The eye is a complex organ made up of several layers. The first is the conjunctiva which covers the sclera, also known as the white of the eye. The next is the cornea, a clear dome-shaped layer of tissue that covers the iris and pupil. Its main function is to help focus light into the lens and pupil.
Keratoconus is a progressive condition characterized by a thinning of the cornea that causes it to lose its symmetrical dome shape. Lopsidedness of the cornea can lead to blurry or distorted vision.
Read on as we dig deeper into keratoconus including its causes, symptoms, and treatment options.
The name keratoconus comes from the Greek “keras” (horn) and “konos” (cone).
Keratoconus is an eye disorder characterized by the transformation of the cornea from a symmetrical dome to an asymmetric or lopsided cone. The primary function of your cornea is to refract light into your pupil. When light passes through your asymmetrical cornea, it can lead to distortion and blurriness in your vision.
Keratoconus was first described in medical literature in
Symptoms may start in one eye, but about
Researchers estimate that the prevalence of keratoconus is approximately
The hallmark sign of keratoconus is a thinning of your cornea that disrupts its natural dome shape. In the early stages of keratoconus, it’s common to not have any symptoms. As the condition progresses, asymmetry of your cornea can lead to blurred vision and mild to significant distortion of your vision.
Some of the early signs of keratoconus include:
- Rizzuti sign. A steeply curved reflection seen by shining a light on the side of your cornea closest to your temple.
- Fleischer ring. A brown ring of iron deposit around your cornea that’s most visible with a cobalt blue filter.
- Vogt’s striae. Vertical lines observed on your cornea that usually disappear when a firm pressure is applied over your eye.
You may also experience:
- corneal swelling
- light sensitivity
- halos in your vision
- eye strain
- a persistent desire to rub your eyes
- poor night vision
- nearsightedness (difficulty seeing far away)
- irregular astigmatism (irregular curvature of the eye)
In rare cases, you may develop corneal blisters that can cause scarring and swelling.
Acute corneal hydrops is an uncommon complication of keratoconus that involves sudden swelling due to a rupture in the Descemet membrane found deep in your cornea.
Researchers still don’t fully understand why some people develop keratoconus. In most cases, it develops for no apparent reason. It’s generally thought that both environmental and genetic factors play a role in its development.
- Family history. It’s thought that some people with keratoconus may carry genes that make them predisposed to its development if they’re exposed to certain environmental factors.
- Underlying disorders. Keratoconus sometimes occurs in the presence of certain underlying disorders, but a direct cause and effect hasn’t been established. These disorders include Down syndrome, sleep apnea, asthma, some connective tissue disorders including Marfan syndrome and brittle cornea syndrome, and Leber congenital amaurosis.
- Environmental risk factors. Some environmental risk factors may contribute to the development of keratoconus including excessive eye rubbing and wearing contacts.
To make a keratoconus diagnosis, your eye doctor with give you a thorough eye exam and examine your medical and family history.
During the eye exam, your eye doctor may examine:
- the overall appearance of your eyes
- your visual acuity
- your visual field
- your eye movements
You may also undergo a slit lamp exam where your doctor examines your eye with a special light under high magnification.
Diagnosis of keratoconus may also involve a specific imaging test called corneal topography to allow your doctor to examine changes to your eye that aren’t otherwise visible. Corneal topography creates a three-dimensional image of the surface of your cornea.
Treatment of keratoconus focuses on maintaining your visual acuity and stopping changes to the shape of your cornea. Treatment options vary based on the severity of the condition and how fast it’s progressing.
Prescription contacts or glasses
Prescription glasses or soft contact lenses can be used to improve visual acuity in mild cases of keratoconus. Due to progressive changes to your cornea, you may require frequent prescription changes.
Other types of contact lenses
Rigid gas permeable contact lenses
Many people with keratoconus need these hard contact lenses. They allow oxygen to pass through the contact lens and help reshape your cornea to help minimize vision distortion.
Some people find rigid gas permeable contact lenses uncomfortable. In these cases, piggyback lenses may be used. Piggyback lenses are when a hard contact lens is placed over a softer lens.
These lenses have a hard center and a soft ring along the outer edge to increase comfort.
Another alternative to rigid gas permeable contact lenses, scleral lenses work similarly to a rigid gas permeable lens in that they provide a liquid layer between the contact lens and the front of the eye. This liquid layer masks the distortion caused by corneal irregularity.
However, these lenses are often more comfortable because they rest on the white part of your eye, which is less sensitive than the cornea.
Some people with keratoconus don’t tolerate contact lenses well due to discomfort, severe corneal thinning, or scarring. If your vision can’t be corrected with lenses, you may require surgery.
- Intracorneal ring segments. Food and Drug Administration (FDA)-approved to treat keratoconus in 2004, this surgery involves inserting two crescent-shaped pieces of plastic called INTACS into the cornea to help support your cornea. Often you’ll still need contacts or glasses even after surgery to correct your vision.
- Corneal transplant or keratoplasty. This surgery involves replacing your corneal tissue with tissue from a donor. It’s usually only used in severe cases.
Collagen cross-linking device (CXL)
The FDA approved the first collagen cross-linking device to treat keratoconus in 2016. CXL is a minimally invasive procedure during which your doctor places special eyedrops with riboflavin in your eye and then uses ultraviolet light to strengthen the collagen fibers in your cornea.
This treatment limits the progression of keratoconus. CXL is an effective treatment for keratoconus for many and may actually stop the progression of the condition. However, according to the American Academy of Ophthalmology, more randomized controlled trials are needed.
- Family history. About
10 to 20 percentof people with keratoconus have a family history.
- Childhood eye-rubbing. Excessive childhood eye rubbing is thought to increase your risk by
- Close genetics relation between parents. Having a close genetic relationship between parents is thought to increase your risk of developing keratoconus by about
Studiessuggest that keratoconus rates are higher in people who are Asian compared to people who are Caucasian.
- Atopy. It’s been suggested that atopy may be associated with the development of keratoconus, possibly due to increased eye rubbing due to eye irritation. Atopy is the genetic tendency to develop allergic diseases such as eczema, asthma, or allergic rhinitis.
Keratoconus is a progressive disorder that tends to get worse over a period of about 10 to 20 years. The rate that the disorder progresses usually slows in your 40s or 50s. It may stop progressing at any point.
According to the American Academy of Ophthalmology, with an early diagnosis and treatment with corneal cross-linking, many people with keratoconus retain adequate vision with glasses or contacts.
If keratoconus progresses to the point it significantly alters your vision, you may need to receive a corneal transplantation. Progression of keratoconus after corneal surgery has been reported, but it isn’t clear how common it is.
Keratoconus is a disorder that causes a thinning of your cornea. This thinning causes your cornea to lose its typical dome shape and can lead to vision distortion. It most commonly develops in teenagers and young adults and typically progresses for about 10 to 20 years before stabilizing.
In many cases, it’s not clear why keratoconus develops. Some people with keratoconus have a family history of the disease. If one of your close family members has keratoconus, or if you have potential symptoms, it’s important to visit your eye doctor for a proper exam.
Diagnosing and treating keratoconus in the early stages gives you the best chance of minimizing permanent changes to your vision.