Not everyone is an ideal candidate for contact lenses. If you have one or more of the following conditions, contact lens wear may be more difficult:

• astigmatism
• dry eyes
• presbyopia
• keratoconus
• post-refractive surgery (such as LASIK)

But "difficult" doesn't mean impossible. Often, people with these conditions can wear contacts quite successfully. Let's take a closer look at each situation - and possible contact lens solutions:

Astigmatism is a very common condition where the curvature of the front of the eye isn't round, but is instead shaped more like a football or an egg. This means one curve is steeper or flatter than the curve 90 degrees away. Astigmatism won't keep you from wearing contact lenses - it just means you need a different kind of lens.

Lenses specially designed to correct astigmatism are called "toric" lenses. Most toric lenses are soft lenses. Toric soft lenses have different corrective powers in different lens meridians, and design elements to keep the lens from rotating on the eye (so the varying corrective powers are aligned properly in front of the different meridians of the cornea).

In some cases, toric soft lenses may rotate too much on the eye, causing blur. If this happens, different brands that have different anti-rotation designs can be tried. If soft lens rotation continues to be a problem, scleral and corneal gas permeable (GP) lenses (with or without a toric design) can also correct astigmatism.

Dry eyes can make contact lens wear difficult and cause a number of symptoms, including:

• a gritty, dry feeling
• feeling as if something is in your eye
• a burning sensation
• eye redness (especially later in the day)
• blurred vision

If you have dry eyes, the first step is to treat the condition. This can be done a number of ways, including artificial tears, medicated eye drops, nutritional supplements, and a doctor-performed procedure called punctal occlusion to close ducts in your eyelids that drain tears away from your eyes.

Once the dry eye condition is treated and symptoms are reduced or eliminated, contact lenses can be tried. Certain soft contact lens materials work better than others for dry eyes. Also, scleral and corneal GP lenses are sometimes better than soft lenses if there's a concern about dry eyes since these lenses don't dry out the way soft lenses can.

Replacing your contacts more frequently and reducing your wearing time each day (or removing them for specific tasks, such as computer work) can also reduce dry eye symptoms when wearing contacts.

Presbyopia is the normal loss of focusing ability up close when you reach your 40's.

Today, there are many designs of bifocal and multifocal contact lenses to correct presbyopia. Another option for presbyopia is monovision. This is wearing a contact lens in one eye for distance vision and a lens in the other eye that has a modified power for near vision.

During your contact lens fitting we can help you decide whether bifocal/multifocal contact lenses or monovision is best for you.

Keratoconus is a relatively uncommon eye condition where the cornea becomes thinner and bulges forward. The term "keratoconus" comes from the Greek terms for cornea ("kerato") and cone-shaped ("conus"). The exact cause of keratoconus remains unknown, but it appears that oxidative damage from free radicals plays a role.

Scleral and Corneal gas permeable contact lenses are the treatment option of choice for mild and moderate keratoconus. Because they are rigid, scleral and corneal GP lenses can help contain the shape of the cornea to prevent further bulging of the cornea. They also can correct vision problems caused by keratoconus that cannot be corrected with eyeglasses or soft contacts.

In some cases, a soft contact lens is worn under the scleral and corneal GP lens for greater comfort. This technique is called "piggybacking." Another option for some patients is a hybrid contact lens that has a GP center, surrounded by a soft "skirt".

More than one million Americans each year have LASIK surgery to correct their eyesight. Sometimes, vision problems remain after surgery that can't be corrected with eyeglasses or a second surgical procedure. In these cases, gas permeable contact lenses can often restore visual acuity and eliminate problems like glare and halos at night.

Scleral and corneal GP lenses are also used to correct vision problems after corneal transplant surgery, including irregular astigmatism that cannot be corrected with eyeglasses.

Scleral and corneal GP lenses prescribed after LASIK and corneal transplants sometimes have a special design called a "reverse geometry" design to better conform to the altered shape of the cornea. The back surface of these lenses is flatter in the center and steeper in the periphery. (This is the opposite of a normal scleral and corneal GP lens design, which is steeper in the center and flattens in the periphery.)