Introduction:
Darshan Ke Karan is a chapter in Class 8 Bihar Board science textbook which focuses on the various reasons and factors behind vision.

Causes of Vision:
- The chapter discusses the anatomy of the eye and how light enters the eye through the cornea and passes through the lens to form an image on the retina.
- It explains how the retina contains light-sensitive cells called rods and cones which convert light into electrical impulses that are sent to the brain for processing.

Importance of Vision:
- Vision is crucial for our daily activities as it helps us navigate our surroundings, recognize faces, read, and perform tasks.
- The chapter highlights the importance of protecting our eyes from harmful factors such as bright light, UV rays, and injuries.

Common Vision Problems:
- The chapter also covers common vision problems such as nearsightedness, farsightedness, astigmatism, and color blindness.
- It explains how these vision problems can be corrected with the help of glasses, contact lenses, or surgery.

Preventive Measures:
- The chapter emphasizes the importance of regular eye check-ups to detect any vision problems early on.
- It also suggests tips for maintaining good eye health such as eating a balanced diet, wearing protective eyewear, and taking breaks from screens to reduce eye strain.

Conclusion:
Darshan Ke Karan is a comprehensive chapter that educates students about the importance of vision, common vision problems, and preventive measures to maintain good eye health. It is essential for students to understand the anatomy of the eye and take care of their vision for overall well-being.