眼 reinforces 目 — itself already a picture of an eye turned vertical — with 艮 for sound. As 目 drifted into formal compounds, 眼 became the living, blinking everyday eye.
眼 sees everything: 眼睛 (eyes), 眼泪 (tears), 眼镜 (glasses — 'eye mirrors'). A discerning person has 眼光 (eye-light: taste, vision); love at first sight is 一见钟情 but choosing by instinct is 眼缘 (eye-affinity). 开眼界 ('open the eye's horizon') means a mind-broadening experience. Chinese trusts the eye as the honest organ: 眼见为实 — seeing is believing.
The eye 目, spoken aloud — the EYE that sees the world.
眼镜 'eye mirrors' = glasses; 眼光 'eye light' = taste/vision. Chinese eyes emit as much as they receive.