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Keratoconus - Frequently asked Questions: Keratoconus

 

What is Keratoconus?

Keratoconus (kehr-uh-toh-KOH-nus) is an eye condition in which the shape of the cornea becomes distorted. The cornea is a clear structure that covers the front of the eye and allows light to enter the eye. In a healthy eye, the cornea curves like a dome. In an eye with keratoconus, the center of the cornea slowly thins and bulges, so that it sags and has a cone shape.

In Keratoconus, the posterior layer may tear in rare cases. When this happens, the cornea may suddenly become swollen with water (termed hydrops).Wrinkles and scars may also form on a Keratoconus cornea.

 

How does Keratoconus interfere with vision?

People with Keratoconus may lose vision in two ways:

l. From distortion of the cornea: Seeing through a misshapen cornea is like taking pictures with a camera whose lens has an irregular (not smooth) surface. Parts of the picture or field of vision are in focus and parts are out of focus. This visual problem is called irregular astigmatism.

2. From scarring or swelling of the cornea: Seeing through a scarred or swollen cornea is like taking pictures with a camera with a dirty or cloudy lens. The picture or vision is blurred.

 

How common is Keratoconus?

Keratoconus occurs in 50 to 230 per 100,000 population.

 

Who gets Keratoconus?

Keratoconus has been found in all races and in both sexes, but there may be differences in what is experienced with Keratoconus due to gender.* Also it can be at a raised level more in certain ethic groups.* It occurs more frequently in patients with Down’s syndrome, allergies or congenital amaurosis (a rare form of blindness at birth). Keratoconus may also develop in persons who have worn contact lenses for a long time and who often rub their eyes with too much force.

*Source: Fink BA, Wagner H, Steger-May K, et al. (Collaborative Longitudinal Evaluation of Keratoconus [CLEK] study group). Differences in keratoconus as a function of gender. Am J Ophthalmol. 2005;140(3):459.e1-459.e12.
Pearson AR, Soneji B, Sarvananthan N, Sandford-Smith JH. Does ethnic origin influence the incidence or severity of keratoconus? | Eye. 2000 Aug;14 ( Pt 4):625–8

 

What are the symptoms of Keratoconus?

The symptoms of keratoconus usually start in puberty (in the teens) and may progress for the next 10 to 20 years.* The early symptoms of Keratoconus include decreased vision and worsening nearsightedness. Sometimes Keratoconus is diagnosed when sudden swelling (hydrops) develops. This occurs most often in patients with Down’s syndrome.

*Source: Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol. 1984 Jan-Feb;28(4):293–322.

 

Some of the early initial symptoms experienced for patients to seek medical advice are as follows:

  • Deteriorating monocular acuity.
  • Frequent changes in refraction.
  • Monocular diplopia or ghosting.
  • Squinting or pressure on the globe improves acuity.
  • High myopia and astigmatism with poor best corrected vision.
  • Glare at night

Symptoms usually start in one eye and then frequently both eyes becoming involved to an extend, because it is normally a bilateral eye condition.* When this happens the symptoms has become ever more noticeable and problematic. As the Keratoconic disorder progresses it becomes more and more increasingly complex and unsatisfactory to correct with corrective action, both for the patient and eye professional.

*Source: Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol. 1986 Mar 15;101(3):267-73.

 

What causes Keratoconus?

The cause of Keratoconus is not fully known.

 

Is Keratoconus hereditary?

While most patients with Keratoconus have no relatives suffering from the disorder, many have relatives with (high) astigmatism and this may be a form of early Keratoconus. It is often discussed that only about one in ten patients has a relative who is suffering from keratoconus. However studies indicate close family members may be affected ranging from from 6% to 19%.* 

*Source: Hammerstein W. Zur genetic des keratoconus. Albrecht Von Graefes Arch Klin Exp Ophthalmol, 1974;190:293-308.
Edwards M, McGhee CN, Dean S. The genetics of keratoconus. Clin Experiment Ophthalmol, 2001;29(6):345-51.
Zadnik K, Barr JT, Edrington TB, Everett DF, Jameson M, McMahon TTTT, Shin JA, Sterling JL, Wagner H, Gordon MO. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Invest Ophthalmol Vis Sci, 1998;39(13):2537-46.
 

 

How is Keratoconus diagnosed?

Keratoconus usually is discovered when a patient sees an ophthalmologist because of decreased vision. The diagnosis can be made through an ophthalmologist’s examination of the eye, often involving computerized mapping of the corneal shape.

If there is a mild to moderate distortion of the cornea, contact lenses usually provide good vision. Usually these lenses are the hard or rigid type. Contact lens wear gives the cornea a smoother surface, so that the patient can see clearly. However at modern clinics Corneal Crosslinking may be offered as a first line treatment.

Swelling (hydrops) in a Keratoconus cornea may require treatment with prescribed eye drops.

Tuft et al did an comprehensive study of 2523 Keratoconus patients. They found that 21.6% of the patients required a corneal transplant with a mean duration of 8.8 years (median 7 years) from the time of diagnosis.

If the cornea has progressed to a point where there is severe distortion or scarring and all contact lenses and fit's has been proven not to be possible, or does not provide adequate vision (including also after less invasive surgical procedures has been discussed, or tried before-hand), a corneal transplant is indicated. A corneal transplant replaces a diseased cornea (fully or partially) with a normal cornea from a deceased donor. Most people who receive corneal transplants see much more clearly, mostly with the use of corrective lenses. In long-term studies, five and 10-year full thickness (penetrating) graft survival rates of over 90% in primary transplants has been observed.*

Researchers found in their analysis of data from a large multicenter Australian Corneal Transplant Registry - Kaplan-Meier survival rates of first (penetrating) grafts for keratoconus were 89% at 10 years after transplant, 49% at 20 years, and 17% at 23 years.

*Source: Muraine M, Sanchez C, Watt L, Retout A, Brasseur G. Long-term results of penetrating keratoplasty. A 10-year plus retrospective study. Graefes  Arch Clin Exp Ophthalmol 2003;241(7):571-6.
Thompson RW Jr, Price MO, Bowers PJ, Price FW Jr. Long term graft survival after penetrating keratoplasty. Ophthalmology 2003;110(7):1396-402.
Barraquer CC, Rodriguez-Barraquer T. Five year results of laser in-situ keratomileusis (LASIK) after penetrating keratoplasty. Cornea 2004;23(3):243-8.
Tufts, S.J., Moodaley L.C., Gregory W.M., Davison, C.R., and Buckley, R.J. "Prognostic Factors for the Progression of Keratoconus." Ophth 1994; 101:439-447.


Can Keratoconus lead to blindness?

Blindness in the classic sense will not happen. Legal blindness and partial-sightedness/low vision can occur if proper corrective treatment is not given timely.

 

How much does Keratoconus effect someones quality of life ?

It is not know how many suffer in silence with their sub-standard vision (with or with-out corrective lenses) or if what people communicate about with their daily struggles is just the "tip of the ice-burg" with there being many more out there struggling.

It is not known how many can't see well enough to even be able to use a computer due to living in a "visual prison" or if they even have use of a computer to go on-line to find information, as the greater majority is believed to be located in under developed parts of the world.

The quality of life for patients is poor due to Keratoconus currently being diagnosed too late, when the patients Keratoconus has become obvious, problematic and a "cone" has developed on the front window of their eye. Its a process which takes away their uncorrected vision and often their corrected vision too. 

However milder cases of Keratoconus have a much better chance of doing well with many of the treatments available. This is why advanced Keratoconus should be avoided, and it can be. Treatment for progressive Keratoconus is available and should be discussed when the patients Keratoconus is at an early enough stage to see if the patient meets the criteria to under-go treatment if they wish to. 


What research is being done on Keratoconus?

There is much interest in Keratoconus now than ever before, most of it since we have been around. Researchers are actively studying Keratoconus. At various Eye Centers, biochemists are trying to find the cause of keratoconus. Investigators at various Contact Lens Services are studying the effects of different contact lenses on keratoconus corneas to find the best treatments. Many Corneal specialists are studying Keratoconus patients and are trying to reduce the chances of graft rejection after corneal transplants.

 

Eye Test

 
The top of this eye chart should measure 5 inches (127 mm) across on your screen! Stand 10 feet (3.05 meters) from the screen (about 3 large steps) and test one eye at a time. This test may be inaccurate for a number of reasons and can only be considered a personal indicative test when recovering from a treatment or hydrops, or for general use. It is not intended to replace a routine professional eye exam that you should do with your own eye care specialist (6 months to every year, or as required). It can give you an approximated idea of your visual acuity. You may test yourself both with and with-out glasses or contact lens correction.

  

All content is intended as an informational series and should not be used as a substitute for medical advice.

 

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