To Learn

Question 1

What assumptions are there in tonometry?

Answer 1

• The eye is spherical and uniform
• The eye is perfectly flexible
• The eye has an infinitely thin wall
• 3.06mm contact area will balance out the surface tension

Question 2

What does bandwidth stand for?

Answer 2

The frequency range that is not less than 3bD below the maximum gain. This frequency range the gain remains constant and all components are amplified equally

Question 3

Why do we need a higher voltage if the skin is drier?

Answer 3

Because of a higher resistance. Voltage/Resistance. Ohms law.

Question 4

What do Oscillatory Potentials look like on a graph?

Answer 4

Ripples on the B-wave

Question 5

How does achiasma look on a VEP?

Answer 5

Stimulate LE, lateralised to L hemisphere responses which is recorded by an electrode on the R hemisphere due to a lack of crossing

Question 6

What does the stimuli look like in an mfERG?

Answer 6

Structured stimulus consisting of multiple elements that stimulate many retinal areas simultaneously following a pseudorandom pattern

Question 7

What conditions have increased peak times on VEPs?

Answer 7

Demyelinating conditions and optic nerve compression

Question 8

Why might patient not be completely blind even if they have no recordable VEP?

Answer 8

A VEP recording takes 1,000 neurons to fire but only a few neurons are needed to see a flash

Question 9

How do we record a Sweep VEP?

Answer 9

Rapid presentation fo checkers in as little as 10 seconds. Amplitudes plotted and a straight line extrapolated from peak function to 0 microvolts to give cortical acuity in cycles per degree which is converted to Snellen equivalent. This method determines when response vanishes opposed to when it is simply invisible amongst background noise