Comparing sagittal heights calculated using corneal parameters and those measured with profilometry.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optometry

Background:

• Accurate measurement of ocular surface geometry is crucial for custom contact lens fitting.
• The sagittal height of the anterior eye (OC-SAG) is a key parameter for designing and fitting contact lenses.
• Discrepancies in OC-SAG calculation can lead to suboptimal lens fit and patient discomfort.

Purpose of the Study:

• To compare the anterior eye's sagittal height (OC-SAG) calculated from corneal parameters with profilometry measurements.
• To evaluate the accuracy of different calculation methods for OC-SAG in soft contact lens wearers.
• To determine the clinical significance of differences in OC-SAG measurements for contact lens fitting.

Main Methods:

• Retrospective analysis of 70 soft contact lens wearer eyes using the ESP profilometer.
• Calculation of OC-SAG using corneal parameters (mean k-values, eccentricity, corneal radius) at various chord diameters.
• Comparison of calculated OC-SAG with profilometrically measured OC-SAG, including analysis with and without a shape factor.
• Evaluation of a custom soft lens manufacturer's formula for OC-SAG calculation.

Main Results:

• Statistically significant differences were found between calculated and measured OC-SAG, increasing with larger chord diameters (p < 0.001).
• Including a shape factor reduced differences, but they remained significant for larger diameters.
• Using the inner best-fit sphere for OC-SAG estimation showed minimal differences for specific chord diameters (14 and 14.5 mm).
• Correlation coefficients ranged from 0.53 to 0.90, indicating moderate to strong agreement depending on the method and diameter.

Conclusions:

• Calculated OC-SAG using corneal parameters shows statistically and clinically significant differences compared to profilometry, especially at larger chord diameters.
• These differences have implications for the accuracy of contact lens fitting.
• Further research is needed to address the impact of these OC-SAG discrepancies on contact lens fitting outcomes.