Final answer:
The best diagnosis for a patient presenting with a red, swollen, and purulent eye discharge is conjunctivitis or pinkeye, which is inflammation of the conjunctiva characterized by such symptoms.
Step-by-step explanation:
Based on the description of the patient's symptoms, which include a red, swollen eye with purulent (pus-like) discharge, the best diagnosis would be conjunctivitis. Conjunctivitis, also known as "pinkeye," involves inflammation of the conjunctiva, the membrane that lines the white part of the eyes and the inner side of the eyelids. This condition can be caused by bacteria or viruses but is characterized by redness, swelling, and discharge from the eye. Bacterial conjunctivitis tends to produce a more purulent or thick discharge, which is consistent with the patient's symptoms.
On the other hand, glaucoma, cataract, and retinal detachment do not typically present with purulent discharge. Glaucoma is characterized by elevated intraocular pressure, which can lead to vision loss if not treated. A cataract is the clouding of the eye's lens, causing blurry vision but not discharge. Retinal detachment is a serious condition where the retina at the back of the eye pulls away from its normal position, leading to potential vision loss, but again, no discharge is typically present.