The Reliability Of Haigis Formula In Calculation Of Intraocular Lens Power In Patients With Cataract And High Myopia

Objective To study the accuracy of Haigis formula in predicting a target postoperativerefraction in patients with cataract and high myopia undergoing phacoemulsification and IOLimplantation, and assess the impact of the changes of anterior chamber depth (ACD) onpostoperative refraction.Methods This study comprised98eyes of72patients with cataract and high myopia(axial length≥26mm), including male41persons (55eyes),female31persons (43eyes). Thepatients were divided into three groups based on ocular axial length (AL):26mm＜AL<28mm group (32eyes),28mm≤AL <30mm group (40eyes).The IOL power wascalculated using Haigis formula. The refraction was done at1day,1week,1month and3months after surgery. The differences between actual postoperative refraction and assumedtarget refraction were analyzed. P<0.05was considered statistically significant.Thepreoperative and postoperative ACD was measured using Visante OCT. The correlationbetween changes of ACD and the axial length and the differences between actual ACD andassumed ACD were analyzed. The difference between the effective lens position (ELP）predicted with Haigis formula and actual postoperative ACD was evaluated. The impact ofACD changes on postoperative refraction was analyzed.Results (1) There was no statistical significance between the assumed target refractionby Haigis formula and actual postoperative refraction value in26mm＜AL＜28mm groupat1day,1week,1month and3months after surgery（P＞0.05）.There was statistical significance between the assumed target refraction by Haigis formula and actual postoperativerefraction in28mm≤AL＜30mm group and AL≥30mm group at1day,1week,1month and3months after surgery（P＜0.05）.(2) The differences were statistically significant between the mean preoperative ACDand postoperative ACDs in26mm＜AL＜28mm,28mm≤AL＜30mm group and AL≥30mmat1day,1week,1month and3months after surgery respectively（P＜0.05）.The differencewas no statistically significant between postoperative ACD at1day after surgery and1week,1month and3months after surgery.(3) The mean postoperative ACD change1.34±0.31mm.The correlations between theACD changes and the axial lengths was statistically significant（r=0.544，p=0.000）.As theaxial lengthening, the bigger the ACD changes.(4) The differences were statistically significant between the effective lens position(ELP）predicted with Haigis formulaand actual postoperative ACDs at1day,1week,1monthand3months in every group.The mean change1.19±0.24,the correlations between thechanges of ELP and actual postoperative ACD and the refraction prediction error wasstatistically significant（r=0.852，p=0.000）.the regression equation is y=0.27x+0.015，thestandardized regression coefficient is0.852.The mean predicted refractive outcome from a1.0mm difference in ACD was0.27D.Conclusion Haigis formula has higher reliability in predicting a target postoperativerefraction in patients with cataract and high myopia with axial length in26mm to28mmundergoing phacoemulsification and IOL implantation and less reliability in patients withaxial length more than28mm. The postoperative ACD was deepened obviously, comparingwith preoperative ACD. The postoperative ACD was relatively stable and there was noobvious change during3months observation. Postoperative ocular axial length werepositively correlated with the change of ACD. The mean predicted refractive outcome from a 1.0mm difference in ACD was0.27D,we should consider the changes in postoperative ACDwhen predicting IOL refraction with Haigis formula.