RESUMO
Objective:To explore the damage of panretinal photocoagulation (PRP) to the subbasal nerve plexus (SNP) and its related mechanisms by comparing SNP changes in wide-field mosaic between before and after PRP treatment in diabetic patients.Methods:A randomized controlled study was conducted.Fifty-seven patients (114 eyes) with type 2 diabetes mellitus and binocular diabetic retinopathy (DR) stage IV to receive PRP treatment in Shanxi Eye Hospital from April to November 2019 were enrolled.The subjects were randomly divided into horizontal-vertical laser group and vertical-horizontal laser group according to a random number table.Twenty-nine eyes from 29 patients were assigned to the horizontal-vertical laser group with the photocoagulation sequence of temporal-nasal-inferior-superior.Twenty-eight eyes from 28 patients were assigned to the vertical-horizontal laser group with the photocoagulation sequence of inferior-superior-temporal-nasal.The severer eyes of each subject were chosen as the treatment eye and the contralateral eyes were chosen as the control eye.Corneal confocal laser scanning microscopy (CCM) was performed before PRP treatment, 1 week after each photocoagulation, and 1 month after the completion of PRP treatment to collect images of the SNP over an area of 2-3 mm around the whorl-like pattern.Captured images at each time were merged into one image by using the Photoshop CC 2017 image processing software, and then the nerve fiber length (NFL) of whorl-like pattern was measured by Neuron J image analysis software.McGill pain questionnaire was used to investigate the pain of patients after each photocoagulation.The NFL changes of SNP at different time points were compared between different eyes and different photocoagulation sequence groups.The study protocol adhered to the Declaration of Helsinki and was approved by an Ethics Committee of Shanxi Eye Hospital (No.201804b). Written informed consent was obtained from each patient prior to entering the study cohort.Results:After PRP treatment, there were different degrees of neural structure loss of SNP nerve fibers in 11 treatment eyes, but there was no significant change in SNP nerve fibers in the control eyes.There were significant differences in NFL between the treatment eyes and the control eyes at various time points ( Feyes=2.020, P=0.039; Ftime=4.062, P=0.001). In the horizontal-vertical laser group, different degrees of neural structure loss on the photocoagulation side were found in SNP nerve fibers after the first and second photocoagulation.In the vertical-horizontal laser group, different degrees of neural structure loss on the photocoagulation side were found in SNP nerve fibers after the third and fourth photocoagulation.There was no significant difference in NFL of treatment eyes between the two groups ( Fgroup=0.099, P=0.754), but there was a significant difference in NFL at various time points before and after treatment ( Ftime=5.231, P<0.001). There were 9 (9/57) patients who complained of pain after PRP, which occurred at the first time of photocoagulation in 7 of them. Conclusions:SNP damage may occur after PRP in patients with DR, and SNP is prone to be damaged on the photocoagulation side when performing horizontal photocoagulation.
RESUMO
Objective:To estimate the correlation between DR and diabetic corneal nerve damage by comparing changes of corneal sub-basal nerve plexus (SNP) in the whorl-like region in different DR stages.Methods:In this cross-sectional study, 66 eyes of 66 type 2 diabetes patients aged 50-65 years old in Shanxi Eye Hospital from September 2018 to January 2019 were included.The subjects were divided into non-diabetic retinopathy group (NDR), non-proliferative diabetic retinopathy group (NPDR) and proliferative diabetic retinopathy group (PDR) accordingly, the right eyes were enrolled.20 eyes of 20 age and gender matched age-related cataract patients were also included as control group.All the subjects underwent confocal corneal microscopy to observe the morphology of SNP in the whorl-like region and measure the nerve fiber length (NFL) in this area.Covariance analysis using disease course as the covariate was used to analyze the differences of NFL value among groups, and Spearman rank correlation analysis was used to analyze the correlation between NFL value and DR stages.The study protocol was approved by the Ethics Committee of Shanxi Eye Hospital.Written informed consent was obtained from each patient prior to entering the study cohort.Results:The whorl-like region were observed in all the eyes.In the control group, nerve fibers were uniform in thickness, densely distributed with regular course, and most of the tested eyes had intact whorl-like structure.Nerve fibers in different DR groups all showed generally decrease in diameter and density, with increase in tortuosity, accompanied by different degrees of whorl-like structure loss.Eyes in the NDR group and NPDR group mainly showed nerve structure loss in the whorl-like center; while some eyes in the PDR group also showed nerve structure loss in the inferior and temporal of the whorl-like region.The NFL values were (21.08±4.74), (16.47±6.35), (14.95±3.90), and (11.61±3.24)mm/mm 2 in the control group, the NDR group, the NPDR group, and the PDR group, respectively, the overall difference was statistically significant ( F=10.541, P<0.001). The NFL value in the control group was significantly higher than those in the different DR groups, the differences were statistically significant (all at P<0.01). Spearman rank correlation analysis showed that there was a significant negative correlation between NFL value and DR stages ( rs=-0.356, P=0.003). Conclusions:Diabetic SNP damage occurs earlier than DR, and progress gradually with the development of DR; Different stages of DR are accompanied by different degrees of nerve structure loss; The structure loss begins at the whorl-like center and gradually develops to downward and the temporal side.The ophthalmologists should take the condition of ocular surface into account when treating ocular fundus diseases of diabetic patients.