Where is the concentration of collagen the lowest in the vitreous?

The concentration of collagen is indeed lowest in the primary vitreous. The primary vitreous is the earliest form of vitreous that develops during embryonic development and is primarily composed of a gel-like substance with a lower density of collagen fibrils compared to the secondary and tertiary vitreous.

During the development of the eye, the secondary vitreous forms later and contains a more organized arrangement of collagen fibers that contribute to its structural integrity. The tertiary vitreous presents an even more complex and denser network of collagen, which helps maintain the shape and stability of the vitreous body throughout life. As a result, the progressive increase in collagen concentration from the primary to the secondary and tertiary vitreous reflects its increasing structural requirements as the eye matures.

This understanding highlights why the primary vitreous is characterized by a lower concentration of collagen compared to the more developed, subsequent forms.