Proptosis, commonly referred to as a bulging eye, is one of the most recognizable signs of Thyroid Eye Disease (TED) and other orbital conditions (1). While the cosmetic impact of a bulging eye is often what patients notice first, the more serious consequences involve eyelid function and corneal health. When the eye protrudes forward beyond its normal position, the eyelids may no longer protect the eye adequately. This can lead to dryness, irritation, corneal injury, and in severe cases, vision-threatening complications (2). Understanding the connection between proptosis, eyelid closure, and corneal health is essential for recognizing risks early and preventing long-term damage.
What Is Proptosis and Why Does It Happen?
Proptosis occurs when the eye gets pushed forward out of the orbit (eye socket or the bony cavity in the skull containing eyes) 3. This forward displacement is typically due to the swelling or enlargement of the tissues behind the eye, such as the muscles, fat, or connective tissue. While TED is one of the most common causes, proptosis can also result from inflammation, tumors, infections, or trauma.
TED is a complex autoimmune condition affecting the tissues around the eyes and is commonly associated with thyroid conditions such as Graves’ disease (4). It is characterized by inflammation, pain, swelling or protruding eyeballs (proptosis), eyelid retraction or inability to close the eyes completely, eye surface dryness, double vision (diplopia), and in severe cases, compression of the optic nerve (5). TED is an autoimmune inflammatory condition (the body’s immune system starts attacking itself) involving tissues around the eyes, including muscles, fat, and connective tissue. In thyroid eye disease specifically, immune-mediated inflammation causes orbital tissues to expand. Because the orbit is a rigid bony cavity, the increase in tissue volume has nowhere to go except pushing the eye outward. While mild proptosis is primarily an aesthetic issue that affects appearance, more significant forward displacement can disrupt normal eyelid function and compromise eye health.
How Eyelids Protect the Eye
The eyelids play a critical protective role, and every blink spreads tears across the cornea, the clear, dome-shaped surface at the front of the eye, ensuring that it stays both lubricated and protected. Normal eyelid functions serve several essential purposes, such as keeping the cornea moist, protecting against dust, debris, and environmental exposure, distributing nutrients through the tear film and preventing infection by clearing irritants. In addition, lysozyme in tears is an essential part of the arsenal of our innate immune system. Also, complete eyelid closure is especially important during sleep, when tear production decreases and physical protection from closed eyelids is essential to prevent the eyes from drying out.
How Severe Proptosis Affects Eyelid Closure
When the eye protrudes forward, the eyelids can no longer reach far enough to fully cover the cornea. This condition is known as lagophthalmos, or incomplete eyelid closure, which can lead to exposure keratopathy. Proptosis results in several mechanical changes which contribute to incomplete eyelid closure:
1. Increased Distance Between Eyelids
Due to the enhanced protrusion that happens in proptosis, the eyelids must travel a greater distance to completely close. Even if eyelid muscles function normally, they may not be able to fully form a full seal around the more prominent eye.
2. Eyelid Retraction
In TED, inflammation can cause the eyelids, especially the upper eyelids, to retract upward. This widens the eye opening and further limits the eyelids’ ability to properly protect the surface of the eye. It is important to note that eyelid retraction is different from proptosis. While both conditions may occur in thyroid eye disease and are often related, eyelid retraction refers to the abnormal elevation of the eyelid itself, whereas proptosis refers to the forward bulging of the eye.
3. Increased Orbital Pressure
Swelling behind the eye can create tension on surrounding tissues, restricting both normal eyeball and eyelid movement. These changes mean that even when a person blinks or sleeps, the cornea may remain partially exposed.
What Happens When the Cornea Is Exposed
When the cornea is not fully protected by the eyelids, it becomes vulnerable to chronic environmental exposure. This can lead to a condition known as exposure keratopathy, which develops when the cornea dries out or becomes irritated from exposure to the elements (6). Early symptoms may include dryness, burning or gritty sensation, redness, excess tearing (a reflex response to dryness) and light sensitivity. Paradoxically, patients may experience excessive tearing even though the eye is dry. This happens because irritation triggers reflex tear production, but these tears often evaporate quickly without proper eyelid coverage. Late stage can lead to recurrent corneal abrasions, ulcerations of the cornea, and can lead to blindness if untreated. Severe exposure keratopathy can also lead to the need for surgical intervention, such as a corneal transplant.
How Incomplete Closure Damages Corneal Health Over Time
Tear Film Instability and Dryness
The tear film consists of three layers: oil, water, and mucus which work together to protect and nourish the cornea. When we blink, this ‘tear mixture’ is evenly spread over the cornea and incomplete eyelid closure disrupts this system. When tears evaporate faster than they can be replaced, the corneal surface becomes dehydrated. This dryness can damage corneal cells and impair healing.
Corneal Surface Injury (Corneal Abrasions)
An exposed cornea is more susceptible to scratches from minor irritants like dust, debris, or even eyelid friction due to excessive dryness. These scratches on the surface of the cornea, known as corneal abrasions, can cause sharp pain in the eyes, increased tearing, blurred vision and light sensitivity. While minor abrasions can heal, repeated injury increases the risk of complications such as corneal ulcers, scarring, and infections.
Corneal Ulcers and Infection
When the corneal surface becomes compromised, bacteria can invade the dry damaged tissue, causing corneal ulcers. Corneal ulcers are serious and can result in severe pain, vision loss, permanent scarring and increased risk of corneal perforation in extreme cases. As the cornea has no blood vessels, infections can be difficult to treat once established.
Corneal Scarring and Vision Loss
Chronic exposure and repeated injury can lead to corneal scarring. Scar tissue disrupts the cornea’s transparency, reducing visual clarity. If scarring occurs in the central visual axis, it can permanently impair vision.
Why Symptoms Worsen at Night
Incomplete eyelid closure during sleep can worsen corneal damage. This is because at night tear production decreases as the eye remains partially exposed for hours. Blinking also ceases, eliminating uniform tear distribution. Henc,e patients may wake up with dry, painful eyes, blurred vision and increased redness. These symptoms can significantly affect daily comfort and quality of life.
How Doctors Evaluate Eyelid Closure and Corneal Health
Early detection allows intervention before serious complications develop. Eye specialists perform several tests to assess risk. Some of these are:
- Eyelid closure assessment: doctors observe whether the eyelids close completely during blinking and gently during forced closure.
- Corneal staining: doctors sometimes use special dyes that highlights areas of dryness or damage to the cornea.
- Tear film evaluation: tests measure tear production and stability.
- Measurement of proptosis: devices called exophthalmometers measure the degree of forward eye displacement.
Treatment Options to Protect the Cornea
Management focuses on non-surgical options for restoring lubrication and protection and surgical interventions for decompressing the orbital tissues to reduce eyelid bulging. Non-surgical treatment options are artificial tears during the day, lubricating ointments at night, moisture goggles during sleep, using a humidifier at night, eyelid taping to promote closure and anti-inflammatory treatments for thyroid eye disease. These measures help protect the cornea while the underlying inflammation is treated.
Surgery is necessary when proptosis is severe and corneal exposure persists despite medical therapy and vision is threatened. Some common procedures are orbital decompression surgery (reduces forward eye displacement), eyelid repositioning surgery and temporary or permanent eyelid closure procedures. These interventions restore protection and reduce long-term risk.
Why Early Intervention is Crucial
Corneal damage from exposure is often preventable but only if recognized early. Prompt treatment can prevent corneal injury, preserve vision, improve comfort and reduce the need for more invasive procedures. Ignoring symptoms only increases the risk of permanent damage and early assessment allows effective intervention before complications develop.
Protect Your Vision and Schedule Your Appointment Today
Bulging eyes is more than a cosmetic issue as it can disrupt eyelid closure and expose the cornea to ongoing damage. Without proper protection, the cornea can become dry, scratched, infected, or scarred, potentially leading to vision loss.
If you have TED or notice signs of proptosis, do schedule an appointment with Dr. Raymond Douglas without delay as regular monitoring by an eye specialist is essential to prevent complications and maintain long-term eye health.
References
- Shah, S. S. & Patel, B. C. in StatPearls   (2025).
- Topilow, N. J., Tran, A. Q., Koo, E. B. & Alabiad, C. R. Etiologies of Proptosis: A review. Intern Med Rev (Wash D C) 6 (2020). https://doi.org/10.18103/imr.v6i3.852
- Butt, S. & Patel, B. C. in StatPearls   (2025).
- Wiersinga, W. M., Eckstein, A. K. & Zarkovic, M. Thyroid eye disease (Graves’ orbitopathy): clinical presentation, epidemiology, pathogenesis, and management. Lancet Diabetes Endocrinol 13, 600-614 (2025). https://doi.org/10.1016/S2213-8587(25)00066-X
- Johnson, B. T., Jameyfield, E. & Aakalu, V. K. Optic neuropathy and diplopia from thyroid eye disease: update on pathophysiology and treatment. Curr Opin Neurol 34, 116-121 (2021). https://doi.org/10.1097/WCO.00000000000008946 Mathenge, W. Emergency management: exposure keratopathy. Community Eye Health31, 69 (2018).
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