Theoretics Flashcards
The Goldmann applanation tonometer measures the force necessary to flatten an area of cornea of what diameter?
At a diamter of 3.06m, the resistance of thecornea to flattening is counterbalanced by capillary of the tear film to the tonometer tip
Aqueous humor - more than plasma
hydrogen, chloride, ascorbate
Aqueous humor - less than plasma
bicarbonate
Outflow facility value
0.3 uL/min/mmHg
Visual field pattern of sleepy or inattentive patient
“cloverleaf” pattern
What happens to aqueous formation and outflow facility as one gets older
formation and outflow both decrease
mean IOP
15.5mmHg with a standard deviation of 2.6mmHg
IOP - what type of distribution in epidemiology
non-gaussian distribution with a skew toward higher pressures
infant - when to perform tonometry under anesthesia?
immediately after general anesthesia is induced and before intubation
M cells (RGC type)
large diameter axons. largest perceptive field. sensitive to light in scotopic conditions. motion vision
P cells (RGC type)
80% of all RGCs. small diameter axons. small perceptive field. color and fine-detail vision. concentrated in the macula
koniocellular neurons (RGC type)
blue-yellow color. activated preferentially by short-wavelength perimetry (SWAP)
Main site of resistance to aqueous humor outflow
juxtacanalicular trabecular meshwork
order of drainage of aqueous humor via the trabecular outflow
Schlemm canal –> collector channels –> episcleral veins –> anterior ciliary vein –> superior ophthalmic vein
which parts of the VF is last affected
central island of vision, inferotemporal VF
Average rate of aqueous formation. when lower nad higher
2-3 uL/min. decreases by half during sleep. higher 8AM to 12AM
prevalence of glaucoma after 40yo
2%
uveoscleral outflow - describe
pressure-independent mechanism, where aqueous passes from the ciliary muscle into the supraciliary and suprachoroidal spaces
Which adrenergic receptors are the most prevalent in the ciliary epithelium
beta-2
aqueous formation - mechanism
active secretion by the inner nonpigmented ciliary epithelium. involves membrane-associated Na+-K+-ATPase
pigmented / nonpigmented ciliary epithelium - which inner / outer
inner nonpigmented, outer pigmented
What risk of glaucoma is sibling suffers
10%
Total internal reflection - which interference
air-tear interference
Can much can IOP vary during a day
2-6mmHg
Which type of retinal ganglion cell does frequency-doubling technology activate?
M (magnocellular) cells
Main conclusion from the Collaborative Initial Glaucoma Treatment Study
initial medical and initial surgical therapy resulted in similar visual field outcomes after 5 years of follow-up
Supply - nerve fiber layer portion of the optic nerve
CRA
Supply - anterior optic nerve
10-20 short posterior ciliary arteries
Supply - laminar portion of the optic nerve
circle of Zinn-Haller + short posterior ciliary arteries
each 1 mmHg decrease in IOP is associated with what percentage reduction in progression of glaucoma
10%
Uveoscleral outflow - what increases, dependence on IOP, % outflow
increased by atropine, independent of IOP, resposible for 20% outflow
Fluorophotometry
measures aqueous production
rate of aqueous production
2 ul/min
Manometry
measures EVP
Tonography
measures facility of aqueous outflow
Which perimetry allows earlier detection of glaucoma
frequency doubling technology
Scleral Spur - definition
anatomic junction between the inner wall of the trabecular meshwork and the sclera
