There is very little science behind the reason why rabbits are used. It has more to do with practical considerations—they are small and gentle and so easy to handle; they are relatively cheap to maintain if only basic standards are adhered to; and they breed fast, creating new test subjects quickly. Rabbits also have no tear ducts so, unlike humans, they can't cry out harmful substances from their eye. This means that in the Draize eye test the rabbit's eye is exposed to more of the test chemical for longer periods, which is one of the main reasons why rabbits are chosen for this procedure.