Leah Tee, 17, has cone-rod dystrophy, a severe form of colour blindness which affects her ability to differentiate colours and blurs her vision slightly.
Laura Lee, also 17, has moderate hearing loss in both ears, which makes hearing soft or individual voices in group settings a challenge.
The two CHIJ Secondary alumni have been best friends since they were "table buddies" in primary one.
"Both of us loved ponies and horses then so that's how we became friends," recalled Leah.
"She's always been my ears and I'll be her eyes, so that works out well ," Laura said.
Having been classmates in primary one, two and throughout secondary school, the girls have been each other's pillar of support in their studies.
Last year, both sat for the O-level examinations, where Leah ended up scoring six distinctions and Laura had five.
Leah was exempted from the Chemistry practical examination, which requires differentiating the colours of solutions.
Her exam scripts were printed in a larger font and she was given 20 to 30 minutes of extra time for each paper.
Laura had to take her papers in a separate room from her peers.
Without consulting each other, both girls applied for St Joseph's Institution's International Baccalaureate Diploma Programme as their top choice.
They will be receiving their posting results today and are eager to find out if they will be classmates again.
When Leah was born, "she was eight weeks premature and her eyes were jiggling," said her father, Mr Adrian Tee, who runs his own media production firm.
Mr Tee, 47, and his wife Jennifer Tee, 44, were worried about the initial diagnosis from the Singapore National Eye Centre, which was that their daughter had Nystagmus, a condition which would result in Leah eventually becoming blind.
After further observation, Leah was diagnosed with cone-rod dystrophy instead when she was a toddler.
Leah also had long-sightedness when she was six months old and has worn spectacles ever since.
As a toddler, Laura could not repeat certain words spoken to her slowly and directly, said her mother, Mrs Vanessa Lee, 48.
That triggered an initial visit to KK Women's and Children's Hospital, where "the doctors dismissed it as ear wax and simply cleaned that out".
Upon her sister-in-law's advice, she later consulted a specialist, who diagnosed Laura with moderate hearing loss in both ears.
CAN'T KEEP SECRETS
"I can't keep secrets with my siblings because I can't gauge how loud my whisper is and I can't hear whispers too," Laura, who is the eldest of four children, said with a chuckle.
Her condition had previously resulted in misunderstandings at home, where her siblings thought she was being arrogant whenever she did not respond to them.
Till this day, Mrs Lee has to constantly remind her other children to speak loudly and clearly when talking to Laura.
Leah also faces her share of daily challenges.
"It's annoying when I miss the bus to school in the morning because it goes past too fast for me to see the numbers so I would ask for my sisters' help".
Her sisters, Christiane Tee, 15 and Trina Tee, 13, are both studying in CHIJ Secondary.
"I have had to sit out PE lessons because I couldn't see a basketball flying towards me. I got hit quite a few times," Leah added.
But the girls have never seen their conditions as a disadvantage and neither have their classmates.
When Leah could not see the whiteboard, Laura would share her notes, and when Laura could not hear what her teachers were saying, Leah would repeat it for her.
Despite having to squint to see the whiteboard from the front row, Leah refused special treatment in class, said her former English and literature teacher Wendy Lee, 42.
Their classmates were also very helpful and accommodating, said their ex-form teacher, Mr Tristan Fernandez, 51.
And both girls are glad for the friendship they have developed over the years.
Laura said: "I think it's safe to say I've met a friend for life."
This article was first published on Jan 02, 2017.
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