Tom Gray had shown no other symptoms to make his parents Simon and Carly think anything was wrong.
But an MRI scan just four days before his eighth birthday confirmed the youngster, from Victoria, Australia, had inoperable brain cancer.
He passed away 14 weeks later in 2016.
Dad Simon said aside from his lazy eye and failing vision, they had no reason to believe their son had cancer.
He told MailOnline: "There were no other symptoms. He was always doing something - a very active body and active mind.
We made the choice not to tell him. We wanted him to try to enjoy everything we threw up at him without the thought in his head that he was going to die
Simon Gray
"The only other thing, and we thought about this later on, was that his movement wasn't as crisp as what it used to be."
Mum Carly told Nine News: "He had the MRI and we got the phone call that day to say you've got an appointment with the oncologist tomorrow.
"We knew things couldn't be good. But you still don't anticipate that you're going to be told there's really nothing they can do."
His parents decided not to tell Tom he had Diffuse Intrinsic Pontine Glioma (DIPG) following the devastating diagnosis.
What is Diffuse Intrinsic Pontine Glioma (DIPG)?
Diffuse Intrinsic Pontine Glioma also known as 'DIPG' is the second most common type of primary, high grade brain tumour in children.
DIPG is a type of high grade brain tumour, which means it tends to grow quickly and is more likely to spread to other parts of the brain or spinal cord. They are sometimes referred to as being 'malignant' or 'cancerous'.
DIPGs originate in an area of the brain, and more specifically the brainstem, called the pons. The pons is an area deep within the lower part of the brain which is responsible for a number of critical bodily functions, such as breathing, sleeping and blood pressure.
The cause of brain tumours, including DIPG, is not yet known.
The signs of a DIPG vary as the pons and surrounding structures (where DIPGs are located) are responsible for a variety of different body functions. A child with a DIPG may display:
- Abnormal alignment of the eyes or/and double vision (diplopia).
- Weakness of facial muscles or facial asymmetry (one side of the face appearing different from the other).
- Arm and leg weakness.
- Unstable balance and co-ordination.
- Difficulties walking and speaking.
The standard of treatment for DIPGs is radiotherapy, which is usually administered over 3 to 6 weeks depending on the type of radiotherapy that is deemed best for your child (with a daily dose given Monday to Friday). Your child might also be given steroids during this period to help reduce some of the pressure caused by the tumour and radiation treatment.
Source: The Brain Tumour Charity
Simon told the broadcaster: "We made the choice not to tell him. We wanted him to try to enjoy everything we threw up at him without the thought in his head that he was going to die."
In his final days, he managed to play a couple of games of football and was made captain of his friend's boat for a day.
They are now helping raise awareness about childhood brain cancer with a unique art exhibition at Kyneton Hospital, with portraits of Tom from birth to death adorning the corridors.
The collection by artist Daniel Butterworth includes one striking painting of Tom lying peacefully in his casket.
