title: Schirmer tear test, phenol red thread tear test, eye blink frequency and corneal sensitivity in the guinea pig.
abstract: OBJECTIVE
  To establish reference values for Schirmer tear tests (STT) I and II, phenol red thread (PRT) tear test and eye blink frequency, and to determine corneal sensitivity for normal guinea pigs.
  
  
  METHODS
  One hundred and eight eyes of 54 adult Duncan-Hartley guinea pigs.
  
  
  METHODS
  Schirmer tear test (STT) I and then STT II were performed in 36 guinea pigs. PRT and STT I were compared in 18 adult Duncan-Hartley guinea pigs. Corneal sensitivity was determined in 23 guinea pigs by evaluating the corneal touch threshold (CTT) of five different regions using a Cochet-Bonnet esthesiometer. Eye blink frequency was measured in 10 guinea pigs over a period of 20 min and in 17 guinea pigs over a period of 10 min.
  
  
  RESULTS
  Mean STT I was 0.36 mm +/- 1.09 mm (wetting/min) and mean STT II was 0.43 mm +/- 1.29 mm (wetting/min). There was no significant difference between mean STT I and mean STT II (P = 0.79). The mean PRT-value was 16 +/- 4.7 mm (wetting/15 s), and the mean STT I-value in the same guinea pigs was 0.6 +/- 1.83 mm (wetting/min). Corneal sensitivity was significantly higher in the center than in the four limbal regions. The mean CTT for central, ventral, nasal, temporal and dorsal regions was 2, 1.7, 1.7, 1.7 and 1.6 cm or 3.7, 5.2, 5.6, 5.7 and 6.4 g/mm(2), respectively. Eye blink frequency was between two to five (mean 3.4 +/- 1.04) blinks per eye over 20 min in guinea pigs in their home environment, while in handheld and restrained guinea pigs eye blink frequency showed a variation between 0 and 17 blinks per eye (mean 3.24 +/- 3.64 blinks per eye) over 10 min.
  
  
  CONCLUSIONS
  As there were no significant differences between STT I and STT II results, reflex tear secretion in the guinea pig may not exist. The most likely explanation is a lower corneal sensitivity in the guinea pig than in other species, such as cats, dogs and horses. Because of the small amount of tears, PRT is the preferred test for tear measurement in the guinea pig.
authors: Department for Small Animals and Horses, Clinic for Surgery and Ophthalmology, University of Vetinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria. katrinstadtbaeumer@hotmail.com
authors: Katrin
authors: K
authors: Trost
authors: M
authors: M
authors: Skalicky
authors: Barbara
authors: B
authors: Nell
mesh_terms: D000818:Animals; D001767:Blinking / Q000502:physiology*; D004396:Coloring Agents; D003315:Cornea / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological / Q000662:veterinary*; D005260:Female; D006168:Guinea Pigs / Q000502:physiology*; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D010637:Phenolsulfonphthalein; D011934:Reagent Strips; D012016:Reference Values; D013666:Tears / Q000378:metabolism*
chemical_list: D004396:Coloring Agents; D011934:Reagent Strips; D010637:Phenolsulfonphthalein