Pupil Reflex & Accommodation

What is the pupil reflex?

An automatic response that changes pupil size according to light intensity.

What happens to the pupil in bright light?

It constricts, reducing the amount of light entering the eye.

What happens to the pupil in dim light?

It dilates, allowing more light to enter.

How does the iris make the pupil smaller?

Circular muscles contract and radial muscles relax.

How does the iris make the pupil larger?

Radial muscles contract and circular muscles relax.

Why does the pupil constrict in bright light?

To reduce the amount of light entering the eye and protect the retina.

Why does the pupil dilate in dim light?

To increase the amount of light reaching the retina.

What is accommodation?

The process of changing lens shape to focus light from near or distant objects onto the retina.

How does the eye focus on a near object?

Ciliary muscles contract, suspensory ligaments loosen and the lens becomes thicker and more curved.

How does the eye focus on a distant object?

Ciliary muscles relax, suspensory ligaments tighten and the lens becomes thinner and less curved.

Why does the lens become thicker when viewing nearby objects?

To refract light more strongly, bringing it to a focus on the retina.

Why does the lens become thinner when viewing distant objects?

Less refraction is needed, so the lens becomes less curved.

What happens to the ciliary muscles when looking at a near object?

They contract.

What happens to the suspensory ligaments when looking at a near object?

They loosen.

What happens to the ciliary muscles when looking at a distant object?

They relax.

What happens to the suspensory ligaments when looking at a distant object?

They tighten.

What is the difference between the pupil reflex and accommodation?

The pupil reflex controls light entering the eye, whereas accommodation controls the focus of light on the retina.