# Schiotz Tonometry

## Overview

This module describes how to test a patient’s intraocular pressure with a Schiotz tonometer.

## Indications

1. Screening for glaucoma

## Contraindications

1. Conjunctivitis—could spread the infection via the tonometer

2. Suspected eye injury

3. Epithelial defect or corneal ulcer

## Patient information & consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“I need to test the pressure in your eyeball with a small scale. It is important to measure the pressure because if it is too high, you may have glaucoma and you could lose your eyesight if it’s not caught early.”

### What can my patient expect?

“I will put a numbing drop in your eyes. Lie back and I will place the scale on each eyeball and measure the pressure. It will not hurt at all, but it may be a little uncomfortable.”

### What is my patient’s role?

“Try to stay relaxed and keep your eyes open. Keep your eyes focused on one spot on the ceiling and do not look away.”

## Preparation

###

### Documentation

1. Patient notes

### Equipment

1. Alcohol-based hand rub

2. Schiotz tonometer

3. Alcohol swab

4. Anaesthetic eye drops
   Anaesthetic eye drops

   Kept in the fridge. Check the expiry date.

## Site & Positioning

The patient should be supine.

## Procedure

Follow medical asepsis without gloves.

1. Perform hand hygiene.

2. Remove and clean the tonometer footplate and plunger with alcohol. Use the pipe cleaner supplied to clean the plunger bore. Rinse and dry the footplate and plunger.

3. Check for proper calibration by putting the tonometer footplate with the weighted plunger in place on the testing plate. It should register 0 on full depression.

4. Instil anaesthetic eye drops into each eye.

5. Ask the patient to focus on a point on the ceiling.

6. Open the eyelids and fix them to the orbital rim with your non-dominant hand’s fingers. Do not apply any pressure to the globe.

7. Hold the tonometer between the finger and thumb of your dominant hand with the scale facing you.

8. Put the footplate of the tonometer, containing the 5.5 g weight, on the central cornea, keeping the instrument vertical.

9. Note the reading. If less than 2.0, replace the weight with the 7.5 g weight. If still less than 2.0, replace the weight with the 10 g weight.

10. Convert the reading to mmHg using the conversion table supplied with the tonometer.

11. Repeat this test on the other eye.

12. Record the results in patient notes.

13. Clean the tonometer after use.

## Troubleshooting

My patient has an abnormal test result.

Intraocular pressure exceeding 20 mmHg is abnormal. Refer urgently to an ophthalmologist.

I don’t have a conversion table.

Conversion tables are available on the Internet.

## Risks

1. Patient exposure to eye infection

2. Corneal abrasion

## References

1. Pons J. How To Examine The Eye. In: Mash B, Blitz-Lindeque J, eds. South African Family Practice Manual. 2nd ed. Pretoria: Van Schaik Publishers; 2010: 134-137.