Soft Contact Lens Fitting for Irregular Corneas
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Solution Overview
Problem
Fitting soft contact lenses on irregular corneas is challenging due to the lack of effective methods for assessing the fit, requiring a high degree of skill and significant trial and error, as traditional fluorescein techniques are not applicable and provide limited information.
Innovation Solution
A method involving corneal profile inference using analytical techniques, selection of test fitting lenses based on pre-determined profiles, and assessment of parameters like movement, rotation, centration, comfort, and visual acuity to optimize the fitting process, with optional adjustments to achieve a desired fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If soft contact lenses are used for irregular corneas, then comfort and oxygen permeability are improved, but the ability to assess fit using traditional fluorescein techniques is lost
Solution Approach 1:
The patent uses a rigid test lens as an intermediary tool during the fitting process. The rigid lens temporarily replaces the soft lens to allow fluorescein staining and proper fit assessment using traditional techniques. Once the optimal fit is determined with the rigid test lens, the soft lens parameters are adjusted accordingly. This mediator approach enables the use of reliable assessment methods while ultimately achieving the comfort benefits of soft lenses.
Solution Approach 2:
The patent performs preliminary fit assessment using rigid lenses and fluorescein staining before finalizing the soft lens prescription. By conducting the fit evaluation in advance with a rigid test lens, the practitioner can determine the appropriate base curve and diameter for the soft lens without relying on unreliable fluorescein assessment during soft lens fitting. This preliminary action resolves the contradiction by separating the assessment phase (where rigid lenses excel) from the final wearing phase (where soft lenses provide comfort).
2Difficulty of detecting and measuring
If rigid contact lenses are used for irregular corneas, then fit assessment using fluorescein is improved, but comfort and oxygen permeability deteriorate
Solution Approach 1:
The patent segments the fitting process into two distinct phases: an assessment phase using rigid lenses with fluorescein staining, and a final fitting phase using soft lenses. The rigid test lens is used solely for determining the optimal base curve and diameter through reliable fluorescein assessment. Once these parameters are established, the soft lens is selected or customized to match these specifications. This segmentation allows each lens type to perform its optimal function - rigid for assessment, soft for comfort.
3Adaptability or versatility
If trial and error method is used for soft contact lens fitting, then adaptability to individual corneas is improved, but time and number of lenses required increase
Solution Approach 1:
The patent performs preliminary determination of the optimal base curve and diameter using rigid test lenses and fluorescein staining before selecting the final soft lens. This preliminary action eliminates the need for extensive trial and error with multiple soft lenses, as the critical fitting parameters are already optimized. The practitioner only needs to select a soft lens that matches the predetermined specifications, significantly reducing fitting time while maintaining high adaptability to the individual corneal shape.
Solution Approach 2:
The patent uses the rigid test lens as a template or copy to determine the specifications for the final soft lens. The base curve, diameter, and overall fit characteristics are copied from the successfully fitted rigid test lens to the soft lens selection process. This copying approach ensures that the soft lens will replicate the optimal fit achieved during assessment, reducing the need for multiple trials while maintaining high adaptability to the patient's specific corneal geometry.
Data Source
AI summary
Disclosed is a method of determining an appropriately shaped soft contact lens for a subject with an irregular cornea, the method comprising the steps of: inferring or deducing the profile of the cornea over at least a portion thereof: selecting a first choice fitting lens, the selection being based on the profile of the cornea obtained in the preceding step; assessing the fit of the contact lens to the cornea, by investigating each of the following parameters; (i) translational movement of the lens on eye; (ii) rotation of the lens on eye; (iii) centration of the lens on eye; (iv) the perceived comfort of the lens for the subject; (v) the visual acuity of the subject when wearing the lens; and adjusting the choice of fitting lens, if required, according to the assessment and reiterating until a desired fit of lens to the cornea has been obtained.