You’ve probably heard about the iris of the eye. But what exactly is it, and what does it do? In this article, we’re breaking down the function of the iris along with where it’s found, its anatomy and characteristics, and common eye conditions that affect the iris.
What is the Iris?
When someone tells you that “you have nice eyes”, in all likelihood it’s the iris that is responsible for the compliment. That’s because the iris is the coloured part of the eye surrounding the pupil. This is the part of the eye we’re referring to when we describe someone’s eye colour as steel blue, green, or hazel brown.
The Iris Function
Like every other part of your eye, the iris plays an important role in helping us see. Vision is complicated, and it relies on components of the eye to work together. The unique function of the iris is to control how much light enters the eye. Using very tiny muscles with the coloured area of the eye, the iris works together with the pupil, also known as the pupillary light reflex, to control the amount of light that enters. The pupil will dilate (widen) to let more light in, and contract (narrow) to close out light.
The iris plays a vital role, constantly pressuring the pupil to change the amount of light that enters the eye. Thanks to the iris, we’re able to retain our vision in dimly lit spaces and very bright areas. To see your iris hard at work, just step outside into the sun on a bright day for the first time. You’ll notice your eyes squinting and an uncomfortable feeling in the eye until your iris has closed off the pupil enough.
Anatomy of the Iris
Surrounding the pupil of the eye, the iris is found at the center of the eye and is recognized by its distinct colour. But the iris is not confused to be confused with the cornea, which is located in the same area but on a different layer. The cornea is found on the outer layer. Under that is the iris, which is on top of the lens layer.
The most visible characteristic of the iris is the colour. Although it seems like there are only a few available eye colours for humans, the colour of the iris is actually unique, meaning no two people have exactly the same-coloured iris. The iris gets its colour from the amount of melanin, a naturally occurring pigments that also affects skin and hair colour, available in the body.
Looking more closely at the iris, there are two distinct regions – the ciliary zone and pupillary zone. The ciliary zone is the larger zone found at the exterior region of the iris, while the pupillary zone is found at the edge of the pupil and iris. The area where these two regions join is known as the collarette, home to tiny little nerves and blood vessels.
Eye Conditions & Diseases that Affect the Iris
Unfortunately, the iris is prone to all kinds of eye conditions and diseases. Here are a few of them:
- Melanoma – Because the iris is made of pigment (like the skin), it’s also possible to have melanoma in these cells. When looking for melanoma, your eye doctor will look for small dark spots in the iris.
- Glaucoma – There are different types of glaucoma, and some start in the iris. Pigmentary glaucoma occurs when pigment begins flaking off the iris, which then blocks fluid from draining properly.
- Inflammation – Inflammation can occur for a number of reasons, but most commonly an infection or an injury. Inflammation can be painful, and could lead to blindness if not treated.
- Synechiae – Synechiae is an adhesion between the iris, lens, or cornea. This can be painful and disrupt vision, as the iris will stick to the clear tissue surrounding it.
Protecting Your Irises
Protecting the iris and maintaining good eye health can be thought of similar to general health. The best way to maintain healthy irises and eyes is to eat well, exercise, and keep yourself hydrated. It’s also important to be mindful of the sun and harmful UV rays by always wearing eye protection in the sun – especially during the warmer months.
But eye conditions and diseases can happen to anyone. That’s why the best defense against eye conditions and diseases are regular trips to the optometrist. With a standard comprehensive eye exam, your eye doctor will be able to spot issues before they become too serious and affect your vision and overall health. That’s why it’s so important to visit your optometrist once every couple of years – regardless of whether your vision is good or not.
Inner Harbour Optometry has two locations in downtown Victoria, where we offer comprehensive eye exams, plus dry eye treatment, imaging, eyewear, and even facial rejuvenation and skin tightening. Book your appointment today.