Cornea & Sclera: Why Transparency?

[blitz.km]

My teacher told me the reason about the cornea being transparent and the sclera being opaque as.. the sclera contains disorganized fibres.. and the cornea contains organized ones.. like being orthogonal or kind of some graphite like structure.
(i know i am being very vague)

She wasn't sure of the answer.. maybe something related to the properties of light..

Can someone please explain the exact reason to me?

 

[AyazM]

In cornea there are two factors responsible for transparency. Your teacher is correct about the fibres. The collagen fibres are arranged parallel to each other in a manner to make sure ALL points in all meridians of the cornea focus on exactly the same point; that is to say that they all have the same FOCAL length. If that wasn't true, the clinical condition that results is known as astigmatism and requires either spectacles, lens or surgical correction.

Light refraction is same for all points, however light scattering effect is minimal and therefore the reason for the transparency.

The other reason is that cornea is avascular. This means there are no blood vessels running within cornea. This is not true of sclera because sclera has an abundant blood supply with the circulation system running WITHIN the fibrous structure. Blood vessels are definitely not designed to transmit light neatly so their presence renders maximal light absorption and scattering, and therefore the opaqueness. The fibrous arrangement in sclera is analogous to the fibrous arrangement in the connective tissue structures throughout the human body, such as in the Skin, blood vessels etc and therefore lacks transparency.

I think I answered your question from a more medical perspective. Hopefully someone else would provide an opinion of a physicist on this matter.

 

[quicknote]

The transparency of the cornea and the opacity of the sclera are both important for the function of the eye. The cornea is responsible for refracting and focusing light onto the retina, while the sclera provides structural support and protection for the eye.

The reason for the transparency of the cornea lies in its unique structure. The cornea is made up of several layers, including a layer of epithelial cells on the outer surface and a layer of endothelial cells on the inner surface. In between these layers is a layer called the stroma, which is composed of organized collagen fibers. These fibers are arranged in a specific pattern that allows light to pass through without being scattered or absorbed. Additionally, the stroma contains a high percentage of water, which also contributes to the transparency of the cornea.

On the other hand, the sclera is made up of mostly disorganized collagen fibers and fewer water molecules. This disorganized structure causes light to be scattered and absorbed, giving the sclera its opaque appearance. The function of the sclera is to provide protection for the eye and maintain its shape.

In summary, the transparency of the cornea is essential for allowing light to pass through and focus on the retina, while the opacity of the sclera serves to protect and support the eye. This is all due to the unique structures and compositions of these two tissues.