Guide to Keratoconus - Causes, Symptoms and Treatment
Keratoconus is when the cornea begins to bulge unnaturally, causing problems with vision. The cornea is the clear front surface of the eyeball and is usually round. Occasionally, pressure within the eye causes a weak cornea to bulge outwards like a cone. The cone shape deflects the light as it enters the eye and causes a distorted image on the retina. It can occur in one or both eyes and often appears during a sufferer’s teens or 20s and gets worse over time. In most people, keratoconus affects both eyes and while its progress does eventually stop, treatment is always required to improve the quality of the remaining vision.
Symptoms of keratoconus
Keratoconus usually develops very slowly, although in rare cases it may develop rapidly. As the diseases progresses, the cornea becomes more irregular in shape and the normally smooth surface of the cornea becomes wavy, causing nearsightedness and distorted and blurred vision. This may be accompanied by a sensitivity to light and glare from bright lights. Sufferers will notice they have to have new prescriptions in their eyeglasses each time they visit their eye doctor. It is often some time before keratoconus is diagnosed if the practitioner is not familiar with the symptoms of this disease.
Causes of keratoconus
A weakening of the corneal tissue is thought to lead to keratoconus, which may be caused by an imbalance of enzymes within the cornea. This imbalance can make the cornea more susceptible to damage from free radicals, causing the weakening and bulging effect over time. It is likely a genetic problem, as it often runs in families. It is also associated with exposure to ultraviolet light from the sun, excessive eye rubbing, chronic eye irritation and a history of poorly fitted contact lenses.
Treating keratoconus with contact lenses
If the keratoconus is mild, eyeglasses or soft contact lenses may be sufficient to correct vision at first, but as the cornea thins and the corneal shape becomes more irregular, other treatments will likely be needed.
When soft contact lenses or eyeglasses are insufficient to treat the keratoconus, rigid gas permeable (RGP) lenses may be used. Since rigid lenses hold their shape, rather than conform to the bulging cornea as soft contacts would, they can sometimes improve vision by creating a smoother, rounder eye surface. However, some keratoconus sufferers find the RGP lenses uncomfortable to wear and fitting them is often difficult and time consuming. Patients may have to make many visits to have the lenses fitted, especially if the cornea continues to change.
A better solution may be a combination of lenses (a technique sometimes referred to as “piggybacking” lenses). A soft silicone hydrogel contact lens is placed on the eye and then a gas permeable contact lens is fitted over it. Wearing double lenses in this way can improve comfort and vision, but the patient must be monitored regularly by a specialist to ensure that the eye is receiving enough oxygen to remain healthy.
There are also hybrid contact lenses which combine a rigid center with a soft outer skirt to give the vision benefits of a RGP lens with the cushioned comfort of a soft contact lens. The ClearKone version is specially made for those with keratoconus and is available in many shapes to fit the irregular shape of the cornea.
Other lens options include using scleral and semi-scleral lenses, which have a larger diameter than typical contact lenses and fit onto the sclera (white part) of the eye. These can be more comfortable and stable for keratoconus sufferers than other lenses, which move with each blink of the eye because they cover only a small area.
Treating keratoconus with Intacs
Intacs are tiny, plastic, C-shaped rings which are implanted at the edge of the cornea. The shape of the insert causes the cornea to flatten, improving vision. Getting Intacs is a simple outpatient procedure which can take as little as 15 minutes and requires only a small incision. Intacs are especially useful in keratoconus patients who have very poor vision which cannot be improved with glasses or contact lenses.
Other treatment options for keratoconus
One promising new treatment method, called Corneal Cross Linking, involves eyedrops containing riboflavin (vitamin B2) being placed on the cornea and activated with ultraviolet light. This strengthens the connective tissue or collagen fibers within the cornea.
A last resort for those who cannot benefit from or cannot tolerate contact lenses or other treatments is a corneal transplant (also called a penetrating keratoplasty). This surgery can be very successful, but the eye may take a year or more to fully heal, and most people will still require glasses or contact lenses for clear vision afterward.
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