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Analysis of the Z CALC™ toric calculator in predicting lens power

Poster Details

First Author: T.Yeo SINGAPORE

Co Author(s):    D. Pek   H. Fam           

Abstract Details


To assess the refractive outcomes of toric intraocular lenses (IOL) using the Carl Zeiss Z CALC&trade toric calculator, and compare to other lens formulae in predicting IOL power.


Department of Ophthalmology, Tan Tock Seng Hospital, Singapore


130 eyes underwent cataract surgery via phacoemulsification by a single surgeon. All were implanted with either a AT TORBI® 709M (n = 49) or AT LISA® toric 909M (n = 81) intraocular lens (IOL). The IOLs were selected based on the Carl Zeiss Z CALC&trade toric calculator. Patients were examined 1 day, 1 week and 1 month post-surgery. Clinical examination at 1 month included uncorrected visual acuity, best-corrected visual acuity by refraction, slit-lamp biomicroscopy, intraocular pressure, and dilated fundus examination. The spherical equivalent mean error (ME) and mean absolute error (MAE) were calculated and compared with that of other optimised IOL formulae (HofferQ, Holladay I, Haigis, SRK/T). Further analysis was performed for different axial lengths.


There were 47 males and 80 females. Mean axial length was 23.99 and 24.54, and mean K was 44.47D and 44.12D for 709M and 909M groups respectively. Mean cylinder in 709M group was 1.85 and that for 909M group was 1.54. For 709M, 75.5% of eyes achieved uncorrected visual acuity (UCVA) of ≥6/12 and 95.9% achieved best-corrected visual acuity (BCVA) of ≥6/12. For 909M, 88.9% of eyes achieved UCVA of ≥6/12 and 100% achieved BCVA of ≥6/12. For 709M, ME was 0 for HofferQ, Holladay I, Haigis and SRK/T while that for Z CALC&trade was 0.44. The MAE was 0.51, 0.48, 0.50, 0.47 and 0.54 for HofferQ, Holladay I, Haigis, SRK/T and Z CALC&trade respectively. For 909M, ME was 0 for HofferQ, Holladay I, Haigis and SRK/T while ME for Z CALC&trade was 0.13. The MAE was 0.30, 0.33, 0.29, 0.35 and 0.33 for HofferQ, Holladay I, Haigis, SRK/T and Z CALC&trade respectively. For different axial lengths, the MAE for Z CALC&trade was ≤0.64 for 709M. For 909M, the MAE was ≤0.40 for most axial lengths but was 0.81 for axial lengths of ≤22mm.


The Z CALC&trade is efficacious in predicting the correct IOL power, equivalent to other optimised IOL formulae, especially in eyes of average to long axial lengths. FINANCIAL INTEREST: NONE

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