A15-year-old high school student presents to the emergency department with his mother for evaluation of an area of blood in the left eye. he denies trauma or injury but has been coughing forcefully with a recent cold. he denies visual disturbances, eye pain, or discharge from the eye. on physical examination, the pupils are equal, round, and reactive to light with a visual acuity of 20/20 in each eye and 20/20 bilaterally. there is a homogeneous, sharply demarcated area at the lateral aspect of the base of the left eye. the cornea is clear. based on this description, what is the most likely diagnosis?