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The purposes of this study were to determine (1) the pressure required to express the first nonliquid material from nonfunctional lower lid meibomian glands, (2) the pressure required to evacuate all of the expressible material from the glands (simulating the authors' methodology for therapeutic meibomian gland expression), and (3) the level of pain associated with these procedures.All patients (n=28) were recruited from those presenting for ocular examinations at a single practice. Custom instrumentation exerting pressures from 1.0 to 150.0 psi was developed to quantify the pressure applied during expression. The instrument was applied to the inner surface of the lower lid. The lid was then compressed between the thumb and the contact surface of the instrument. The applied pressure was displayed on a digital meter. The first procedure evaluated the pressure required to obtain the first nonliquid material from nonfunctional glands. The second evaluated the pressure required for evacuating all expressible gland contents. The pain response was monitored throughout the procedure.The pressure to obtain the first nonliquid material ranged from 5 to 40 psi (mean=16.1±8.2 psi) and for the evacuation of expressible contents, from 10 to 40 psi (mean=25.6±11.4 psi). Only 7% of the patients could tolerate the pressure necessary to administer complete therapeutic expression along the entire lower eyelid.Forces of significant magnitude are required for therapeutic expression. Pain is the limiting factor for the conduct of this treatment.