Power of accommodation

ICSE calls this accommodation of the eye. The eye lens is soft and jelly-like. It hangs from the ciliary muscles by thin threads, the suspensory ligaments. The ciliary muscles change its shape:

• Near object: the ciliary muscles contract and the lens becomes thicker. Its focal length shrinks.
• Far object: the ciliary muscles relax and the lens becomes thinner. Its focal length grows.

There is a limit. The nearest point you can see clearly without strain is the near point. For a young adult with normal vision it is about 25 cm. The far point is at infinity for a normal eye. The iris does a different job: it controls how much light enters.

A small example

You read a book held 30 cm away, then look up at a tree 20 m away. Your ciliary muscles relax, the lens thins, and the tree comes into focus. Bring the book to 10 cm and the print blurs. That is closer than the 25 cm near point.

Where marks go

In CBSE, Question 39 of the 2026-27 Science sample paper opens with two 1-mark parts. One asks what accommodation means. The other asks for the near point of a normal eye and what it means. The 2026-27 Science marking scheme expects about 25 cm and its meaning: the closest point seen clearly. Give the number and what it means; the scheme's answer has both.

In ICSE, the 2024 Biology paper asked which part adjusts the focal length of the lens. The answer was the ciliary muscles. CISCE's 2024 Biology report records "iris" as the error. In 2025, CISCE's report records "suspensory ligament" given instead of "ciliary body". Learn where each part sits on a labelled diagram.

About the author

Deepti Sardana

Founder Member & Academic Lead

An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.

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