**Question:** A young adult presents with night blindness and tubular vision. On examination, Intraocular Pressure was observed to be 18mm and the anterior segment was unremarkable. Fundoscopy showed attenuation of arterioles and waxy pallor of the optic disc with bony corpuscles like spicules of pigmentation in mid peripheral retina. Ring scotomas were observed on perimetry. Which of the following is the most likely diagnosis –

A. Leber's hereditary optic neuropathy
B. Vitamin A deficiency
C. Glaucoma
D. Diabetic Retinopathy

**Correct Answer:** C. Glaucoma

**Core Concept:**

Glaucoma refers to a group of eye disorders characterized by elevated intraocular pressure (IOP) leading to optic nerve damage and visual field defects, particularly in conditions where there is compromise to the aqueous humor outflow pathways. Glaucoma is classified into two broad types: open-angle glaucoma (OAG) and closed-angle glaucoma (CAG).

**Why the Correct Answer is Right:**

In this case, the patient presents with night blindness (nyctalopia) and tubular vision, which are indicative of optic nerve damage. The intraocular pressure is elevated (18 mmHg), which is a key feature of glaucoma. The fundoscopy reveals waxy pallor of the optic disc, indicating nerve fiber layer damage. Additionally, the presence of bony corpuscles (spicules of pigmentation) in the mid-peripheral retina suggests chronicity and further confirms the diagnosis of glaucoma. Finally, the presence of ring scotomas on perimetry indicates visual field defects, also consistent with glaucoma.

**Why Each Wrong Option is Incorrect:**

**A.** Leber's hereditary optic neuropathy (LHON) is a genetic mitochondrial disorder causing optic atrophy due to mitochondrial DNA mutations. Although it can cause visual loss, it is not characterized by elevated intraocular pressure and does not have the typical fundoscopy findings like waxy pallor and bony corpuscles.

**B.** Vitamin A deficiency is responsible for xerophthalmia, characterized by corneal lesions, conjunctival hyperemia, and optic atrophy. It does not present with elevated intraocular pressure and does not have the typical fundoscopy findings like waxy pallor and bony corpuscles.

**C.** Dilated pupils, raised IOP (18 mmHg), and typical fundoscopy findings like waxy pallor of the optic disc and bony corpuscles in the mid-peripheral retina are indicative of glaucoma.

**D.** Diabetic retinopathy is a complication of diabetes mellitus affecting the retina and not the optic nerve head. It presents with microaneurysms, hemorrhages, and edema, along with diabetic retinopathy features.

**Clinical Pearls:**

1. Elevated intraocular pressure is a crucial finding in glaucoma, which is not present in options A, B, C, and D.