Determination of reference values for intraocular pressure and Schirmer tear test in clinically normal ostriches (Struthio camelus).

The purpose of this study was to establish normal physiologic reference values for intraocular pressure (IOP) and Schirmer tear test (STT) results in clinically normal ostriches (Struthio camelus). Twenty ostriches of both sexes, 10 juveniles (1.5-2 yr of age) and 10 adults, were included in this study. Complete ophthalmic examination was performed prior to this investigation. STT was performed by inserting a standard sterile STT strip over the ventral lid margin into the ventral conjunctival sac for 60 sec. Following the STT, IOP was measured using applanation tonometry with the Tono-Pen Vet tonometer after topical instillation of one drop of 0.5% proparacaine ophthalmic solution. The mean +/- SD and range of Tono-Pen readings of IOP for all birds was 18.8 +/- 3.5, with a range of 12-24. Mean IOP in juvenile ostriches was 19.7 +/- 3.6. Mean IOP in adult ostriches was 16.9 +/- 2.9. There was no statistically significant difference between young and adult birds (P = 0.07). The mean STT values in the present study were 16.3 +/- 2.5 mm/1 min when measurements from both eyes were averaged. Mean STT in juvenile and adult ostriches was 15.4 +/- 1.8 and 17.2 +/- 2.9 mm/1 min, respectively. There was no statistically significant difference between young and adult birds (P = 0.11). No statistically significant differences between genders were found for any of the results (P > or = 0.41). In conclusion, this study provides normal reference range values for STT and IOP in clinically healthy ostriches.