Intraocular pressure before and after capsulorhexis using two viscoelastic substances and two surgical approaches in enucleated porcine eyes

AIM:To investigate the influence of ophthalmic viscoelastic devices(OVDs)and different surgical approaches on the intraocular pressure(IOP)before and after creation of the curvilinear circular capsulorhexis(CCC)as a measure for anterior chamber stability during this maneuver.METHODS:Prospective experimental WetLab study carried out on enucleated porcine eyes.IOP was measured before and after CCC with the iCare Rebound tonometer(iCare ic200;iCare Finland Oy,Vantaa,Finland).The OVDs used were a cohesive one[Z-Hyalin,Carl Zeiss Meditec AG,Germany;hyaluronic acid(HA)]and a dispersive[Z-Celcoat,Carl Zeiss Meditec AG,Germany;hydroxy propylmethylcellulosis(HPMC)].The CCC was created using Utrata forceps or 23 g microforceps in different combinations with the OVDs.RESULTS:Using the Utrata forceps the IOP dropped from 63.65±6.44 to 11.25±3.63 mm Hg during the CCC.The use of different OVDs made no difference.Using the 23 g microforceps the IOP dropped from 65.35±8.15 to 36.55±6.09 mm Hg.The difference between IOP drop using either Utrata forceps or 23 g microforceps was highly significant regardless of the OVD used.CONCLUSION:Using the sideport for the creation of the capsulorhexis leads to a lesser drop in IOP during this maneuver compared to the main incision in enucleated porcine eyes.The use of different OVD has no significant influence on IOP drop.

Monitoring of central corneal thickness after phacoemulsification—comparison of statical and rotating Scheimpflug pachymetry,and spectral-domain OCT

AIM:To explore the possibility of deploying three contactless devices(static and rotating Scheimpflug technology,spectral domain optical coherence tomography)for measuring central corneal thickness(CCT)in preoperative and postoperative examinations of cataract patients.METHODS:Totally 72 patients who had undergone surgery without complications were selected.The CCT was measured prior to the operation,as well as on the first,5th-7th and 28th day following the operation using the Nidek NT 530-P,Sirius?,and Topcon OCT-2000 devices.RESULTS:A significant postoperative increase and subsequent decrease in CCT was identified with all three devices.The correlations were highly significant and thus reflect a very good degree of comparability at all times with the exception of the rotating Scheimpflug camera.The postoperative results from the latter differed significantly from the other devices.The correlations were Sirius/Topcon(P=0.010)and Sirius/Nidek(P<0.0005).No statistically significant difference could be identified in the comparison between Topcon and Nidek(P=0.056).CONCLUSION:All three devices are suitable for postoperative monitoring of CCT.The measurement results are only comparable to a limited extent and not interchangeable in the course of treating a single patient.This is due to the different imaging technology used in the devices and the resulting modalities for conducting the measurements.