Clear central covering of the eye representing a cone
Keratoconus is a degenerative disease of the cornea that causes it to gradually thin and bulge into a cone-like shape. This shape prevents light from focusing precisely on the macula. As the disease progresses, the cone becomes more pronounced, causing vision to become blurred and distorted. Because of the cornea's irregular shape, patients with keratoconus are usually very nearsighted and have a high degree of astigmatism that is not correctable with glasses.
Keratoconus is sometimes an inherited problem that usually occurs in both eyes.
Signs and Symptoms
• Blurred vision - even when wearing glasses and contact lenses
• Glare at night
• Light sensitivity
• Frequent prescription changes in glasses and contact lenses
• Eye rubbing
Detection and Diagnosis
Keratoconus is usually diagnosed when patients reach there 20's. For some, it may advance over several decades, for others, the progression may reach a certain point and stop. Keratoconus is not usually visible to the naked eye until the later stages of the disease. In severe cases, the cone shape is visible to an observer when the patient looks down while the upper lid is lifted. When looking down, the lower lid is no longer shaped like an arc, but bows outward around the pointed cornea. This is called Munson's sign. Special corneal testing called topography provides the doctor with detail about the cornea's shape and is used to detect and monitor the progression of the disease. A pachymeter may also be used to measure the thickness of the cornea.
The first line of treatment for patients with keratoconus is to fit rigid gas permeable (RGP) contact lenses. Because this type of contact is not flexible, it creates a smooth, evenly shaped surface to see through. However, because of the cornea's irregular shape, these lenses can be very challenging to fit. This process often requires a great deal of time and patience. When vision deteriorates to the point that contact lenses no longer provide satisfactory vision, corneal transplant may be necessary to replace the diseased cornea with a healthy one.
Images and information related to Eye Conditions on this website have been kindly provided courtesy of St. Luke's Cataract & Laser Institute and adapted for the International Guide Dog Federation website. This on-line information is for educational and communication purposes only and should not be construed as personal medical advice. Information published on this website is not intended to replace, supplant, or augment a consultation with an eye care professional regarding the viewer/user's own medical care. The International Guide Dog Federation disclaims any and all liability for injury or other damages that could result from use of the information obtained from this site