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Andre Messias, Rodrigo Faeda Dalto, Ferreira Miriam, Wilian Queiroz, Roberto Pinto Coelho, Jayter Silva Paula; Corneal curvature is a key determinant of Haigis and SRKT formulae accuracy of for intentional myopic overcorrection. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3103. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the influence of the biometric parameters on the accuracy of Haigis and SRKT formulae predicting postoperative target refraction (TR).
Retrospective analysis of 108 eyes (70 patients) that had uneventful phacoemulsification surgery with implant of Alcon-SN60WF intraocular lens (IOL). In 45 eyes, IOLs were intentionally targeted to myopia (-0.75 to -1.25 dpt), while the other 63 eyes targeted between 0 and -0.75 dpt. Preoperative axial length (AL) and keratometry (K) were measured with optical biometry (LENSTAR – Haag-Streit). Postoperative spherical equivalent (PSE) was assessed 12 ± 3 months after surgery.
Overall, mean PSE - TR showed a small myopic shift of 0.16 ± 0.04 dpt (p<0.05) for Haigis; and -0.02 ± 0.04 dpt (p>0.05) for SRKT formula. The differences between PTR and PSE were significantly correlated with PSE for Haigis (r=-0.65; P<0.01) and SRKT (r=-0.66; P<0.01). There was also a significant difference between Haigis and SRKT predictions: -0.18 ± 0.03 dpt (P<0.001), and the difference between the two formulae is highly dependent on K (r=-0.75; P<0.01). Splitting the data according to preoperative K median, eyes with K < 43.75 targeted at myopia (n=23) showed a significant myopic shift of -0.26 ± 0.09 dpt (P<0.05) with Haigis, but a hyperopic shift of 0.24 ± 0.09 dpt (P<0.05) with SRKT.
Divergences between Haigis and SRKT formulae cause uncertainty choosing the IOL. These data indicate that, in eyes with lower preoperative K, an IOL targeted at myopia might result in a small, but significant myopic shift for Haigis formula, while with SRKT a hyperopic shift can be expected.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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