Corneal Dystrophy
Corneal dystrophy is a group of rare genetic eye diseases that affect the clear front part of your eye. While some people live without symptoms, others may experience blurred vision, eye pain, or sensitivity to light. There are more than 20 different types, each affecting different layers of the cornea.
Table of contents
- What is corneal dystrophy?
- Types of corneal dystrophy
- Symptoms
- Causes and inheritance
- Diagnosis
- Treatment options
- Living with corneal dystrophy
What is corneal dystrophy?
Corneal dystrophy is an umbrella term for over 20 different diseases that affect the cornea, which is the clear, dome-shaped front part of your eye[1]. The cornea has two important jobs: it protects the rest of the eye from dust, germs, and other harmful materials, and it acts as the eye’s outermost lens, bending incoming light so you can see clearly[5].
The cornea is made up of five distinct layers. From the outermost to innermost, these are: the epithelium (the protective outer layer), Bowman’s membrane (a tough protective layer), the stroma (the thickest layer that gives the cornea its strength and clarity), Descemet’s layer (a thin protective barrier), and the endothelium (the innermost layer of specialized cells that pump excess water out of the cornea)[5].
- Cornea
- Eye
Corneal dystrophies are genetic conditions, meaning they happen because of changes in your DNA[1]. You are born with these conditions, and they are lifelong[1]. These diseases cause abnormal material to build up in one or more layers of the cornea, which can make the cornea lose its transparency and become cloudy[3].
Think of your cornea like clear, flawless glass. When corneal dystrophy develops, it’s like looking through glass that has flaws or cloudiness in it, making it harder to see through[1].
Types of corneal dystrophy
Corneal dystrophies are grouped based on which layer or layers of the cornea they affect[1]. The main categories are epithelial and subepithelial dystrophies, epithelial-stromal dystrophies, stromal dystrophies, and endothelial dystrophies.
Epithelial and subepithelial corneal dystrophies
These dystrophies affect the outer layers of the cornea. They include epithelial basement membrane dystrophy, epithelial recurrent erosion dystrophies, gelatinous drop-like dystrophy, Lisch epithelial dystrophy, Meesmann dystrophy, and subepithelial mucinous dystrophy[1].
Most of these develop during early childhood, but epithelial basement membrane dystrophy (also called map-dot-fingerprint dystrophy) usually appears in adulthood, most commonly in people ages 40 to 70[2][1].
Epithelial-stromal dystrophies
These dystrophies include granular corneal dystrophy (types 1 and 2), lattice corneal dystrophy, Reis-Bückler’s dystrophy, and Thiel-Behnke dystrophy[1]. These conditions most likely develop during childhood, though lattice corneal dystrophy type 1 can appear as late as age 20[1].
Lattice dystrophy gets its name from the lattice or grid pattern that forms when abnormal protein deposits build up on the cornea[4][2].
Stromal dystrophies
The stromal dystrophies affect the middle and thickest layer of the cornea. They include macular dystrophy, Schnyder crystalline dystrophy, congenital hereditary stromal dystrophy, fleck dystrophy, posterior amorphous dystrophy, pre-Descemet dystrophy, and central cloudy dystrophy of François[1].
Most stromal dystrophies affect people during childhood. However, Schnyder corneal dystrophy can develop as late as age 30, and pre-Descemet corneal dystrophy usually develops after age 30[1].
Endothelial corneal dystrophies
These dystrophies affect the innermost layers of the cornea. They include Fuchs endothelial dystrophy, posterior polymorphous dystrophy, congenital hereditary endothelial dystrophy, and X-linked endothelial dystrophy[1].
Of all the corneal dystrophies, Fuchs endothelial corneal dystrophy is the most common. It accounts for about 39% of all corneal transplants in the United States[1]. It is also the most common corneal dystrophy overall in the United States, affecting 1 in 2,000 Americans[2].
Keratoconus
Keratoconus is usually diagnosed in teenagers and young adults. It causes the middle and lower parts of the cornea to get thinner over time. While a normal cornea has a rounded shape, a cornea with keratoconus can bulge outward and become cone-shaped. This different shape can cause vision problems[2].
Fuchs’ dystrophy
Most people with Fuchs’ dystrophy start to have symptoms around age 50 to 60[2]. This disease makes a type of cornea cell called endothelial cells stop working. When these cells stop working, the cornea swells and gets thicker, which can cause vision problems[2].
Fuchs’ dystrophy affects the corneal endothelium, which is a single layer of specialized cells. Normal people are born with about 4,000 endothelial cells per square millimeter. These cells work like water pumps to remove excess fluid from the cornea. In people with Fuchs’, these cells die off faster and at a younger age than normal, and abnormal cobblestone-like bumps called guttata form among the cells[13].
Symptoms
The symptoms of corneal dystrophy depend on which specific type you have. Some people never have any symptoms at all[1][3]. When symptoms do develop, they usually affect both eyes and get progressively worse over time[1].
The abnormal formations or buildups in the cornea can make it harder to see through the affected layers. This makes symptoms like blurred vision or clouded vision common in people with corneal dystrophy[1].
Common symptoms
The most common symptoms include blurred or cloudy vision, difficulty seeing in bright light or at night, glare and halos around lights, and reduced sharpness of vision[1][4]. Many people also experience light sensitivity[2].
Eye discomfort and pain
A common symptom for many forms of corneal dystrophy is recurrent corneal erosion. This happens when the outermost layer of the cornea doesn’t stick to the eye properly and starts to erode or wear away[2][5].
Recurrent corneal erosion can cause severe discomfort or pain, especially in the morning when you first wake up. Other symptoms include feeling like there’s something in your eye (a gritty sensation), watery eyes, and sensitivity to light[2][5].
Symptoms specific to certain types
Symptoms of keratoconus include itchy eyes, double vision, blurry vision, nearsightedness (when far-away objects look blurry), astigmatism (when things look blurry or distorted), and sensitivity to light. As keratoconus gets worse, it may cause eye pain and more serious vision problems[2].
Symptoms of Fuchs’ dystrophy include blurry vision that’s worse in the morning and gets better later in the day, glare and halos in your vision that make it hard to see things at night or in low light, cloudy corneas, and sensitivity to light. As Fuchs’ dystrophy gets worse, it may cause eye pain and more serious vision problems[2].
Causes and inheritance
Corneal dystrophies are genetic conditions. That means they happen because of DNA changes[1]. Some of those changes are ones you can inherit from your biological parents, while others happen spontaneously[1].
Different corneal dystrophies are caused by mutations in various genes, including CHST6, KRT3, KRT12, PIP5K3, SLC4A11, TACSTD2, TGFBI, and UBIAD1 genes[3]. Mutations in the TGFBI gene cause several forms including granular corneal dystrophy, lattice corneal dystrophy, epithelial basement membrane dystrophy, Reis-Bucklers corneal dystrophy, and Thiel-Behnke dystrophy[3].
How corneal dystrophies are inherited
Most corneal dystrophies are inherited in an autosomal dominant pattern. This means only one copy of the faulty gene (inherited from either parent) is required to cause disease. Each child of a person with an autosomal dominant corneal dystrophy has a 50% chance of inheriting the condition, regardless of gender[3].
Some corneal dystrophies are inherited in an autosomal recessive pattern. In this type of inheritance, two faulty copies of a gene are needed to cause disease[3].
Corneal dystrophies tend to run in families, affect the right and left eyes equally, are not caused by outside factors such as injury or diet, and usually begin in one of the five corneal layers and may later spread to nearby layers[3].
Diagnosis
The only way to know for sure if you have a corneal dystrophy is to get a comprehensive eye examination[2]. Your eye doctor will use a special microscope with a bright light attached, called a slit lamp, to check your eyes for signs of corneal dystrophies[2][5].
During the eye clinic appointment, you may undergo further tests using specialized cameras and microscopes to help better identify the type of corneal dystrophy[5]. The presence of a corneal dystrophy may be found during a routine eye examination[5].
Diagnostic tests
Tests to help diagnose corneal dystrophies may include a cornea examination and grading, where the doctor uses a slit lamp to look for drop-shaped bumps called guttae on the back surface of the cornea[11].
A test called corneal pachymetry may be used to measure the thickness of the cornea[11]. Corneal tomography involves taking a special picture of your cornea to look for swelling[11].
Sometimes a doctor uses a special instrument to record the number, shape, and size of the cells that line the back of the cornea, though this test is not always required[11].
Genetic testing
Genetic testing can be undertaken to help identify the gene responsible for the condition, which allows families to have more informed discussions about inheritance patterns[5]. Some specific corneal dystrophies can be diagnosed with molecular genetic tests even before symptoms develop[5].
Sometimes the doctor may ask to examine first-degree relatives, as identification of other affected family members can help in diagnosing a particular type of corneal dystrophy and understanding how the condition runs in the family[5].
Treatment options
Treatment for corneal dystrophies varies depending on the type and severity of symptoms. Individuals who do not have symptoms or only have mild symptoms may not require treatment and may instead be regularly observed to detect potential progression of the disease[5].
Medications and supportive care
Specific treatments may include eye drops, ointments, specialized contact lenses, laser therapy, and corneal transplant[5]. Lubricating eye drops and artificial tears can help relieve dry eye symptoms and improve comfort[4].
For Fuchs’ dystrophy, salt-based eye drops containing saline (5% sodium chloride) or ointments can help reduce the amount of fluid in your cornea and reduce swelling[2][11][7].
Soft contact lenses can act as a covering to relieve pain and smooth the corneal surface for better vision[11][10]. Some people may benefit from special hard contact lenses that change the shape of the cornea[2].
Treatment for recurrent corneal erosions
Recurrent corneal erosions may be treated with lubricating eye drops, ointments, antibiotics, or specialized bandage soft contact lenses[5]. Special eye patches or contact lenses can stop your eyelid from rubbing against your cornea[2].
If recurrent erosions persist, additional measures such as corneal scraping or the use of excimer laser therapy, which can remove abnormalities from the surface of the cornea (a procedure called phototherapeutic keratectomy), may be used[5].
Surgical treatments
In individuals with severe vision impairment, corneal transplant surgery may be necessary[5]. People who have surgery for advanced corneal dystrophy can have much better vision and remain symptom-free for years[11].
For keratoconus, your doctor may recommend a procedure called corneal cross-linking to strengthen your cornea. If keratoconus causes severe corneal scarring or you have trouble wearing contact lenses, you may need a corneal transplant[2].
Several types of corneal transplant procedures are available. Descemet membrane endothelial keratoplasty (DMEK) is a procedure where the back layer of the cornea is replaced with healthy donor tissue. This is a partial transplant that replaces only the damaged layer without disturbing unaffected parts of the cornea[11][7].
Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) is another partial transplant option[7]. These advanced partial thickness corneal transplant procedures typically result in faster recovery and fewer complications than older full-thickness transplants[7].
In severe cases, a traditional full-thickness corneal transplant called penetrating keratoplasty may be necessary[7]. A surgeon can either replace the inner layer of your cornea or the entire cornea, with healthy corneal tissue transplanted from a donor[10].
Living with corneal dystrophy
Many people have corneal dystrophy without experiencing vision problems or other symptoms. However, when the disease progresses, symptoms can interfere with day-to-day life[12].
Managing daily life
There are many simple and practical ways to make the most of your vision. Simple visual aids like magnifiers can help you better see details. Using independent living skills can help manage day-to-day life at home. Introducing more contrast to your home environment makes finding items easier[12].
Good lighting can help reduce eye strain and improve vision. Use bright, even lighting when reading or doing close work, and avoid bright lights or glare[4]. Wearing sunglasses can help protect your eyes from harmful UV rays and reduce glare and light sensitivity[4].
Regular monitoring and care
Regular eye exams are important for monitoring the progression of corneal dystrophy and identifying any changes in vision. Your eye doctor can help develop a personalized management plan for your specific condition[4].
Try to avoid rubbing or touching your eyes whenever possible, as rubbing the eyes can irritate the cornea and worsen symptoms[4]. If you wear contact lenses, follow proper cleaning and disinfection procedures to reduce the risk of infection or irritation[4].
Following a healthy lifestyle can help improve overall eye health. Eating a balanced diet, getting enough rest, and reducing stress can all help reduce the risk of complications from corneal dystrophy[4].
Work and driving considerations
People with corneal dystrophy can live for many years without symptoms. If you begin having symptoms, your employer should give you time off for appointments and make reasonable adjustments to support you to continue working[12].
You must report any eye condition that affects both eyes to the appropriate driving authority. If your eyesight still meets the eyesight rules for driving, you may be able to carry on driving. Always speak to your eye care professional for advice first[12].
