Comparison of postoperative anterior segment changes associated with pars plana vitrectomy with and without vitreous base shaving

AIM:To compare changes in anterior segment topography and axial length(AL)evaluated with Pentacam and IOL Master after pars plana vitrectomy(PPV)performed with and without vitreous base shaving.METHODS:This prospective study included patients who underwent PPV or phacoemulsification+PPV(Phaco+PPV)for various indications.Patients who underwent total posterior hyaloid detachment and excessive vitreous base shaving with scleral indentation were referred to as complete PPV(c-PPV).The patients whom posterior hyaloid was separated as far as the posterior arcades and vitreous base shaving with scleral depression was not performed were classified as the partial PPV(p-PPV)group.All patients underwent detailed ophthalmologic examinations preoperatively and lwk,I,and 3mo postoperatively.Changes in the anterior chamber depth(ACD),anterior chamber volume(ACV),iridocorneal angle(ICA)f central corneal thickness(Cd),and keratometric measurements(K1 and K2)were evaluated with Pentacam HR.Changes in the AL measurements were analyzed with IOL Master.RESULTS:A significant increase in ACD was observed in c-PPV cases(P=0.02),but this increase was not significant in the p-PPV group(P=0.053).In contrast,ICA increased significantly in the c-PPV group(P=0.02)but decreased in the p-PPV group(P=0.09).BCVA was significantly improved in the c-PPV group from week 1(P<0.001)while the increase in the p-PPV group reached significance at 3mo(P=0.035).Cd increased in the first week and later returned to baseline in both groups.No significant differences in the other parameters were observed between the groups,and there were no significant changes in intraocular pressure,ACV,AL,K1 or K2 values(P>0.05 for all).CONCLUSION:Incomplete posterior hyaloid excision and not removing the vitreous base in PPV surgeries may create a more stable anterior chamber,thus preventing the downward movement of the lens-iris diaphragm,and may cause ciliary body retraction,thereby reducing ICA.Awareness of these effects can provide some amount of guidance to physicians in selecting the appropriate PPV procedure and preempting surgical complications.