**Question:** Commonest cause for bilateral proptosis in children is -

A. Optic neuritis
B. Congenital glaucoma
C. Graves' disease
D. Hypertension

**Core Concept:** Proptosis refers to the protrusion of the eyeball due to an enlarged orbital contents. In children, the most common cause is a systemic disorder rather than local orbital pathology.

**Why the Correct Answer is Right:** C. Graves' disease is the most common cause of bilateral proptosis in children. Graves' disease is an autoimmune disorder characterized by overproduction of thyroid hormones. It is associated with a range of systemic and ocular manifestations, including proptosis.

**Why Each Wrong Option is Incorrect:**

A. Optic neuritis typically presents with visual disturbances and pain on eye movement, rather than proptosis.
B. Congenital glaucoma usually presents with elevated intraocular pressure, photophobia, and reduced visual acuity, not proptosis.
D. Hypertension does not directly cause proptosis unless there is a coexisting orbital pathology like aneurysm or aneurysmal bone cyst.

**Clinical Pearl:** Although Graves' disease is the most common cause of bilateral proptosis in children, it is essential for the examiner to consider other potential causes like orbital inflammation or tumors, and to perform a thorough ophthalmologic examination to rule them out.

**Correct Answer:** C. Graves' disease (Thyroid-Associated Ophthalmopathy)

**Correct Answer Explanation:** Graves' disease is the most common cause of bilateral proptosis in children due to orbital inflammation and enlargement. This autoimmune disorder affects the thyroid gland and can lead to systemic manifestations and ocular complications. In this case, the inflammation extends to the orbit, resulting in proptosis. Other causes, such as orbital inflammation or tumors, should be ruled out during clinical examination.