LACRIMAL SYSTEM

I-               Schirmer’s tear test (STT)

1-     Quantitative abnormalities.

2-      If epiphora is due to overproduction of tears, the eye is usually red and the STT values  are higher than normal.

II-              Nasolacrimal duct cannulation (Fluorescein passage test   - Rose Bengal stain).

1-    Rose bengal stain  to detect epithelial abnormalities caused by quantitative and qualitative disorders.

2-    Fluorescein passage or Jones test  for drainage disorders and corneal ulceration is reliable only when its result is positive. Because of communications between the nasolacrimal duct and the nasal cavity, false-negative results occur even though the duct is patent.

Fig.4: Nasolacrimal duct cannulation in donkey.