Allergic Conjunctivitis: This condition is characterized by watery, itchy eyes and injected sclera, which matches the symptoms described. It is a common and benign condition often associated with allergies.

Viral Conjunctivitis: This condition can cause watery eyes, itchiness, and an injected sclera. It's highly contagious and can be caused by various viruses, including adenovirus.
Blepharitis: Although primarily causing dryness and irritation, some forms of blepharitis can lead to watery eyes and itchiness due to the body's response to the condition.
Dry Eye Syndrome: Paradoxically, dry eye can sometimes cause watery eyes as the body overcompensates for the lack of tears. Itchiness and mild injection can also be present.

Acute Angle-Closure Glaucoma: Although the fundoscopic exam is normal, this condition can cause sudden onset of watery, painful eyes with blurred vision and injected sclera. It's an emergency that requires immediate treatment.
Keratitis: Inflammation of the cornea can cause pain, watery eyes, and injection. Certain types, like herpes simplex keratitis, can lead to serious complications if not promptly treated.
Uveitis: Inflammation of the uvea can cause eye pain, sensitivity to light, and injection. It can be associated with systemic diseases and requires prompt diagnosis and treatment.

Sjögren's Syndrome: An autoimmune disorder that can cause dry eyes but also occasionally presents with watery eyes due to overcompensation. It's associated with other systemic symptoms.
Mycobacterial or Fungal Infections: These can cause chronic conjunctivitis or keratitis with similar symptoms, especially in immunocompromised patients or after trauma.
Ocular Rosacea: A condition that can cause eye irritation, itchiness, and injection, often associated with skin rosacea.