In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

The cornea, a transparent covering, and a spherical lens make up the eye's lens system, just like any other camera. The retina is a kind of 'reusable film'. This is the (1 ), __________ for images. The size of the opening, the shape of the lens and the movements of the eye are all controlled by various sets of muscles.
There are three things that happen when you look at an object:
1. To fit on the retina, your eye's tiny 'screen', the image must be reduced in size.
2. It is necessary to focus the scattered light at the retina's (2) _________.
3. To match the retina's curve, the image must be curved.
The image is focused on the retina by the lens and cornea working (3) __________ . When the eye is unable to focus the image onto the retina, the majority of vision problems occur. The cornea is reshaped during laser eye surgery, which alters the eye's focal point. The primary objective is to precisely focus the image on the retina, just like in an ordinary eye. The corneas of most people are either too long or too short. In the first scenario, corneal flattening is accomplished through laser eye surgery. The cornea is reshaped in the latter scenario by becoming rounder. This corneal tissue is amazing because it heals and rebonds immediately, (4) __________ the need for stitches.
To make precise cuts as (5) __________ as a quarter micron in length, a laser beam is sharply focused. A laser can remove 0.5% of a human hair's width at once, and the typical human hair has a diameter of fifty microns! Although they are able to significantly improve their vision, many laser eye surgery patients never attain normal vision.