What is Corneal Mucous Plaque?
The top layer of the cornea, which includes Bowman’s membrane, the epithelium, and a protective layer of tears, can be affected by various environmental factors. These can include things like infections, systemic illnesses, different substances from the tear film such as iron, calcium, mucus, and antibodies, as well as abnormal growth of cells.
These factors can cause damage to the cornea, leading to conditions that cause ulceration, as well as conditions that do not cause ulceration. Non-ulcerative conditions can form unique patterns. The key patterns to look out for are plaque, dendriform, vortex, linear, and punctate keratopathy. While these patterns are distinct, they are not exclusive to one disease. Thus, a single disease can cause various patterns, and various diseases can cause a single pattern.
Corneal mucous plaques are a clump of mucus, epithelial cells (which are cells from the surface of the cornea), fats, and proteins that stick firmly to the cornea. These plaques can vary in transparency, they can be either clear or opaque. They can also vary in number and size, ranging from small single plaques to large groups that can cover more than half of the cornea’s surface.
What Causes Corneal Mucous Plaque?
Changes to the surface of the cornea (the clear front surface of the eye) or the composition of tears can lead to the formation of mucus plaques.
Mucus plaques are commonly caused by:
- Tear deficiency, like in a condition known as keratoconjunctivitis sicca.
- Systemic diseases that affect the eyes, such as Sjogren syndrome and rheumatoid arthritis.
- An eye infection called Herpes zoster keratitis.
- Conditions that affect the eye’s surface like superficial limbic keratoconjunctivitis and vernal keratoconjunctivitis.
- After undergoing corneal surgeries, for example, laser-assisted in situ keratomileusis (LASIK) and penetrating keratoplasty (PK).
- Wearing contact lenses for too long.
- A condition called Staphylococcal blepharitis, which is an inflammation of the eyelid.
Risk Factors and Frequency for Corneal Mucous Plaque
Corneal mucous plaques are most often found in people suffering from a condition known as keratoconjunctivitis sicca. This condition, when it’s associated with Sjogren syndrome, is more frequently seen in women than in men. As people age, the likelihood of developing corneal mucous plaques increases; it’s especially common among older adults.
Signs and Symptoms of Corneal Mucous Plaque
People with conditions associated with sicca (dryness) often have a history of dry mouth, dry skin, joint pains, and there may even be a family history of connective tissue disorders. However, if the dryness is due to a condition like herpes zoster keratitis, the individual may have a history of skin problems. Other conditions linked to dryness may have a history of allergy, contact lens wear, or past eye surgery.
The symptoms often start showing before any visible sign of damage on the eye, like plaque formation. In cases of dryness associated with plaque, the person will start feeling a sensation of dryness and the feeling of a foreign body in the eye long before any plaque forms.
Here are some of the most common symptoms:
- Feeling of foreign body in the eye
- Blurred vision
- Dryness in the eyes
- Pain in the eyes
- Thick, sticky eye discharge
- Sensitivity to light and spasms that close the eyelids
During an examination with a slit-lamp, symptoms like eyelid inflammation, conjunctivitis, or eye redness may be revealed. The cornea (front part of the eye) may show signs of thin, thread-like material (filament) stuck to the surface of the eye, epithelial irregularities, corneal scars, decreased corneal sensation, or swelling. In some cases associated with herpes zoster keratitis, a mild iris inflammation can be seen.
The plaques vary in size and shape according to the underlying cause. They could be small and round in dry eye states or large and weirdly shaped in herpes zoster keratitis. These plaques are semi-transparent to opaque, whitish-grey with a dry surface, and usually present in the middle section of the eye horizontally. They are firmly stuck to the surface of the eye and leave a raw surface when removed.
Testing for Corneal Mucous Plaque
Investigations for eye conditions can include both simple tests done in the doctor’s office and more detailed laboratory tests.
Office-based tests may include the Schirmer’s test, which checks for dry eyes due to a condition known as keratoconjunctivitis sicca. Low Schirmer’s test values are a sign of this condition.
Doctors can also use different types of stains to help them see more details in the eye:
– Fluorescein stain can highlight dead cells and defects on the surface of the eye
– Rose Bengal and Lissamine green stains can make plaque in the eye stand out
– Alcian blue and eosin stains give a mild color to the plaque, allowing it to be seen more easily
In cases where dry eyes are related to a condition known as Sjogren syndrome, blood tests might be necessary. Although testing a small piece of the salivary gland is the clearest way to diagnose Sjogren syndrome, there’s a gentler way to do it too. Doctors can check your blood for certain markers (like ANA, SS-A/Ro, SS-B/La, and rheumatoid factor) that suggest the presence of this condition.
If a person has plaque in the eye that didn’t appear right away or pseudodendrites (a specific type of change to the eye), a test may be done to check for the DNA of the herpes zoster virus. This is done with a process called a polymerase chain reaction.
Treatment Options for Corneal Mucous Plaque
Acetylcysteine, a type of mucolytic agent used to break down mucus, can be applied topically 1-4 times a day at a 10-20% concentration to dissolve mucus and loosen plaque found in the eye. However, it’s worth noting that the plaques may reappear once the usage of these drops is stopped. Acetylcysteine is an amino acid derivative, which lessens the thickness of mucus in a variety of disorders. It does this by reducing the action of the free sulphydryl group in the disulfide bonds of the mucus proteins, lowering the viscosity.
Artificial tear substitutes, preferably those with lower osmotic pressure (hypotonic), are often recommended to be used together with these mucolytic drops, especially for those suffering from dry eyes. Substitutes without preservatives are often preferred as certain preservatives, like benzalkonium chloride, can damage the epithelium and can make the condition worse.
Topical cyclosporine A and mild corticosteroids like fluorometholone and loteprednol etabonate can be used when there’s inflammation such as in keratoconjunctivitis sicca, a condition otherwise referred to as ‘dry eye’ disease.
Those with Staphylococcal blepharitis, a type of eyelid inflammation frequently paired with mucus plaques in the eyes, should be treated with warm compresses, lid hygiene, and antibiotic ointment. Plaques linked to herpes zoster keratitis can be treated with antiviral therapy.
For plaques causing severe discomfort, they can be physically removed by debridement, which involves scraping or using a cotton bud. After this process, a soft bandage contact lens can be applied to the eye.
In cases where there are larger plaques, especially those linked with vernal keratoconjunctivitis (a chronic inflammatory disease of the eye), Excimer laser phototherapeutic keratectomy (PTK) could be helpful. PTK uses a specific type of laser and relies on the principle of ‘photoablation’, this is, breaking the bonds between molecules with light. The use of the laser is highly targeted, affecting around 0.25 microns of the corneal surface with each pulse, leaving the underlying tissue untouched.
What else can Corneal Mucous Plaque be?
Corneal mucous plaques, a type of eye condition, can sometimes be hard to distinguish from other similar surface disorders. These may include:
- Epithelial dysplasia (an abnormal growth or development of tissue on the surface of the eye)
- Corneal keloid (an excessive growth of scar tissue on the eye)
- Ocular surface squamous neoplasia (a type of eye cancer)
- Band shaped keratopathy (a type of eye disorder where calcium builds up on the cornea)
- Spheroidal degeneration (a condition where small, round protein masses form on the surface of the eye)
- Salzmann nodular degeneration (a condition where small lumps form on the cornea)
Making the correct diagnosis can be challenging and requires careful examination from a medical professional.
What to expect with Corneal Mucous Plaque
Corneal plaques, which are patches on the surface of the eye, can last anywhere from a few days to several weeks. If the underlying medical condition causing the plaques is not managed, they may reappear at any time. The outlook for most patients with corneal plaques is cautious.
People experiencing a serious form of this condition often face a decline in their quality of life. Dry eyes, commonly associated with corneal plaques, can cause considerable discomfort and health issues. As a person ages, these symptoms often become more severe.
Possible Complications When Diagnosed with Corneal Mucous Plaque
The complications of something called corneal mucous plaque, which is a condition of the eye, generally happen because of other underlying conditions. If the plaque is connected to a severe dry eye condition known as keratoconjunctivitis sicca, it can lead to a number of issues. These range from scarring of the clear front surface of the eye (the cornea) as well as the tissue lining the inside of the eyelids and the white of the eye, to the growth of new blood vessels in the cornea, and in rare cases, even tearing of the cornea.
When there is prolonged inflammation tied with this dry eye condition, it could also lead to a binding together of the eyelid and eyeball. When the plaque is a result of another eye condition known as herpes zoster keratitis, it can result in the same set of corneal issues, along with the development of sores on the cornea. If the plaque is seen in very young patients with a specific type of eye allergy known as vernal keratoconjunctivitis and it goes untreated, it might eventually lead to visual impairment due to the brain’s inability to recognize images received from that eye.
Key Complications:
- Scarring of the cornea and conjunctiva
- Growth of new blood vessels in the cornea
- Tearing of the cornea in rare cases
- Binding together of the eyelid and eyeball due to prolonged inflammation
- Sores on the cornea
- Visual impairment in young patients if left untreated
Preventing Corneal Mucous Plaque
Patients should be guided on the fact that it might take some time before their symptoms start to improve. Emphasizing the importance of strictly following the treatment plan is necessary. Patients should also be informed about the possibility of their condition returning and the potential need for additional treatments. This ensures they are not expecting immediate or complete disappearance of their disease.
If the eye issues are associated with a broader health concern, it is crucial to make the patient understand the need for regular follow-up visits with all their healthcare providers.