What Role Do Eyelids Play in Vision?
The eyelids perform the functions of protection and support to the eye, which includes tear film production and spread. The thinnest skin of our body is located on the lids. Beneath this skin are thin orbicularis muscle fibers and connective tissue that, when in protective mode, can squeeze the lids tightly to protect the eye from external injury.
Beyond the muscles is a structure called the tarsal plate. The tarsal plate has Meibomian Glands that secrete an oil called meibum at the lid margin. This oil forms one of three main layers of the tears: the Lipid Layer.
If you’ve ever flipped your upper lid (fyi: that little rectangle shape within the lid that you feel getting flipped is the tarsal plate) you will see the pink/red backside tissue of the lid. This back layer of the lid is the conjunctival mucosa , and it’s red because it is vascular (blood vessel) rich. The cornea receives oxygen from these blood vessels during closed eye (such as sleep) periods.
This conjunctiva on the lid is referenced as the palpebral (lid’s) conjunctiva and it loops around onto the bulbar (surface of the eye’s) conjunctiva that overlies the white of our eye, the sclera. This looping of a continuous conjunctiva prohibits the contact lens and all other external materials from “rolling” behind our eye.
The conjunctival tissue helps produce the other two main layers of the tears: the Aqueous Layer (a “watery” layer created from glands such as the lacrimal gland and accessory lacrimal glands -glands of Wolfring and Krause), and the Mucin Layer (a “glycoprotein” later produced by goblet cells).
How Do Eyelids Help Vision?
The eyelids support the protective role of the eyelashes to the eye. The base of each lash sinks into a follicle in the thin skin tissue of the eyelid where Zeis glands provide a lubricative oil to the lash, and Moll glands secrete immune system support.
There are three layers that make up tears
- Lipid Layer
These layers all work together to provide moisture, lubrication, nourishment, oxygen, and immune support to the cornea and other structures of the external eye so that the eye can remain healthy, and, therefore, light can pass clearly through the cornea and into the eye for visual sensory.
Our human eyes blink approximately once every four seconds under normal conditions. In every blink, the lids release micro- amounts of mucin, oil, and water into every blink in a continuous flow of a balanced tear. At the same time, a continuous flow of tears must leave the eye to make way for the new tears. Some of the tears are evaporated or absorbed, while the rest of the tears are directed by the lids (the lids seal shut from outer edge to inner edge – like a zipper) toward small holes in the nasal corner of the lid (called puncta) which drains the tears into the nose.
This constant flow of new and fresh mucin, oil, and water provides a necessary balance (referred to as homeostasis) of healthy ingredients throughout the eye while eliminating unhealthy microbes and particles at the same time. This homeostasis must be maintained continuously for proper tear function and stability.
Eyelids and Contact Lenses
Inserting a contact lens onto the eye threatens the homeostasis of a tear. Contact lenses are continuing to evolve to incorporate not only increased oxygen transfer to the cornea, but also assist in stabilizing tears so they do not disrupt the tear function or optics of the eye. If tears are disrupted, then a contact lens may create effects such as blur, irritation, redness, swelling, and discomfort.
The lid’s various glands are controlled by a finely-tuned sensitive feedback mechanism that apparently responds to micro changes in our tears and cornea. Inserting a contact lens is obviously not going to go undetected. The sensors of the cornea, conjunctiva, and lid will each respond to the contact len intrusion to maintain homeostasis of the tear layers.
Not only are the tears affected by contact lenses, but our eyelids are as well. For example, when a contact lens is inserted into an eye for the first time, it is the nerve endings on the lid margin that “feels” the lens. Soft contact lenses , when “sitting” properly, are wide enough to tuck under the upper and lower lids and have a tapering edge that is designed to reduce this lid perception. Over continued use of contact lenses, however, this perception of the contact lens diminishes. This desensitization can also reduce our sensitivity to damage and tear disruption, therefore allowing for greater amounts of damage to occur to the eye before a contact lens wearer becomes aware that there is even a problem.
Tear Dysfunction of the Lid
Inflammation of the lids
Meibomian Gland Dysfunction (MGD)
Reduced function of the oil producing glands. This loss of function leads to a thinner lipid layer, increased evaporation, and ultimately dry eye conditions. This occurs with most people with age.
Dry Eye Syndrome
A condition where the tear is insufficient for maintaining a stable tear. This instability can occur due to various reasons, but the most common is a reduced Lipid Layer. A typical sign of Dry Eye is a watery eye. The “waterworks” of tears turn on in response to the eye being dry in the first place.
Mechanical Problems of the Lid
A benign “lid twitch” that is often associated with eye irritation, electrolyte imbalance, change in diet, new medication, dehydration, lack of sleep, a change in caffeine intake, or increased stress levels.
Outward turned lid and lashes that usually allow for excessive drying of the tears causes the eye to become dry due to an ineffective seal if the lower lid margin.
Inward turned lid and, therefore, lashes that causes a direct irritation of the eye from the lashes.
Gland Problems of the Lid
A noninfectious focal inflammation of a lid gland of Zeiss or meibomian gland that can be tender, but often is not.
Hordeolum (aka: Stye)
An infectious focal inflammation of a lid gland of Zeiss or meibomian gland that tends to be very painful and red in early stages.
Severe infectious swelling of the eyelid commonly from an “out-of-control” hordeolum, injury, scratch, or insect bite that may be associated with fever and chills and requires antibiotic treatment.
Severe infectious swelling of the entire eye’s orbit which bulges the globe of the eye forward (proptosis) from the increased swelling, including the lid that necessitates hospital intervention.
Cysts of Moll
Clear bumps filled with clear fluid at the lid margin around the base of lashes.
Cysts of Zeis
White bumps filled with sebaceous material at the lid margin near the base of lashes.
Skin Lesions of the Lid
Epidermal Inclusion Cyst
Yellow/white/skin toned bumps filled with keratin protein on the skin around the eye.
Squamous Papilloma (aka: “Skin Tag”)
Usually skin colored lesions formed from benign fast growing cells that give it a “stuck on” appearance.
Yellow elevations, like little islands, filled with lipid-laden macrophages that usually occur on the nasal (nose) side of the eye’s upper lid and are associated with high levels of systemic cholesterol.
“Waxy” raised brown-black skin lesion that is benign that looks as if they have been “dripped onto the skin by a candle”.
“Scaly” skin lesions that are considered precancerous.
Cancer of the Lid
Basal Cell Carcinoma
– most common eyelid malignancy –
Variant appearance skin lesion that tends to have ulcerated, unhealing tissue and an area of ulceration. This type of lesion has a low likelihood for metastasis, but there is still the potential for metastasis.
Squamous Cell Carcinoma
-uncommon, eyelid malignancy –
Cariant appearance skin lesion that tends to have ulcerated, unhealing tissue and an area of ulceration. This type of lesion has a very high risk of metastasizing (spreading to other areas of the body).
-uncommon, eyelid malignancy –
Yellowish lesion that affects the Meibommian glands and Zeis glands of the lid, and may easily be misidentified as a hordeolum. This type of lesion has a very high risk of metastasizing (spreading to other areas of the body).
-very rare, least common malignancy of the eyelid –
The lesion (more common in the lower lid) that originates in the melanocytes of the skin. Therefore, they tend to be pigmented (dark) in color, but not always. This type of lesion has a very high risk of metastasizing (spreading to other areas of the body).
Eye Health Tips Specific to Eyelids
Here are a few tips for maintaining good eyelid health:
- Protective Sunwear: the growing lesions and cancerous lesions of the eyelid are often attributed to exposure to UV light from sun exposure
- Good Hygiene: keep the lids and lashes clean with non irritating cleansers and shampoos
- Hot Compresses: not so hot that they will burn your skin, but heat will increase blood flow to the lid and assist in maintaining smooth gland fluid flow
- Wear cosmetics carefully:
- Never wear eyeliner beyond the lash line, it may block the exit holes of the meibomian glands
- Wear mascara only on the outer half of the lashes ( this will keep the lid clean and prevent access “clumping” of the lashes from sticky mascara, leading to not only increased health, but improved cosmetics)
- Any sign of cosmetics (including false lashes) being irritating to the lids should be discontinued immediately
- Diet: Maintaining a balanced nutritional diet, especially one that is rich in omega 3 (such as fish) are known to promote vascular flow in the lid and support meibomian function.
- Fish Oil Supplement: if your diet does not consist of enough omega 3, fish oil is rich in omega 3 which is known to promote vascular flow in the lid and support meibomian function.
Taking Care of Your Eyelids for Eye Health
Our eyelids play a significant role in maintaining healthy eye conditions for sight. Contact lens wear increases the amount of work that the lids need to perform. Keeping our contact lenses clean and replacing them at the proper interval will help our tears manage the extra task that we require of them during wear.
As you can probably imagine, extra buildup on the lens disrupts the tears ability to function and makes maintenance of a healthy tear for the lids nearly impossible.
And always keep in mind… our tears are produced, spread, maintained, and removed by the actions of the eyelids… the lids maintain the health of the eye to make vision possible. So if your lids appear to be unhealthy, remove your contact lenses (even if your eye “feels” good) and consult an eye doctor before continuing wear.
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