Sitting in the doctor’s chair, you see that familiar E-topped Eye Chart. Imagine your eyes working like a camera, and you’re using that camera to capture what you are seeing. Your eyes see the chart by taking a ‘picture’
of it. This happens when light enters your eye through the clear window-like cornea. It bends the light, which is called refraction, to focus it.
Then, your pupil, controlled by your iris, opens, or, closes like the aperture on a camera to let in just the right amount of light. At night, it opens more, and during a bright sunny day, it gets smaller.
Right behind the pupil is the lens which works like the auto focus on a camera to fully focus the image. The lens changes shape to make sure that the light bends just enough so the ‘picture’ on the retina is as clear as
Next, the eye chart letters are projected on the light-sensitive retina at the back of your eye. It acts like a movie screen and captures the image upside down. The retina has millions of light sensitive cells called
rods and cones which when hit by light turn the picture on the retina into an electrical signal that goes to your brain through the optic nerve. Your brain makes sense of the image and you see the letters on the chart.
Surrounding the eyeball are the clear cornea and the sclera, that’s what you call the ‘white of your eye’. The retina is the light sensitive focusing screen. Inside, there’s two types of fluid, one watery behind the
lens, and further back, a thicker one that helps the eyeball hold its shape.