What is keratoconus?
Keratoconus is a progressive disease of the cornea, generally affecting both eyes. It results in the thinning and deformation of the cornea (the outermost layer of the eye) and ends up causing scarring and refractive instability due to the appearance of an irregular high astigmatism cornea–the cornea reshapes as if it were a cone–seriously affecting the eyesight.
Keratoconus generally appears during adolescence with a quick increase in myopia and astigmatism and gradually reduced vision without glasses. In the initial stages, the only symptoms of keratoconus are increased blurred vision or reduced visual acuity, but no other associated symptoms.
In these cases, keratoconus is usually diagnosed during a general check-up, especially in situations where the patient has had a sudden increase in their myopia or astigmatism. To diagnose it, it is necessary to undertake a study using a corneal topography, a device that shows the microscopic elevations of the cornea, just like a map shows mountains and valleys.
Sometimes, the patient's own local optician detects a significant difference in their prescription and refers them to a specialist for an exhaustive study. Other times, keratoconus is diagnosed when a patient who has it goes to see the optician about refractive surgery so they can stop wearing glasses and the issue is detected by the topography. In these cases, laser corneal refractive surgery is completely contraindicated.
Causes and risk factors
A genetic component and a certain hereditary predisposition play a part in keratoconus. That is why it's important for close relatives to have an eye check-up before an initial diagnosis of keratoconus.
This condition is strongly linked to rubbing the eyes either in a conscious or unconscious manner (for example, sleeping face down with your eye closed on your knuckles).
It is also related to allergies, mainly eye allergies, as the stinging usually leads to the individual rubbing their eyes. That's why it's important to ask patients or their relatives if they rub their eyes and why they do it, start treatment for an eye allergy if there is one, and stop any type of eye rubbing as this will make the disease worse.
The treatment will differ depending on the stage of the disease, the age of the patient and the progression of the disease (or lack thereof).
In the initial stage in which the corneal deformity is minimal or slight, the use of glasses or contact lenses is recommended in order to correct the eyesight.
If progression is detected, especially in a young person with good eyesight, a UV light and vitamin B12 treatment (corneal crosslinking) can be administered. This treatment "hardens" the corrnea, stopping it from becoming more mishaped, impeding its progression and maintaing visual acuity.
At moderate stages wheren the vision is still good with contact lenses despite a high to moderate astigmatism, rings or intrastromal segments can be used. They are small plastic implants that are inserted into the cornea and act like "little ribs" or "pillars" to tighten the cornea and regulate its form, reducing the astigmatism and improving vision.
In advanced cases with a high corneal deformity, the presence of scarring or in cases where the disease is progressing, a cornea transplant will be required, either partial (deep anterior lamellar keratoplasty) or full (penetrating keratoplasty).
Professionals who treat this pathology
Frequently asked questions
Can I get refractive eye surgery with a keratoconus? Will I have to get a cornea transplant?
A cornea transplant was the only solution to a keratoconus up to a few decades ago, but there are now different options to halt or even correct the keratoconus without resorting to a cornea transplant, particularly in incipient or moderate cases with a little astigmatism. Nowadays, a cornea transplant is solely reserved for very advanced cases where there is an evident and marked deformation of the cornea. It is important to emphasise the fact that laser refractive surgery with a corneal laser is contraindicated in cases of keratoconus.
I have keratoconus and have had crosslinking, intracorneal rings have been inserted and my prescription is stable. What are my options if I want to stop wearing glasses?
In cases of mild and stable keratoconus with astigmatism and low myopia (short-sightedness), whenever the eye can handle it, a pre-crystalline intraocular lens implant (behind the iris and in front of the crystalline lens) can be considered in order to correct your prescription. It is important to remember that corneas with keratoconus are anomalous corneas that can respond unpredictably to any surgical manoeuvre performed (for example, an incision or cut in the cornea to insert the lens into the eye). These eyes have a higher risk of retaining part of the prescription than normal eyes.