| Objective: Amblyopia is the low visual function caused byvision system’s failure of subject to the effective stimulus duringdevelopment. The treatment principles hereof are eliminating theabnormal visual experience within the visual development sensitiveperiod. Recovering visual function by means of etiological treatment，functional training and binocular interaction is the traditional treatment,which is of uncertainty to individuality. For the past20years, scholars aredevoted to the amblyopia drug treatment related research, expectingbetter efficacy. Of which, the research upon levodopa has already showna certain clinical application value. However, its long-term effect isdoubted by a large amount of research results. Different opinions of itsefficacy are held by researchers, its mechanism remains unclear.Therefore, further research shall of necessity.The amblyopia treatmentprinciples, currently, derived from the sensitive period of visualdevelopment, which suggested the efficacy of which is closely related tothe patients’ age. Once the age of patient exceed the mentioned period, her/his vision system is not of maturation and with no plasticity. It iscoincided with the clinical practice results that the patient with amblyopiaexceed12-year-old is hard to cure by traditional methods. A large amountof patients over the age of12with amblyopia abandon treatment for thereason of difficult therapy resulted in corresponded approximately10,000,000amblyopia patients.Proved by plenty of basic medicalsciences and clinical practice recent years, even the above mentionedperiod exceed, the vision system is still of a certain of plasticity. However,most of clinicians are still of uncertainty to the patient whose age hasexceeded the period hereof. The patient compliance is poor, and suchsituation can be overwhelmed if index of recovery can be found.Foundedin the previous research, applied upon amblyopia patients with singledosage of Levodopa, visual evoked potential, PVEP with shortenedprepetent and improved amplitude can be detected in a short term. If theabove mentioned changes reflect the potential function of the stimulatedvision system, it may be reference to the recovery of the amblyopiatreatment.Thus, the objective of this experiment is discussing the relationbetween the PVEP reflection after the application of single dose oflevodopa and efficacy of amblyopia treatment, exploring the possibilityof the index of recovery with PVEP as the detected method, researchingthe difference of both patients with amblyopia in or out the sensitiveperiod of visual development with levodopa accompanying traditional treatment, and investigating the therapeutic significance of levodopa todifferent age patients group with amblyopia.Methods:Twenty nineamblyopic patients (45eyes) were selected in this study. They werediagnosed with amblyopia according to the diagnostic criteria establishedby Strabismus and Amblyopia Group of the Ophthalmology Society,Chinese Medical Association in2010. Additionally, all the patients (aged6~18years) showed hyperopic ametropia, and received no treatment foramblyopia prior to the study. The patients were divided into group A(levodopa plus comprehensive therapy, aged≥12yrs,15eyes), group B(levodopa plus comprehensive therapy, aged <12yrs,15eyes), andgroup C (comprehensive therapy, aged <12yrs,15eyes). Thecomprehensive therapy included correction of refractive error, occlusiontherapy, refined eyesight examination, Haidinger brush, and red lightflashing.Pattern visual evoked potential (PVEP) was determined aftercorrection of refractive errors. Prior to the administration of levodopa,checkerboard was used to stimulate the PVEP using2degree,1degreeand0.5degree, respectively. Then the P100peak latencies and theamplitudes of PVEP were recorded at the time of60/75/90/105min.Subsequently, single dose of Siliba (containing125mg levodopa pertablet) was given, followed by the determination of the P100peak latenciesand the amplitudes of PVEP. The treatment duration was three months asset in the protocol. Visual check was performed per week. After treatment, repeated determination of the P100peak latencies and the amplitudes ofPVEP were performed. The treatment efficiency was as follows: thosewith increased visual acuity of more than two lines were designated asimprovement; those with increased visual acuity of less than one linewere designated as inefficiency; and those with decreased visual acuity ofmore than one line were designated as retrogression. Comparison ofPVEP was performed in the patients with improvement or inefficiencypatients after single dose of levodopa, based on which to investigate theassociation between PVEP and the treatment efficiency. Intergroupcomparison (group A vs group B; group B vs group C) of the progressand the degree of visual function was performed, based on which to studythe efficiency of levodopa on the amblyopic patients.Results:No patientreported decrased visual acuity. Improvement of visual acuity was notedin9eyes in group A,11eyes in group B, and10eyes in group C,respectively. No statistical difference was observed in the number of eyeswith “improved” or “inefficient” treatment efficiency in group Bcompared with those of group A and C, respectively (P>0.05).Comparedwith the patients in group A, no statistical difference was noted in theonset time in the patients with improved visual acuity in group B (P>0.05). However, the onset time in those with improved visual acuity ingroup B was earlier than that of group C (P <0.05). For the PVEPobtained after single dose of levodopa, no statistical difference was noted in the latencies in the eyes with improved (n=30) and inefficient (n=15)visual acuity as stimulated by1degree spatial frequency (P <0.05).However, no statistical difference was noted in the amplitudes of PVEP inthe eyes with improved and inefficient visual acuity (P>0.05). For therest amplitudes and latencies, no signifciant difference was noted. Withregards to the latencies stimulated by1degree spatial frequency, nostatistical difference was noted in the four times points of different groupsafter single dose of levodopa. Nevertheless, statistical difference wasnoted in the four times points in each group, among which the peakamplitude of PVEP was obtained at60minutes after administration oflevodopa. Conclusion: After single dose of levodopa, changes of PVEPlatencies induced by1degree spatial frequency was statistically relatedwith the therapeutic efficiency and achieved the peak amplitude at60minutes after administration. This indicated that levodopa could be usedto predict the treatment efficiency of amblyopia. Significant improvementof visual acuity was observed in patients aged <12years afteradministration of levodopa, while no significant difference was notedamong the patients received levodopa plus comprehensive therapy andthose received comprehensive therapy after3months treatment. Itindicated that levodopa was not necessary for the treatment of theamblyopia during the sensitive period of visual development. Theefficiency of levodopa plus comprehensive therapy was satisfactory for the patients aged≥12years. We speculated that this may be associatedwith the improvement of visual acuity induced by levodopa, as well asthe enhanced visual stimulation obtained during the comprehensivetherapy. Our results demonstrated that levodopa could be used in thetreatment of amblyopia after the sensitive period of visual development.Inthe near future, studies with large sample size were needed to investigatethe efficiency of levodopa for the prediction of visual potential. |
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