A bitoric gas permeable hard contact lens with spherical power effect

Area of Science:

• Ophthalmology
• Optometry
• Contact Lens Technology

Background:

• Gas permeable (GP) bitoric contact lenses offer customized fits for astigmatic eyes.
• Polycon II lenses provide a range of parameters for fitting complex corneal shapes.
• Accurate fitting is crucial for visual acuity and patient comfort.

Purpose of the Study:

• To evaluate the in vivo fitting performance of a 36-lens set of Polycon II gas permeable hard bitoric contact lenses.
• To determine the proportion of patients successfully fitted with spherical power effect (SPE) versus cylinder power effect (CPE) lenses.
• To assess the relationship between lens parameters and corneal topography.

Main Methods:

• A fitting set of 36 Polycon II gas permeable hard bitoric lenses was utilized.
• Fifty patients were fitted with these lenses to assess in vivo performance.
• Corneal topography (K readings) was used to guide lens selection and evaluate fit parameters.

Main Results:

• Thirty-six patients (66 eyes) were successfully fitted using spherical power effect (SPE) lenses.
• Fourteen patients (27 eyes) required cylinder power effect (CPE) lenses for optimal correction.
• The mean flat base curve was 0.45 D.K. flatter than the mean flat corneal K reading, and mean base curve toricity was 0.50 D.K. less than mean corneal toricity.

Conclusions:

• The Polycon II gas permeable hard bitoric lens system demonstrates high success rates for fitting patients with astigmatism.
• A significant portion of patients can be effectively managed with SPE lenses, simplifying the fitting process.
• The lens design allows for adjustments in base curve and toricity to match corneal contours, leading to excellent patient satisfaction in most cases.