Reverse Geometry RGP Lenses Can Reduce Higher-Order Aberrations in Post-LASIK Patients

Reverse Geometry contact lenses may relieve some LASIK side effects

To date, the topic of whether reverse geometry rigid gas permeable (RGP) contact lenses have the ability to reduce higher-order aberrations and the associated symptoms in post-LASIK Patients has not been explored in detail. The following article attempts to explain the significance of wearing such contact lenses in patients who have already undergone LASIK surgery.

History and background
Reverse geometry lenses were first developed in late 1980s to match the corneal shape of post-refractive surgery patients who had RK (Radial Keratomy) procedures. These lenses were sometimes referred to as plateau lenses because of their design. The secondary curve was made steeper than the central base curve to better match the reverse geometry cornea created through RK surgery. In fact, post-refractive surgery was one of the first reasons reverse geometry lenses were developed. However, their usage has decreased in everyday optometric practice over the past 15 years. Today, reverse geometry lenses are often used to fit irregular and compromised corneas.

Why are they called reverse geometry lenses?
Reverse geometry lenses are so called because their curves are opposite of traditional lenses. The base curve is much flatter than the central cornea and the first peripheral curve is steeper. This allows the central corneal tissue to be pushed away from the center of the cornea, providing a "ripple effect", like dropping a pebble in the water. The displaced corneal tissue moves into the peripheral curve area of the contact.

Advantages of reverse geometry lenses:

  • Reverse geometry RGP lenses have significantly advanced corneal reshaping.
  • A slightly greater than average edge lift is often preferred in reverse geometry lenses. This helps insure enough tear exchange and helps prevent seal-off.
  • Large diameter reverse geometry lenses often are a good choice for corneal grafts. Because of their larger diameter, they cover almost the entire cornea.
  • Reverse Geometry Lenses create a significantly shorter time to achieve good visual results. Instead of taking weeks to months to reduce nearsightedness, it only takes days to a few weeks.
  • Researchers have also found that wearing a reverse geometry lens for a specific number of hours each day reduces nearsightedness.

Some advantages of wearing reverse geometry lenses only overnight are that the endpoint of clear vision without glasses can be achieved much sooner than daytime wear and that lens awareness and frequent lubrication are greatly reduced.

Wave-front aberration reduction - A special benefit of RGRGP
It has been shown that wearing of reverse geometry rigid gas permeable contact lens reduces higher-order aberrations and the associated symptoms in post-LASIK patients and allows them to achieve supernormal vision, with better than 'normal' visual acuity and contrast sensitivity after LASIK.

What are wave-front aberrations?
The propagation of 'light' has been described as a rapid movement of energy particles (photons) that travel in a wave-like manner. Aberrations are focusing errors that prohibit proper image formation. In a perfect optical system, spherical wave fronts of light from an object point should converge to a single point focus at the desired image location, such as the retina of the eye.

In the presence of optical aberrations, however, these wave fronts become either too steep, too flat, or distorted from their ideal shape.

What is the evidence?
The most recent clinical studies or scientific evidence also support the wearing of RGRGP lenses in patients who have undergone LASIK surgery. For example, during a 60-day clinical trial, after just seven nights of wearing reverse-geometry gas permeable contact lenses, researchers saw improvement in the daytime eyesight of seven out of eight nearsighted - or myopic - subjects. The patients actually wore rigid gas permeable lenses every night of the study during at least seven hours of sleep.

Conclusion
The application for reverse geometry lenses in LASIK patients is just now beginning to be considered as a fitting option for such procedures. However, the future for the application of this design looks very promising because of its effectiveness, safety and various other advantages over traditional contact lenses.

Learn more about how contact lenses can help with LASIK complications on our forums!