Valencia - Real Madrid forward Cristiano Ronaldo was forced to leave Sunday's 2-1 win over Levante after injuring his head in a collision in the opening minutes.
Levante defender David Navarro's elbow opened a gash above Ronaldo's left eye that required treatment on the sideline before returning to the pitch.
Ronaldo scored Madrid's opener in the 21st minute but could not continue after halftime.
Madrid coach Jose Mourinho said that his star forward "lost vision in both eyes and couldn't go on."
Mourinho said Ronaldo will undergo tests.