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Accommodating action of CrystaLens IOL observed in human eye model
Flexible plate-haptics permit forward movement of the IOL, offering the potential for true accommodation.
Cataract surgery with IOL implantation has evolved considerably over the past several decades. One of the limitations of modern surgery is the lack of accommodation following implantation of an IOL. Although multifocal IOLs have been developed in an attempt to alleviate the lack of accommodation, these lenses have potential problems regarding visual aberration and contrast sensitivity. A truly accommodative IOL, which would provide adequate near and distance vision without subsequent visual aberrations, has recently been developed. This lens was studied in a human eye model.
The C&C Vision CrystaLens accommodative IOL was developed to move forward to accommodate without dislocation of the IOL. A human eye model using the Miyake-Apple viewing technique was developed to study this accommodative IOL.
The CrystaLens accommodative IOL is a silicone plate-haptic IOL with a 4.5-mm optic and peripheral poly amide mini-loops. A hinge-type modification exists at the junction of the optic and the plate-haptics to allow the IOL to flex forward with accommodative action. The proposed mechanism of accommodation is forward movement of the IOL secondary to ciliary muscle contraction and redistribution of the ciliary body mass, which increases the vitreous pressure to allow forward movement of the IOL. This will result in near objects coming into a clearer focus.
Human cadaver eyes were sectioned coronally and fixed to a glass slide. Following removal of the cornea and the iris to improve visualization, a continuous curvilinear capsulorrhexis was performed with thorough hydrodissection. Phacoemulsification was then used to completely remove the lens nucleus and cortex. The IOL was then directly inserted into the lens capsular bag following expansion with viscoelastics.
Because we were unable to directly stimulate accommodation in this cadaver eye model, viscoelastic was injected into the vitreous cavity in order to manipulate vitreous volume. Injecting the viscoelastic caused anterior movement of the IOL to simulate accommodation. This change in near focus with anterior movement of the IOL was demonstrated by observing print coming into and out of focus as the position of the IOL was changed. The plate haptics of the IOL were found to flex at the hinged junction with the forward movement of the IOL, which brought near objects into focus.
We found that the forward movement of the CrystaLens IOL made possible by the flexible plate haptics demonstrated in this cadaver eye model offers the potential for a truly accommodative implant.
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A note from the editors:
The video demonstrating this accommodative IOL was a winner in the film festival at the recent American Society of Cataract and Refractive Surgery meeting in San Diego.
For Your Information:
- Nick Mamalis, MD, is a professor of ophthalmology at the University of Utah. He can be reached at the Moran Eye Center, University of Utah, 50 North Medical Drive, Salt Lake City, UT 84132; (801) 581-6586; fax: (801) 581-3357. Dr. Mamalis has no direct financial interest in any product mentioned in this article, nor is he a paid consultant for any companies mentioned.
- C&C Vision, manufacturers of the CrystaLens accommodative IOL, can be reached at 6 Journey, Suite 270, Aliso Viejo, CA 92656; (949) 916-9352; fax: (949) 716-8362.