**Question:** A 30-year-old women pretests a history of amenorrhoea and impaired vision of six-month' duration. Physical examination shows everything except for pale optic discs and diminished visual acuity. The most likely diagnosis is -

A. Vitamin A deficiency
B. Macular degeneration
C. Diabetes mellitus
D. Glaucoma

**Correct Answer:**

**Core Concept:** The symptoms mentioned in the question are indicative of a disorder affecting the visual system. Amenorrhea and impaired vision are non-specific symptoms, while pale optic discs and diminished visual acuity are more specific markers for optic nerve dysfunction.

**Why the Correct Answer is Right:** The correct answer is **D** - Glaucoma. Glaucoma is a group of eye disorders characterized by optic nerve damage and associated visual field defects. The optic nerve is responsible for transmitting visual information from the eye to the brain. In glaucoma, the optic nerve is damaged due to increased pressure within the eye (intraocular pressure - IOP), leading to optic disc pallor (pale optic discs) and reduced visual acuity.

**Why Each Wrong Option is Incorrect:**

**A** - Vitamin A deficiency: This condition, also known as xerophthalmia, primarily affects the retina and leads to night blindness and dry eyes, but does not result in optic disc pallor or reduced visual acuity.

**B** - Macular degeneration: Macular degeneration is a disorder affecting the macula, the central part of the retina responsible for sharp vision, not the optic nerve or optic disc. It is not associated with optic disc pallor or reduced visual acuity.

**C** - Diabetes mellitus: Though diabetes can cause various ocular complications, optic nerve damage leading to disc pallor and reduced visual acuity is not a common manifestation of diabetes.

**Clinical Pearl:**

When assessing patients presenting with symptoms of vision loss or eye pain, it is essential to consider differentials like glaucoma, which can lead to optic disc pallor and reduced visual acuity due to optic nerve damage. Early diagnosis and management are crucial to preserve vision and prevent further damage.