All day measurements of eye pressure (phasing)

Patient Information Leaflet

Introduction

This leaflet is for people having all day measurements of eye pressure. It explains what happens during the procedure.

What is eye pressure?

The eyeball contains a fluid called aqueous humour, which is constantly produced by the eye. Usually, any excess fluid drains out through tubes. The normal pressure in the eye is between 10 and 24 millimetres of mercury (mmHg). If, for any reason, the fluid is blocked and cannot get out, the pressure can rise. This is known as the intraocular pressure.

What is all day measurement of eye pressure?

Eye pressure can vary by as much as 6mmHg during the day, and this can be more in glaucoma patients. Typically, measurements are higher in the early morning, although this is not always the case. Therefore, we may need to assess the pressure in your eyes every two hours over an eight hour period. This is called phasing.

What are the benefits?

It is a useful test if your eye pressure is border line, or if glaucoma is progressing even though you have normal eye pressure measurements. It gives the ophthalmologist information that can be used in the diagnosis and monitoring of your eye condition.

What are the alternatives?

This is one of a number of tests used to diagnose and monitor your eye condition. You do not have to have this test, but it will help your ophthalmologist to assess your eye condition.

What happens during the procedure?

The phasing will take place in the Eye Clinic between the hours of 8am and 4pm. You will be looked after by a phasing nurse, who will measure your eye pressure every two hours. You are welcome to come and go between the measurements, or you can stay in our waiting rooms.

Measurement of the pressure within the eye is called tonometry. It uses an instrument called a tonometer to measure the pressure inside your eye.

The nurse will put some drops of anaesthetic (a painkilling medication) into your eye. Then, yellow / orange dye is used to temporarily stain the tears. You will need to put your head in a headrest, and then the ophthalmologist will shine a blue light on your eye.

We use a small, round, flat instrument to painlessly flatten the cornea of your eye. We can measure the pressure of your eye by how much the cornea flattens.

While you are at hospital, you can buy meals and refreshments from the restaurant situated in the main entrance, or you can bring your own.

This can be a long day, so you may wish to bring someone with you. You may also want to bring something to read or do while you are waiting.

What if I have any problems or questions after reading this leaflet?

If there is anything you do not understand, or you are concerned or worried about any part of the treatment, contact:

The Urgent Referral Clinic team at Russells Hall Hospital Eye Clinic on 01384 456111 ext. 3633.

Eye emergency, out of hours

In case of an eye emergency after the closing hours of the Eye Clinic at Russells Hall Hospital (including weekends and bank holidays), please contact:

Birmingham and Midland Eye Centre on 0121 507 4440

The doctor on call is usually based at the Eye Centre, City Hospital, Dudley Road, Birmingham. They may need to call you back, and if necessary, they will arrange for you to visit them.

Note: the information in this booklet is provided for information only. The information found is not a substitute for professional medical advice or care by a qualified doctor or other healthcare professional. Always check with your doctor if you have any concerns about your condition or treatment. This is only indicative and general information for the procedure. Individual experiences may vary and all the points may not apply to all patients at all times. Please discuss your individual circumstances with your eye doctor.

Author: Julia Phillips (advanced glaucoma practitioner), RGN, Ophthalmic Nurse Training, BSc (Hons), Glaucoma Specialist MSc modules and training, Non-Medical Prescriber.

If you have any questions, or if there is anything you do not understand, please contact the Russells Hall Hospital switchboard number on 01384 456111 and ask for the relevant department who issued this leaflet.

If you have any feedback on this patient information leaflet please email dgft.patient.information@nhs.net

This leaflet can be made available in large print, audio version and in other languages, please call 0800 073 0510.

Phasing JP/ST/DP/09.2024 v4 review 06.2027 DGH ref.: DGH/PIL/01157