Imaging
Imaging modality that provides quantitative information regarding corneal endothelial cells
specular microscopy
typically the central cornea is how many diopters steeper than the peripheral cornea
3D
define the optical zone
area of cornea that overlies the pupil
define angle kappa
if angle kappa is above ___ mm, clinicians might avoid multifocal IOL placement
angle kappa = angle between visual axis and optical (or pupillary axis)
if angle kappa is above 0.4 mm, clinicians might avoid multifocal IOL placement
how do you measure TBUT and what times are considered abnormal
instill fluroescein
hold eyelids open after 1-2 blinks
count until dry spot appears
<10 seconds = abnormal
Endothelial cell density of children
Endothelial cell density of adults
Children normally exceeds 3500 cells/mm^2
Adults ~2400 cells/mm^2
diameter of central zone
central zone closely resembles a ____ surface
1-3 mm
spherical
define the corneal apex
what is its typical spatial relationship to the center of the pupil
point of maximum curvature
typically temporal to center of pupil
___ can be represented by a central cone or inferotemporal steeping
keratoconus can be represented by a central cone or inferotemporal steeping
___ detects disruption of intercellular junctions and stains punctate and macro ulcerative epithelial defects
fluorescein detects disruption of intercellular junctions and stains punctate and macro ulcerative epithelial defects
the coefficient of variation is defined as
SD of the mean cell area divided by the mean cell area
the para central zone is _ to _ mm doughnut with a outer diameter of of _ to _ mm
3 to 4 mm
7 to 8 mm
what point corresponds to intersection of the patient's line of fixation and the corneal surface
corneal vertex
Define the I-S value in topography
The inferior-superior value is derived by calculating the difference between inferior and superior corneal curvature measurements at a defined set of 5 points above and below horizontal meridian
these entities stain epithelial cells of the cornea and conj when a disruption occurs in the protective mucin coating
rose Bengal and lissamine green stain epithelial cells of the cornea and conj when a disruption occurs in the protective mucin coating
imaging modality that is useful in determining etiology of infectious keratitis
confocal microscopy
differentiate between Acanthamoeba, fungal keratitis, microsporixdiosis, and herpetic eye disease
these two zones make up the apical zone which are primary responsible for the refractive power of the cornea
central and paracentral zones
refractive index of:
air
aqueous and tears
corneal stroma
refractive index of:
air 1
aqueous and tears 1.336
corneal stroma 1.376
I-S values above ___ and central corneal powers above ___ D are suggestive of corneal ecstatic disorders
I-S values above 1.4 and central corneal powers above 47.2 D are suggestive of corneal ecstatic disorders
tear osmolarity is considered abnormally high above ____ and are highly indicative of ATD
tear osmolarity is considered abnormally high above 306-308 mOsm/L
resolution of anterior segment oct
5-10 microns
list the zones of the cornea in order
central, paracentral, peripheral/transitional, limbal zones
average refractive power of cornea
average refractive power of air stroma interface
average refractive power of endothelium aqueous interface
average refractive power of cornea = +43D
average refractive power of air stroma interface = +49 D
average refractive power of endothelium aqueous interface = -6D
corneal topography is based on this principle which employs reflecting images of multiple concentric rings onto the cornea
The placido disk principle
Descemet membrane folds are first seen when corneal thickness increases by ___% or more
Epithelial edema occurs when corneal thickness is greater than ___ microns
Descemet membrane folds are first seen when corneal thickness increases by 10% or more
Epithelial edema occurs when corneal thickness is greater than 700 microns