19. The eucharist is the most august sacrament, in which Christ the Lord himself is contained, offered, and received, and by which the Church constantly lives and grows. It is the summit and the source of all Christian worship and life, signifying and effecting the unity of the people of God, providing spiritual nourishment for the recipient, and achieving the building up of the Body of Christ. The celebration of the eucharist is the center of the entire Christian life (Canon 897).
20. Parents, those who take the place of parents, and pastors are to see to it that children who have reached the use of reason are correctly prepared and are nourished by the eucharist as early as possible. Pastors are to be vigilant lest any children come to the Holy Banquet who have not reached the use of reason or whom they judge are not sufficiently disposed (Canon 914). It is important to note, however, that the criterion for reception of holy communion is the same for persons with developmental and mental disabilities as for all persons, namely, that the person be able to distinguish the Body of Christ from ordinary food, even if this recognition is evidenced through manner, gesture, or reverential silence rather than verbally. Pastors are encouraged to consult with parents, those who take the place of parents, diocesan personnel involved with disability issues, psychologists, religious educators, and other experts in making their judgment. If it is determined that a parishioner who is disabled is not ready to receive the sacrament, great care is to be taken in explaining the reasons for this decision. Cases of doubt should be resolved in favor of the right of the baptized person to receive the sacrament. The existence of a disability is not considered in and of itself as disqualifying a person from receiving the eucharist.
21. Eucharistic celebrations are often enhanced by the exercise of the diverse forms of ministry open to the laity. In choosing those who will be invited to use their gifts in service to the parish community, the parish pastoral staff should be mindful of extending Christ's welcoming invitation to qualified parishioners with disabilities.
SOURCE: Guidelines for the Celebration of the Sacraments with Persons with Disabilities (USCCB)