Corneal Disorders
Diagnosis and treatment of conditions affecting the clear front surface of the eye
What is corneal disorders?
The cornea is the clear dome at the very front of the eye. It does about two-thirds of the focusing work, and it does it only because it is perfectly transparent and regularly curved. Transparency depends on collagen fibres laid down in a precise lattice and on a single layer of pump cells on the inner surface that keeps water out of the tissue.
Things go wrong with that arrangement in a few recognisable ways. Infection and injury damage the surface and heal with scar that scatters light. Inherited dystrophies lay down deposits in one layer or another over decades. The pump cells can fail with age or after surgery, and the cornea swells and clouds. The tissue can thin and bulge into a cone, which distorts vision progressively and typically starts in the teenage years and is made worse by eye rubbing.
The cornea has no blood vessels, which is what keeps it clear and also what makes it slow to heal and quick to scar. In India, injury from crop material during farm work and infection related to contact lens wear are the two largest avoidable causes of corneal blindness, and both are much more treatable in the first two days than in the second week.
What you might notice
- Blurry or dim vision
- An eye that waters constantly
- Eye pain with haloes around lights
How it is diagnosed
The examination is at the slit lamp, where a narrow beam of light cuts an optical section through the cornea and lets your doctor see which layer the problem is in. Layer is the whole question: a surface problem, a mid-thickness problem and a pump-layer problem look similar to you and are treated completely differently.
Orange dye is used to stain any break in the surface, and its shape matters. A branching pattern points at one cause, a round ulcer with a white base at another, and the difference changes the treatment on the same day.
A topography scan maps the curvature and thickness of the cornea point by point and picks up thinning and early coning long before it affects the reading on a vision chart. Where the pump layer is in question, a specular microscope counts the cells per square millimetre. In a suspected infection, a scraping is taken from the base of the ulcer under numbing drops before any treatment is started, because treatment started first makes the organism much harder to identify.
Recovery
An abrasion on the surface heals in one to three days and is genuinely painful for the first of them. Keep any pad or lens on as instructed and do not drive while one eye is covered.
An infected ulcer is intensive work. Drops are often hourly day and night for the first two or three days, then tapered over several weeks, and you will be reviewed daily at the start so the doctor can see whether the ulcer is shrinking. Expect two to four weeks away from work and no contact lens wear for months afterwards.
A graft is the longest commitment in eye surgery. Useful vision returns over three to twelve months depending on the technique, sutures may stay in for a year or more and are removed a few at a time, and anti-rejection drops continue for at least a year. Sudden redness, pain, light sensitivity or a drop in vision in a grafted eye means rejection until proved otherwise and needs seeing that day.
If it is left untreated
An untreated corneal infection is one of the fastest ways to lose an eye. An ulcer deepens over days, can perforate the cornea, and can spread into the inside of the eye, at which point sight is usually not recoverable. The window in which drops alone will fix it is measured in days.
Less dramatic problems cost sight more slowly. Scar sitting over the pupil scatters light permanently and cannot be polished away. Progressive thinning and coning that is caught early can often be stabilised, and once the cornea has distorted badly the only remaining option is replacing the tissue. Long-standing swelling from a failed pump layer blisters the surface and becomes painful as well as blurred.
Rules worth keeping. A red painful eye in a contact lens wearer is an emergency until an eye doctor says otherwise, and the lens comes out and stays out. Any injury from plant material, a fingernail or a metal fragment is seen the same day. Steroid drops are never used on a red eye without a doctor having examined it, since they turn a treatable infection into a sight-threatening one.
Questions about corneal disorders
I sometimes sleep in my contact lenses. Does it really matter?
Yes. Sleeping in lenses raises the risk of a corneal infection several times over, because a closed lid deprives the cornea of oxygen and traps organisms against a surface that has no blood supply to defend it. An infection in the cornea can deepen over two or three days and leave a scar across the pupil that permanently blurs vision. The rules that prevent almost all of this are simple: take lenses out at night unless they are specifically licensed for overnight wear, never rinse or store them in tap water, replace the case every three months, and take the lens out and see an eye doctor the same day if the eye becomes red or painful.
Will a corneal scar clear on its own?
Partly, and slowly. A superficial scar can fade over six to twelve months as the surface layers remodel, and vision often improves alongside it. A scar that involves the deeper layers is permanent, because the cornea has no blood vessels and repairs with disorganised collagen that scatters light. Whether it affects your vision depends more on position than on size, so a small scar over the pupil can matter more than a large one to the side. Where an irregular surface is the problem, a rigid contact lens frequently restores good vision without surgery, and that is usually tried before replacing any tissue is discussed.
How urgent is a red, painful eye?
Urgent enough to be seen the same day, particularly if you wear contact lenses, have had an injury, or the eye is sensitive to light and the vision has dropped. The reason is timing: a corneal ulcer treated in the first two days usually heals with little or no scar, and the same ulcer two weeks later can have deepened, perforated or spread inside the eye. Take contact lenses out and leave them out, and take the case and solution with you. Do not use anyone else's steroid drops on a red eye, since steroids allow an infection to grow rapidly and turn a treatable problem into a sight-threatening one.
Other ophthalmology treatments
Removal of a cloudy natural lens and replacement with an artificial lens to improve vision
Day CareLaser vision correction that reshapes the cornea to reduce dependence on glasses or contact lenses
Day CareTalk to a care coordinator about corneal disorders
Leave a number and a care coordinator calls you back with what the treatment involves and which hospital it would be at. They book a consult only if you want one