Jockey George Baker suffered "some bleeding in the brain" and faces a long rehabilitation process after falling during a race at St Moritz on Sunday.
Baker was aboard Boomerang Bob on the frozen lake track when the horse was brought down and fatally injured.
The bleed was discovered in an MRI scan on Friday, but the Professional Jockeys Association are "hopeful he will make a positive recovery".
Baker, 34, remains in intensive care in a Swiss hospital.
Racing has taken place for decades on the frozen lake at St Moritz, with horses fitted with special shoes to cope with the wintry conditions.
Race organiser White Turf said a crack was found in the ice when the track was checked after Baker's fall.
It added: "This meant that water had come up to undermine the racetrack."
Oxfordshire-based Baker won the world's oldest classic, the St Leger, last September on Harbour Law.
His fellow jockey Christophe Soumillon, who was also riding at St Moritz, told French news agency Equidia: "Turning into the straight, the snow was only up to the horses' shoes.
"You could see by the prints afterwards that there was water between the ice and the snow."