| High myopia is caused by various reasons,containing genetic factors,environment factors,form-deprivation,lens-induced,adjustment disorder and other diseases,or result of interaction of different factors.High myopia is a refractive system syndrome,which often associated with different degrees of fundus and/or ocular pathological changes,and cause visual function lesion gradually.High myopia is also called as progressive myopia,pathological myopia or degenerative myopia.With high incidence and serious complication,high myopia often lead to serious vision loss,low vision and even blindness,if not treated timely and appropriately.The main features of high myopia contain younger onset,continuous deepening myopia diopter,faster progression than common myopia and long sagittal axis of eyeball.High myopia often accompanied by various complications such as the scleral staphyloma,optic disk leaning,retinal degeneration,choroid atrophy,vitreous opacity,even some other serious complications,containing retinal detachment,macular degeneration,and macular hemorrhage.High myopia not only lead distant vision loss,but also damage the near vision with aggravation of the location and extent of lesions,resulting in a bad therapeutic effect with concave lens.At present,high myopia has become one of the leading causes of blindness in many developed and developing countries.High myopia,accounting for 0.5% ~ 2.5% of the total population,has become the leading cause of blindness following diabetic ophthalmopathy.High myopia is very common in Asia and the Middle East,where yellow race are the majority people.It is reported that the total number of patients with high myopia in Japan accounted for 6% ~ 18% of total myopia patients,1% of the total population.With the popularity of electronic products in China,the incidence of myopia increases year by year.Incidence of teenagers especially above junior high school students have reached more than 50%,and the incidence of high myopia in the proportion is also increasing in myopia patients.Low vision or blindness caused by high myopia in patients with retinochoroidopathy has accounted for 20% of the low vision clinic in our country.High myopia is usually regarded as synonymous with pathological myopia,but strictly speaking,they are not synonymous.Only when there is obvious retinal atrophy,high myopia can be diagnosed as degenerative myopia or pathological myopia.At present,it is considered that myopia with more than-6.00 D is called high myopia.However,it is also reported that myopia with more than-5.00 D can be called high myopia in 2015.No matter which definition of high myopia is more reasonable,there will be some patients may not have fundus pathological lesion.But for myopic patients with-3.00 ~-6.00 D,especially for moderate myopia of teenagers or children,leopard grain shape changes caused by retinal atrophy can be seen from early fundus examination.So for patients of different ages,the concept of high myopia which is defined by the degree of refraction is still needs further discussion.Posterior sclera reinforcement(PSR)is a surgical approach for reinforcing the posterior pole of the eye,especially the posterior pole of the macular region.This procedure,with good safety,almost have no damage to intraocular tissue structure,is a good method for inhibition of further development and protecting visual acuity.This surgical method was once considered to be the only surgical method to inhibit the development of high myopia.In addition to operative procedure,the materials also have a great impact on the effect and prognosis of posterior sclera reinforcement.An ideal reinforcing material should be non-toxic,good tissue compatibility,have certain elasticity and toughness,easy to get and synthetic,easy conservation and sterilization,with low price,convenient for intraoperative application,etc.Sclera-fortifying injection(SFI)of reinforcement materials is a new method for sclera reinforcement over the recent 20 years.Comparing with PSR,SFI has the advantages of simple operation,small trauma,fewer complications,rapid recovery,and effective for progressive myopia.Thus it is gradually recognized by ophthalmologists.Although mechanical PSR is effective for high myopia,it is not perfect.First of all,no matter what kind of reinforcement strip,only local sclera rather than the entire posterior sclera can be reinforced.Second,the surgery inevitably bring some complications containing increased intraocular pressure,ocular movement limitation,vortex vein compression.Finally,and most importantly,due to the development of medical ethics,it is difficult to obtain the reinforcement materials from the allogeneic scleral,allograft,the dura mater and autogenous broad fascia because of ethical problems.To some extent,all of these have limited the extensive development of posterior scleral reinforcement.However,doctors in the former Soviet union carried out sclera-fortifying injection to promote the formation of fibrous tissue for the treatment of high myopia,which replaced mechanical posterior scleral reinforcement in twenty years ago.In recent years,animal collagen produced in Russian has been used in the clinical treatment of patients with high myopia by sclera-fortifying injection.In short,during the last 20 years,the treatment of high myopia by the injection of strengthening materials at home and abroad has been further developed.It is believed that with further research on treatment of high myopia by sclera-fortifying injection,the injection materials and injection methods will gradually be improved,and the effect will be gradually confirmed and improved.This study focused on the clinical treatment of adolescent myopia in the early stage.To observe the effect of sclera-fortifying injection,one week old guinea pigs were used for inducing myopia model.This study was divided into three parts: The first part,the collagen was extracted from porcine eye sclera and was prepared for ophthalmic gel,the safety was observed.The second part,the therapeutic effect of the gel polymer was observed in the treatment of lens induced myopia in guinea pig.The third part,investigate the effect of gel polymer injection in the treatment of high myopia in adolescents.Part 1: The preparation and safety observation of ophthalmic injectable collagen gel with porcine scleraPurposes: To provide a method for extracting and preparation of porcine scleral collagen gel,and observe its safety.Methods: Collagen was extracted from porcine sclera using enzyme hydrolysis-salt extraction method,and was made into ophthalmic injectable gel.And the tissue compatibility and complication of the gel were observed after retrobulbar injection.The incidence of adverse reactions in the two groups was expressed as a percentage.The statistical analysis was performed using SPSS 22.0.Mann-Whitney U test was applied to test for differences between groups.For all of the analysis,P <0.05 were considered to be statistically significant.Results: Ophthalmic injectable collagen gel was successfully extracted from pig sclera using enzyme hydrolysis-salt method.The gel is safe,non-toxic,free soluble in water,good histocompatibility,with stable p H value around 7.2,similar osmotic pressure to ocular tissue,good histocompatibility and fewer complications.Conclusion: Ophthalmic injectable collagen gel made from porcine scleral showed good tissue compatibility,less complications and safety,can be used in animal researches.Part2: Effect of Sclera-fortifying injection with gel polymer in the treatment of induced myopia in guinea pigsObjective: To establish the model of induced myopia in guinea pig,and investigate the effect of sclera-fortifying injection with animal gel polymer in the treatment of induced myopia.Methods:Total of 105 male guinea pigs with 1 week were chose in the study,and were randomly devided into control group and experimental group.The control named group A contained 15 guinea pigs(30 eyes),without any interventions.60 guinea pigs were selected for induced myopia model: 60 right eyes wearing-10.0 D lens for 6 weeks to induce myopia.Then the lens induced group was randomly divided into groups B,C and D,30 guinea pigs in each group.Group B didn’t receive any interventions after myopia successfully induced.Group C and D received peribulbar injection with saline and Russian gel polymer respectively.Axial length and refractive power of the right eyes in the three groups were observed at days 3,20 and 40 postoperatively.Ten guinea pigs from each group were executed at days 3,20 and 40 postoperatively,and both eyeballs were enucleated.HE staining was used to detect histopathological variation of sclera,immunohistochemical method was used to observe the expression of matrix metalloproteinase-2(MMP-2).And the content of hydroxyproline(Hyp)in posterior sclera was tested by hydrochloric acid method.Data were analyzed by SPSS 22.0.The measurement data were recorded as mean ± standard deviation(`x ± s),repeated measurement data were analyzed by ANOVA.Pairwise comparisons between groups were analyzed by Bonferroni method.All data were statistically significant with P <0.05.Results: All of 105 guinea pigs completed the whole study successfully.Group with Russian gel polymer only showed good biocompatibility and mild adverse events,containing conjunctival congestion and hemorrhage which can restore after regular treatment,and showed no serious stimulus reaction.Ocular axis test: guinea pigs in lens induced myopia group exhibited significant longer ocular axial than control(P < 0.05).Guinea pigs in group D showed shorter ocular axial than Group B and C after 3 days,20 days,40 days.The difference is statistically significant(P < 0.05).Diopter test results: guinea pigs in lens induced myopia group exhibited significant higher diopter than control(P < 0.05).Guinea pigs in group D showed lower diopter than Group B and C after 3 days,20 days,and 40 days.The difference is statistically significant(P < 0.05).Morphological changes: the thickness of retina,choroid,and sclera of the right eyes in group B,C and D all was thinner than the control.Thinner and disorganized scleral collagen fiber,and less retinal cells were detected.Sclera of guinea pigs in group D contained more pink collagen component than in group B and C.Determination of the content of hydroxyproline(Hyp): guinea pigs in lens induced myopia groups exhibited less Hyp than that of group A,the difference was statistically significant(P < 0.05).And group D exhibited more Hyp than group B and C,the difference was statistically significant(P < 0.05).Immunohistochemical staining detection: staining of MMP-2 in sclera of group A showed faint yellow,which was brown in group B,C and D.The expression MMP-2 is markedly improved in lens induced myopia group,the difference of average optical density value was statistically significant(P < 0.05).Among them,MMP-2 content in the sclera tissues of group D were lower than that of group B and C after 20 days,40 days,average optical density value difference was statistically significant(P < 0.05).Conclusion:Lens-induced myopia in guinea pig showed longer eye axis length,increased diopter,reduced hydroxyproline content and higher MMP-2 express in the sclera.Sclera-fortifying injection of Russian gel polymer can effectively inhibit axial length growth,maintain the relative stability of refraction,and induce reconstruction of sclera collagen,decreasing of MMP-2,increasing of collagen content,enhance of tensile force,inhibit further development of lens-induced myopia.Part 3 Sclera-fortifying injection with collagen polymer in the treatment of high myopia in adolescentsObjective: To evaluate the effectiveness of sclera-fortifying injection of collagen in the treatment of high myopia in adolescents..Methods: In perspective study,a total of 56 teenagers(56 eyes)with high myopia were ex amined in our hospital from May 2013 to December 2013.25 cases(25 eyes)were tre ated with sclera-fortifying injection,and the other 31 cases(31 eyes)were studied as control without any treatment.Uncorrected visual acuity(UCVA),best corrected visu al acuity(BCVA),axial length and refractive error were examined before and 1m,3m,6m after operation in the two groups.Data were analyzed by SPSS 22.0 statistical so ftware.Chi-square test was used to analyze the enumeration data.The measurement d ata were recorded as mean ± standard deviation(`x±s).T-test of independent sampler was used to analyze all the values of the two groups before operation.Variance analy sis of repeated measurement data was applied to compare the corresponding values in different time points between the two groups.All data were statistically significant w ith P<0.05.Results: A total of 56 patients completed the whole follow-up.Complications of sclera-fortifying injection: there were 5 cases with conjunctival reactive hyperemia which is the most common complication,2 cases with transient increasing intraocular pressure,2 cases with subconjunctival hemorrhage,all of the complications recovered after regular treatment.Uncorrected visual acuity,BCVA,and ocular axis at different time in therapeutic group were improved than that in the control,the difference was statistically significant(P <0.05).But there was no statistically significant difference between the two groups for refractive error.Uncorrected visual acuity and BCVA in the control decreased,diopter and ocular axis continued increasing.Conclusion: Sclera-fortifying injection with collagen polymer can effectively improve visual function,slow the axial growth,restrain the development of high myopia,is an effective therapy for the treatment of high myopia in adolescents. |
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