The icons seen on church walls are not merely images or paintings: an icon is a focus of real presence. St John Chrysostom advises us, before we start praying, to take our stand in front of an icon and to shut our eyes. He says ‘shut your eyes’, because it is not by examining the icon, by using it as a visual aid, that we are helped by it to pray. It is not a substantial presence in the sense in which the bread and wine are the body and blood of Christ. An icon is not, in this sense, Christ, but there is a mysterious link between the two. By the power of grace an icon participates in something which can best be defined in the words of Gregory Palamas as the energies of Christ, as the active power of Christ working for our salvation.
An icon is painted as an act of worship. The wood is chosen and blessed, the paint is blessed, the man who wishes to paint prepares himself by fasting, oy confession, by communion. He keeps ascetical rules while working and when his work is completed, it is blessed with holy water and chrismated (this last part of the blessing is now often omitted, unfortunately). Thus, by the power of the Holy Spirit, the icon becomes more than a painting. It is loaded with presence, imbued with the grace of the Spirit and linked with the particular saint it represents in and through the mystery of the communion of saints and the cosmic unity of all things.
One cannot say of the icon that the indwelling of the saint is identical with or even similar to that which we find in the holy gifts, and yet it is a focus of real presence as it is experienced and taught by the Church. An icon is not a likeness, it is a sign. Certain icons have been singled out by the power and wisdom of God to be miraculous icons. When you stand in their presence you feel challenged by them.
A priest who visited Russia recently took services in a church where there was a well-known wonder-working icon of Our Lady and was deeply conscious of her active participation in the service. The icon had become very dark in the course of centuries, and from the place where he stood he could not distinguish the features, so he continued to celebrate with his eyes shut. Suddenly he felt that the Mother of God in the icon was as it were compelling him to pray, directing his prayers, shaping his mind. He became aware of a power originating from the icon that filled the church with prayer and guided the diffuse thoughts. It was almost a physical presence, there was a person standing there, compelling a response.
~Archbishop Anthony Bloom, Living Prayer