Reducing Conjunctival Pressure in Silicone Hydrogel Contact Lenses

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Solution Overview

Problem

Silicone hydrogel contact lenses cause increased conjunctival pressure, leading to discomfort, redness, and the formation of conjunctival epithelial flaps due to their rigidity and mechanical interaction with the eye, which existing designs fail to adequately address.

Innovation Solution

The development of contact lenses with reduced peripheral stiffness, optimized sagittal depth, and modified edge designs such as bicurve surfaces, rounded edges, and microchannels to minimize conjunctival pressure and interaction, while maintaining high oxygen permeability and comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If silicone hydrogel contact lenses are used to provide high oxygen permeability and extended wear capability, then oxygen transmissability is improved, but conjunctival pressure and mechanical interaction with eye tissues increase

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidconjunctival pressure

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The contact lens is designed with non-uniform thickness distribution, featuring a thinner peripheral edge region compared to the central region. This local variation in thickness reduces the rigidity and mechanical interaction at the lens periphery where it contacts the conjunctiva, while maintaining adequate thickness and oxygen permeability in the central optical zone. The edge region thickness is specifically controlled to be between 0.05-0.20mm to minimize conjunctival pressure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent modifies the physical parameters of the contact lens by reducing the overall diameter from conventional sizes to a smaller diameter of 13.0-14.0mm. This parameter change reduces the surface area of the lens that contacts the conjunctiva, thereby decreasing mechanical interaction and conjunctival pressure while maintaining sufficient oxygen permeability through the reduced lens material volume.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the contact lens diameter is reduced to minimize conjunctival interaction, then conjunctival pressure is reduced, but optical coverage and visual quality may be compromised

Engineering Contradiction:

Improveconjunctival interactionVSAvoidoptical zone area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The contact lens incorporates an asymmetric design where the optical zone is optimized for the specific reduced diameter, with enhanced refractive index material or surface curvature in the central optical region to compensate for the smaller area. The peripheral regions are minimized to reduce conjunctival contact while the central optical quality is maintained through localized optimization of optical parameters.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If the contact lens edge is designed with a knife-point configuration to improve lens stability, then lens positioning is improved, but conjunctival staining and epithelial damage increase

Engineering Contradiction:

Improvelens stabilityVSAvoidconjunctival staining

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The contact lens periphery is designed with a fully rounded edge configuration, eliminating sharp knife-point edges. The rounded edge has a radius of curvature that smoothly transitions from the central optical zone to the periphery, reducing mechanical stress concentration and preventing conjunctival epithelial damage and staining while maintaining adequate lens stability through the rounded contour.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Duration of action of stationary object

If silicone hydrogel material is used to provide extended wear capability, then duration of lens wear is improved, but papillary conjunctivitis and superior epithelial splits occur

Engineering Contradiction:

Improvewear durationVSAvoidepithelial damage

Core Design Contradiction:

Duration of action of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The contact lens employs a thin-film design with reduced peripheral thickness (0.05-0.20mm) that increases flexibility and conformability to the ocular surface. This flexible thin-film structure reduces mechanical stress on the conjunctiva and epithelial tissues during extended wear, preventing papillary conjunctivitis and superior epithelial splits while maintaining the extended wear capability provided by the silicone hydrogel material composition.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS7360890B2Contact lenses and methods for reducing conjunctival pressure in contact lens wearers

Publication Date: 2008.04.22 COOPERVISION INT LTD

AI summary

Contact lenses, such as silicone hydrogel contact lenses, which are effective in reducing conjunctival pressure, and conjunctival epithelial flap formation or occurrence of a lens wearer's eye, and methods of reducing conjunctival pressure by a contact lens and/or formation of conjunctival epithelial flap formation are described. The present contact lenses reduce the interaction and/or pressure of the contact lens, or portion thereof, with or on the conjunctiva of a lens wearer's eye.