Effect Of Pars Plana Vitrectomy Combined With Retinal Laser Photocoagulation For Proliferative Diabetic Retinopathy On Corneal Tissue Structure

Purpose:To assess the effect of 25 G pars plana vitrectomy combined with retinal laser photocoagulation for proliferative diabetic retinopathy(PDR)on human corneal tissue structure and effect of 25 G pars plana vitrectomy for patients with non-DM on corneal tissue structure by in vivo confocal microscope(IVCM).Methods:This research was a prospective study and conducted at the Ophthalmology Center of Second affiliated Hospital of Jilin University.47 patients(62 eyes)with PDR who received 25 G pars plana vitrectomy combined with retinal laser photocoagulation from November 2012 to November 2012 were enrolled for this study Included in the PPV combined with laser group,and patients with non-DM(13 eyes)with macular epiretinal membrane or macular hole who received 25 G pars plana vitrectomy were Included in the PPV group.In vivo confocal microscopy using the corneal module of the Heidelberg Retina Tomograph(HRT Ⅲ;Heidelberg Engineering Gmb H,Heidelberg,Germany)was performed to capture images of Central corneal epithelium,corneal subbasal nerve plexus(SBNP)and corneal endothelium of all selected eye of each patient before surgery,1month and 3 months after surgery.Corneal nerve fiber length(CNFL)was analyzed using a computer software(Image J and Neuron J software),corneal epithelial cell density and corneal endothelial density(ECD)was measured by HRT-3 Rostock operating software.The changes of corneal tissue structure of PPV combined with laser group and PPV group at 1 month and 3 months after surgery were compared with those before surgery,and explore the correlation with surgical time,the number of laser points,vitreous silicone oil filling,high intraocular pressure after surgery,supplementary retinal laser photocoagulation therapy after surgery and other factors.Statistical analysis was performed with SPSS 26.0,and P value of less than 0.05 was considered significant.Results:1.The corneal epithelial cell density and corneal CNFL in the patients with PDR were significantly lower than those in the patients with non-DM before surgery,the differences were statistically significant(P<0.05).2.The patients with PDR who underwent PPV combined with retinal laser photocoagulation,the corneal epithelial cell density decreased significantly at 1month postoperatively compared with that before surgery(P<0.05),It was significantly improved 3 months after surgery compared with 1 month after operation(P < 0.05),and there was no significant difference compared with that before surgery(P > 0.05).3.The patients with PDR who underwent PPV combined with retinal laser photocoagulation,the corneal CNFL decreased significantly both at 1 month and3 months postoperatively compared with that before surgery(P<0.05),but there was no significant difference between 3 months postoperatively and 1 month postoperatively(P > 0.05).4.The patients with PDR who underwent PPV combined with retinal laser photocoagulation,the corneal ECD decreased significantly both at 1 month and 3months postoperatively compared with that before surgery(P<0.05),but there was no significant difference between 3 months postoperatively and 1 month postoperatively(P > 0 05).5.The patients with non-DM who underwent PPV,did not show any significant changes in corneal epithelial cell density,CNFL and ECD at 1 month and 3 months postoperatively compared with those before surgery,The differences were not statistically significant(P > 0.05).6.The decrease of corneal epithelial cell density at 1month postoperatively in patients with PDR was related to surgical time and high intraocular pressure after surgery(r=-0.312,P<0.05;r=-0.731,P<0.05);The decrease of corneal CNFL at 1month postoperatively in patients with PDR was related to the number of laser points,vitreous silicone oil filling and high intraocular pressure after surgery(r =-0.630,P < 0.05;r=-0.296,P < 0.05;r=-0.165,P < 0.05);The decrease of corneal ECD at1 month postoperatively in patients with PDR was related to surgical time,the number of laser points,vitreous silicone oil filling and high intraocular pressure after surgery(r =-0.412,P < 0.05;r=-0.499,P < 0.05;r=-0.333,P < 0.05;r=-0.298,P < 0.05).7.There were 2 patients(2 eyes)in the PPV combined with laser group(3.2% of the total eyes in this group)occurred Severe keratopathy During the period of postoperative follow-up.Conclusions:1.The corneal tissue structure of patients with PDR has been damaged before surgery,so it is a high-risk cornea.2.Pars plana vitrectomy combined with retinal laser photocoagulation for PDR can lead to further damage in corneal tissue structure,in which the changes of corneal epithelial cells can recover slowly,Corneal nerve fiber length and corneal endothelial cell counts decrease significantly in a short time,and the long-term changes need to be observed.3.There was no significant effect on corneal tissue structure in non-DM patients treated with pars plana vitrectomy,PPV is relatively safe for cornea.4.The changes of corneal tissue structure in patients with PDR after pars plana vitrectomy combined with retinal laser photocoagulation are related to surgical time,total laser energy of single retinal laser therapy,vitreous silicone oil filling and high intraocular pressure after surgery.5.The patients with PDR who underwent PPV combined with retinal laser photocoagulation is one of the high risk factors of severe keratopathy.