When I went to the eye doctor they put in eye drops that blurred my vision for 4 hours. What was the purpose of that?

They dilated your eyes so they can see better to the back of them. This is a common procedure optician's carry out to help them exam your eyes. You would have found you were light-sensitive this is caused by your pupils not reacting to the light the drops would have worn off after a few hours.

They were probably used to dilate your eyes. Dilation makes your pupil larger and stay large when lights are shown in them. Just like you can see more looking through a window than you can looking through a key hole, you can see more through an 8 mm pupil than you can through a 3 mm pupil. The cornea can be evaluated without dilation. Cataracts generally be diagnosed without dilation. Dilation is required to get a good look at the retina and optic nerve. The same drops that dilate your eyes also temporarily paralyze the muscles that focus your eyes. Sometimes this is the effect that the doctor is actually after so he can better determine your glasses prescription. Dilation does not make the inside of the eye appear larger.

The purpose was to dilate the pupils of the eye so the doctor can see if you have cataracts or some other disease of the eye.

They dilated your pupils to see in the back of your eye.

The drops likely dilated your pupils significantly so they could see into your eye better.

it allows them to see the insides of your eye like the CORNEA RETINA she also checking to see if the pupil that's the center part is healthy the pupil is supposed to change in size depending on the brightness of the room you are in

Those were "dilating" drops.

They allow more light into your eyes, and give the doctor a better way to see and examine the back of your eye.

They dilated them so that they could see inside the eye better. It is like using a magnifying glass but, a magnifying glass cannot be put inside the eye so they blow up the inside of the eye, making it appear larger, so the doc can see better.