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Haigis and SRKT formulae accuracy for intentional myopic overcorrection
Rodrigo Faeda Dalto1, Miriam A Ferreira1, Wilian Queiroz1
1Department of Ophthalmology, Otorhinolaryngology and Head and Neck Surgery, Ribeirão Preto Medical School, University of São Paulo, Avenida Bandeirantes 3900, Ribeirão Preto, SP, 14049-900, Brazil.
International Ophthalmology
|June 23, 2017
Summary
Preoperative keratometry influences refractive outcomes. Lower keratometry values with the Haigis formula may lead to myopic shifts, while the SRKT formula may cause hyperopic shifts in targeted myopia eyes.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Refractive Surgery
Background:
- Accurate prediction of postoperative refraction is crucial for successful intraocular lens (IOL) implantation.
- Existing formulae, such as Haigis and SRKT, have varying degrees of accuracy.
- Preoperative biometric parameters may influence the predictive accuracy of these formulae.
Purpose of the Study:
- To evaluate the impact of preoperative biometric parameters on the accuracy of the Haigis and SRKT formulae.
- To compare the predictive performance of these two formulae in eyes undergoing cataract surgery.
Main Methods:
- Retrospective analysis of 108 eyes from 70 patients who underwent phacoemulsification with Alcon-SN60WF IOL implantation.
- Preoperative axial length and keratometry (K) were measured using optical biometry (LENSTAR-Haag-Streit).
- Eyes were targeted for myopia or emmetropia, and postoperative spherical equivalent was assessed.
Main Results:
- A significant correlation was found between mean keratometry (K) and the prediction differences between Haigis and SRKT formulae (P < 0.001).
- Lower preoperative K values (<43.75 D) showed significant myopic shifts with Haigis and hyperopic shifts with SRKT when targeting myopia.
- K alone did not influence prediction error, but the difference between formulae was dependent on K.
Conclusions:
- Divergences between Haigis and SRKT formulae introduce uncertainty in IOL selection.
- In eyes with lower preoperative K, targeting myopia may result in a myopic shift with Haigis and a hyperopic shift with SRKT.
- These findings highlight the importance of considering preoperative K when selecting IOL power and formula.