Does a glass enclosure violate the right to defense?

I saw news that during a court hearing, the accused was in a glass enclosure, not next to their defense counsel, but the court decided that this does not violate their right to defense. I don't quite understand if this is actually permissible, and if it's normal for a person to be isolated from contact with a lawyer precisely during the consideration of their case? I am interested in whether being in such an enclosure is considered full provision of the right to defense, or if there might be any exceptions or limitations here?