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How do the cornea and lens focus light onto the retina?

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Compound eye — Senses Vespid wasps (Vespidae), similar to other insects, have compound eyes that consist of thousands of tiny optical units known as ommatidia, which contain light-sensitive photoreceptor cells.

The eye’s optical system focuses light onto the retina by acting as a complex convex lens system, where refraction occurs at four distinct surfaces: the anterior and posterior surfaces of both the cornea and the crystalline lens.1

As light enters the eye, the greatest degree of bending occurs at the air-cornea interface due to the significant difference in refractive index between air and the corneal tissue. The light then passes through the aqueous humour and the lens, where further convergence occurs. Because the lens has a higher refractive index than the surrounding fluids, its surfaces contribute significantly to focusing the rays.1

To maintain a clear focus on objects at varying distances, the eye employs a process called accommodation. By contracting the ciliary muscle, the tension on the zonular fibres is slackened, allowing the elastic lens to become rounder and thicker, thereby increasing its refractive power. This precise coordination ensures that light rays converge into a sharp, inverted image on the retina.2314