Possible Future Presbyopia Treatments

For many years, presbyopia has been treated with reading glasses, bifocals, or contact lenses. More recently, FDA approval for correction of presbyopia has been given to Conductive Keratoplasty (CK), Refractive Lens Exchange, and LASIK monovision.

Two Presbyopia treatment Difficulties

Presbyopia is a progressive condition. As a person ages, visual blurriness increases, extending from near to intermediate to far distances. When the cornea is modified as a presbyopia treatment, as done in LASIK monovision, retreatment may be needed later.

So far nobody knows for certain what causes presbyopia. Briefly:

• The standard theory is that age makes the lens increasingly stiff so that it cannot become steep enough in its curvature for near vision
• Another long-favored theory is that the ciliary muscle which controls lens curvature becomes weaker and less able to contract strongly enough to steepen the lens for near vision.
• A more recent theory is that the lens continues to grow throughout life, expanding into the space needed by the ciliary muscle, which therefore has insufficient space to fully contract.

Despite these two difficulties, research is pushing ahead to find effective presbyopia treatments and several are in the experimental stages or in FDA testing.

PresbyLASIK

Just as a multifocal IOL has a built-in design for clear vision at all distances, so PresbyLASIK seeks to use a laser for doing the same thing right on the cornea. It is multifocal laser eye surgery and reshapes the cornea with three zones for near, intermediate, and far distances. Each zone refracts light differently and the brain will learn to choose which one to accept for a given object.

PresbyLASIK has been performed in several other countries with success but in the U.S. is still in the FDA testing period.

Surgical Reversal of Presbyopia (SRP) With Scleral Expansion Bands (SEB)

This treatment is based on the third theory bulleted above. Four thin segments are positioned just beneath the surface of the sclera. This creates more space between the circular ciliary muscle around the lens and the lens itself. It is thought that this extra distance between them allows for more tension in the ciliary muscle, which enables it to contract more and thus steepen the lens curvature for near vision.

This procedure is in FDA testing and yielding mixed results.

Corneal Inlays and Onlays

Contact lenses are placed on top of the cornea to modify the way it refracts light. In a similar way, corneal inlays and onlays are placed beneath the corneal surface for that purpose. They never need to be removed and need no care. They are made of biocompatible materials similar to that of the cornea itself.

• Inlays -- In 2006 FDA clinical trials began for an inlay called the ACI 7000, made by AcuFocus (a company in Irvine, CA) in partnership with Bausch & Lomb. The procedure calls for a thin corneal flap to be created. The inlay is placed beneath the flap and it is repositioned to hold the inlay in place. Anesthetic is used but no stitches are required. The procedure takes just 15 minutes.

This inlay’s design is based on the pinhole idea. If you have any blurriness in your vision, try looking at something blurry through a small hole in a piece of cardboard. You can also make a small aperture with your thumb, index finger, and middle finger. Hold it in front of one eye, close the other, and you will see more clearly. The ACI 7000 blocks some light just as your small hole does, thus allowing depth of focus and clarity at all distances.

• Onlays – These are made of genetically engineered material that resembles collagen, a fibrous protein found throughout the body. No corneal flap is required as with inlays. Instead, onlays are positioned in a specially-created pocket below the top corneal layer (epithelium). Researchers at the University of Ottawa are working on corneal inlays.

A potential advantage of both inlays and onlays is that a LASIK procedure could later reshape them, adjusting them to age-related changes in the eyes.

Bubbles in the Lens

The eye’s lens is made of water and protein fibers. In an interesting new approach based on the increasingly-stiff-lens theory of presbyopia causation (first bullet above), researchers at the University of Michigan at Ann Arbor are using a laser to increase lens flexibility.

They first create tiny bubbles in the lens, using a pulsed laser. Then ultrasound is used to push the bubbles against protein fibers in the lens and keep track of their locations. This is the same technology used in ultrasound imaging. Part of the ultrasound is reflected back from the lens, giving the researchers data as to bubble location.

Based on bubble locations, a laser targets the nearby fibers to loosen them and restore lens flexibility.

So far, this procedure has had good results in pig eyes but has not been tested on human eyes. The research team has been looking for a company to partner with in commercial development.

More Time Is Needed

The process of treatment development and then the 3-phase FDA testing takes years and is very expensive. So far FDA approval is not imminent for any new presbyopia treatments, but no doubt some will eventually be approved.

To learn more about new developments in the treatment of presbyopia, please contact a qualified ophthalmologist in your area.