Visual Optics Flashcards
Focal length
distance behind a convex lens at which parallel lights rays converge
If light sources is moved [closer/farther], point of focus moves further behind lens
closer
Diopter =
1 / focal length
Unit describing refractive power of a lens
diopter
Thickening the lens [increases/decreases] focal length
decreases
Two types of fibers associated with ciliary muscles
1) meridional fibers
2) circular fibers
What happens when meridional fibers are contracted
ligaments are pulled forward and medially, releasing tension
What happens when circular fibers contract
tension on ligaments decreases (functions like a sphincter)
Ciliary muscles are regulated by ____ nervous system
parasympathetic
Parasympathetic activity causes ciliary muscles to _____
contract. Lens becomes more convex, refractive power increases
Has reflex control over pupil diameter
autonomic nervous system
Symathetic activation causes pupil _____
pupil dilation (mydriasis)
Parasympathetic activation causes pupil ____
constriction (miosis)
Small diameter pupil results in ___ depth of focus
long
Large diameter pupil results in ____ depth of focus
short
When eye fixated on nearby object, three reflexes are evoked
1) convergence of eyes, to center object on fovea
2) accommodation to focus object
3) miosis (pupil constriction) to maximize depth of focus
Bilateral small pupils that constrict when patient focuses on near object but do not constrict when exposed to bright light
Argyll Robertson pupil
Condition strongly associated with Argyll Robertson Pupil
neurosyphyllis
Eye with no visual defects
Emmetropia
Hyperopia (farsightedness)
caused by eyeball that is too short or lens system that is too weak. Light rays are not bent enough when lens is completely relaxed
Myopia (nearsightedness)
Caused by eyeball that is too long or lens system which is too strong. No way to reduce lens strength when ciliary muscle is fully relaxed.
Light from one plane is focused at a different distance than light from a second plane
Astigmatism
Why can’t a spherical lens correct for an astimatism?
different degrees of correction are required in different planes
Mechanism of exchange between aqueous and vitreous humors
diffusion
