American Board of Opticianry (ABO) Practice Test

What is the role of the limbus in conjunction with the cornea and sclera?

1. The blue portion of light on the visible spectrum

2. Power times 0.5

3. Measures vertex distance

4. None of the above

The correct answer is: None of the above

The limbus plays a crucial role in maintaining the structure and function of the eye, particularly as it interfaces between the cornea and sclera. It is located at the junction where the transparent cornea meets the opaque sclera, serving several important functions. Firstly, the limbus houses the stem cells that are essential for the regeneration of corneal epithelial cells. These stem cells ensure that the outer layer of the cornea can repair itself after injury, maintaining clarity and proper functioning of this vital part of the eye. Additionally, the limbus contains the trabecular meshwork, which is involved in the drainage of the aqueous humor, the fluid that provides internal pressure to the eye and nourishes its avascular tissues. This drainage system is crucial for maintaining intraocular pressure, which is important for eye health and preventing conditions like glaucoma. Also, the limbus has a role in the vascular supply and immune response of the eye through its connections with blood vessels. It provides a site for nutrient exchange and helps in the defense against pathogens. Understanding these functions helps clarify why options related to light spectrum, optical power calculations, or vertex distance do not apply to the role of the limbus. Thus, it becomes clear that the correct choice is that none of