Post-surgical ectasia is a condition resembling keratoconus but comes from a different origin. Although LASIK and PRK and other laser vision correction procedures have a high success rate, they don’t produce perfect vision for everyone. The results depend largely on the unique way your corneas respond to laser energy and how your eyes heal after surgery. During procedures such as LASIK, the corneal “wall” has been made thinner and internal pressure from within the eye can cause expansion or distension of the cornea. This results in irregular astigmatism with accompanying blurred and/or distorted vision. Glare, halos and starbursts around headlights and street lights are other symptoms that can occur after these procedures. For some people, post-surgery vision problems can decrease overall quality of life with side effects such as eye strain, headaches and difficulty driving at night.
Because gas permeable contacts (GP) are rigid, they maintain their shape on the eye, unlike soft lenses, which are pliable and conform to the surface of the cornea.
The space between the cornea and the back surface of a GP lens is filled with tears; this covers the irregularities on the cornea’s surface. The smooth front surface of the GP lens then optically replaces the irregular corneal surface, eliminating blur and visual distortions. For this reason, soft lenses, which mold to the surface of the cornea, cannot achieve the same effect that GP lenses provide.
Conventional eyeglasses, which do nothing to change corneal irregularities, cannot correct the vision problems these irregularities cause. Glasses usually can correct only the basic refractive errors — nearsightedness, farsightedness, and regular astigmatism.
Because LASIK and other laser refractive surgery can significantly alter the shape of the cornea, fitting contact lenses on a post-surgery eye is more challenging and time-consuming than fitting lenses on a normally shaped cornea. Special gas permeable or hybrid lens designs usually are required in these circumstances.
Modified GP lens designs may include a larger lens diameter, aspheric optics or a design where the center of the lens is significantly flatter than the periphery (called a reverse geometry design.
Often, scleral lenses are the best option for people who need non-surgical vision correction after LASIK. These large-diameter GP lenses vault over the entire corneal surface and rest on the “white” of the eye (sclera).
Because scleral lenses cover the entire cornea, they can be particularly effective in correcting corneal aberration and irregular astigmatism. They also can be helpful in relieving dry eye symptoms after vision surgery.
Special computerized instruments (not needed for regular contact fitting), such as corneal topographers, are usually necessary in order to to obtain highly accurate measurements of the post-surgery corneal surface. This allows the contact lens specialist to obtain the best possible fit and vision correction. Because of these added complexities, contact lens fittings after refractive surgery typically are more time-consuming and involve a higher fee than regular contact lens fittings. Also, if you’ve never worn GP lenses before, be aware that it takes longer to adapt to them than to soft contacts. You may have to wear the lenses at least part-time every day for several days before they feel completely comfortable.
Fitting GP contacts on an eye that has undergone refractive surgery requires special skills similar to those needed to fit lenses irregular-shaped corneas caused by keratoconus or a cornea transplant. Several lens modifications may be required to achieve the optimum fit, comfort and visual acuity.
Alternatives to gas permeable contacts for correcting vision after eye surgery include hybrid contact lenses. These lenses are designed to offer the best of both worlds: aberration-correcting optics of a rigid GP lens and wearing comfort comparable to that of soft lenses.
In most cases, hybrid contact lenses are equally effective as GP lenses in correcting aberrations after vision surgery, and may be easier to adapt to than GP lenses.
Currently, the only FDA-approved hybrid contacts sold in the United States are made by SynergEyes.
If you have unacceptable results from LASIK or other refractive surgery, you may want to consider custom gas permeable (GP) or hybrid contact lenses to improve your vision. The smooth, rigid surface of these lenses can correct optical imperfections that eyeglasses and soft contacts can’t address, making gas permeable contact lenses or hybrids the best choice if you’re looking for the sharpest vision possible.