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Soft toric lens power accuracy and reproducibility
R E Payor1, S R Robirds, X Zhang
1Clinical Studies Department, CIBA Vision Corporation, Atlanta, Georgia 30136, USA.
Summary
Accurate soft toric lens power is crucial for vision. A new method found 83.5% of tested lenses met visual acuity standards, estimating a 3.3% clinical problem rate for power reproducibility.
Area of Science:
- Ophthalmology
- Optometry
- Optical Engineering
Background:
- Reproducible soft toric lens performance relies heavily on accurate lens power.
- This accuracy is paramount for planned replacement soft toric lenses due to frequent replacement cycles.
- Current evaluation methodologies for toric lens power accuracy lack reproducibility.
Purpose of the Study:
- To develop a reproducible methodology for evaluating soft toric lens power accuracy.
- To quantify the optical error and its effect on visual acuity.
- To estimate the clinical problem rate associated with power variability in soft toric lenses.
Main Methods:
- Developed a novel power measurement method eliminating measurement error.
- Employed geometric optical calculations to determine resultant optical error.
- Utilized the relationship between visual acuity loss and optical errors to predict visual impact.
- Applied the method to a sample of 457 Focus Toric soft contact lenses.
Main Results:
- 83.5% +/- 1.7% of tested lenses demonstrated sufficient power accuracy for ≤1 line of visual acuity loss.
- The estimated clinical problem rate due to power reproducibility issues was 3.3% +/- 0.9% of lens pairs.
- Monthly replacement of lenses would result in approximately one problematic pair every 30 months.
Conclusions:
- The developed method provides a reproducible means to assess soft toric lens power accuracy.
- A significant majority of tested soft toric lenses meet acceptable power accuracy standards.
- Power variability remains a potential source of clinical issues, particularly with frequent lens replacement schedules.