Our eyelids are like tiny curtains for our precious eyes. They serve several functions, including covering the eyeball from any damage, limiting the quantity of light entering the eye, and working like windscreen wipers moisturising the eyeball with tears released by the lacrimal gland while blinking. But have you ever thought about what’s happening under that thin layer of skin? It turns out that our eyelids are full of small parts that all work collectively to keep our eyes healthy and happy.
We’ll know everything about eyelid anatomy in this blog and break it down into three main areas: the upper eyelid, the lower eyelid, and the outer corner where they meet.
By understanding what each part does, we can appreciate how crucial these tiny curtains are to our vision!
Eyelashes
Eyelashes are the hairs that grow on the edge of the upper and lower eyelids and are more than just for show. Like nature’s built-in dust filters, they are constantly on guard against pollen, dust, and other eye irritants. When a foreign object comes too close to the eye, the sensitivity of the eyelashes prompts them to send signals to the eyelids to close.
Eyelashes have a natural cycle of falling out and taking around 6 to 8 weeks to regrow. However, pulling out eyelashes can cause damage to the follicles they grow from. Eyelashes have a fixed and limited length and do not need to be trimmed. Additionally, eyelash colour may vary from hair colour, with darker hair typically corresponding to darker lashes and lighter hair to lighter lashes.
Some ocular conditions, such as blepharitis and Demodex mites, can impact eyelashes, leading to flakiness or loss. False eyelashes and lash glue can impact the health of the eyelids.
Eyelids
The upper and lower eyelids create a wet area around the eye and protect it from harm and dryness. They have muscles to open and close and are covered with skin. The inside of the eyelid is lined with a wet layer, and the outside has eyelashes.
When the eyelids open and close, they spread tears over the eye, keeping it moist. The eyelids also remove the tears by pushing them into the tear duct.
The edges of the eyelids are kept wet by an oily substance from the meibomian glands inside the eyelids. This oily substance helps make the tears and stops them from drying up too quickly.
We need to take good care of our eyelids, as they are a delicate and essential part of our eye health. Just like the skin on the rest of our face, the skin around our eyelids can show signs of ageing, such as sagging, drooping, and puffiness. If left unaddressed, this excess skin can even interfere with our vision.
Fortunately, blepharoplasty can help to correct these issues. By removing excess skin and tightening the muscles around the eyelids through blepharoplasty treatment, you’ll get a more youthful appearance.
Conjunctiva – Invisible Lubrication Layer of the Eyes
The conjunctiva is a clear layer that forms the lining of the inner layer of the eyelid and the white of the eye (also called the sclera). It keeps the eyes moist, lubricated, and free of small particles and pollutants.
Moisture and lubrication keep your eyes comfortable and prevent them from drying out, which can cause irritation and strain. They act as a protective shield which helps keep dust and other tiny invaders at bay, reducing the risk of infections that could blur your vision.
The palpebral conjunctiva covers the eyelids’ inner surface, which extends into the fornix. The conjunctiva lining the eyelid fuses directly to the tarsus, a plate-like structure within the eyelid, forming the tarsal conjunctiva. It covers the white part of the eye and is known as the bulbar conjunctiva.
Orbicularis Oculi Muscle
The orbicularis oculi muscle is important for controlling the eyelids and making facial expressions. When it tightens and relaxes, it moves the skin around the eyes. The muscle is connected to the skin through tissue.
There are two main parts of the orbicularis oculi muscle. One part helps close the eyelids tightly, while the other part helps with winking and blinking. This facial muscle receives instructions from the facial nerve and works in concert with other muscles. The part that helps close the eyelids is connected to the bones around the eye and to other facial muscles.
The muscle fibres interact with nearby muscles, joining to form a structure at the edges of the eyelids. This muscle also attaches to a bony structure on the outer side of the eye called the lateral orbital tubercle.
Tarsal Plates
The tarsal plates are like a supportive structure for our eyelids. There are two plates: the upper eyelid and the lower eyelid. The upper tarsus also serves as the place where the levator palpebrae superioris muscle attaches.
Inside the tarsal plates, there are special glands called Meibomian glands. These glands produce an oily substance that goes into the eye to stop tears from evaporating too quickly. This oily stuff also stops the eyelids from sticking together when we close our eyes.
Glands
Glands in our body release substances that help it work well. In our eyes, there are special glands that release liquids to keep our eyes moist and comfortable. Meibomian glands make oil to keep our eyes lubricated, while others release sweat to cool them down. The glands in our eyelids also produce oil for our eyelashes.
When we cry, most of our tears come from lacrimal glands above our eyes and then spread across the front of our eyes. The extra tears are drained into our noses, which is why our noses run when we cry.
Nerves – Connectors for Movement and Sensation
It really requires a lot of control to make your eyes blink right. These control our eye movement and feelings:
Movement –
- Three types of nerves send signals from the centre of the body that help the eyelids move.
- The seventh cranial nerve, also called the facial nerve.
- The third cranial nerve, also called the oculomotor nerve.
- Sympathetic nerves, which make the eyelids move without us thinking about it.
Feeling –
Parts of the fifth cranial nerve (trigeminal nerve) reach the surface of the eyelids, providing feelings like touch, heat, and itching.
The nerves that manage your eyelids also affect how your face looks. If our eyes are the way we show our feelings, then the nerves of the eyelid decide if people can really see them or not.
Extraocular Muscles
There are six muscles on the outside of the eye that help it move around. These muscles can move the eye up, down, and to the sides. Together, they can shift the eye in any direction.
- Medial Rectus (MR) – moves the eye towards the nose.
- Lateral Rectus (LR) – displaces the eye from the nose.
- Superior Rectus (SR) – moves the eye upward and inward.
- Inferior Rectus (IR) – moves the eye inward and downward.
- Superior Oblique (SO) – moves the eye outward and downward.
- Inferior Oblique (IR) – moves the eye upward and outward.
Fat Pads
In and around the eyelids, there are different layers of fat. One layer of fat is found behind the orbital septum and in front of the levator aponeurosis. In the upper eyelid, there are two more fat pads located in the middle and towards the nose. The lower eyelid fat pads have a slightly different structure.
The central fat pad is separated from the medial fat pad by the inferior oblique muscle. There is also a small amount of fat in front of the inferior oblique muscle. The inferior oblique muscle starts from the lower border of the orbital floor and moves behind the orbital margin and towards the upper aspect of the nasal lacrimal canal.
It then goes underneath the inferior rectus muscle and through the Tenon capsule, ultimately getting close to the macula of the eye.
Conclusion
The eyelid, while appearing simple, is a wonder of complex parts functioning together. Knowing about these different parts is essential as they help us understand how our eyes stay protected, moist, and able to function well.
Consult a professional if you are experiencing dryness, puffiness, or drooping of your eyelids. At Perfect Eyes Ltd., Dr. Sabrina Shah Desai, a leading oculoplastic surgeon, offers a variety of eyelid treatments to address a variety of eye problems.
