The World Inside the Eye: Let's Learn About the Choroid That Gives Life to Our Vision

Have you ever wondered how our eyes work like a super camera? Everything we see, that is, colors, light, shapes, all of this is sent to the brain in a matter of seconds, allowing us to see this world. Inside this little eye, there is a little-known hero that is indispensable to our vision, but we don't talk about it much. That's what we call the 'Choroid'. Although the name is a little strange, its job is very important. So let's talk about this simply and kindly today.

Simply put, what is this choroid?

Imagine that our eye is a ball made up of three layers. The middle layer is called the uvea. The choroid is a very important part of that middle layer. Its main function is to provide blood, which is the nourishment needed by other important parts of the eye that are essential for our vision. In addition, it also helps to control the amount of light entering the eye and give us clear vision.

What are the two main functions of the choroid?

The service that the choroid provides to our eyes can be divided into two main parts.

1. Blood Supply

This is the most important and main function of the choroid. It is like a main power plant that supplies water and electricity to a city. The retina and optic nerve inside our eye are like two factories that work non-stop. Because they are constantly sending signals to the brain, they need much more blood and nutrition than other tissues.

So, inside this choroid is a network of fine blood vessels , stacked on top of each other. It is through this blood vessel system that the retina and optic nerve receive a continuous supply of oxygen and nutrients. If this supply is even slightly reduced, our vision can be seriously damaged.

2. Light Absorption

This is a little-known, but very important, function. Have you ever seen the black, porous foam that is stuck to the walls of recording studios to stop sound from echoing? That's exactly what the choroid does inside the eye.

You may have heard of melanin , the pigment that gives our skin its brown color. This melanin is also found in large quantities in the choroid. Melanin is used in the skin to protect against harmful ultraviolet rays from the sun.It protects the skin by absorbing UV rays. Inside the eye, this melanin prevents the light coming in from being scattered unnecessarily inside the eye.

Where is this choroid located?

The choroid is located in the back two-thirds of our eyeball. Simply put, it is located between the outermost white wall of our eye (sclera) and the innermost layer of the eye, the retina . It is like the middle layer of a sandwich.

This is a very thin membrane. That is, it is only as thick as an A4 sheet of paper that we usually print. But inside that small thickness is the huge network of blood vessels that I mentioned. Sometimes, just like we have birthmarks on our skin, this choroid can also have birthmarks (nevi). We cannot see these from the outside. These are only seen when an ophthalmologist examines the eyes.

What conditions can affect the choroid?

Many things that affect the blood circulation in our body, such as inflammatory diseases, can also affect the choroid. Because it is made up entirely of blood vessels. Some of the main conditions that can be seen are:

• Albinism: A genetic condition that reduces the melanin pigment in the skin and eyes. This lack of melanin causes the eyes to be unable to tolerate light (photophobia) and causes vision impairment.
• Congenital conditions: For example, conditions like choroideremia can cause damage to the retina.
• Diabetes-related retinopathy: Diabetes can damage the blood vessels in the eye, which can also affect the choroid.
• Macular degeneration: Especially in the 'wet' type, new, weak blood vessels grow in the choroid, which can damage vision.
• Eye cancers: Cancers, especially intraocular melanoma, can occur in the choroid.
• Eye ischemia: Impaired blood supply to the eye, such as in an eye stroke.
• Glaucoma: When increased pressure in the eye damages the optic nerve and retina, the choroid can also be affected indirectly.
• Eye injuries.
• Inflammatory conditions: Inflammation and infection of the inside of the eye, such as uveitis or chorioretinitis.

How do you identify a problem with the choroid?

When there is a problem with the choroid, it directly affects our vision. Therefore, it is very important to pay attention to any changes in vision.

What tests are done to diagnose such conditions?

When you see an eye specialist, they will ask about your symptoms and examine your eyes. If they suspect a problem with the choroid, they may do the following tests:

• Visual acuity test: A general test that measures the sharpness of your vision.
• Visual field test: A test to see if there is any impairment in your field of vision (how far you can see without moving your head).
• Slit lamp exam: In this, the doctor carefully examines the inside of your eye with a special microscope-like instrument.
• Retinal imaging tests: Due to the connection between the choroid and the retina, examining the retina can also provide information about the choroid.
• Fluorescein angiography: A special dye is injected into a vein in the arm, and images of the blood vessels inside the eye are taken.
• Optical Coherence Tomography (OCT): This is like taking a cross-section scan of the inside of the eye. It can check the thickness of the layers of the eye and whether there is any swelling.

What are the treatments for diseases related to the choroid?

Often, rather than treating the choroid directly, the underlying condition that is affecting it is treated. This means that when the cause is treated, the condition of the choroid also improves. Treatment methods can vary greatly depending on the disease.

Depending on your condition, you may need additional treatments, which your doctor will explain to you in detail.

How to maintain the health of the choroid and eyes?

Our eyes are a very precious resource. So we should all try to protect them. There are several things you can do to maintain the health of the entire eye, including the choroid.

• Get regular eye exams: Whether you wear glasses or not, it's important to have your eyes checked by an eye doctor at least once a year. This way, any problems can be identified before symptoms appear.
• Protect your eyes: If you are welding, working with chemicals, or working in dusty areas, be sure to wear safety glasses/goggles.
• Avoid smoking and tobacco use: Smoking and chewing tobacco directly damage our circulatory system. Since the choroid is a layer of blood vessels, smoking can directly damage it.
• Manage chronic diseases: If you have diseases like Diabetes Mellitus and Hypertension , manage them well according to your doctor's instructions. If these diseases are not controlled, the damage to the eyes can be very serious.
• Take care of your overall health: Eating a balanced diet, maintaining a healthy weight, and exercising regularly are not only good for your eyes, but also for your entire body.

The choroid is a silent, but very important part of our eye. It gives life to our vision and helps us see the world clearly. So, it is our responsibility to be aware of it and take care of our eyes.