Science of the Eye

Science of the Eye is the part of the CPO exam that checks whether you know the organ everyone in an optometric office works on: what its parts are called, what each does, and what commonly goes wrong. It makes up 11.1% of the exam. You use it daily to follow the optometrist's notes, chart what patients describe in accurate terms, explain in plain words a diagnosis the doctor has already made, and notice when a phone call or front-desk complaint is more urgent than it sounds.

The easiest way to learn the eye is to follow a ray of light. It enters through the cornea, the clear front surface, then passes through a pool of clear fluid and the pupil, the opening in the colored iris. The lens fine-tunes the focus, and the light crosses a clear gel to the retina, the light-sensing lining at the back of the eye. The retina turns light into nerve signals, and the optic nerve carries them to the brain, which does the actual seeing. Most conditions that affect sight sit at one stop along that path: something blocks the light, focuses it in the wrong place, damages the tissue that senses it, or interrupts the signal to the brain.