What is the ruling on the ablution of one who places a medical patch over an old wound on his face and does not remove it during ablution, citing hardship?

As long as the adhesive is on the face (which is a limb that must be washed), the person responsible must remove it during ablution because it prevents water from reaching the skin, and ablution is not valid with its presence. He must repeat the prayers he performed with ablution in which he did not remove the adhesive. If he forgets their number, he must pray what he believes is most likely to absolve his responsibility.