Abstract
Purpose: Standard intraocular lenses (IOLs) are mostly designed for far distance vision. Although accommodative IOLs have been proposed, the current designs only provide a modest range of accommodation in the best-case scenario. We describe here a new optical design providing a wide-range of potential accommodation change that could be incorporated in an IOL.
Methods: The mechanical properties of the capsule and the zonula are known to solely slightly change as the eye ages. The ciliary muscle essentially maintains its function during the life span. Consequently, there is a possibility to use the accommodation apparatus to eventually transmit the subtle mechanical changes into an IOL able for modulating its optical power. A family of optical designs with a variable power, sensitive to small compression forces has been devised. If incorporated within an IOL, power would change in response to small variations in their equatorial diameter. Regular materials available for standard IOL have been employed, as acrylics and silicones.
Results: The proposed design is a triplet-like optical structure that produces unprecedented gains between the equatorial compression and the subsequent change in lens power. Some of the generated IOL models exhibit an increase in their power of up to 10 D once implanted in the eye. The gain is approximately 1 D/µm of equatorial compression. The proposed IOL also permits the incorporation of aspheric or toric surfaces for optimizing ocular spherical aberration or correcting astigmatism. Chromatic aberration and ghost images analysis have been also accomplished showing a similar performance to monofocal standard IOLs currently available. The typical central thickness of the triplet is 1 mm, showing an optical zone of 6 mm of diameter. These dimensions and the structure of the proposed haptics might allow the implantation of the IOL through a corneal incision of 2-3 mm of diameter. The accurate control of the equatorial diameter of the accommodative IOL and its changes during accommodative efforts can be solved by using a special intracapsular ring. The distribution of radial forces of the implanted IOL combined with the ring showed an efficient mechanism to transmit the changes from the ciliary muscle to the lens.
Conclusions: A new triplet-type optical design in combination with a capsular ring for the precise control of its equatorial diameter may have the potential to restore accommodation after cataract surgery.
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