Gonioscopy allows Dr. Low to evaluate the "drain" in your pets eye. The eye produces fluid 24 hours a day, and that fluid has to leave the eye through a "drain" at that same rate 24 hours a day. When the drain becomes plugged, whether it be due to debris in the eye or a malformation of the drain, the pressure will increase in your pets eye. This leads to glaucoma, and can be very painful. Gonioscopy is performed with your pet awake and is non-painful. After a drop is placed in the eye to numb the surface, a special lens is placed on the eye to allow Dr. Low to evaluate the "drain".