Vision Structure and Function Flashcards
What is the Iris
- Gives the eye colour
- Enlarges in dim light and contracts in bright light
What is the Retina
The lining at the back of the eye (it is also part of the brain)
What is the Fovea
- A pit in the retina
- High photoreceptor density –> leading to high visual acuity
Optic Nerve
- Conducts visual impulses from the retina to the brain
What is the Optic Disc
It is the head of the optic nerve
- Has no photoreceptors
What is the Cornea
Clear and transparent structure that allows light to pass
What is the Conjunctiva
Clear membrane covering the eye
- produces tears and mucous
What is Conjunctivitis?
Inflammation of the conjunctiva
What is the role of the lens?
Helps to focus the light onto the fovea
- also functions to separate the internal cavity into anterior and posterior segments
Anterior Segment of the Eye
Has 2 chambers
1) Anterior Chamber - located behind the cornea and infront of the lens & iris
2) Posterior Chamber - Behind the iris and infront of the lens
Posterior segment of the Eye
Contains Vitreous humour
- supports posterior surface of the lens and also the shape of the eye
What is Macular degeneration?
Loss of central vision (can only see periphery)
What is Choroid?
The blood supply to the outside third (photoreceptors)
What does the central artery and vein supply?
Inner 2 thirds of the of the eye (Bipolar and ganglion cells)
Where is Aqueous Humour found?
In the Anterior Segment
Lacrimal gland
Located in the top right of the eye
- Produces tears
- CN VII
Types of Photoreceptors in the Retina
(2)
1) Rods - responsible for night vision (black and white vision)
- Higher density in the periphery (none located in the Fovea)
- High convergence —> Hence Visual Acuity is low
2) Cones - important for day vision (colour vision)
- More towards the centre of the retina
What is the Blind spot?
Where is it located?
Blind spot is caused due to the optic disk not containing any photoreceptors
- Present in the nasal retina –> in the temporal field
Shortsighted
Also known as myopia
- Lens is too strong for the length of the eyeball
- Biconcave lens push focal point backwards
Longsighted
Also known as hyperopia
- Lens is too weak for the length of the eyeball
- Biconvex lens pushes the focal point towards retina
What is Astigmatism?
Cornea or lens has unequal surface curvatures
What is Presbyopia?
= Old eye
- decrease focusing power of the eye due to old age
- decreased elasticity in the lens
