Glaucoma is defined as the increase in the intraocular pressure (IOP) causing visual loss due to the circulation deficits of the aqueous humor. The IOP measurement can be obtained without any problem in calm animals. However, some animals do not allow IOP measurement without sedation or anesthesia. The purpose of this study is to determine the effect of xylazine HCl (as a sedative) and ketamine HCl (as an anesthetic in combination with xylazine HCl) on the IOP in dogs. In this study, 35 dogs of different breed, age and gender that were brought to Istanbul University Veterinary Faculty Education and Research Hospital Surgery Department with different surgical indications were used. As a result xylazine HCl sedation and xylazine HCl + ketamine HCl anesthesia decrease the intraocular pressure significantly and the IOP measurements in glaucoma suspicious dogs must be obtained without xylazine HCl sedation or xylazine HCl + ketamine HCl anesthesia were determined.