Generally, blinkers are used to assist a horse to focus in its races. Blinkers can help a horse to race genuinely. A horse that is “field-shy”, or that runs about while racing, will often improve with the addition of blinkers. Other horses may simply lack zest in their races, and may be too relaxed. Blinkers can often help these horses to “switch on”.
I have also seen blinkers used to help horses relax, both in their morning work, and in races. Shutting out part of the busy-ness around them seems to assist some horses to settle down.
Care should be taken when considering the application of blinkers; they can have a dramatic effect on some horses, and they can be dangerous if the horse hasn’t had a chance to become accustomed to them. They can also cause problems for some horses at the start of races – because visibility of other runners is restricted, horses that tend to jump as they see other horses jumping, may start coning away a bit slower.
It should also be noted that some horses will improve when blinkers are removed. An improvement in performance regularly occurs when blinkers are removed from a horse that has carried them in its races for a long time.
Many, many trainers have explained form reversals solely through the application of blinkers. They are a critical tool in the kit of a thoroughbred trainer, and, used judiciously, will help to win races.