Okay, let's tackle this question. The patient is a chronic alcoholic with symptoms around the lateral canthus, burning, and eye discomfort. The question is about the probable diagnosis.

First, I need to recall conditions related to chronic alcoholism that affect the eyes. Chronic alcoholism can lead to various nutritional deficiencies, especially B vitamins. Thiamine (B1) deficiency is common and causes Wernicke's encephalopathy, but that's more neurological. Another B vitamin deficiency is riboflavin (B2).

Riboflavin deficiency can cause symptoms like angular stomatitis, conjunctival congestion, and photophobia. The lateral canthus is the outer corner of the eye, so congestion there might be part of a deficiency. Also, burning and discomfort could be due to dryness or inflammation.

Another possibility is blepharitis, which is inflammation of the eyelids. But blepharitis is more about crusting, redness, and maybe dandruff-like scales, not specifically related to B vitamin deficiency.

Chronic alcoholism also leads to poor nutrition, so deficiencies like B2, B3, B6, B12 are possible. But the key here is the location around the lateral canthus and the burning sensation.

Wait, riboflavin deficiency (avitaminosis B2) specifically presents with angular cheilitis, conjunctival congestion, and photophobia. The lateral canthus congestion might be part of conjunctival involvement. Also, the burning sensation could be due to corneal involvement or dryness from the deficiency.

So the probable diagnosis here is avitaminosis B2. Let me check other options. Maybe the answer is B2 deficiency. The other options might include other deficiencies or conditions. Let's make sure.

Angular stomatitis is a classic sign of B2 deficiency. The conjunctival congestion and burning could be due to the deficiency leading to ocular symptoms. So the correct answer is avitaminosis B2.

**Core Concept**
Chronic alcoholism often leads to **B-vitamin deficiencies**, particularly **riboflavin (B2)**, due to poor dietary intake and impaired absorption. Riboflavin deficiency manifests with **conjunctival congestion**, **angular stomatitis**, and **photophobia**, linked to its role in maintaining mucosal integrity and oxidative metabolism.

**Why the Correct Answer is Right**
**Avitaminosis B2 (riboflavin deficiency)** directly causes **congestion around the lateral canthus** (outer corner of the eye) and **burning ocular discomfort** due to impaired epithelial cell function. Riboflavin is a cofactor for flavin enzymes involved in energy production and antioxidant defense. Deficiency leads to corneal vascularization, conjunctival injection, and dryness, mimicking the described symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** *Vitamin C deficiency* causes scurvy (e.g., bleeding gums, ecchymosis), not ocular symptoms.
**Option B:** *Vitamin A deficiency* leads to xerophthalmia (dry eyes, night blindness), but not lateral canthal congestion.
**Option C:** *Vitamin B12 deficiency* causes neurological and hematological issues (e.g., neuropathy, megaloblastic anemia), not localized ocular

✓ Correct Answer: C. Angular conjunctivitis