The human eye is a complex optical system composed of several components that bend or refract incoming light rays to focus them on the retina. The ability to focus light sharply is quantified by the dioptric power, measured in diopters (D), which is the inverse of the focal length (in meters). Different structures of the eye contribute differently to the total refraction.

Components Contributing to Eye’s Dioptric Power

• Cornea: The transparent, curved front surface of the eye that provides approximately 70% of the eye’s total dioptric power.

• Lens: The flexible, biconvex structure behind the pupil that adjusts its shape to fine-tune focus; it contributes less power than the cornea but allows accommodation for near vision.

Dioptric Power Distribution in a Normal Human Eye

• The cornea has the largest refractive index difference with air and has a strongly curved anterior surface, contributing roughly 43 diopters of refractive power.

• The lens provides about 19 diopters in the relaxed state but can vary due to accommodation.

• Other structures like the anterior and posterior surfaces of the lens contribute to total refractive power, but these are part of the overall lens system rather than separate entities.

Addressing the Options

• (1) Retina: The retina is the light-sensitive layer where the image forms; it does not refract light and provides no dioptric power.

• (2) Cornea: The correct answer; the cornea provides the maximum dioptric power in the eye.

• (3 & 4) Anterior and posterior surfaces of the lens: While the lens does refract light, its contribution is less than that of the cornea. The lens adjusts its power during accommodation but is not the principal source of dioptric power.

Conclusion

In the normal human eye, maximum dioptric power for sharp image formation on the retina is provided by the cornea.

Correct answer:

(2) cornea