What is the principal refractive element of the eye that provides most of the focusing power and is avascular?

What is the principal refractive element of the eye that provides most of the focusing power and is avascular?

• A. Cornea
• B. Lens
• C. Sclera
• D. Retina

Answer: (A)

The cornea is the principal refractive element, providing most of the eye's focusing power. Its curved, transparent front surface creates a strong bend in incoming light because of the large difference in refractive index between air and the corneal tissue, contributing roughly two-thirds of the eye’s total refractive power. Its avascular nature is crucial for transparency, so nutrients reach it from tears and the surrounding fluids rather than blood vessels. The lens also helps focus and can adjust its shape for near or far vision, but it contributes less power than the cornea. The sclera is the opaque white protective coat, and the retina is the light-detecting tissue at the back of the eye, neither of which serves as the main refractive surface.

The cornea is the principal refractive element, providing most of the eye's focusing power. Its curved, transparent front surface creates a strong bend in incoming light because of the large difference in refractive index between air and the corneal tissue, contributing roughly two-thirds of the eye’s total refractive power. Its avascular nature is crucial for transparency, so nutrients reach it from tears and the surrounding fluids rather than blood vessels. The lens also helps focus and can adjust its shape for near or far vision, but it contributes less power than the cornea. The sclera is the opaque white protective coat, and the retina is the light-detecting tissue at the back of the eye, neither of which serves as the main refractive surface.