What is keratoconus?
It is an uncommon non-inflammatory condition of the eye where the usual round dome-shaped cornea (the black central portion of the eye) progressively thins out leading to the development of a cone-shaped bulge.
The thinning and changes in the shape of the cornea result in scarring. These changes cause lack of corneal transparency, thereby impairing the eye’s ability to focus and ultimately leading to reduced vision.
Keratoconus is common in people of Asian origin and affects one in every thousand people. It is common in teenagers and young individuals. A study reported that the prevalence of keratoconus in central India to be 2300 per 100,000 people.
The cause of keratoconus is still a matter of research. Several pathological processes are believed to cause keratoconus.
- Genetics: Family history of keratoconus
- Down’s syndrome
- Vigorous rubbing of eyes
- Hay fever
- Marfan’s disease
- Vernal (Inflammation happening in spring) keratoconjunctivitis
- Retinitis pigmentosa
- Retinopathy of prematurity
Keratoconus typically affects both the eyes. Nonetheless, symptoms in each eye can vary. The symptoms and signs vary with the gradual progression of the disease:
- Bulging of the cornea
- Distorted or blurred vision
- Light sensitivity
- Worsening or clouding of vision
- Frequent changes in your eyeglass prescription
- Inability in wearing contact lens
- Increase in nearsightedness or astigmatism
Keratoconus can be diagnosed via:
- Keratometry: The curve of the cornea is determined by focussing a circle of light on the cornea.
- Slit-lamp examination: A vertical beam of light is directed on your eye surface and using a microscope of low power, the doctor examines the eye. Potential problems and shape of the cornea can be evaluated in this procedure.
- Computerised corneal mapping: The topographical mapping of your eye’s surface is done from a picture of your eye.
- Eye refraction: Using a special device, your doctor evaluates the eyes for any vision problems.
Based on the progression and severity of the keratoconus, treatment is initiated. In early stages, eyeglasses can correct the vision problems. With the progression of the disease, rigid contact lenses are prescribed to allow even refraction of light and prevent vision distortion.
Different types of contact lenses are used for treatment of keratoconus:
- Soft contacts: Distorted and blurry vision can be corrected in early stages by the use of contact lenses.
- Rigid gas permeable contact lenses: These are used for the treatment of progressive keratoconus. These provide an adequate correction of vision and the lenses are made to fit the cornea.
- Scleral lenses: Such lenses fit over the sclera (white part of the eye) and are used for addressing irregular corneal changes.
- Piggyback lenses: In this type of contacts, a hard contact lens sits over a soft contact lens. It is prescribed in situations when the rigid lenses are uncomfortable.
- Hybrid lenses: Special lenses with rigid centre and a soft ring are prescribed for added comfort.
Surgery may be required in individuals where scarring prevents the use of contact lenses.
For improving the contact lens fit, Intacs (two pieces of plastic polymers inserted into cornea for reshaping front of the eye) and intracorneal rings are occasionally used.
Keratoplasty: Corneal transplantation may be necessary in cases where the cornea has become extremely thin or scarred.
In Deep Anterior Lamellar Keratoplasty, only the cornea’s front and middle layer are transplanted. This procedure is more advantageous regarding lesser healing time, compared to complete corneal transplantation.
Follow-up visits, once in 6-months or on a yearly basis are needed for monitoring the corneal thinning steepening, and evaluating the changes in the vision.
There are no known ways to prevent keratoconus. Individuals with keratoconus are asked not to rub their eyes often.
Keratoconus can lead to complications like
- Acute corneal hydrops – Development of corneal oedema due to leakage of aqueous humour into cornea
- Decreased vision
- High refractive error
- Corneal scarring
- Irregular astigmatism
Visit your eye doctor immediately if you notice a rapid worsening of your eyesight.
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- About Keratoconus Eye Disease. National Keratoconus Foundation. http://www.nkcf.org/about-keratoconus/ Accessed 8 Jun. 16.
- Gokhale NS. Epidemiology of keratoconus. Indian Journal of Ophthalmology. 2013;61(8):382-383. doi:10.4103/0301-4738.116054.
- Jonas JB, Nangia V, Matin A, Kulkarni M, Bhojwani K. Prevalence and associations of keratoconus in rural Maharashtra in central India: the central India eye and medical study. Am J Ophthalmol. 2009 Nov; 148(5):760-5
- Global Keratoconus Foundation. http://kcglobal.org/content/view/14/26/ Accessed 8 Jun. 16.
- What Is Keratoconus? American Academy of Ophthalmology. http://www.aao.org/eye-health/diseases/what-is-keratoconus. Accessed 8 Jun. 16.