?
Cilliaris causing the ciliary muscle to contract
What causes the pupil to constrict?
Constrictor pupillae
What causes the eyes to intort?
Medial rectus of both sides contact
In which refractive error is the eyeball too long?
Myopia
What do hyperopes use their accommodation for?
Use all their accommodative power to see far away so they run out of accommodative power to see up close
What is astigmatism?
Non spherical curvature of the cornea or lens
S+S of astigmatism
Hazy image
2 images being formed
What type of contact lenses do astigmatic people wear?
Toric lenses
What’s presbyopia?
Longsightedness of old age
What’s emmetropia?
Perfect vision
What does CYL mean?
The power needed to correct astigmatism
What causes presbyopia?
Lens gets less mobile due to the ciliary muscle not being able to change as it used to
what is rhodopsin?
A protein
What happens when light hits 11 cis-retinal?
Bond becomes straight and becomes 11 trans retinal
What can vitamin A deficiency lead to?
Bitot’s spots in conjunctiva
Cornelia ulceration
Corneal melting
-leads to further opacification of the cornea
Epithelium type in cornea
Stratified squamous non-keratinised
Where’s bowman’s membrane?
Basement membrane of corneal epithelium
How is transparency maintained in the cornea?
Regular arrangement of collagen in stroma
No blood vessels
Endothelium has a pump which actively keeps the aqueous humour out
Why is the avascularity of the cornea an advantage in performing corneal graft surgery?
Less chance of it being rejected ad there’s less foreign antigens present
It’s an immune privileged site
The 10 layers of the retina and choroid?
◦ 10=inner limiting membrane ◦ 9=nerve fibre layer ◦ 8=ganglion cell layer ◦ 7=inner plexiform layer ◦ 6=inner nuclear layer ◦ 5=outer plexiform layer ◦ 4=outer nuclear layer ◦ 3=outer limiting membrane ◦ 2=layer of rods and cones ◦ 1=pigment of epithelial layer
How do the outer layers of the retina get blood?
By diffusion
How do the inner layers of the retina get blood?
Branches of the retinal artery
What’s lens opacification more commonly known as?
Cataracts
4 functions of tear film
Keep the cornea moist, prevent it from drying out
Washes away particulate from foreign bodies
Antibodies and lysosomes to kill microbes
Smooths outer layer of the cornea providing smooth surface for refraction
What’re the 3 layers of the tear film?
Layer 1=mucinous layer
Later 2=aqueous layer
Later 3=oily layer
What’s the innervation of tear secretion into the conjunctival sac?
Parasympathetic 7
What happens to the tear film when the eyes are open?
Aqueous layer begins to evaporate and oily layer comes close to mucin layer
When these 2 layers touch each other the tear film breaks up which stimulates further blinking
