Accuracy Of Intraocular Lens Calculation Formulae In Short Eyes

PURPOSETo compare the accuracy of intraocular lens calculation formulas(SRK/TN Hoffer Q、 Haigis-1. Haigis-3) in short eyes, we want to find the major relative factors which induce prediction error, and to search the most accurate formula for short eyes.METHODSThere are tow parts of the study.The first part is theoretical analysis, using the current formula of intraocular lens calculation formulas(SRK/T、Hoffer Q、Haigis-1、Haigis-3), mainly through the single variable analysis, comparing the consistency of different formula, so as to find differ-ences of the theoretical calculation results between different formulae.The second part is a self-retrospective comparative was made including 36 person (48 eyes) who had axial length less than 22mm,and be taken phacoemulsification and IOL implantation during April 2012 to November 2014, in department of the second hospital of Shandong university. All biometry measurement which before surgery were done by 10LMaster, which 3 to 8 weeks after surgery were done by 10LMaster and autorefractor. The mean absolute errors(MAEs) predicted by SRK/T、Hoffer Q、 Haigis-1(only a0 optimized)and Haigis-3 (a0,aland a2 optimized) were compared. The correlations between anterior chamber depth (ACD), Keratometry and predicted refractive error calculated by the 4 formulae were analyzed. The data was analyzed by SPSS 17.0RESULTS:In the first part,, every formulae’s results have better consistency when the AL is greater than 24 mm, As AL decreased, differentials among SRK/T, Haigis-1 and Hoffer Q are increased; In short AL cases, Differentials between Haigis-1/SRK/T and Haigis-1/Hoffer Q are bigger than that of Haigis-3 formula; Haigis-1 formula’s results significantly deviate from the other with ACD’s change, results of Haigis-3 formula and Hoffer Q formula is most closed and form a cross, the average error is 0.35 D, when 2.3 mm< ACD< 3.3 mm, the deviation is less than 0.35D, so that 2.3 mm and3.3 mm can be used for the cut-off point.From part 2, there were no significant differences in the MAEs predicted by SRK/T、 Hoffer Q、Haigis-3 except Haigis-1(0.81D, P<0.05). The others MedAEs value is 0.38D (by Haigis-3),0.50D (by Hoffer Q.) and 0.45D (by SRK/T). There were no significant correlation between the MedAEs predicted and Keratometry by SRK/T% Hoffer Q、 Haigis-3 except Haigis-1(P<0.01). The difference among the refractive errors predicted by the 4 formulas increased significantly as ACD decreased. In group of ACD less than 2.3mm, the MedAEs predicted by the Haigis-3(0.35D) was significantly smaller than that predicted by the Hoffer Q (0.61D) and SRK/T (0.62D).There were no significant difference found among SRK/T% Hoffer Q、Haigis-3 in eyes with an ACD of 2.3mm or more, but the Haigis-1.Conclusion:The predicted refractive errors increased as ACD decreased in short eyes therefore, ACD should be considered when choosing the IOL power calculation formulae in short eyes. The Haigis with aO optimized only will produce a significantly refractive errors. Haigis with a0,a1 and a2 optimized can predict accurate, should be taken firstly in short eyes. When there no Haigis formula with a0,a1 and a2 optimized, SRK/T and Hoffer Q. formulae can be chosen if an ACD is 2.3mm or more.