Objection 1. It would seem that those who are deformed should not be anointed in those parts. For just as this sacrament demands a certain disposition on the part of the recipient, viz. that he should be sick, so it demands that he should be anointed in a certain part of the body. Now he that is not sick cannot be anointed. Therefore neither can he be anointed who lacks the part to be anointed.
Objection 2. Further, a man born blind does not sin by his sight. Yet in the anointing of the eyes mention is made of sins by sight. Therefore this anointing ought not to be applied to one born blind, and in like manner as regards the other senses.
On the contrary, Bodily deformity is not an impediment to any other sacrament. Therefore it should not be an impediment to this one. Now each of the anointings is essential to the sacrament. Therefore all should be applied to those who are deformed.
I answer that, Even those who are deformed should be anointed, and that as near as possible to the part which ought to have been anointed. For though they have not the members, nevertheless, they have, at least radically, the powers of the soul, corresponding to those members, and they may commit inwardly the sins that pertain to those members, though they cannot outwardly.
This suffices for the Replies to the Objections.
Source: Summa Theologica (New Advent)