| Anterior segment changes after Pars plana vitrectomy(PPV) have an important role on clinical outcomes for their influence to recovery time ,dioptric media, even the whole eye. The Pentacam (Oculus Optikger te GmbH) offers evaluation of the entire anterior segment from the anterior corneal surface to the posterior lens surface using a rotating Scheimpflug camera. The purpose of this study were to observe and analysis the corneal topography, SIA, pachymetry, the anterior chamber and the IOL decantation and tilt changes induced by the operation. Futher analyses were to determine the effect of two different operation mode (PPV or combined cataract surgery), two instrumentation systems (conventional 20G PPV or 23GTSV) and Diabetic mellitus on anterior segment changes, if exist.Methods:This clinical study was prospectively self-controlled consecutive comparative trial. Eighty eyes of 76 patients who underwent conventional 20G or 23G PPV combined or uncombined with 3.2mm clear corneal incision phacoemulsification cataract extraction and IOL implantation were analyzed. Pentacam were performed preoperatively and postoperatively at 1 week, 1 month, and 3 months to compare the anterior segment changes in different follow-up time. The parameters included the horizontal and vertical corneal curvature, surgical induced astigmatism (SIA), the corneal thickness, the anterior chamber depth , volume and angle, IOL decentration and tilt before and after surgery were analysed by the SPSS 13.0 statistical software package.Results:1. The SIA was highest at postoperatively 1 week, then fluctuated during the next 3 months. The different operative modes, different instrumentations and DM show no statistically independent influence on SIA. It was also found that the horizontal curvature increase, while the vertical curvature decrease, but it is only statistic significant in horizontal axis of left eye. The axis changes after surgery trend to be opposite between right and left eye.2. Pachy P, Pachy T, Pachy I, Pachy V were increased statistically after surgery. Influence of DM on Pachy V and Pachy T are statistically singnificant. However Pachy L didn't change before and after surgery.3. The anterior chamber depth (ACD), anterior chamber angle (ACA) and anterior chamber volume (ACV) increased after surgery in the eyes underwent combined CE/PPV group, then the changes stabilized postoperatively. Different vitreous tamponades didn't influcence ACD, ACA and ACV.4. ACD and ACA didn't change after PPV, while only ACV decreased statistically. But the changes were similar among different vitreous tamponade groups.5. IOL decentration and tilt didn't change postoperatively. The IOL positions were statistically same in 3 endotamponade groups.Conclusion:1. SIA was affect by many factors, such as combined CE, DM, location of the incision, but none of them can determine SIA separately. The location of incision can affect the axis of SIA. Till 3 months after surgery, the SIA still fluctuated, so the further study still needed to make sure the stabilization time of SIA. One should take into consideration that patients's visual acuity would be certainly impaired severely by SIA, some methods could be done against it preoperatively.2. The corneal thickness, what were supposed to reflect corneal endothelial function, were increase after PPV or combined CE/PPV. Diabetic mellitus were another risk factor. Hence routine examination of endotheliocyte may be necessary for patient preoperatively.3. ACV decreased, ACD and ACA were stable after PPV. ACD, ACA and ACV increased after combined CE/PPV. So PPV or combined CE/PPV is safe procedure for angle-closure glaucoma.4. IOL position was stable postoperatively in the combined CE/PPV eyes, ignoring different endotamponades.5. However, larger and better designed evidence-based studies are required to better understand the detail effect of DM, instrument, tamponade to anterior segment changes.
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