My dad ducked into the dim interior of the trailer and approached the filly, whispering softly. She still seemed agitated, but only fidgeted as the lead rope was unclipped and Dad pulled her towards the outside world.

No sooner did he give a gentle tug at the halter than the filly took off, galloping wildly in the narrow space, her hoofbeats echoing painfully, ears flat against her neck, nostrils flared. She thundered down the ramp, but missed her footing and went down, rolling the rest of the way and landing hard at my feet.

The spooked horse scrabbled to her hooves, and tried to make a break for it; I snatched the lead rope and dug my heels in. She resisted with all her strength and reared.

Dad was at her other side in a flash, taking hold of the halter. For three minutes we stroked and soothed her, though she still trembled.

The reason for her terror became instantly clear when I looked in her hazelnut eyes: the horse was blind.