The Study On The Mechanism Of Accommodation And The Analysis Of Clinical Treatment Effects Of Myopia And Presbyopia

Myopia and presbyopia are two major optometry problems facing society.The mechanism of accommodation is the basis for studying the mechanisms of myopia and presbyopia.However,the key mechanism of accommodation has eluded clarity for over400 years,resulting in a stagnation in the prevention and treatment of myopia and presbyopia.With the continued development of experimental technologies and equipment,some significant progress has been made.However,the current hypotheses either do not comprehensively the accommodation mechanism or lack the necessary experimental and clinical evidence.Basing on previous studies,this dissertation proposed a novel hypothesis,that is,the accommodation is completed through the contraction of the radial muscles-the instantaneous filling of the capillaries in the ciliary processes and then forward and inward movement-the change on the tension of the zonules-and the deformation of the lens,which offers a more detailed theoretical understanding of the accommodation process.To verify the hypothesis this dissertation proposed,an ultrasound biomicroscopy(UBM)instrument was to measure the morphological changes in the ciliary body of rhesus monkeys.Accommodation and non-accommodation were stimulated by anterior chamber injections of carbachol or atropine sulfate,respectively.Under anesthesia,the common carotid artery was isolated,and the flow of blood to the ciliary processes was controlled by either clamping or unclasping the artery.The experiments were divided into seven steps:1-normal;2-clamp;3-unclasp 4-inject after clamping;5-unclasp;6-clamp again;7-unclasp again.After each step,the ciliary body images were captured with UBM.Then the ciliary muscle thickness(cmt),ciliary body thickness(cbt),ciliary process width(cpw),ciliary muscle-cornea angle(cmc),ciliary process-cornea angle(cpc),ciliary muscle-ciliary process angle(cmcp),and the ciliary muscle thickness at interval of 1-4mm from the scleral spur(cmt1-4)were measured.In the accommodative experiment,whether the common carotid artery was clamped or not showed no significant effect on the ciliary body parameters prior to accommodative stimulation.After injecting carbachol with the common carotid artery clamped,cmt and cbt increased,and cpw,cmc,and cpc decreased,but these changes lacked statistical significance;after stimulating accommodation,only cmt1 showed a significant increase,while changes in cmt2-4 were statistically insignificant.In the non-accommodative experiment,all ciliary body parameters changes were statistically insignificant.The results suggest that arterial blood pressure plays minimal role in accommodation without an accommodative stimulus.Without arterial blood pressure,the accommodative response could not be generated.Accommodation only occurred when both arterial blood pressure and an accommodative stimulus were present in this experiment.This points towards a potential crucial relationship between arterial blood pressure and accommodation.In addition to exploring the mechanisms of accommodation,this dissertation also analyzed the clinical treatment effects of myopia and presbyopia to provide evidence-based recommendations for clinical treatment.To investigate the effects of accommodation on the biological parameters of the human lens,the literature search databases used were:CNKI,CBM,VIP,Wan Fang,Pub Med,Web of Science,EMBASE,and the Cochrane Library from inception to June2022.Outcomes:mean diopter(D)change in lens diameter(LD),lens thickness(LT),anterior curvature radius(ACR),posterior curvature radius(PCR),lens center position(LCP),and total cross-sectional area(TCSA).The weighted mean difference(WMD)and its 95%confidence interval(CI)were used to estimate the measured data.The results showed that sixteen studies were included,comprising 399 cases with 444 eyes.LT increased by 0.04 mm/D(95%CI,0.04～0.05;I~2,4.4%;p<0.001);at the same time,LD,ACR,and PCR decreased by 0.06 mm/D(95%CI,-0.08～0.05;I~2,0.0%;p<0.001),0.58mm/D(95%CI,-0.73～-0.44;I~2,95.6%;p<0.001)and 0.16 mm/D(95%CI,-0.22～-0.09;I~2,92.0%;p<0.001)during accommodation,respectively.Besides,LCP shifted anteriorly by 0.01 mm/D(95%CI,-0.02～0.00;I~2,0.0%;p=0.057),and TCSA by 0.58 mm~2/D(95%CI,0.49～0.82;I~2,97.0%;p=0.457)during accommodation.The changes in LT,LD,ACR,and PCR supported Helmholtz’s theory.To analyze and compare the efficacy of different interventions for prevention and control of myopia in children,the literature search databases used were:CNKI,VIP,Wan-Fang,CBM,Chinese Clinical Registry,Pub Med,The Cochrane Library,Web of Science,Embase and Clinical Trials.gov from inception to July 2022.The main outcomes included the mean annual change in axial length(AL)(millimeters/year)and spherical equivalent(SE)(diopters/year).The WMD and its 95%CI were used to estimate the measured data.The results showed that a total of 80 studies(27103 eyes)were included.Compared to control,orthokeratology(AL,-0.36[-0.53,-0.20],p<0.05;SE,0.56[0.34,0.77],p<0.05),1%Atropine(AL,-0.39[-0.65,-0.13],p<0.05;SE,0.54[0.31,0.77],p<0.05),0.01%Atropine+orthokeratology(AL,-0.47[-0.80,-0.14],p<0.05;SE,0.81[0.43,1.20],p<0.05)could significantly slow myopia progression;furthermore,Progressive Multifocal Spectacle Lenses(PMSL)(0.42,[0.06,0.79],p<0.05),bifocal soft contact lenses(0.40,[0.03,0.77],p<0.05),0.5%Atropine(0.67[0.25,1.10],p<0.05),0.1%Atropine(0.42[0.15,0.71],p<0.05),0.05%Atropine(0.57[0.28,0.86],p<0.05),0.01%Atropine(0.33[0.15,0.52],p<0.05),1%Atropine+Bifocal Spectacle Lenses(BSL)(1.30[0.54,2.00],p<0.05),1%Atropine+PMSL(0.66[0.23,1.10],p<0.05),0.01%Atropine+Single Vision Spectacle Lenses(SVSL)(0.70[0.23,1.10],p<0.05),0.01%Atropine+orthokeratology(0.81[0.43,1.20],p<0.05),BSL+Massage(0.85[0.22,1.50)],p<0.05),SVSL+Red light(0.59[0.06,0.79],p<0.05)showed a significant slowing effect on the increase of SE.The results suggest that the combined measures were most effective at AL and SE,followed by Atropine.Furthermore,to investigate the effects of laser in situ keratomileusis(LASIK)in the treatment of presbyopia,we searched CNKI,VIP,Wan-Fang,CBM,Chinese Clinical Registry,Pub Med,The Cochrane Library,Web of Science,Embase and Clinical Trials.gov from inception to March 2023.Outcomes were efficacy,safety,predictability,and stability.Count data were expressed by relative risk(RR)and its95%CI.The measurement data were expressed by the WMD and its 95%CI.The results showed that a total of 28 studies(15861 eyes)were included.After LASIK,distance efficacy decreased(MD,0.02;95%CI,0.0～0.03;p<0.05)and near efficacy increased(MD,-0.01;95%CI,-0.19～-0.02;p<0.05);distance safety decreased(MD,0.07;95%CI,0.04～0.10;p<0.0001)and near safety increased(MD,-0.19;95%CI,-0.39～0.02;p>0.05);predictability within±1.00 and±0.50 D was 94%(RR,0.94;95%CI,0.90～0.98;p<0.001)and 80%(RR,0.80;95%CI,0.74～0.86;p<0.001);and 6 months postoperatively,the percentage of change in spherical equivalent within±0.50 D was 95%(RR,0.95;95%CI,0.89～0.99;p<0.001).The results suggest that the near efficacy,predictability,and stability of LASIK for presbyopia correction were satisfactory;however,the distance efficacy and distance safety decreased.This dissertation explored the accommodation mechanism through animal experiments and evidence-based methods,and deepens people’s understanding of the accommodation process;on the other hand,it analyzed the clinical treatment effects related to myopia and presbyopia from an evidence-based perspective,providing evidence-based recommendations for the clinical treatment of presbyopia and presbyopia.