The cornea must be transparent to visible light and have a precise curvature to provide the correct refractive power. These properties are governed by its structure. Corneal transparency arises from constructive interference of visible light due to the ordered arrangement of collagen fibrils in the corneal stroma. This arrangement is controlled by negatively charged proteoglycans surrounding the fibrils. Small changes in fibril organization can be tolerated, but larger changes cause light scattering. Corneal keratocytes do not scatter light because their refractive index matches that of the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The corneal stroma has a lamellar structure with collagen fibrils in each lamella making a large angle with those of adjacent lamellae. X-ray scattering shows preferred orientations in the human cornea: inferior-superior and nasal-temporal in the central cornea and circumferential at the limbus. Elastic fibres are present in the limbus with fibrillin microfibrils surrounding an elastin core, while in the cornea's center, they exist as thin bundles of fibrillin-rich microfibrils. A model based on this structure explains how the cornea withstands repeated pressure changes due to the ocular pulse. The cornea is the primary lens of the eye, responsible for about two-thirds of the refractive power. Most refraction occurs between the air and the tear film, due to the difference in refractive index. The cornea's transparency is due to the ordered arrangement of collagen fibrils and proteoglycans. Keratocytes do not scatter light because their refractive index matches the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The corneal stroma is composed of about 90% of the total tissue thickness and contains collagen, proteoglycans, and keratocytes. The nanostructure and microstructure of the corneal stroma are dynamic systems that promote and maintain transparency and correct refractive power. Collagen fibrils in the cornea are about 30 nm wide and arranged in lamellae with short-range order maintained by proteoglycans. Proteoglycans are highly negatively charged and attract counterions and water, pushing fibrils apart and extending proteoglycan bridging dimers. This leads to dynamic local movement of neighboring fibrils. Light scattering from collagen fibrils occurs due to Rayleigh scatter, with constructive interference in the forward direction and destructive interference in other directions. However, sufficient local disorder can cause significant light scattering. Keratocytes do not scatter light because their refractive index matches the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The refractive index of keratocytes is 1.381 ±The cornea must be transparent to visible light and have a precise curvature to provide the correct refractive power. These properties are governed by its structure. Corneal transparency arises from constructive interference of visible light due to the ordered arrangement of collagen fibrils in the corneal stroma. This arrangement is controlled by negatively charged proteoglycans surrounding the fibrils. Small changes in fibril organization can be tolerated, but larger changes cause light scattering. Corneal keratocytes do not scatter light because their refractive index matches that of the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The corneal stroma has a lamellar structure with collagen fibrils in each lamella making a large angle with those of adjacent lamellae. X-ray scattering shows preferred orientations in the human cornea: inferior-superior and nasal-temporal in the central cornea and circumferential at the limbus. Elastic fibres are present in the limbus with fibrillin microfibrils surrounding an elastin core, while in the cornea's center, they exist as thin bundles of fibrillin-rich microfibrils. A model based on this structure explains how the cornea withstands repeated pressure changes due to the ocular pulse. The cornea is the primary lens of the eye, responsible for about two-thirds of the refractive power. Most refraction occurs between the air and the tear film, due to the difference in refractive index. The cornea's transparency is due to the ordered arrangement of collagen fibrils and proteoglycans. Keratocytes do not scatter light because their refractive index matches the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The corneal stroma is composed of about 90% of the total tissue thickness and contains collagen, proteoglycans, and keratocytes. The nanostructure and microstructure of the corneal stroma are dynamic systems that promote and maintain transparency and correct refractive power. Collagen fibrils in the cornea are about 30 nm wide and arranged in lamellae with short-range order maintained by proteoglycans. Proteoglycans are highly negatively charged and attract counterions and water, pushing fibrils apart and extending proteoglycan bridging dimers. This leads to dynamic local movement of neighboring fibrils. Light scattering from collagen fibrils occurs due to Rayleigh scatter, with constructive interference in the forward direction and destructive interference in other directions. However, sufficient local disorder can cause significant light scattering. Keratocytes do not scatter light because their refractive index matches the surrounding matrix. When activated, they become fibroblasts with a lower refractive index, increasing light scatter. The refractive index of keratocytes is 1.381 ±