Depois de tomar poção polissuco, ele vê a visão de Goyle (sem ajuda). Seus óculos "nublam" seus olhos, sugerindo que sua visão (com óculos) deve estar a pelo menos 4 a 5 pontos abaixo de 20:20. Qualquer coisa menor e sua visão seria simplesmente distorcida, em vez de borrada:
Then he realised that his glasses were clouding his eyes, because Goyle obviously didn’t need them - HP: CoS
Ele não consegue enxergar bem o suficiente para distinguir que o que ele está olhando é um cão grande, mas ele consegue enxergar bem o suficiente para dizer que é um animal de algum tipo:
Harry set down his goblet and was about to turn back to his bed when something caught his eye. An animal of some kind was prowling across the silvery lawn. - HP: POA
Ele consegue distinguir sua localização e distinguir seus amigos facilmente do outro lado da sala. Se ele apertar os olhos, ele pode trazer sua visão para algo próximo da normalidade:
Everything was slightly blurred. Somebody had removed his glasses. He was lying in the dark hospital wing. At the very end of the ward, he could make out Madam Pomfrey with her back to him, bending over a bed. Harry squinted. Ron’s red hair was visible beneath Madam Pomfrey’s arm - HP: PoA
Pessoas familiares têm "contornos confusos", mais uma vez, sugestivos de miopia moderada
He could see the fuzzy outlines of Mrs Weasley and Bill close by. Mrs Weasley was on her feet. ‘That’s Fudge’s voice,’ she whispered. ‘And that’s Minerva McGonagall’s, isn’t it? But what are they arguing about?’ - HP: GoF
A sala está desfocada
Harry emerged from behind his towel; the changing room was blurred because he was not wearing his glasses, but he could still tell that everyone’s face was turned towards him. - HP:OotP
Ele não consegue distinguir faíscas de fogo de artifício individuais
He got into bed, yawning. With his glasses off, the occasional firework passing the window had become blurred, looking like sparkling clouds, beautiful and mysterious against the black sky. - HP: OotP