title: Changes in the evaporation rate of tear film after digital expression of meibomian glands in patients with and without dry eye.
abstract: OBJECTIVE
  To evaluate the effect of excess meibum on tear evaporation rate in patients with and without dry eye.
  
  
  METHODS
  Eleven healthy subjects and 16 patients with dry eye were tested. The dry eye group was divided into 2 subgroups: classic keratoconjunctivitis sicca (KCS) with clear and easily expressed meibum and KCS with meibomian gland dysfunction (MGD) with turbid secretions and difficult-to-express meibum. Evaporative measurements were performed at baseline and after digital expression of meibomian glands at 12, 24, 36, and 48 minutes. Two ranges of relative humidity were used, 25% to 35% and 35% to 45%. The data were expressed as microliters per square centimeter per minute.
  
  
  RESULTS
  An increase in the evaporation rate of the tear film was noted for all measurements at both relative humidities in the classic KCS and KCS with MGD groups compared with healthy subjects (P < 0.05). The average evaporation rates at relative humidities of 25% to 35% and 35% to 45% were 0.056 ± 0.016 and 0.040 ± 0.008 for the classic KCS group; 0.055 ± 0.026 and 0.037 ± 0.019 for the KCS with MGD group and 0.033 ± 0.012 and 0.023 ± 0.008 for the healthy group. Also, a decrease in the evaporation rate was observed in the healthy and KCS with MGD groups between baseline and the first measurement after digital expression for both relative humidities (P < 0.05). The classic KCS group did not show any changes after expression.
  
  
  CONCLUSIONS
  Classic KCS and KCS with MGD groups showed an increase in tear evaporation rates compared with the healthy group. Aqueous tear evaporation diminished in the healthy and KCS with MGD groups after expression of meibomian glands. However, this effect was transient and negligible after the second measurement.
authors: Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, TX 75390-9057, USA.
authors: Juan Carlos
authors: JC
authors: Arciniega
authors: Jadwiga Cristina
authors: JC
authors: Wojtowicz
authors: Engy Mostafa
authors: EM
authors: Mohamed
authors: James Parker
authors: JP
authors: McCulley
mesh_terms: D000328:Adult; D000368:Aged; D005141:Eyelid Diseases / Q000378:metabolism*; D005260:Female; D006801:Humans; D006813:Humidity; D007638:Keratoconjunctivitis Sicca / Q000378:metabolism*; D008297:Male; D008405:Massage; D008537:Meibomian Glands / Q000378:metabolism*; D008875:Middle Aged; D013666:Tears / Q000378:metabolism*; D013997:Time Factors; D014835:Volatilization; D055815:Young Adult