The cornea is the clear, front part of the eye that transmits light into the inside of the eye, allowing us to see clearly. The cornea1 is made up of five layers - the outer epithelium (or skin), Bowman's membrane, Descemet's membrane, the stroma (or middle area) and the endothelium ( a very delicate, single-celled inner lining). The endothelium keeps the water inside the eyeball from moving into the other layers of the cornea. The cells of the endothelium pump water from the cornea into the eye.
When the endothelium is not properly working, the water leaves the eye and flows into the cornea, this causes swelling. When the cornea swells, it causes blurred vision and clouding of the cornea.
The more corneal swelling (also called edema) that occurs, the more vision is blurred. The epithelium eventually takes on water, which causes pain and severe vision impairment. Vision is reduced because epithelial swelling changes the normal curve of the cornea causing a haze to develop. Additionally, epithelial swelling can cause small "blisters" to form on the cornea and when the "blisters" break it can cause extreme pain.
Most individuals are born with about 4,000 endothelial cells per square millimeter of the endothelial surface. As you age, endothelial cells are last gradually. They do not divide and can't be replaced or reproduced. It is possible to count the number of endothelial cells in your eye using special photographic methods.
Because endothelial cells do not grow back, the remaining cells spread out and attempt to cover the empty spaces by pumping water from a larger area. Because of this, the pump system loses efficiency and can cause corneal clouding, swelling, and reduced vision. Most people have enough endothelial cells that corneal swelling, or edema, does not occur.
As little as 500 endothelial cells per square millimeter can maintain a clear cornea if the cells are healthy and function properly. If the cells are unhealthy, corneal swelling or edema can result with fewer than 1000 cells per square millimeter.
The cornea is the clear, outer part of the eye. The term corneal abrasion refers to a scratch in the skin (epithelium) on the outer layer of the cornea. Cornea abrasions typically heal quickly, sometimes within a few hours with deeper or larger abrasions taking up to a week. Corneal abrasions can be painful because there are quite a few nerve endings located within the cornea.
Your eye doctor can identify corneal abrasions by examining your eyes with magnifying instruments; they will also check your eye and eyelid to make sure there are no foreign materials present. Fluorescein dye may be used to help find corneal abrasions. After locating the abrasion, the doctor may perform attest called the Seidel test. During a Seidel test, the wound is painted with dye and observed for any leakage that may indicate deeper injuries.
To relieve the pain of a corneal abrasion, the doctor may give you topical anesthesia. Often, the doctor will place a tight patch over the eye, which should allow a small abrasion to heal overnight, it may take little longer for large abrasions and the doctor may decide to prescribe an antibiotic to prevent infection. The most important thing to remember is not to rub your eye, especially during the healing process.
The cornea is the clear, front part of the eye that transmits light into the inside of the eye, allowing us to see clearly. Corneal disease is fairly serious and can cause visual distortion, clouding and eventually lead to blindness. There are several types of corneal disease, with the three most common being: keratoconus, Fuchs' endothelial dystrophy and bullous keratopathy.
Keratoconus: is the thinning and weakening of the cornea, which develops a cone-shaped deformity. Keratoconus3 can progress rapidly, gradually or become intermittent. It usually occurs in both eyes but has been known to occur in only one.
Fuchs' endothelial dystrophy: is hereditary that occurs when the inner cell layer of the cornea, called the endothelium, becomes abnormal. The endothelium pumps fluids out of the cornea, keeping the cornea thin and clear. If the endothelium becomes unhealthy fluids are not pumped out and the cornea swells, causing vision to decrease and become cloudy.
Bullous keratopathy: is when the cornea is permanently swollen because the endothelium (inner layer of the cornea) is damaged and is not pumping fluids out of the cornea.
The doctor will check for corneal disease and trauma by using a special slit lamp instrument as well as advanced diagnostic technology, such as corneal topography. Using corneal topography the doctor can detect corneal scars, the early signs of cataracts and many other problems associated with the front portions of the eye. The doctor will then dilate your eyes and examine your retina for early signs of disease.
Corneal disease, just like any serious eye infection, should be treated immediately. A corneal transplant is almost always the necessary treatment for restoring vision to the cornea after it becomes cloudy. However, there are other steps that can be taken to prolong vision, if the disease is treated in the early stages.
The cornea is the very thin, transparent membrane that covers the front portion of your eye. It protects the interior of the eye. A corneal ulcer develops if there is a break in the epithelium (or outer layer) of the cornea and the underlying stroma is damaged. Typically, the ulcer is caused when microorganisms enter the stroma through the tear in the epithelium.
Usually, corneal ulcers heal well if they are caught early and treated aggressively. If they are neglected, clouding or a hole in the cornea may develop, which will result in a serious loss of vision and maybe the loss of the eye. A corneal ulcer is a very serious condition that requires immediate medical attention.
Corneal ulcers are vision threatening and should be taken very seriously, they require immediate medical attention. If corneal ulcers are not treated, they may break through the cornea and allow the infection to enter the eyeball. This can cause permanent vision loss and possible eye loss. Your doctor can examine your eyes with special instruments and perform a culture study to determine if you have a corneal ulcer or infection. They will also check your eye and eyelid to make sure there are no foreign materials present. Fluorescein dye may be used to help find corneal defects. After locating the abrasion, the doctor may perform a test called the Seidel test. During a Seidel test, the wound is painted with dye and observed for any leakage that may indicate deeper injuries.
Corneal ulcers can be cured in two or three weeks if treatment begins early. Typically, patients are given antibiotic eye drops to treat corneal ulcers. Topical steroids may be prescribed to reduce the risk of scarring and inflammation.
Fuchs' dystrophy is inherited and affects the endothelium layer (thin, inner layer) of the cornea. Individuals with Fuchs' dystrophy have endothelial cells that do not function as efficiently as normal cells, as well as age and deteriorate more rapidly than normal cells.
Fuchs' dystrophy is a little more common in women than in men and it affects both eyes. Typically one-half of the family members of an affected person will carry or be diagnosed with Fuchs' dystrophy. While the exact cause is unknown, heredity, hormonal and inflammatory factors are thought to play a role.
Individuals experiencing the early stages of Fuchs' dystrophy may have blurred vision first thing in the morning, which gradually gets better as the day goes on. This is because water continuously evaporates from the eye's surface during the day and it is replaced with water from the inner portions of the eye. While our eyes are closed for sleeping, water doesn't evaporate off the surface of our eyes. Instead, it gathers on the cornea and causes slight swelling – which is the cause of the blurred vision. As our eyes stay open during the day, the water evaporates allowing the vision to clear. As the Fuchs' dystrophy worsens, evaporation isn't enough to remove the excess water and vision remains blurred all day.
Often doctors notice the early signs of Fuchs' dystrophy in people in their 30s and 40s, however, it doesn't typically affect vision until individuals are in their 50s or 60s. Doctors use a slit lamp microscope to diagnose Fuchs' dystrophy; the microscope enables them to examine the cornea and magnifies the endothelial cells thousands of times. The doctors then measure the health of the endothelium with an instrument called a pachymetry, which measures the thickness of the cornea, they will also utilize specular microscopy, which photographs the cells for counting. As Fuchs' dystrophy worsens it may become impossible to count the cells because of corneal clouding.
Cataracts often develop as people grow older and the lens of their eye becomes cloudy. Cataract surgery is a very common and very successful surgery. However, any eye surgery causes damage to the endothelial cell layer, which means a reduction in the number of cells that are able to pump water from the cornea. If, after cataract surgery, there are not enough endothelial cells remaining, corneal swelling will occur and vision will be reduced. This may make a corneal transplant necessary in order to restore vision. If a patient with Fuchs' dystrophy develops a cataract, it is important to consider how much endothelium remains and whether the cornea will be able to function after cataract surgery. The doctor may recommend combining cataract surgery with a corneal transplant; this combination can achieve what would have required two surgeries with longer post-operative recovery time.
1 Cornea. Available: https://www.aao.org/eye-health/anatomy/cornea-103
2 Corneal Conditions. Available: https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/corneal-conditions
3 What Is Keratoconus? Available: https://www.webmd.com/eye-health/eye-health-keratoconus
Written by Dr. Shah