A Lens Implant with Adjustable Focus
The Crystalens™ implant is intended to accommodate or adjust for close focus. It is not a perfect replacement for the eye’s natural lens; at best it can accommodate to a limited extent (about 1.5 diopters), slightly less than the accommodative capacity of the young adult eye (about 4.0 diopters). However, it can certainly allow improved distance, intermediate and near vision compared to previous monofocal lens designs. Glasses may still be necessary for sustained reading of small print.
The Crystalens enables people over 50 to:
- Reduce or eliminate pre-existing near- or far-sightedness, and
- Restore a significant amount of close-focusing capability
The combination of clear distance, intermediate and near vision creates the potential to see clearly without glasses at all these ranges!
Standard lens implants are single-focus lenses (“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 (viewing 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, enabling a wider range of vision than what monofocal lenses provide. 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 Crystalens affords improved distance, intermediate and near vision compared to monofocal IOLs. Reading glasses may still be necessary for sustained reading of small print.
A Crystalens can be placed only at the time of initial cataract or 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 lens implant surgeon. He has treated thousands of Los Angeles cataract patients. He has treated many cataract patients, as well as those seeking clear lens replacements.