Final answer:
The patient's symptoms are suggestive of dacryocystitis, an infection and inflammation of the lacrimal sac. Immediate medical attention is necessary to treat with antibiotics and potentially surgery, to avoid further complications.
Step-by-step explanation:
The symptoms described suggest a diagnosis of dacryocystitis, an infection of the lacrimal sac.
The cluster of symptoms - left eye watering, fever, redness, pain in the left medial canthal region, and tender swelling below the medial canthal tendon - are indicative of dacryocystitis. This condition is an inflammation of the lacrimal sac, which may occur due to obstruction of the nasolacrimal duct and secondary bacterial infection. The presence of systemic symptoms such as fever, along with local signs of infection, suggests acute dacryocystitis.
Treatment commonly involves antibiotics and, if symptoms persist, surgical intervention may be needed to relieve duct obstruction. It's important to differentiate this condition from other eye infections like conjunctivitis, blepharitis, and keratoconjunctivitis, which can present with overlapping symptoms but are typically managed differently. Immediate evaluation by a healthcare professional is essential to prevent complications such as corneal damage or spread of the infection.