**Core Concept:** Phacoemulsification is a surgical procedure for removing the cataract from the lens of the human eye, followed by intraocular lens implantation to restore vision. The most common cause of hazy vision post-surgery is often due to the intraocular lens (IOL) becoming subluxated or luxated from its proper position.

**Why the Correct Answer is Right:** In this scenario, the patient has undergone phacoemulsification and intraocular lens implantation a year back. Presently, he is experiencing hazy vision in the operated eye, with no other ocular symptoms like redness, pain, or watering. Given the history and clinical presentation, the most probable cause of the patient's symptoms is the intraocular lens (IOL) becoming subluxated or luxated from its proper position.

**Why Each Wrong Option is Incorrect:**

A. Post-operative endophthalmitis: This is a severe infection involving the eye, with prominent symptoms like pain, redness, and inflammation. The patient's symptoms are different, featuring only hazy vision.
B. Post-operative retinal detachment: This is a complication involving the retina, causing symptoms like sudden vision loss, floaters, and scotoma. The patient's symptoms are specific to the lens and vision quality, not retinal issues.
C. Post-operative glaucoma: This is a secondary elevation of intraocular pressure, causing symptoms like pain, redness, and visual disturbances. The patient's symptoms are not indicative of glaucoma.
D. Post-operative corneal edema: This is swelling of the cornea due to an inflammatory response or other causes, featuring symptoms like pain, redness, and photophobia. The patient's symptoms are different, focusing on hazy vision.

**Clinical Pearl:** In cases of suspected subluxated or luxated intraocular lens, detailed clinical examination is required to identify the displaced IOL. This may include slit-lamp examination, fundoscopy, and other tests to confirm the diagnosis. Treatment usually involves surgical removal of the displaced IOL and replacement after the inflammation and swelling subside.