[Can the scattering of differences from the target refraction be avoided?]

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optics

Background:

• Stochastic error in intraocular lens (IOL) power calculations is a critical factor in achieving desired refractive outcomes.
• Two common IOL formulae, SRK-II and Haigis, were evaluated for their impact on stochastic error.

Purpose of the Study:

• To compare the effect of the SRK-II and Haigis formulae on stochastic error in IOL power calculations.
• To analyze the propagated error in IOL power calculations using different biometric measurements.

Main Methods:

• IOL power was calculated using SRK-II and Haigis formulae.
• Eye length was measured using ultrasound and IOL Master.
• Gauss error analysis was applied to examine propagated error.

Main Results:

• No significant difference in postoperative refraction was observed between the SRK-II and Haigis formulae across different biometry methods.
• The SRK-II formula exhibited a smaller propagated error compared to the Haigis formula.
• The Haigis formula's propagated error is calculated as DeltaP = sqrt((deltaL x -4.206)^2 + (deltaVK x 0.9496)^2 + (DeltaDC x -1.4950)^2).
• The SRK-II formula's propagated error is calculated as DeltaP = sqrt((DeltaL x -2.5)^2 + (DeltaDC x -0.9)^2).

Conclusions:

• While complex formulae like Haigis can limit systematic error, they may increase refractive dispersion due to more parameters.
• A balance between formula complexity and the number of measured parameters is necessary for optimal refractive outcomes.
• The SRK-II formula is considered a practical and still relevant option in IOL power calculation.