What is Tonometry Test?
Tonometry is a quick and easy diagnostic test that measures the pressure inside the eye (intraocular pressure (IOP). It is done to determine the risk of glaucoma.
Glaucoma is a disease in which the optic nerve of the eyes is gradually damaged. This results in loss of vision. This disease is often associated with an increase in eye pressure.
According to the American Association of Opthalmology (AAO), glaucoma is a leading cause of blindness in adults over 60 years of age.(1)
Identifying the eye pressure can help prevent blindness from glaucoma. It can protect the eyesight and slow down vision loss.
Goldmann applanation is the most common type of tonometry test.
Who Needs Tonometry Test?
A tonometry test is advised to a person if the doctor suspects the risk of glaucoma.
According to AAO, the risk of glaucoma increase in the following conditions:(2)
- If you are over 40 years of age
- Those who are black, Hispanic, or Asian
- Those with a family history of glaucoma
- Nearsighted or Farsighted
- Those with chronic eye conditions
- Someone who has injured eye in past
- Hypertension patients
- Those with poor blood circulation
- Those on corticosteroid medications for prolonged periods
Tonometry test is also prescribed to those who are experiencing:
- Gradual peripheral vision loss
- Tunnel vision
- Blurred vision
- Severe eye pain
- Reddening of the eye
- Halos around light
All the above symptoms could signal glaucoma.
How is Tonometry Test Done?
Before the Tonometry test, the doctor puts numbness eye drops, so that the person doesn’t feel anything touching it.
Once the eyes are numb, a small strip of paper containing the orange dye is touched on the surface of the eye to stain it. This helps in increasing the accuracy of the tonometry test.
After this, a machine known as a slit lamp is put in front of the person where he puts his chin and forehead on the support provided. The lamp is then moved towards the eye till the tip of the tonometer probe touches the cornea.
The tonometer can detect eye pressure by flattening the cornea just a bit. The doctor adjusts the tension till they get a proper reading.
Tonometry is a safe procedure. There is a little risk of the cornea getting scratched when the tonometer touches the eye. If it happens the eyes normally heals in a few days.
Tonometer Test Result
A normal test means the pressure in the eye is normal and there is no risk of glaucoma or any other pressure-related eye problem.
According to the Glaucoma Research Foundation, 12-22 mmHg is the normal eye pressure.(3)
If the test shows a reading of 20 mmHg, it may indicate that you may have glaucoma or pre glaucoma. The doctor might do further testing to confirm the diagnosis.
The doctor may keep a close watch on the symptoms if high pressure in the eye is detected. He may also advise regular testing. He might also prescribe eye drops to put in the eyes every day to lower the pressure. These drops might protect the optic nerve from future damage in a long run.