Asymmetric Pseudotruncation for Translating Presbyopic Contact Lens
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Solution Overview
Problem
Conventional translating contact lenses often compromise comfort due to a relatively flat edge, which can cause discomfort for wearers, and fail to fully engage the lower eyelid for effective lens translation.
Innovation Solution
A translating contact lens design featuring a pseudotruncation that is asymmetric about the vertical meridian, with a thickened portion that engages the lower eyelid to facilitate translation and improve comfort, utilizing a mathematical smoothing function to optimize the lens's surface for refractive correction and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a truncated shape is used with a flat edge to facilitate lens translation, then lens translation capability is improved, but wearing comfort deteriorates
Solution Approach 1:
The patent applies asymmetry by positioning the thickest portion of the lens off-center, specifically nasalward and inferiorward from the geometric center. This asymmetric thickening creates an engagement feature that interacts with the lower eyelid to enable translation while maintaining a rounded, comfortable periphery that does not cause discomfort. The asymmetric placement allows the thick portion to engage the eyelid for translation facilitation while the rest of the periphery remains smooth for comfort.
Solution Approach 2:
The patent implements local quality by creating a localized thickened portion at a specific location (nasalward and inferiorward from center) rather than uniformly thickening the entire lens. This localized thickening serves the specific function of eyelid engagement for translation, while other portions of the lens maintain their normal structure for comfort. The thickest portion acts as a focal engagement point that facilitates translation without compromising overall comfort.
2Ease of operation
If a uniformly thickened peripheral portion is used to contact the lower lid, then lens translation is improved, but asymmetry with natural eyelid movement is created reducing effectiveness
Solution Approach 1:
The patent directly addresses eyelid movement asymmetry by positioning the thickest portion of the lens asymmetrically - specifically nasalward and inferiorward from the geometric center. This asymmetric positioning matches the non-symmetrical nature of lower eyelid movement during blinking and gaze shifts. The thickest portion serves as the primary engagement point that follows the asymmetric path of eyelid motion, enabling effective translation that adapts to natural eyelid behavior rather than opposing it.
Data Source
AI summary
Lenses for correcting presbyopia are translating, multifocal contact lenses with pseudotruncations which are asymmetric about the vertical meridian.