What Is Keratoconus?
Keratoconus is a condition in which the shape of the cornea gradually changes. The cornea becomes thinner than normal and begins to bulge outward, taking on a more cone-like shape instead of its normal dome-like form.
The cornea is the transparent front part of the eye, and its main function is to help focus light onto the retina to produce a clear image. However, when the cornea changes shape and its surface becomes irregular, as in keratoconus, light is no longer focused properly. As a result, the patient may experience blurred vision and difficulty seeing fine details clearly, especially in low-light conditions or at night.
Keratoconus often affects both eyes, although not necessarily to the same degree. One eye may be more affected than the other. The condition usually begins during adolescence or early adulthood and may gradually progress over several years.
What Are the Main Symptoms of Keratoconus?
In the early stages, a person with keratoconus may notice that vision has become less clear or that lights seem more bothersome than usual. These changes may gradually become more noticeable as the condition progresses.
Symptoms of Keratoconus in the Early Stages
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Mild blurred or distorted vision, with straight lines appearing curved or wavy.
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Increased sensitivity to light.
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Seeing halos or streaks of light around light sources.
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Difficulty seeing clearly at night.
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Eye redness, irritation, or discomfort.
Symptoms of Keratoconus in Advanced Stages
As the condition progresses and the shape of the cornea changes further, vision problems may become more noticeable, including:
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Increased blurring and distortion of vision.
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Greater difficulty seeing distant objects clearly.
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Worsening nearsightedness or astigmatism.
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Frequent changes in eyeglass prescription due to unstable vision measurements.
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Difficulty wearing regular contact lenses or discomfort while using them because of increased corneal steepening and thinning.
What Causes Keratoconus?
The exact cause of keratoconus is still unknown. However, several factors are associated with an increased likelihood of developing the condition or with its progression, including:
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Family history of keratoconus
Having a parent with keratoconus may increase the likelihood of developing the condition. It has been reported that about 1 in 10 people with keratoconus also has a parent with the condition.
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Frequent and vigorous eye rubbing
Rubbing the eyes forcefully is considered one of the important factors associated with the progression of keratoconus, especially in people who have eye allergies or persistent itching. Repeated pressure on the cornea may contribute to further weakening and accelerate changes in its shape.
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Weakness of collagen fibers in the cornea
Some people may have structural abnormalities that make the collagen fibers within the cornea less strong, which can make the cornea more susceptible to thinning and bulging forward.
Certain Health Conditions
The likelihood of developing keratoconus may be higher in people with certain conditions, including:
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Down syndrome.
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Ehlers-Danlos syndrome.
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Marfan syndrome.
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Asthma.
Other Possible Factors
Some studies suggest that other factors may also be associated with keratoconus, such as:
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Reduced antioxidant levels within the cornea.
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Chronic eye inflammation.
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Sleep disorders such as obstructive sleep apnea.
How Is Keratoconus Diagnosed?
The doctor usually begins by asking about the patient’s symptoms, including whether there have been any changes in vision or frequent changes in eyeglass prescription, as well as reviewing the medical and family history. This is followed by an eye examination and vision assessment.
After that, certain tests can help confirm the diagnosis and determine the extent of corneal involvement, including:
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Corneal Topography
Corneal topography provides a detailed map of the cornea’s shape and curvature and can identify areas of irregularity or protrusion. For this reason, it is considered one of the most important tests for detecting keratoconus, particularly in its early stages.
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Corneal Thickness Measurement (Pachymetry)
This test measures the thickness of the cornea and identifies areas that have become thinner. It also helps the doctor assess the severity of the condition and monitor any changes over time.
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Slit-Lamp Examination:
The doctor examines the cornea closely to identify any visible changes in its shape or transparency, such as thinning, scarring, or other abnormalities. However, early cases of keratoconus may not be clearly detected through this examination alone.
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Keratometry:
Keratometry measures the curvature of the cornea and helps identify changes in its shape, which are among the findings the doctor considers when evaluating the condition.
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Refraction and Visual Acuity Testing:
These tests help determine how vision has been affected and identify changes in the degree of myopia or astigmatism. They are used alongside corneal examinations to achieve a more accurate diagnosis.
Keratoconus Treatment: Is There One Treatment for All Cases?
Keratoconus treatment varies from one patient to another depending on the degree of corneal change, the extent to which vision is affected, and whether the condition is stable or still progressing. Some patients may only need a method to improve visual clarity, while others may require treatment aimed at strengthening the cornea and limiting further changes in its shape.
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Eyeglasses and Contact Lenses
In mild cases, vision may be improved with prescription eyeglasses or soft contact lenses. However, as the corneal shape becomes more irregular, eyeglasses may no longer provide sufficiently clear vision.
In such cases, specialized lenses may be used, such as rigid gas-permeable (RGP) lenses or larger rigid lenses, including scleral lenses. These lenses can help improve visual quality despite the irregular surface of the cornea. However, their role is to correct vision rather than stop the progression of keratoconus.
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Corneal Collagen Cross-Linking
If follow-up examinations show that keratoconus is still progressing, corneal collagen cross-linking may be considered as an option to help limit further progression.
The procedure involves applying riboflavin (vitamin B2) eye drops to the cornea and then exposing it to ultraviolet light. This aims to strengthen the bonds between collagen fibers and stabilize the corneal structure. The primary goal of cross-linking is to slow or stop the progression of the condition, rather than necessarily eliminating the need for eyeglasses or contact lenses after the procedure.
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Intracorneal Ring Segments
In some cases, small ring segments may be implanted within the cornea to help reduce its protrusion and improve its shape. This may improve vision or make contact lens use easier.
Intracorneal ring segments do not stop the progression of keratoconus on their own. Therefore, some patients may also require another treatment, such as corneal cross-linking, depending on the condition of the cornea and the results of the examinations.
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Corneal Transplantation
Corneal transplantation may become an option in advanced cases, particularly when significant scarring develops, the cornea becomes severely thinned, or contact lenses no longer provide adequate vision or become difficult to wear.
During the procedure, the damaged part of the cornea or the entire cornea is replaced with healthy donor corneal tissue. The ophthalmologist determines the most appropriate type of transplantation based on the condition of the cornea.
What Are the Complications of Keratoconus?
Complications do not occur in every person with keratoconus, but they may develop as the condition progresses and the cornea becomes thinner and more protruded. The most important complications include:
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Corneal scarring or opacity:
This may develop in advanced cases, particularly in the most protruding area of the cornea. Scarring can reduce corneal transparency and further impair vision.
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Acute Corneal Hydrops:
This is an uncommon complication that occurs when fluid suddenly enters the corneal tissue, causing the cornea to swell and resulting in a noticeable decrease in vision. It may also be accompanied by pain, redness, and sensitivity to light. After the swelling resolves, a scar may remain and affect vision.
As keratoconus progresses, visual impairment may become more pronounced and more difficult to correct with eyeglasses or contact lenses, particularly when corneal scarring is present. Some advanced cases may eventually require corneal transplantation.
Frequently Asked Questions
Does every case of astigmatism mean that keratoconus is present?
No. Having astigmatism does not necessarily mean that a person has keratoconus. Astigmatism is a common refractive error and may result from a slight difference in the curvature of the cornea or lens.
However, the doctor may suspect keratoconus if the astigmatism is irregular or changes noticeably over time. In such cases, corneal topography and imaging can help assess the shape of the cornea and confirm or rule out changes associated with keratoconus.
Can keratoconus affect only one eye?
Keratoconus usually affects both eyes, but not necessarily to the same degree. Changes may be more pronounced in one eye while remaining very mild in the other, which can make the patient feel that the problem is present in only one eye.
For this reason, the doctor examines both corneas even if the symptoms are more noticeable in one eye.
When does vision improve after corneal cross-linking?
After corneal cross-linking, it is normal for vision to be blurred or unstable at first. It may then begin to improve gradually as the cornea heals. Improvement often becomes more noticeable after about two to three months, while vision may take three to six months to reach a greater degree of stability.
The recovery period varies from one patient to another depending on the condition of the cornea and the cross-linking technique used. It is also important to note that the primary goal of the procedure is to slow or stop the progression of keratoconus rather than directly correct vision. Therefore, the patient may still need eyeglasses or contact lenses after the procedure.
Does keratoconus disappear after a certain age?
No. Keratoconus does not disappear with age, but its rate of progression often slows over time, particularly as corneal tissue becomes naturally stiffer with age.
Are the symptoms of keratoconus different in children?
The main symptoms of keratoconus in children are not very different from those seen in adults. A child may experience blurred or distorted vision, increasing myopia or astigmatism, glare, or halos around lights.
However, detecting the condition in children can be more difficult. A child may not realize that their vision has changed or may be unable to describe the problem clearly. In addition, one eye may see well enough to compensate for poorer vision in the other eye, making vision seem normal to the child despite a clear difference between the two eyes.
Closer attention may be needed if the eyeglass prescription changes rapidly, if there is a high or increasing degree of astigmatism, or if the child frequently rubs their eyes because of allergies. Keratoconus may progress more rapidly in children and adolescents than in adults.
Can LASIK be performed if I have keratoconus?
LASIK is generally not recommended for people with keratoconus because the procedure involves reshaping the cornea and removing part of its tissue, which may further weaken the cornea and increase its protrusion over time.
For this reason, before any refractive surgery, the cornea should be examined, its thickness measured, and detailed corneal maps and imaging performed to ensure that keratoconus or early signs of the condition are not present. The corneal specialist can then determine the most appropriate options based on each patient’s condition.
How does a person with keratoconus see?
Keratoconus affects the way light is focused inside the eye, so vision may appear blurred or distorted, and fine details may lose their sharpness even when eyeglasses are worn.
The patient may notice that straight lines appear curved or wavy, or may see halos and glare around light sources. These problems often become more noticeable in low-light conditions, which can make night driving more difficult because of glare from vehicle headlights and blurred vision.
Vision is not the same in every patient. It varies depending on the degree of corneal shape change and the severity of the condition, and one eye may be more affected than the other.
Can keratoconus cause blindness?
Having keratoconus does not mean that the patient will become blind. The effect on vision varies from person to person, and in many cases vision can be improved with eyeglasses or specialized contact lenses while the condition is monitored and treated when necessary.
However, if keratoconus becomes advanced, blurred and distorted vision may worsen, and corneal scarring or opacity may develop and significantly affect vision. In severe cases, visual impairment may become considerable.
Visiting an ophthalmologist and undergoing corneal examinations at the appropriate time can help detect and monitor the condition and reduce the likelihood of progression to stages that have a greater impact on vision.
If you notice any persistent changes in the quality of your vision or suspect that you may have keratoconus, you can book an appointment with the Royah Hakim team for a comprehensive corneal examination, assessment of your condition, and discussion of the most appropriate treatment options.