**Night-blindness and Vitamin A Deficiency**

Night-blindness is a condition in which an individual experiences difficulty in seeing in dim light or at night. It can occur due to various factors, but one of the primary causes is a deficiency of vitamin A. Vitamin A is a fat-soluble vitamin that plays a crucial role in maintaining healthy vision.

**Role of Vitamin A in Vision**

Vitamin A is essential for the proper functioning of the retina, which is the light-sensitive tissue at the back of the eye. The retina contains specialized cells called rods and cones that are responsible for converting light into electrical signals that the brain can interpret as vision. Vitamin A is necessary for the production of a pigment called rhodopsin, which is found in the rods and helps them detect low levels of light.

**Deficiency of Vitamin A and Night-blindness**

When there is a deficiency of vitamin A, the production of rhodopsin is impaired. This leads to a reduced ability to see in dim light or darkness, resulting in night-blindness. Without adequate levels of vitamin A, the rods in the retina cannot function optimally to detect light, and as a result, the individual may experience difficulty in adjusting to low-light conditions.

**Other Symptoms of Vitamin A Deficiency**

In addition to night-blindness, a deficiency of vitamin A can also lead to other ocular manifestations such as dryness and inflammation of the eyes. These symptoms can progress to more severe conditions like xerophthalmia, which can cause corneal damage and blindness if left untreated.

**Sources of Vitamin A**

Vitamin A can be obtained from various dietary sources, including animal-based foods such as liver, fish, eggs, and dairy products. It is also present in certain plant-based foods in the form of beta-carotene, which the body can convert into vitamin A. Examples of such foods include carrots, sweet potatoes, spinach, and kale.

**Conclusion**

In conclusion, night-blindness may develop due to a deficiency of vitamin A. Vitamin A is essential for the proper functioning of the retina and the production of rhodopsin, the pigment responsible for detecting low levels of light. Ensuring an adequate intake of vitamin A through a balanced diet can help prevent night-blindness and maintain healthy vision.