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The impact of A constant optimization on postoperative refraction after cataract surgery.

Poster Details

First Author: T.Haite LATVIA

Co Author(s):                  

Abstract Details


To optimize intraocular lens (IOL) A constants for partial coherence interferometry (PCI) with IOLMaster device. To investigate, describe and quantify the advantages and effect of optimization of A constant, for a given surgeon/intraocular lens (IOL) combination, on postoperative refraction after cataract surgery.


Department of Ophthalmology, Paul Stradins Clinical University Hospital, Riga, Latvia.


All preoperative and postoperative data were prospectively collected for uneventful phacoemulsification cataract surgery with in-the-bag placement of the IOL performed by a single surgeon between August, 2011 and January, 2012. Biometry performed using the IOLMaster PCI device for axial length measurments and keratometry. The IOL prediction was based on the SRK/T formula. Subjective postoperative refraction and corrected distance visual acuity (CDVA) at least 6 weeks after surgery were determined. Exclusion critea were: any previous ocular surgery, ocular comorbidity, no PCI biometry, any operative complication, other posterior chamber IOL, CDVA worse than 0.5. Data for AcrySof Natural Single-Piece IOL, model SN60AT, a manufacturerÂ’s A constant 118,4 (Alcon) and AcrySof IQ Aspheric Natural IOL, model SN60WF, A constant 118,7 (Alcon) were analyzed. Mean error (ME) of prediction and mean abolute error (MAE) were calculated.Optimization of A constants was performed using IOLMaster optimization programme. An ME of prediction and an MAE using the optimized lens constants was then calculated for the same eyes which had been operated using the manufacturerÂ’s nominal A constants.


The mean age was 71.69±8.51 years and 75.42±8.74 years, the mean axial length was 23.70±1.15mm and 24.06±1.42mm, the mean keratometry was 43.75±1.42D and 44.23±1.65D, the optimized A constants were 118.8 and 119.1 for AcrySof Natural Single-Piece IOL and AcrySof IQ Aspheric Natural IOL, respectively. There was statistically significant difference between nominal and optimized A contants in terms of the MAE, the ME of prediction and in terms of the proportion of eyes within ±0.25D, ±0.5D, ±0.75D of target refraction. Optimization of IOL constants reduced the MAE from 0.41±0.21D and 0.40±0.21D to 0.17±0.14D (t=7,70, p<0,001) and 0,22±0,22D (t=3,78, p<0,001) for the AcrySof Natural Single-Piece IOL and AcrySof IQ Aspheric Natural IOL, respectively. The percentage of eyes within ±0.25D, ±0.5D, ±0.75D of target refraction improved from 23%, 69%, 92% to 73% (p<0,006), 96% (p<0,001) and 100% (p<0,001) for AcrySof Natural Single-Piece IOL and from 21%, 71%, 92% to 63% (p<0,06), 83% (p<0,06) and 100% (p<0,001) for AcrySof IQ Aspheric Natural IOL, respectively.


Optimized A constants showed statistically significant refractive advantages over nonoptimized A constants. IOL constants optimization for IOLMaster biometry improved postoperative refraction predictability after cataract surgery. FINANCIAL DISCLOSURE?: No

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