Eye pain, blurred vision and vomiting are all tell-tale signs of an incurable condition known as the ‘silent thief of sight’.
However, the symptoms of glaucoma, which affects two per cent of over-40s in the UK, can vary considerably.
They can range from cloudy vision and teary eyes to vomiting.
Glaucoma, which develops slowly over many years in most cases, can lead to a loss of vision if not treated promptly.
Here, MailOnline reveals five of the lesser-known signs of the condition — and some of the celebrities living with it.
Caryn Johnson, also known professionally as Whoopie Goldberg, first revealed her diagnosis in 2014
The condition is usually caused by fluid slowly building up in the front part of the eye, which increases pressure inside it.
As a result, the optic nerve, which connects the eye to the brain, becomes damaged.
Around 700,000 people in the UK and more than 2million in the US are living with glaucoma, which is usually symptomless in its early stages.
It mostly affects those in their seventies and over, but people of any age can get it.
The condition is diagnosed by opticians during routine eye exams, which measure the pressure inside the eye.
Treatment aims to lower this pressure through prescription eye drops, oral medicines, laser retreatment, surgery or combination of these options.
Dr Elizabeth Hawkes, a consultant ophthalmic and oculoplastic surgeon at Cardogan Clinic in London, told MailOnline: ‘It can take a few years to be diagnosed as an adult as it tends to develop slowly.
‘It is often only picked up during a routine eye test, which is why they are so important especially if you have a family member with glaucoma — [eligible people] should use the NHS screening service for over 40s, every year.
‘Early diagnosis is associated with better visual prognosis, loss of vision is a late and usually avoidable sign if picked up early.’
The eyes appearing whiter and cloudy could be a warning sign of glaucoma.
The eye continuously recycles a clear fluid called aqueous humor.
But in those with glaucoma, the drainage channels for this liquid become blocked or narrowed.
This creates tension on the optic nerve, which sends the image the eye sees to the brain for processing.
This leads to the fluid being pushed into the cornea — the transparent part of the eye that covers the iris.
Dr Elizabeth Hawkes said: ‘If the pressure in your eye rises too high, fluid will be pushed into the cornea, which will make it cloudy and waterlogged and leads to white looking eyes.’
Dilated blood vessels
Dilated blood vessels can be another sign of glaucoma.
When the blood vessels are dilated, the white part of the eye — the conjunctiva — becomes red due to the blood vessels becoming more prominent on the surface of the eye.
This occurs because when the pressure within the eye has increased and the eye’s drainage channel is blocked.
If the pressure builds up suddenly, it can permanently damage the optic nerve.
Dr Hawkes explained: ‘Blood vessels do not generally become dilated with glaucoma. In the conjunctiva, the white part of the eye, you have lots of blood vessels.
‘They can sometimes, in rare circumstances, become dilated, which could be associated with underlying conditions.
‘It could be an indication that intraocular pressure could be high. Raised pressure is associated with glaucoma.’
While glaucoma almost always develops slowly over many years, it can very occasionally develop suddenly.
The resultant pain resulting from the pressure build-up in the eye can be very intense.
When someone experiences such high levels of discomfort, a chemical can be released, such as adrenaline, that signals the brain to vomit.
Dr Hawkes explained: ‘Severe eye pain is the most obvious sign of glaucoma and is usually unbearable.
‘This will cause redness to the eye, headaches and potentially vomiting, due to the pain.’
Loss of vision in one eye
The optic nerve, which connects the eye to the brain, is compromised of nerve fibres.
Glaucoma causes these fibres to die, which can interfere with the connection to the brain.
This can cause the vision to fade and eventually be lost completely.
Dr Hawkes said: ‘If you notice a loss of vision or a blind spot, you need to go and see your eye doctor.
‘If you experience sudden blindness, it is an emergency. With glaucoma, there is a very short period of time to get treatment to prevent permanent blindness.’
Eyes may become more teary with glaucoma.
This excess water is typically a result of the drainage channels for aqueous humor becoming obstructed.
The internal fluid pressure is out of balance and so the eyes become more teary.
Teary eyes are typically present in babies born with congenital glaucoma — a very rare form of the condition.
Teary eyes alone don’t always indicate glaucoma. But combined with other issues mentioned above it can indicate a defeat in the drainage channel angle of the eye.
There are many factors which increase your chances of developing glaucoma, such as age, ethnicity, family history and other medical condition such as diabetes.
It is not clear whether you can do anything to prevent the condition but regular eye test are recommended.
Here, Mail Online reveals five celebrities who are living every day with the incurable condition.
Caryn Johnson, also known professionally as Whoopie Goldberg, first revealed her diagnosis in 2014.
The beloved American actress revealed that the headaches caused by glaucoma ‘come on like freight trains’.
The 67-year-old claimed her symptoms were so bad that she used a vaporiser pen — filled with cannabis — to cope with the pain.
The 67-year-old revealed that the headaches caused by Glaucoma ‘come on like freight trains’
Whoopie, who has had a long and illustrious career in film, described her symptoms in an article for The Cannabist as ‘BOOM, my head starts hurting, my eyes start bugging, my whole body starts to tense up’.
The comedienne, from New York suffers from angle-closure glaucoma, which is an uncommon type of glaucoma, caused by the drainage in the eye becoming suddenly blocked, which can raise the pressure inside the eye very quickly.
Paul Hewson, also known by his stage name Bono, was diagnosed in 2014.
The U2 frontman debunked a common misconception that he constantly wore glasses, regardless of the weather, to keep up his rock-star image.
Paul Hewson, also known by his stage name Bono, was also diagnosed in 2014
The 62-year-old revealed that he wears the shades to alleviate the difficulties
In an interview on BBC One’s Graham Norton show, the 62-year-old revealed that he wears the shades to alleviate the difficulties caused by the chronic eye condition.
The philanthropist from Dublin said: ‘This is a good place to explain to people that I’ve had glaucoma for the last 20 years. I have good treatments and I am going to be fine.’
The Irish band were on the Graham Norton show to promote their album, Songs Of Innocence.
The supermodel took to social media in 2021 when she was diagnosed with acute angle closure glaucoma during a routine eye exam.
The 69-year-old posted a photograph of herself warning her 800,000 followers to check their eyes.
The entrepreneur from Michigan wrote: ‘They can fix it by, brace yourselves, drilling a hole thru your eye! It’s not as gruesome as it sounds. In fact I just had it done in this photo, piece of cake.
The supermodel was diagnosed with Acute Angle Closure during a routine eye exam in 2021
The 69-year-old wrote on social media: ‘They can fix it by brace yourselves, drilling a hole thru your eye!
‘But if left untreated it could have resulted in vision loss…So I’m very grateful! Thank you Dr Coles! And friends keep your eye on your precious eyes!
Former Dutch midfielder Edgar Davids, recognised by many for playing football games with goggles, is also a sufferer.
The 49-year-old underwent surgery in 1999, while playing for Juventus, to alleviate glaucoma symptoms in his right eye.
His eyewear has been a necessity ever since, to ensure no particulates entered his eye and caused further damage.
The former Dutch midfielder underwent surgery in 1999 to help alleviate his glaucoma symptoms in his right eye
The eyewear ensures no particulates entered his eye and caused further damage
The international star’s has not let his diagnosis get in the way of his career.
James McGuinn, who is known professionally as Roger McGuinn, was first diagnosed with glaucoma during a routine eye exam around two decades ago.
The singer-song-writer, 80, had not yet experienced any symptoms or vision loss.
Since his diagnosis, he has taken daily medication to manage his symptoms.
James McGuinn was first diagnosed in a routine eye exam around 20 years ago
The 80-year-old takes daily medication to help keep his symptoms manageable
The musician from Chicago has expressed how grateful he was to have found the condition early as treatment has allowed him to carry on singing and playing guitar.
He told The Glaucoma Research Foundation: ‘When I was first diagnosed with glaucoma, I was depressed.
‘I didn’t know much about glaucoma, or whether the pressure could be controlled.
‘I had trouble even accepting that something this serious could happen to my eyes.’