When the meibomian glands are blocked there is no way that the oil can get out so they are ineffective and can eventually simply shrivel away. Squeezing oil out of the glands (expression) is essential, it is the one thing that should be done for anyone with dry eye that is primarily MGD (meibomian gland dysfunction). Sometimes the initial assessment where we express the glands to see what the quality of the tears is like is enough to kick start the recovery process.
The expression of the glands can be done with any number of different implements e.g. a Mastrota paddle, and anaesthetic may or may not be used. It is very effective and can have life changing results for the dry eye sufferer. There is a procedure called Lipiflow which is expression done by a machine but some find the cost a bit prohibitive. If so just try having the manual expression first as it can often work very well.