Factors affecting IOP Measurements

Question 1

Pick three that temporarily lower IOP

A. Alcohol
B. Marijuana
C. Excess Water Consumption
D. Exercise
E. Tight Neck
F. Smoking

Answer 1

A. Alcohol
B. Marijuana
D. Exercise

Question 2

Applying pressure on the globe will overesimate/underestimate IOP?

• Blepharospasm will overestimate/underestimate IOP?
• Lid/Lash contact will overestimate/underestimate IOP?

Answer 2

• Pressure on the globe will overesimate IOP
• Blepharospasm will overestimate IOP
• Lid/Lash contact will overestimate IOP

Question 3

Patients with Glaucoma tend to have a higher IOP? TRUE/FALSE

Answer 3

• TRUE

Question 4

Based on the Ocular Hypertension Treatment Study, patients with thicker than average corneas showed an increase risk of POAG? TRUE/FALSE

Answer 4

• FALSE, patients with thinner than average cornea had higher risk

Question 5

Goldmann calculations are used at 540-550 microns and is most accurate at 520 microns. TRUE/FALSE

Answer 5

• FALSE - Goldmann calculations are at 520 microns and most accurate at 540-550 microns.

Question 6

Based on OHTS thick corneas will give falsely HIGH/LOW IOP readings?
- Thin corneas will give falsely HIGH/LOW readings?

Answer 6

• Thick corneas will give falsely HIGH IOP readings

- Thin corneas will give falsely LOW IOP readings

Question 7

LASIK and PRK will overestimate/underestimate IOP readings and why?

Answer 7

• LASIK and PRK thin the cornea thereby underestimating (lowering) IOP readings

Question 8

Stroma edema will lower/raise IOP?

Answer 8

• Stromal edema lowers IOP because of thickened and weaker cornea.

Question 9

What impact does axial length have on tonometry readings? Is it clinically significant?

Answer 9

1. 0 mm increase in axial length lowers tonometry reading by 0.29 mmHg
   - Questionable effect clinically

Question 10

What impact does cyclopentalate have on IOP? What causes the change in IOP?

Answer 10

• Cyclopentalate shows a mean increase of 0.4 mmHg but 7% see 5 mmHg increase.
• Due to ciliary body decreasing the aqueous outflow. May want to recheck IOP for glaucoma/at risk patients.

Question 11

What effect does accomodation have on IOP? (after 30 seconds and after 3.5 minutes)

Answer 11

• Decreases IOP
• 1 mmHg after 30 seconds
• 2 mmHg after 3.5 minutes

Question 12

There is a direct correlation between steeper keratometry readings and IOP? TRUE/FALSE

Answer 12

• FALSE, no correlation in recent literature.