Source:
https://scmp.com/article/489260/blind-arabian-wager-freezes-gates

'Blind' Arabian Wager freezes in gates

Outsider Arabian Wager was declared a starter in the final race last night after he stayed in the gates in extraordinary circumstances - he was rendered 'clinically blind' while in the barriers. The sprinter had been throwing his head around in the gates but Jockey Club vets ascertained he did not hit his head to cause the problem.

However, one theory was that he had thrown out a vertebra in his spine with the restless movement and pinched a nerve which had had an effect on his sight.

When the gates clanged open, Arabian Wager simply froze in fear and refused to move from the stalls. Arabian Wager was being kept at Happy Valley overnight in order to monitor his condition.