Comparison And Observation Of Ocular Biometry Measurements Before And After Cataract Surgery

Back ground:According to statistics, phacoemulsification accounts for more than90%of cataract surgery in developed countries. With matureoperation technology, the improved intraocular lens (IOL) design, the operation equipment and devices, visual acuity in patients was increased and stabilized gradually. However, we found that majority of patients postoperative visual acuity differences compared with preoperative prediction vision in clinic. The refractive error was mainly due to the implantation ofinaccuracy IOL degree. IOL degree was mainly composed of preoperative measurement of corneal curvature, anterior chamber depth and ocular axial length. Small surgical incision reduced the impact on postoperative corneal astigmatism. Axial measurements were also more accurate with the IOL-master applications. Postoperative anterior chamber depth becomes the main cause of postoperative refractive error.The lens thickness was about4-5mm, but IOL was about1mm only. The ocular biological parameters changed because removed the lens. Vitreous chamber depth and anterior chamber depth determines the position of the IOL, The location of IOL determinesthe postoperative refractive state of the patients.We found that different IOL designs shapes seem to have relevance for IOL position after cataract surgery.Let us supposed that postoperative refractive status of one eye was unchanged, the IOL diopter was smaller than before if IOL position to move forward,the IOL diopter was greater than before if the IOL position to move backward.The effective lens position was not available measured because of postoperative ocular measurements were change. Many scholars predicted postoperative anterior chamber depth to improve the accuracy of IOL calculation. The third generation IOL calculation was to join the prediction of postoperative anterior chamber depth, calculation accuracy was higher than the previous two generations formula. Although IOL calculation has been accurate, postoperative refractive error remains because of the postoperative anterior chamber depth prediction deviation.We found that the preoperative prediction of IOL degree was determined the formulas of import inspection instrument, and the constants of these formulas came from regression analysislarge sample size European people ocular biological parameter. There were differences between European and our country people’s eyes structure, whether there were differences ocular biological parameters? Used of imported equipment to predict the IOL degree was error if the difference existed? What were the clinical implications of ocular measurements after cataract surgery? Anterior chamber depth and vitreous chamber depth were changes after cataract surgery? Position changes affected ocular biological parameters? Whether difference shapes of IOL affects the stability of intraocular balance after cataract surgery? As the two most common clinical ocular biometric devices, A-scan ultrasound and IOL-Master measurement results were no difference?Therefore, this study using A-scan ultrasound and IOL-Master as a measuring instrument, using retrospective study of ocular measurements were compared before and after surgery, the clinical significance of statistical analysis in order to provide a new reference for cataract surgery, and further improve the clinical diagnosis and treatments.Objective:To compare the biometry measurements of A-scan ultrasoundand IOL-Master in164eyes128patientswith cataractsurgery. Measurements were made before and14days after theoperation, which includedanterior chamber depth (ACD), lens thickness, Vitreous chamber depth and axial length (AL) andanalyze its clinicalsignificance. Simultaneously, There were divided into three groups according to the different types of IOL:one-piece, three loop-piece and three-piece. Comparison of the three groups ocular measurements and analyze its clinical significance.Methods:1. A-scan ultrasound:The eyes of all the patients after anesthesia,10MHz probe contact measurement. Biologic measurements were made before and14days after the operation by same operator, which including ACD, lens thickness, vitreous chamber depth and AL. Measurements was performed in sittingand decubitus position and measuring10times averaged. Preoperative using refractive mode and postoperative using IOL model measured.2. IOL-Master:The patients in the sitting, continuous measurement of axial length and anterior chamber depth, choose the ultimate instrument detection value.3. Vision:Using international standards chart for testing visual acuity.4. Statistics used SPSS16.0software. P<0.05considered statistically significant differences. Test methods:(1) Visual acuity used paired samples t test before and after operation.(2)Each biological measurement of A-scan ultrasound used Paired samples t test before operation insitting and decubitus position.(3) Each biological measurement of A-scan ultrasound used paired samples t test after operation insitting and decubitus position.(4) The measurements of A-scan ultrasound used paired samples t test before and after operation.(5) Paired samples t test was used to statistically analyze changes of the measurements of A-scan ultrasound before and after surgery. Pearson correlation analysis was used to analyze the statistical significance of the correlation between the changes of lens thickness with the changes of ACD and vitreous chamber depth, respectively. The linear correlation was examined by linear regression analysis.(6)Differences postures of the vitreous cavity depth after operation of three different types of IOL of A-scan ultrasound, used ANOVA.(7)The measurements of IOL-Master used paired samples t test before and after operation.(8) The measurements of IOL-Master and A-scan ultrasound used paired samples t test before operation.(9) The measurements of IOL-Master and A-scan ultrasound used paired samples t test after operation.Result:Ocular biological parameters of all patients were measured used A-scan ultrasound, Only46eyes were measured using IOL-Master. All surgery was uneventful, no intraoperative and postoperative complications.1. Visual acuity:There was statistical significance of visual acuity before and after operation (P<0.05, n=164)2. A-scan ultrasound:(1) ACD:Before and after operation, the difference of ACDs measured by A-scan ultrasound was significant (P>0.05, n=164). There was no statistical significance of ACDs before operation insitting and decubitus position (P>0.05, n=164). Significant difference of the ACDs after operation in sitting and decubitus position was found (P<0.05, n=164).Postural changes in anterior chamber depth before and after surgery was significant (P>0.05, n=164).(2)Lens thickness:There was no statistical significance of lens thickness before operation in sitting and decubitus position (P>0.05, n=164).The difference of lens thickness was significant before and after operation (P<0.05, n=164)(3)Vitreous chamber depth:Significant difference of the vitreous chamber depthbefore and after operation was found (P<0.05).There was no statistical significance of vitreous chamber depth preoperative in sitting and decubitus position(P>0.05, n=164),but postoperative has (P<0.05,n=164).(4)AL:The ALs before and after operation was not significantly different(P>0.05, n=164). Before and after operation, the difference of AL values in sitting and decubitus position were not significant (P>0.05, n=164).(5)Pearson correlation analysis revealed the significant difference between the changes of ACD and visual acuity.(P<0.05, n=164). The corresponding coefficients were0.175.The linear regression analysis showed the linear correlation between them.(6) Pearson correlation analysis revealed the significant difference between the changes of lens thickness and the changes of ACD, vitreous chamber depth (P<0.05, n=164). And also a positive correlation exists between them. The corresponding coefficients were0.262and0.556, respectively.The linear gression analysis showed the linear correlation between the lens thickness and the changes of ACD and vitreous chamber depth.3. One-piece, three loop-piece, three-piece three types IOL A-scan ultrasound measures postural changes of postoperative vitreous cavity depth difference generated by ANOVA test analysis, the three groups showed no significant difference (F=1.158, P=0.317)4. IOL-Master:(1) AL:The ALs before and after operation was not significantly different (P>0.05, n=46).(2)ACD:The ACDs before and after operation was not significantly different (P>0.05, n=46).(3)IOL-Master and A-scan ultrasound: Significant difference of the ALs between A scan and IOL-Master before and after operation was found (P<0.05, n=46). Significant difference of the ACDs between A scan and IOL-Master before and after operation was found (P<0.05, n=46).Conclusion:1. The cataract surgery can improve the patient’s vision significantly.Between visual acuity and postoperative anterior chamber depth has a positive correlation.2. ACD, vitreous chamber depth was deepened after cataract surgery and the existence of the positive correlation between the changes of lens thickness and the changes of ACD and vitreous chamber depth. In addition, different measuring positions have no influence on the result of A-scan ultrasound measure except the postoperative ACD and vitreous cavity depth.3. The stability of iris diaphragm intraocular lens was lower than the preoperative after phacoemulsification cataract surgery.4. Between postoperative vitreous cavity depth difference of postural changes measured A-scan ultrasound and types of IOL was no correlation, indicating IOL in the capsular bag more stable.5. There was has statistical significance between A-scan ultrasound and IOL-Master measures ocular biological parameters.