Effect Of Single-point Laser And Multi-point Scanning Laser On Corneal Nerve In Patients With Diabetic Retinopathy

Objective : To investigate the effects of single-point and multi-point scanning mode panretinal photocoagulation on corneal nerves in patients with diabetic retinopathy.Methods:The research method used in this paper is a prospective study.The included subjects were 91 eyes of 91 patients who were diagnosed as severe non-proliferative diabetic retinopathy(severe NPDR)or proliferative diabetic retinopathy(PDR)from October 2017 to August 2018 at Qingdao Municipal hospital Eye Center and met the panretinal photocoagulation(PRP)criteria.Explain to patients the advantages and disadvantages of single-point laser and multi-point scanning laser,the patients chose to use laser alone.Among them,45 eyes of 45 patients in the experimental group were treated with multi-point scanning mode laser for PRP,46 eyes of 46 patients underwent PRP in a single-point mode laser.Four patients in the single-point laser group underwent macular edema during the first PRP treatment.The final subjects were the experimental group: 45 eyes in 45 patients,and the control group: 42 eyes in 42 patients.Corneal nerves were measured before surgery,1 week,1 month,3 months,and 6months after surgery.Corneal sensory(CS)was used to measure corneal sensation with a central diameter of 4 mm.Measurement of corneal epithelial nerve fiber length(CNFL)at five different sites of upper,lower,temporal,nasal and central points using in vivo confocal microscopy(IVCM).Statistical analysis was performed using IBM SPSS 23.0 statistical software.The measurement data was represented by χ±S and the categorical variable results were represented by N(%).The chi-square test was used to compare the proportion of patients with single-point laser group and multi-point lasergroup,and the proportion of patients requiring laser supplementation.The age,disease duration,HbA1 c,two indexes of CS and CNFL between the two subgroups before and after the operation and laser-related data(laser energy,laser quantity,laser energy density)at 6 months were measured by independent sample t test.For the time difference within the group,the single factor ANOVA method,multiple LSD test and S-N-K test were used to further analyze and compare the differences of each index at each time point before and after operation in each subgroup.P <0.05 is statistically significant.Results:1.Compared the postoperative with preoperative CS and CNFL in the control group and the experimental group,both have decreased,and the difference is statistically significant at each time point(all P<0.05).The degree of decline was greatest at 1 week after surgery,and CS and CNFL gradually recovered over time.The values of both were still lower than those before surgery at 6 months after surgery.2.Compared with each time points of CNFL after operation in the control group and the experimental group,the experimental group was higher than the control group,and the difference was statistically significant(all P<0.05).Compared with each time points of postoperative CS between the two groups,at 1 week after surgery,the difference between the two groups was statistically significant(P<0.05).The CS of the experimental group was more sensitive than the control group.There was no significant difference in CS between the two groups at 1 month,3 months,and 6 months after surgery(all P >0.05).3.There was no significant difference in the number of laser points between the control group and the experimental group(P>0.05);The difference between the laser energy of the control group and the experimental group was statistically significant(P<0.001),the experimental group used less laser energy;The difference between the laser energy density of the control group and the experimental group was statistically significant(P<0.001),the laser energy density of the experimental group was lower.4.FFA was reviewed in the two groups at 6 months after surgery.There was no significant difference in the proportion of patients requiring laser supplementation(P=0.448,P>0.05).Conclusion:1.Retinal laser photocoagulation can damage the corneal nerve of diabetic patients,reducing the CS and CNFL.At 1 week postoperatively,the corneal nerve was most severely damaged and gradually recovered over time.It was observed that the corneal nerve did not return to the preoperative level at 6 months after surgery.2.Single-point mode PRP and multi-point scan mode PRP are equivalent to the treatment of DR.The multi-point scan mode has lower laser energy density and is less sensitive to corneal nerve damage:The CNFL at each time point after multi-point laser group was higher than that of single-point laser group;the CS at 1 week after multi-point laser group was higher than that of single-point laser group.