Complex sentence: Vision is generated by light that hits the retina of the eye, which is transformed into a nerve signal by receptors and sent ultimately to the visual cortex in the occipital lobe.
Split into simpler sentences: Vision is generated by light that hits the retina of the eye. Photoreceptors in the retina transduce the sensory stimulus of light into an electrical nerve signal that is sent to the visual cortex in the occipital lobe.