Keratoconus – symptoms, causes and risk factors

keratoconus cross linking
Keratoconus. Dystrophic disease of the cornea.

The keratoconus is a condition which is happening when the cornea (which is the clear and dome – shaped front surface of the eye) thins and it gradually bulges outward into a cone shape. The cone shaped cornea is causing blurred vision and it can cause sensitivity to glare and light. This condition usually affects both eyes and it generally begins to first affect people between ages 10 – 25. Keratoconus can progress slowly for ten years or longer [1]. When the keratoconus is in the early stages, then you can correct your vision problems using soft contact lenses or glasses. When the keratoconus is in the later stages, then it has to be fitted with rigid gas permeable contact lenses or other types of contact lenses. If the keratoconus progresses to an advanced stage, then you may need a cornea transplant. When people have more severe cases of keratoconus, then a circle or scarring can be seen within the cornea. The cause for keratoconus it is not known but it is believed that is a combination of hormonal, environmental and genetic factors. In one study is said that about 7% of people who have keratoconus, have a family history of this condition [2]. Allergies and rubbing of the eyes are environmental factors. Changes of the cornea to a cone shape can be the underlying mechanism which is involved in the keratoconus.

keratoconus surgery

Keratoconus Symptoms

It is known that the signs and symptoms of keratoconus can change as the disease progresses and they can include:

  • Sudden worsening or clouding of vision
  • A need for frequent changes in eyeglass prescriptions
  • Increased sensitivity to bright light and glare, which can cause problems with the night driving
  • Blurred or distorted vision

Here are the symptoms of keratoconus in the early stage:

  • Eye redness or swelling
  • Increased sensitivity to light and glare
  • Slightly distorted vision, where straight lines look bent or wavy
  • Mild blurring of vision

Here are the symptoms of keratoconus in the later stages:

  • Not being able to wear contact lenses. Contact lenses may no longer fit properly and they are uncomfortable.
  • Increased nearsightedness or astigmatism (this is a condition when your eyes cannot focus as well as they should). As a result of this, doctors often prescribe new eyeglasses.
  • More blurry and distorted vision

Usually, keratoconus takes years to go from early to late stage. In some cases, keratoconus can get worse very quickly. The cornea can swell suddenly and it can start to scar. It is known that when the cornea has scar tissue, then it loses its smoothness and it becomes less clear. As a result of this, the vision grows even more blurry and distorted. If your eyesight is worsening rapidly, which can be caused by an irregular curvature of the eye (a condition which is known as astigmatism), then you should see your doctor as soon as possible. Your doctor will look for signs of keratoconus during routine exams. [1]

Keratoconus causes

It is not known what the real cause for keratoconus is. In some cases, keratoconus appears to be genetic which means that it is passed down in families [3,4]. There are some studies in which are said that about one in 100 people who have keratoconus, have a parent who have this disease too. This condition often starts when people are in their late teens or in their early 20s. The vision symptoms are slowly getting worse over a period of about ten to twenty years.

Keratoconus risk factors

There are some factors which can increase your risk of getting keratoconus, such as

  • Having certain conditions, such as asthma, hay fever, Ehlers – Danlos syndrome, Down syndrome and retinitis pigmentosa
  • Rubbing your eyes vigorously
  • Having a family history of keratoconus

Keratoconus complications

There are some cases when cornea can swell quickly and it can cause sudden reduced vision and scarring of the cornea. [5] This problem is caused by a condition inside the lining of the cornea breaks down which is allowing the fluid to enter the cornea (this is known as hydrops). When keratoconus is in the advanced stages, then the cornea can become scarred and this particularly can happen in the area where the cone forms. The scarred cornea is causing worsening vision problems and this can require corneal transplant surgery.


[1] Godefrooij DA, Ardine de Wit G, Uiterwaal CS, et al. Age-specific incidence and prevalence of keratoconus: A nationwide registration study. American Journal of Ophthalmology. 2017;175:169-72.

[2] Mahdi Opticals. Keratoconus. Retrieved from

[3] Rong SS, Ma STU, Yu XT, et al. Genetic associations for keratoconus: a systematic review and meta-analysis. Scientific Reports. 2017;7.

[4] Nowak DM, Gajecka M. The genetics of keratoconus. Middle East African Journal of Ophthalmology. 2011;18(1):2–6.

[5] Shajari M, Steinwender G, Hermann K, et al. Evaluation of keratoconus progression. British Journal of Ophthalmology. 2019;103(4).


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