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A tonometer refers to the equipment that is used in tonometry – a test that measures the pressure inside your eyes, also known as intraocular pressure or IOP for short. Tonometry is rarely performed at your average comprehensive eye exam unless you are at high risk of or have been already diagnosed with glaucoma. Fortunately, tonometry can be used to detect changes in eye pressure before they cause any symptoms, enabling prompt action to be taken before your vision is affected.
Glaucoma is a common eye condition that occurs when the optic nerve, which connects the eye to the brain, becomes damaged. It’s normally caused by fluid building up in the front part of the eye, which causes the pressure inside the eyes to build. As the pressure increases, the optic nerve becomes increasingly damaged, and this prevents messages from being transmitted between your eyes and brain effectively. As a result, the patient’s vision becomes compromised. Without treatment, the level of vision loss will continue to increase. Unfortunately, any vision that has been lost as a result of glaucoma cannot be restored.
Most of the time, glaucoma develops very slowly which means that many people don’t realize that they are affected until some damage to their vision has already occurred. However, occasionally glaucoma can develop quickly, and symptoms do occur.
These can include:
Tenderness around the eyes
Seeing rings/halos around lights
Nausea and vomiting
If you notice any of these symptoms, it’s important that you make an appointment with your eye doctor right away so that you can be assessed. You are likely to have a tonometry test as part of this assessment.
There are various methods of tonometry testing, but many eye doctors use either Goldmann tonometry, which is the conventional technique to measure eye pressure, or electronic tonometry.
Goldmann tonometry testing is carried out using the Goldmann applanation tonometer, which is attached to a slit lamp microscope. This requires anesthetic eye drops to be used which numb your eyes, before a small probe is pressed gently against the eye, indenting the cornea. The pressure that the cornea pushes back onto the tonometer is what is measured to give your IOP reading. Electronic tonometry is where a handheld, mobile device is gently and quickly applied to the cornea to check the pressure, providing an accurate reading. Some eye doctors also offer non-contact tonometry which is where a puff of air is used to flatten the cornea, although this is reported to be less accurate than the Goldmann technique.
If you would like to find out more about Tonometry testing, please call our office to speak with our dedicated eyecare professionals.