corneal optics Flashcards
(22 cards)
True/False: Cornea is a spherical surface.
False. Cornea is not a spherical surface
Main difference between aspherical and spherical lens?
Aspherical is flatter compared to spherical lens
What is the name for corneas shape?
Conicoid, and conicoid is ellipsoidal
The anterior corneal asphericity (Q) values are usually ________ which indicates that cornea _____________ from the vertex.
negative
flattens away
What is the the significance of corneal flattening?
To reduce spherical aberration
To make a smooth join. (fit well)
Corneal horizontal diameters on average for infants and adults?
10 mm infants
11 mm adults
Corneal vertical diameters on average for infants and adults?
11 mm infants
12 mm adults
True/False: Males have significantly wider horizontal corneal diameter than their female counterparts.
True
True/False: Asians have smaller CD than caucasians.
True
True/False: Hyperopes tend to be flatter than myopes.
True
_________ if the corneal surface flattens and ________ as the cornea becomes steeper
decrease
increase
Cornea is significantly _________ in both radius of curvature and asphericity.
Asymmetric
Cornea too curved leads to a condition called
Keratoconus
Cornea too flat leads to a condition called
cornea plana
What is with the rule astigmatism? in other words what meridian is longer?
vertical meridian of the cornea is the steepest
TRUE/FALSE: Corneal curvature becomes flatter with increasing age due to the changes in the elasticity of the cornea.
FALSE, steeper with increasing age
A thin cornea leads to _____________ of IOP.
underestimation
A thick cornea leads to _____________ of IOP.
overestimation
What is the central corneal thickness (CCT)?
0.5 mm
Does age increase or decrease CCT?
decreases
African americans have _______ CCT than other races.
thinner
Conicoid surface, the radius of curvature at off- axis points depends upon: (2 things)
the distance from the vertex
meridian at that point
