Background: The aim of this study is based on the effects of the treatment, the recombinant tissue plasminogen activator (rTPA), applied to stroke patients in Emergency Departments (ED) by intravenous, to optic nerve sheath diameter (ONSD) measurements. Material and Methods: The study was designed as prospective and observational. A total of 41 patients were included in this study with the following diagnoses: an acute clinical stroke, known well-being within 4.5 hours, and who had a finding for rTPA. Ultrasonographic (USG) ONSD measurements have been performed on a voluntary basis with the consent of the patients and their relatives. Results: A statistically significant difference has been found between the ONSDs measured at the 0th, 15th, 30th and 60th minutes of the patients who were admitted to the ED and were on rTPA treatment due to stroke (p<0.05). Due to a large number of positive differences, the ONSD at the 15th, 30th, and 60th minutes was found higher than at the 0th minute. A statistically significant difference has also been found between ONSD measured at the 15th, 30th, and 60th minutes during rTPA treatment (p<0.05). Since the existence of a large number of positive differences, the ONSD at the 30th and 60th minutes is found to be higher than at the 15th minute. Finally, the difference of statistically significant values between the 30th and 60th-minute ONSD was determined by the Sign Test. According to the result of the Sign Test, a statistically significant difference was found to be between the ONSD differences of the 30th and 60th minutes of rTPA treatment (p<0.05). Conclusions: Serial ONSD measurements performed at the bedside during the early stage in order to follow up on the intracranial complications of stroke patients may be misleading for the follow-up of complications within the first 60 minutes, which is the most critical stage. In this stage, symptom monitoring should be used in combination with ONSD and the decision should be made for treatment continues, accordingly.