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Comparison of the accuracy of intraocular lens power calculations for cataract surgery in eyes that underwent phototherapeutic keratectomy
Session Title: Biometry
Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30
Paper Time: 09:45
Venue: Elicium 2 (First Floor)
First Author: : Y.Yaguchi JAPAN
Co Author(s): : K. Negishi M. Saiki H. Torii T. Shimizu K. Tsubota
To compare the accuracy of several methods of intraocular lens (IOL) power calculations for cataract surgery in eyes that underwent phototherapeutic keratectomy (PTK).
We retrospectively analyzed the preoperative and postoperative data from patients with cataracts who previously underwent PTK and later underwent phacoemulsification with IOL implantation at Keio University Hospital, Tokyo, Japan.
We retrospectively evaluated the medical records of 25 eyes of 15 patients who underwent cataract surgery after PTK. The axial length was measured with the IOLMaster (Carl Zeiss Meditec); the corneal radius was measured with the IOLMaster, ARK-10000 (Nidek), CASIA (Tomey), or Pentacam (Oculus). The anterior chamber depth was measured with the IOLMaster or ultrasound (UD-6000) (Tomey). The lens thickness was measured with ultrasound (UD-6000); the corneal thickness was measured with the Pentacam. The prediction error, that is, the difference between the estimated postoperative spherical equivalent and the postoperative manifest refraction at the spectacle plane, was calculated using six formulas: SRK/T, Holladay, Haigis-L, Shammas, Camellin-Calossi, and OKULIX ray tracing software. The median values of the arithmetic and absolute prediction errors were compared among the six formulas because the errors are not normally distributed.
The median values of the arithmetic errors between the predicted refraction and the refraction after cataract surgery were: SRK/T formula, 1.04 diopter (D) (range, -0.41 to 2.79 D); Holladay formula, 0.88 D (range, -0.37 to 2.80 D); Haigis-L formula, -0.49 D (range, -2.14 to 2.76 D); Shammas formula, -0.29 D (range, -1.89 to 2.71 D); Camellin-Calossi formula, 0.00 D (range, -1.35 to 1.98 D); and OKULIX ray tracing software, 0.72 D (range, -0.61 to 2.60 D). The percentage of errors within ±0.5 D with each formula were: SRK/T formula, 16.0 %; Holladay formula, 32.0 %; Haigis-L formula, 36.8 %; Shammas formula, 23.8 %; Camellin-Calossi formula, 52.0 %; and OKULIX ray tracing software, 25.0 %. Use of the Camellin-Calossi formula resulted in a significantly higher percentage of eyes within ±0.5 D compared with the SRK/T (P=0.008), Shammas (P=0.049), and OKULIX ray tracing software (P=0.049) formulas.
The Camellin-Calossi formula may be a good option for calculating IOLs power in eyes that underwent PTK.