Tonometry

Question 1

Tonometry

Answer 1

Measurement of intra-ocular pressure IOP.
IOP cannot actually be measured as this would mean penetration of the globe.
Instead it is referred from the relationship
IOP= tonometer applied force + surface tension -corneal elasticity/applanated area

Question 2

Indentation tonometry

Answer 2

IOP measured by indenting cornea. The IOP is deduced from from depth of indentation

Question 3

Applanation tonometry

Answer 3

IOP measured by flattening (applanating) the cornea.
IOP deduced from area of flattening produced by applied force

Question 4

Non-contact tonometry

Answer 4

Method of applanation by puff of air produced from piston & cylinder arrangement.
Detects flattening of cornea produced by puff of air hitting it and uses this to determine IOP.

Question 5

Advantages of non-contact tonometry

Answer 5

*Requires no anaesthetic (no contact with cornea)
*No risk of damage to corneal epithelium
*No risk of transferring infection between px’s
*Can be used by trained support staff
*Quicker than contact tonometry
*Some px’s find it less unpleasant than contact tonometry