Study On Self-developed Potential Acuity Meter And Shovel-chopper In Clinical Research Of Cataract

Section 1 The development and clinical research for predicting postoperative visual acuity in cataract patients with the Potential Acuity MeterObjective To discuss the reliability of using the Potential Acuity Meter (PAM)for predicting visual acuity in patients with cataracts.Methods Based on the subjective optometry method, a novel optometrysystem that realizes continuous compensation and measurement of eye diopter waspresented. The optical imaging characteristics of the system were studied, and aPotential Acuity Meter (PAM) was designed for pre-measuring the eye sight aftersurgery. The model instrument has been used in the clinical treatment in the hospital.150 cataract eyes were enrolled in this study. All eyes were evaluated with thedomestic-made PAM, imported PAM and Lotmar line grid interference retinometerbefore surgery. These preoperative predicted visual acuity (PPVA) results were thencompared to the best corrected visual acuity (BCVA) two months after surgery. Withthese 150 eyes, we divided them into 5 grades and 2 groups according to the hardnessof the cataract nuclear. A group included 90 eyes withⅠ～Ⅲgrades nuclear, and Bgroup included 60 eyes withⅣ～Ⅴgrades nuclear. To observe the influence ofnuclei hardness.Results A model instrument was completed. It can continuously compensate theeye diopter by moving the transparent vision pad. The merit of PAM is that the opticalsystem not only images the vision pad just on the retina, but the diameter of the imaging beam at the pupil of the eye must less than 0.1mm so that the imaging beamcan penetrate through the turbidity lens of the eyes with cataract.The clinical outcomes: (1)Complete data were obtained in 150 eyes(100%). Theresults of 94 eyes were less than 2 lines different between PPVA and BCVA withdomestic PAM, and the identical rate was 62.7%. With imported PAM and Lotmar, theresults were 96 eyes(64.0%) and 102 eyes(68.0%) respectively. (2)In group A, therewere no significant differences between PPVA and BCVA with domestic PAM(t=-2.660, P＞0.05), imported PAM (t=-2.469, P＞0.05) and Lotmar (t=0.055,＞0.05).But in group B, the differences were significant with domestic PAM (t=-10.702,P＜0.05), imported PAM (t=-9.984, P＜0.05) and Lotmar (t=-3.530, P＜0.05). (3)All thePPVA of the three instruments were positive correlated with postoperative BCVA(r=0.774, 0.772, 0.369 in A group, r=0.516, 0.496, 0.519 in B group). (4)The rate ofconsistence between PPVA and BCVA were 64.8% and 64.4% in simple cataractgroup and cataract combined with other eye diseases group (x~2=1.96, P＞0.05).According to the different location of lens opacification, we divided the 150 eyes intocombined cataract, nuclei cataract, subcapsular cataract and cortical cataract 4 groups.The identical rates were 65.5%,53.6%,75.0%,53.3% respectively (x~2=3.15,P＞0.05).Conclusion The results of domestic PAM were comparable with that ofimported PAM and Lotmar. In severe cataract patients, the accuracy of predictiondecreased. The combined eye diseases did not impact too much. The domestic-madePAM is relatively reliable to predict the postoperative visual acuity. It is a valuablemethod in the examination of PPVA before cataract surgery. Section 2 Effect of vertical phaco—chop technique with shovel-chopper in phacoemulsificationObjective To study the effect of vertical phaco chop technique withself-designed shovel-chopper in phacoemulsification.Methods 216 cases with senile cataract were observed. With these 216 eyes,we divided them into 4 grades according to the hardness of the cataract nuclear and 2groups operated with conventional phaco-chop and vertical phaco-chop respectively.The differences of mean phaco time, mean phaco power and mean relative energycomplex parameter between the method of conventional phaco-chop and that ofvertical phaco-chop were compared.Results Significant differences between the mean phaco time(t=8.34,p＜0.001), the mean phaco power(t=9.34, p＜0.001) and the AECP of the two groupsexisted.Conclusion The vertical phaco chop technique with self-designedshovel-chopper shows a higher mean phaco power but a much shorter phaco time, andtherefore the AECP of vertical phaco-chop group is lower than that of theconventional phaco-chop group. The bevel-down vertical phaco chop technique withshovel-shaped chopper in this study appears to offer practical and theoreticaladvantages over the traditional phaco chop technique we used before. It is fast,effective, and, most important, safe, especially for cataract with hard nuclei, smallpupil and complicated situations.In conclusion, the technique adjusts to the development tendency of presentcataract surgery technology, also deserves to be widely used and spreaded in clinicalapplication, and is fit for surgeons who are initiating cataract surgeries.