How does light travel through the eye before reaching the retina?

Light enters the eye through the cornea, a transparent "window" that provides the majority of the eye's focusing power. After passing through the cornea, light travels through the anterior chamber, which is filled with a watery fluid called aqueous humour.1

The light then reaches the iris, which acts as a muscular curtain to regulate the amount of light entering the eye by adjusting the size of the pupil. Once through the pupil, the light passes through the lens, which works with the cornea to focus the image onto the retina at the back of the eye.12

Finally, the light travels through the vitreous humour and must pass through the non-sensitive layers of the retina before reaching the light-sensitive rods and cones. In the fovea centralis, however, these inner layers are absent, allowing light an almost unrestricted passage to the photoreceptors for the sharpest vision.13