Crystalline lens (chapter 7)

from the worksheet

What is the average power of the crystalline lens (unaccommodated)?

About +20 diopters (D).

At what age is the average person’s amplitude of accommodation greatest?

Around 10–12 years old.

What is the maximum amount of accommodation for the average person?

About 10–15 diopters (D).

At what age does the amplitude of accommodation reduce to almost zero?

Around 50–60 years old.

What is accommodation and how does it happen?

Focusing on near objects; ciliary muscles contract → lens thickens → near objects focus; relaxation → lens flattens → far objects focus.

What is presbyopia and why does it happen?

Age-related difficulty focusing on near objects; lens becomes less flexible with age → near vision blurry.

How would you explain a cataract to a patient?

A cataract is when the lens becomes cloudy → things look blurry, foggy, or dull.

Name 5 types of cataracts and explain each.

• Nuclear → center of lens, usually age-related.

• Cortical → edges of lens (spokes).

• Posterior subcapsular → back of lens, affects reading and bright light.

• Congenital → present at birth, from genetics or infection.

• Traumatic → caused by eye injury.