And with the age profile of the Irish population increasing, glaucoma is expected to be become an even bigger problem.
The disease needs to be detected at an early stage because, by the time a person notices their sight is affected, it is too late.
“Glaucoma can be described as the thief of sight. This is because someone with early glaucoma will have no symptoms and it is painless,” said Lynda McGivney Nolan of the Association of Optometrists in Ireland (AOI).
Ms McGivney Nolan, who was speaking in advance of World Glaucoma Day on Thursday, said it was crucial that everyone over the age of 40 was regularly tested for the disease.
On Thursday, independent members of the AOI will be offering free glaucoma testing to the public.
Glaucoma causes an increase in the pressure inside the eyes, and if left unchecked causes irreversible nerve damage at the back of the eye.
It is mostly people over the age of 40 who are at risk and the risk increases with age.
Details of the free screening can be obtained by contacting the AOI at 01-4538850.
Information on preventive eye care is available at www.optometrists.ie.