title: Conjunctival and corneal pneumatic sensitivity is associated with signs and symptoms of ocular dryness.
abstract: OBJECTIVE
  To investigate the relationships of dry eye symptoms and corneal and conjunctival sensitivity to pneumatic stimulation, tear film stability, and clinical ocular surface characteristics in symptomatic and asymptomatic subjects.
  
  
  METHODS
  Ninety-seven subjects were enrolled and grouped by a questionnaire-based single score for symptoms of ocular dryness (none to trace, non-dry group; mild to severe, symptomatic group); 43 were symptomatic and 54 were non-dry. Corneal (K) and conjunctival (C) sensitivities were measured with a computer-controlled Belmonte pneumatic (room temperature) stimulus. Symptoms were assessed according to the Ocular Surface Disease Index (OSDI). Ocular surface staining with fluorescein (FL) and lissamine green (LG), noninvasive tear film break-up time (NIBUT), and the phenol red thread test (PRT) were assessed.
  
  
  RESULTS
  The symptomatic group showed lower K and C thresholds (P < 0.01), greater corneal FL and conjunctival LG staining, and shorter NIBUT than did the non-dry eye group (all others P < 0.05). The OSDI scores were higher in the symptomatic group (P < 0.001). K and C thresholds and NIBUT were inversely correlated with the OSDI and corneal and conjunctival staining (all P < 0.05). The K and C threshold and NIBUT (all P < 0.01) correlated positively. Step-wise multiple regression analysis showed that ocular surface sensitivity and NIBUT were significant predictors of the OSDI.
  
  
  CONCLUSIONS
  Ocular irritation assessed with the OSDI is associated with ocular surface hyperesthesia to cooling, corneal epitheliopathy, and tear film instability. Although cause and effect are unclear, the analysis showed that altered corneal and conjunctival sensory processing and tear film attributes are essential aspects of what characterizes dry eye.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Ping
authors.initials: P
authors.lastname: Situ
authors.forename: Trefford L
authors.initials: TL
authors.lastname: Simpson
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
authors.forename: Lyndon W
authors.initials: LW
authors.lastname: Jones
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air; D003080:Cold Temperature; D003228:Conjunctiva / Q000503:physiopathology*; D003315:Cornea / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted; D003941:Diagnostic Techniques, Ophthalmological; D015352:Dry Eye Syndromes / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D019573:Epithelium, Corneal / Q000473:pathology; D005128:Eye Diseases / Q000209:etiology; D005260:Female; D006801:Humans; D006941:Hyperesthesia / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation; D013666:Tears / Q000378:metabolism