Contact lens overrefraction variability in corneal power estimation after refractive surgery

Area of Science:

• Ophthalmology
• Optometry
• Corneal Refractive Surgery

Background:

• Accurate corneal power measurement is crucial after refractive surgery.
• Traditional methods may be less reliable in post-keratorefractive surgery eyes.
• Contact lens overrefraction (CLO) offers an alternative approach.

Purpose of the Study:

• To assess the accuracy and precision of the CLO method for determining corneal refractive power.
• To compare CLO with historical methods in eyes post-myopic laser in situ keratomileusis (LASIK).
• To evaluate the impact of different rigid lens fitting strategies on CLO outcomes.

Main Methods:

• Prospective case series of 14 eyes from 7 subjects post-myopic LASIK with stable refractions.
• Comparison of CLO method with a historical corneal power prediction method.
• Evaluation of 4 rigid lens fitting strategies and 3 pupil scan sizes using cycloplegic CLO with Nidek OPD-Scan ARK-10000.

Main Results:

• CLO-estimated corneal power varied significantly based on lens fit.
• Bias between CLO and historical methods ranged from -0.38 to +2.42 D, differing from zero in most strategies.
• Precision varied substantially, with 95% limits of agreement ranging from 0.50 D to 2.59 D.
• Flat-fitting 9.0 mm diameter lenses yielded the least precise results.

Conclusions:

• The accuracy and precision of the CLO method in post-refractive surgery eyes are highly dependent on rigid lens fitting.
• A common clinical practice of flat-fitting 9.0 mm lenses resulted in the poorest accuracy and precision.
• Employing large-diameter lenses may enhance the outcomes of the CLO method.