A 65-year-old woman is seen in a post-surgical follow-up clinic complaining of worsening left eye pain, decreased vision, and increasing light sensitivity over the past 24 hours. She underwent uncomplicated intraocular lens implantation eight days ago. She also reports a mild headache and feels generally unwell with a temperature of 37.9°C. On examination, her visual acuity is 20/30 OD and hand motion OS. There is marked conjunctival injection, lid swelling, and tenderness to palpation around the globe. Slit-lamp examination of the left eye reveals significant anterior chamber flare and cells, and a visible layering of white blood cells in the inferior anterior chamber. Fundoscopy is obscured by vitreous haze. What is the most likely diagnosis and the critical initial intervention?

A 55-year-old woman presents to her primary care provider's office complaining of severe right eye pain and rapidly deteriorating vision over the past 36 hours. She reports a history of uncomplicated cataract extraction in the affected eye approximately 10 days prior. Her medical history includes well-controlled rheumatoid arthritis managed with low-dose methotrexate and latent tuberculosis, for which she completed prophylaxis years ago. She denies any recent trauma or contact lens use. On examination, her temperature is 38.3°C, blood pressure is 130/80 mmHg, pulse is 92/min, and respirations are 16/min. Visual acuity in the right eye is count fingers at 1 meter, while the left eye is 20/25. Slit-lamp examination of the right eye reveals significant conjunctival injection, corneal edema, and a prominent layering of white cells in the anterior chamber (hypopyon), as depicted in the provided image. Pupillary reflex is sluggish, and there is no red reflex. Given the clinical presentation, which of the following is the most likely diagnosis and the most appropriate initial management strategy?

A 68-year-old man presents to the emergency department with severe right eye pain, significantly decreased visual acuity, and photophobia, which began acutely two days ago. He reports undergoing a routine ophthalmic procedure on that eye approximately one week prior. His current vital signs are: temperature 38.3°C, blood pressure 130/85 mmHg, pulse 92/min, respirations 16/min, and oxygen saturation 97% on room air. Ocular examination reveals marked conjunctival injection, significant lid edema, and the presence of a distinct layering of white cells in the anterior chamber. Given this clinical picture, what is the most probable diagnosis and the critical initial therapeutic intervention?