Crystalens AO™ by Bausch + Lomb

A Unique, Adjustable-Focus Lens Implant 

by David A. Wallace MD

The Crystalens AO (successor to earlier models AT-5.0 and HD500) are revolutionary lens implants, enabling people who are over 50 to: Reduce or eliminate pre-existing near- or far-sightedness, and Restore a significant amount of close-focusing capability The new lenses provide a full range of vision that creates the potential to see near, far and everything in between without glasses! Crystalens Technology Standard lenses as placed in eyeglasses or used at time of lens replacement surgery (such as cataract surgery) are single-focus lenses (also called "monofocal" lenses). Monofocal lenses have for decades been the default lenses used to replace a cloudy natural lens during cataract surgery. Following surgery with monofocal lenses, if distance vision is clear then objects within arm's reach are blurry, such that reading glasses would be required to view a computer monitor, cell phone, wrist watch, restaurant menu, etc.   The Crystalens is one of a new class of lenses  that uses the eye's own focusing muscles to adjust focus from distance to near.

Consider the potential of NOT needing glasses!

Imagine the freedom of playing with grandkids without fumbling for glasses.	The Crystalens has evolved since its introduction in the US in about 2003.  Like other technology including cell phones, computers and digital cameras, Crystalens IOL technology advances incrementally over time.  The new AO (for "aspheric optic") lens is a slightly better design compared to previous versions.  The Crystalens AT-5.0 was introduced in 2003, and the HD (for "high definition") lens became available in the US in early July, 2008.  Dr. Wallace was the first surgeon in Los Angeles to implant the HD-500.  "People that know me know that I've been somewhat of a skeptic about visual quality with multifocal IOLs and earlier versions of the Crystalens.  But what I have heard, and discovered first-hand, shows the HD-500 to be very impressive indeed," he says.
The newest-generation Crystalens, the AO, became available in January 2010.  The aspheric optic enables slightly improved night vision compared to older models, but preserves focus across a rather wide focal range. To understand the full benefit of the Crystalens in comparison to older-style monofocal lens implants, it is important to understand the principles of accommodation and accommodative amplitude.

How Does the Crystalens Work?

This lens responds to the "pull" of the focusing muscles within the eye, slightly shifting its position in response to close focusing or accommodative effort. For distance viewing (when the ciliary muscles are relaxed), the lens sits slightly further back in the eye. When focusing on a near target (and ciliary muscles are contracting or under tension), the lens optic is moved slightly more forward in the eye, causing a focus shift. See the graphic at bottom of page for a visual demonstration.

The Crystalens is not a *perfect* replacement for the eye's natural lens; at best earlier versions had accommodative capacity in the range of about 1.5 diopters (close focus clearly to about 26").  The new Crystalens HD-500 is designed to enhance near vision clarity, and seems to have an accommodative capacity in the range of about 3.2 diopters (clear vision at near to about 12").  This compares very favorably to the normal eye of a 30-year-old, which can accommodate comfortably to about 4.0 diopters (closest comfortable focus to about 10"). However, the Crystalens can certainly allow improved distance, intermediate and near vision compared to monofocal lens designs. Reading glasses may still be necessary for sustained reading of small print.

"I can now shop for sporty sunglasses instead of worrying about prescription lenses or getting dirt in my contacts!"

A Crystalens can be placed only at the time of initial cataract or lens replacement surgery.  If the natural lens is not cloudy but has lost the ability to adjust focus, this is called clear lens replacement surgery. The Crystalens is placed within a thin membranous sheath called the lens capsule, which is connected to the ciliary muscle (focusing muscle of the eye) by tiny fibers called zonules. The capsular bag thus functions to suspend and support the lens implant in a fashion analogous to a hammock. Dr. David Wallace is a highly skilled Los Angeles cataract surgery specialist. He has treated many cataracts patients, as well as those seeking clear lens replacements. Visit the cataracts page to learn more about the implant procedure.