Blepharitis is a condition in which the eyelids are red, thickened, and inflamed. This inflammation may be seen in conjunction with inspissated oil glands that are located at the lid margin. Blepharitis does not usually present with blurred vision. Additionally, it is not associated with confluent redness and conjunctival blanching.

Cataract is a condition that occurs when the lens inside the eye becomes cloudy. Classically, cataract can be classified as nuclear, cortical, or capsular—corresponding to the different anatomical areas of the lens. In this particular situation, cataract would be unlikely given the acute presentation, young age of the patient, and confluent redness of the eye.

There are two types of glaucoma: open angle and angle-closure. These two types are differentiated by the morphologic status of the angle. The angle is open in open angle glaucoma, in which resistance to outflow of aqueous may be related to degeneration of the trabecular meshwork or other material such as cells. The angle is closed in angle closure glaucoma. The typical presentation for the vast majority of cases of glaucoma is that of painless, insidious loss of peripheral visual field. Angle closure glaucoma can present with an acute red eye and blurred vision. However, it would be very unusual to have a bilateral presentation and angle closure glaucoma typically does not present in this age group.