Mia is a beautiful 9-year-old Old English Sheepdog, whose right eye suddenly became red, painful and “odd” looking. Fortunately Mia was brought to the clinic quickly and it became apparent she had developed acute glaucoma in the right eye. Glaucoma is caused by increased pressure in the eye. Once the pressure in the eye starts to increase, dogs can lose vision and suffer permanent damage to the eye within a matter of hours. In Mia’s case the disease was caught early enough that aggressive medical treatment reduced the pressure and save Mia’s vision. Mia’s eye is now comfortable and visual and she is currently on eye drops to try to control the disease. Unfortunately once diagnosed primary glaucoma is a lifetime disease and most dogs eventually develop the disease in both eyes and often do end up losing their vision. Understanding the early signs and breeds at risk can help diagnose the problem earlier and increase the chance of success for dogs at risk of this painful disease.