Which of the following conditions may require a patient's immediate visit to the doctor?

A red eye can indicate a variety of serious conditions in the eye, such as conjunctivitis, corneal ulcers, or uveitis, and may sometimes be associated with more severe issues, like acute glaucoma or a retinal detachment. When a patient experiences a sudden change in vision, eye pain, or significant redness, it necessitates immediate medical attention to prevent permanent damage or loss of vision.

In contrast, regular eye exams, presbyopia, and glaucoma screening are scheduled visits based on routine eye care and do not typically present urgent health concerns. Regular check-ups are essential for monitoring eye health, while presbyopia is a common age-related refractive change that can usually be managed with corrective lenses. Glaucoma screenings are important for early detection of the disease but are planned as part of a preventive care routine rather than an urgent visit. Therefore, red eye is the condition requiring immediate attention due to its potential association with serious underlying issues.