Posted on September 01 2015
In the last article, we discussed the primary parts of the human eye and how they affect vision. There are many other important components of the eye that are less well known. However, these parts are also vital to the health and function of our sight.
Many of the important parts of the eye seem to be in the front (cornea, iris and lens) or in the back (retina and optic nerve). So what’s in the middle section? This part of the eye, between the lens and retina, is called the vitreous cavity, or sometimes the vitreous chamber. It is filled with a transparent, gelatinous liquid called vitreous humor. This substance provides structure to the eyeball, and it is important for it to be transparent so light waves directed by the lens are not blocked before reaching the retina. Along with the vitreous humor, another important structural element of the eye is the sclera, which is the outer layer of the eyeball. The sclera protects the fragile inner parts from dust and other potentially damaging particles. The outer, exposed part of the sclera is also covered by the conjunctiva, a membrane that helps keep the eye moist. The conjunctiva runs along the inner part of the eyelid, as well.
When we start a basic discussion of the parts of the eye, we can say that the iris and pupil are behind the cornea. However, it is worth pointing out that the iris and pupil are not directly behind the cornea. Between the cornea and the iris is a section of the eye called the anterior chamber. In a way similar to how the vitreous cavity is filled with vitreous humor, the anterior chamber is also filled with a humor, called the aqueous humor. As the name implies, the aqueous humor is more watery than the vitreous humor. The aqueous humor services both the cornea and lens, delivering important nutrients to both parts of the eye. Once the aqueous humor has dispatched its nutrients, it will flow out through Schlemm’s canal, a tiny tube near the iris, and back into the bloodstream. Schlemm’s canal also helps regulate the delicate pressure balance of the eyeball.
Our vision is capable of extraordinary dexterity, focusing on a street sign blocks away as well as the small text on our cell phones. This is due to the lens of the eye adjusting shape to focus differently depending on whether we are looking far away or close up. The lens needs help adjusting shape, though, and that’s why the ciliary muscle is important. If we are trying to see distance, the ciliary muscle flattens the eye lens. If we are trying to read small print, the ciliary muscle pulls the lens slightly in order to curve it.
There are still other parts of the eye that perform critical functions, but we have managed to cover many of the most important components of the eye that makes our vision possible.