What is a corneal disease?
The term “corneal disease” encompasses a variety of conditions that affect the cornea, the transparent outer layer of the eye. The cornea can often be repaired after injury or illness, but more serious conditions (infections, degenerative diseases, deterioration) require treatment.
The cornea helps the eye to focus light so that it can see clearly. Its transparency allows light to enter the eye, through the pupil, the lens, and the retina at the back of the eye. The three main corneal layers are the outer layer of the cornea or epithelial layer, the intermediate layer is called the stroma, and lastly, the single layer of cells is called the endothelium.
The curvature of the cornea plays an important role in the concentration of light (refraction or bending). The normal cornea is smooth, clear, and hard. Helps protect the eye from infections and foreign material.
What is the function of corneal disease?
The cornea plays several important roles in eye protection and vision.
- It helps focus light entering the eye and is responsible for up to 75 percent of the eye’s focusing power. Light passes through the cornea and lens and is then centered on the retina. The back of the eye receives and processes light, sending messages to the optic nerves in the brain. Your brain translates these messages into images that you see with your eyes.
- It acts as a barrier against germs, dirt, and foreign particles that can damage the eye.
- It acts as a filter to test the ultraviolet rays coming from the sun.
Symptoms of corneal disease
Symptoms vary from one disease to another, but may include:
- Irritation and redness
- Sensitivity to light
- Blurred vision
- Watery eyes
Types of corneal disease
There are several common diseases that harm the cornea.
Injuries: Minor abrasions (scratches) on the cornea usually heal on their own. Deep scratches or other injuries can cause corneal scarring and vision problems.
Allergies: An allergy to pollen can irritate the eyes and cause allergic conjunctivitis (pinkeye). It makes your eyes red, itchy, and watery.
Keratitis Inflammation: Keratitis inflammation of the cornea caused by a small wound or bacteria, viruses, fungi, or parasites. Neurotrophic keratitis is a rare degenerative disease caused by loss of sensation in the cornea. It causes progressive damage to the upper part of the cornea, including corneal thinning, ulceration, and, in severe cases, perforation.
Dry Eye: Dry eye occurs when you don’t shed enough tears to keep your eyes moist. It can be uncomfortable and cause vision problems.
Corneal dystrophy: Corneal dystrophies affect dark vision when material builds up on the cornea. These diseases are usually hereditary.
Corneal damage: Corneal damage can also be caused by other common eye conditions, such as tear film abnormalities (dry eye), eyelid disorders, glaucoma, and glaucoma-associated iridocorneal endothelial syndrome (ICE).
Causes of corneal disease
- Infection: Bacterial, fungal, and viral diseases are regular causes of corneal damage
- Keratoconus: The cause of keratoconus in most patients is hidden
- Age: Aging methods can change the clarity and health of the cornea
- Cataract and intraocular lens implant surgery: Bullous keratopathy happens in a very small percentage of patients creating these procedures.
- Contact lenses
- Eye trauma
- Some eye conditions, such as retinitis pigmentosa, retinopathy of prematurity, and vernal keratoconjunctivitis.
- Systemic conditions, such as Leber’s congenital amaurosis, Ehlers-Danlos syndrome, Down syndrome, and osteogenesis imperfecta.
Risk factors of corneal disease
Some corneal conditions, such as corneal dystrophy, are inherited. But there are steps you can take to reduce your risk of corneal injury and infection.
To prevent corneal injury, wear protective glasses when you have:
- Play sports that use a ball or puck, such as baseball or hockey.
- Work in the garden, like mowing the lawn or using a weed walker
- Make repairs like painting or hammering
- Use machines such as sanders or drills
- Use chemicals like bleach or pesticides.
If you wear contact lenses, always follow the instructions for cleaning, disinfecting, and storing your lenses. Helps prevent corneal infections such as keratitis.
Diagnosis of corneal disease
Beyond a careful visual examination of your eyes and eyelids and a review of your medical history, we will examine your cornea under a slit lamp microscope. The slit lamp allows you to examine the anterior and posterior segments of the eye, including the eyelid, sclera, conjunctiva, iris, natural lens, and cornea.
Additional tests may include:
- Topography and keratometry to study the corneal shape
- Pachymetry to measure the thickness of the cornea
- Microscopy to assess endothelial cell health and detect infections.
- Tear film evaluation
Treatment for corneal disease
Corneal disease can vary greatly depending on the specific condition or injury. Treatment may include:
- Eye drops: Artificial tear solutions or eye drops supplement the eye’s natural tears to lubricate the cornea and reduce dryness and inflammation.
- Prescription drugs: Some antiviral or antibiotic drugs can help treat corneal infections. These medications come in the form of eye drops or ointments that are applied topically to the eye.
- Eyeglasses or contact lenses: Prescription eyeglasses or contact lenses correct blurred vision caused by corneal astigmatism due to scarring, but do not treat the root cause. Gas permeable visual contact lenses can be used to correct impaired vision from a specific type of dystrophy called keratoconus. These lenses mask the unusual shape of the cornea and act as a new refractive cover for the eye.
- Corneal transplant: During a corneal transplant, the damaged part of the cornea is replaced with healthy human tissue from the donor. Currently, surgeons make lamellar keratoplasty (“incomplete thickness transplantation”) whenever feasible, excluding only diseased tissue and leaving healthy corneal tissue. This procedure leaves the cornea structurally more intact and is associated with fewer problems and better vision improvement. Corneal transplantation is an alternative for some patients with keratoconus, severe corneal scarring, some corneal dystrophy, edema after cataract surgery, and any failure of the cornea after eye surgery.
Prevention of corneal disease
The risk of infectious corneal disease caused by bacteria and viruses can be reduced by protecting the eye from injury and by restricting physical contact with people with contagious forms of conjunctivitis.
- Avoid sharing eye makeup, contact solution, lens cases, and eye drops with infected people.
- Wash your hands thoroughly with soap and warm water for at least 15 seconds after contact with an infected person.