Non-Contact Tonometry Flashcards
how are blood pressure and IOP related
reduced systemic BP is associated with reduced IOP
what is perfusion pressure
the balance between blood pressure and IOP (Diastolic BP- IOP = perfusion pressure)
why is ocular perfusion pressure important
important in damaged optic nerves and autoregulation (maintain flow despite perfusion pressure)
how is the central venous pressure related to IOP
the central venous pressure is half the IOP (linear relationship)
what is the central venous pressure
the amount of blood at the vena cava returning to the heart
what are 2 ways central venous pressure can increase
when given too much IV fluid and myocardial infarction
what is 1 way central venous pressure can decrease
when there is blood loss
what is the triad in glaucoma
increased IOP, optic nerve damage, and visual field loss
is an increase in IOP symptomatic
no if it is gradual, yes if it is acute (nausea, halos, and pain)
what condition can decrease IOP
phtisis bulbi (shrunken, non-functional eye, usually replaced with a prosthesis)
how much change in diurnal variation is suspicious when measuring IOP
more than 4mmHg
how much variation is arterial pulse suspicious in IOP measurement
2-4mmHg
how much higher are IOP measurements when patient is supine
2-3mmHg (decrease in venous return, increase in episcleral pressure)
how can vascular integrity affect IOP measurements
poor perfusion from the carotid will reduce aqueous production on the ipsilateral side
how much can exercise reduce IOP measurements
20%
how much can external pressure on the globe increase IOP measurements
5-20mmHg (digits or blepharospasm)
what 4 medications/drugs can reduce IOP measurements
clonidine, betablockers, marijuana, and alcohol
what type of drug can increase IOP measurements
steroids
how does trauma/inflammation affect IOP measurements
initial injury shuts down ciliary body- reducing IOP then inflammatory cells clog meshwork- increasing IOP
how does corneal hysteresis (elasticity)/thickness affect IOP measurements
thicker corneas may over estimate IOP
what amount of IOP are NCT accurate up to
30 mmHg
why would you need to take multiple readings on the NCT
one reading may be measured at the height of the ocular pulse
what is the standard of care for tonometry
goldmann
what is the average IOP in NCT
15.5mmHg (8-23 mmHg range)
how much asymmetry is abnormal
2mm
what is a normal recording for NCT
OD: 16, 14, 14, mmHg @4:15pm Pulsair NCT
