**Core Concept**
Vitamin A (retinol) is an essential nutrient for the retina, playing a critical role in the visual cycle and maintaining the integrity of the cornea and conjunctiva. A deficiency in Vitamin A can lead to a range of ocular and cutaneous manifestations.

**Why the Correct Answer is Right**
Nyctalopia, also known as night blindness, is one of the earliest symptoms of Vitamin A deficiency. It occurs due to the impaired regeneration of rhodopsin, the light-sensitive pigment in the retina, which is dependent on Vitamin A. As a result, individuals with Vitamin A deficiency experience difficulty seeing in low light conditions, making nyctalopia a key indicator of the disorder.

**Why Each Wrong Option is Incorrect**
**Option B:** Xerophthalmia is a more advanced stage of Vitamin A deficiency, characterized by dryness of the conjunctiva and cornea, often accompanied by Bitot's spots.

**Option C:** Bitot's spots are small, foamy patches on the conjunctiva, typically seen in individuals with Vitamin A deficiency, but they are not the earliest symptom.

**Option D:** Keratomalacia is a severe form of Vitamin A deficiency, where the cornea becomes dry and cloudy, leading to vision loss, but it is not the initial symptom.

**Clinical Pearl / High-Yield Fact**
The World Health Organization (WHO) recommends regular Vitamin A supplementation to prevent and treat Vitamin A deficiency, particularly in children and pregnant women.

**✓ Correct Answer: A. Nyctalopia**