A student feels difficulty in reading the book on the table but reads properly…

The human eye's ability to bring light rays into sharp focus on the retina can be disrupted by a few well-defined refractive errors, each identified by a distinct near-vs-far focusing pattern: myopia leaves near objects clear but blurs distant ones, hypermetropia leaves distant objects clear but blurs nearby ones, and astigmatism blurs or distorts vision at both near and far distances because of unequal lens/cornea curvature. Colour-vision deficiency is a separate condition altogether, involving the retina's colour-sensing cones rather than focusing distance.

The described symptom pattern is: distant writing on the blackboard is read properly, but the nearby book on the table is difficult to read. This is exactly the near-blurred / far-clear pattern that defines Hypermetropia (Long-sightedness) — the eyeball is too short front-to-back (or the lens too weak), so light from nearby objects focuses behind the retina instead of on it, while light from distant objects (needing less convergence) still focuses correctly.

• Short-sightedness (Myopia, निकटदृष्टि दोष): produces the opposite pattern — near objects stay clear while distant objects blur — the reverse of what is described.

• Astigmatism (असमान दृष्टि दोष): caused by unequal curvature of the cornea/lens, it blurs or distorts vision at both near and far distances rather than selectively affecting only one range.

• Colour-blindness (वर्णान्धता): a deficiency in colour discrimination, unrelated to how sharply near or distant objects are focused.

So the defect matching 'clear distance vision, blurred close-up vision' is Long-sightedness (Hypermetropia).