| BackgroundCataract is one of the main causes of blindness, which is the No.1 cause of blindness in China. According to the WHO data (2000), the total blind population was 38 million, in which the cataract patients were 25million, cataract was the No.1 cause of blindness worldwide too.Surgery is the only effective method for cataract patient vision rehabilization. The most important problem postoperatively is after cataract, the total incidence of after cataract was 18-50%, while it was almost 100% in aldolencense. In the surgeries covered by medical insurance in the United States, surgery for cataract was No.1, and surgery for after cataract was No.2. This is the proof of high incidence of cataract and after cataract.At present, the diagnosis for after cataract is mainly based on the clinical observation, including vision acuity, contrast sensitivity, or slit lamp findings, which are not subjective and quantitive. It is quite valuble and important to be able to analyze the after cataract quantitively, to define the severity and range of after cataract. Quantification of after cataract is important in the clinic and research field as well. In clinic, it can help the doctor decide when to treat the after cataract, in research, it can help in the study of after cataract etiology, momitoring its developeing, evaluating the surgery outcome, and the affection of intraocular lens material, design or other factors which may lead to after cataract.With the developing of computer technology, several software for after cataract quantification were developed recently.In which, the EAS-10000(Nidek, Japan) and EPCO software were relatively well used. However, the images analyzed in EAS-10000 system were slit images, which cannot reflect the true and whole situation of after cataract; the EPCO software outcome may influnced by the examiner. What is more, all these instruments and soft were quite expensive, not suitable for China, for EAS-10000 costs 2 million RMB, EPCO software costs 25000 Europian Dollar.There are a great deal of cataract patients in China, the incidence of after cataract is quite high too. It will be of help to improve the clinical and research level to develop a set of software of our own.Materials & MethodsExperiment 1: Set up and evaluation of computerized image analysis system for quantification of posterior capsule opacificationThe after cataract animal model was made in 30 rabbits, fed for 60 days. The pupil was dilate (＞6.5mm), the posterior capsule picturs were ocumented by slit lamp equiped with digital camera under standard condition. The retroillumination images were used for PCO scoring. PCO Score=∑(OD×AI in CR)×2+∑(OD×AI in OR), in which OD means the density of posterior capsule opacification (grade 0-grade 4), AI means the area percentage of certain grade PCO in the total evaluated area. (the round area diametered 6mm aroun visual axis), CR means the central region, OR means the outter ring (3-6mm). To test the reliability of this software, the interindividual difference was evaluated, in which 5 pictures were analyzed by 6 different examiners; the intraindividual difference was evaluated too, in which 1 examiner analyzed 5 pictures in 5 different days.Experiment 2: Comparision of two methods for the quantification of posterior capsule opacification30 animal after cataract model were analyzed by two methods for quantification. Method 1: On 60th day of feeding, the digital images of PCO were collected, and analyzed by the software set up in experiment 1, and the quantative results were recorded; Methed 2: after the PCO images were collected, the rabbits were killed and the eyes enucleated, the capsular bag was prepared for pathological analysis by HE staining, the lens epithelial cell in the capsular bag equator was counted. The results of the two methods was compared for the relativity.Experiment 3: The Effect of Continuous circular capsulorehxis and hydrodisection on the Posterior capsular opacificationThe two eyes of rabbit model were respectively assigned into two groups randomly. In group1, the lens cortex was removed by aspiration, open-can method was used to open the anterior capsule, no hydrodisection; in group 2, the continuous circular capsulorehxis and complete hydrodisection were performed to remove the cortex completely. The two methods in experiment 2 were used to analyzed the PCO in the two groups.ResultsExperiment 1: Set up and evaluation of computerized image analysis system for quantification of posterior capsule opacificationWhen the PCO score was 0-1.5, the standerd difference of interindividual reliability test was 0.05-0.087, there was no statistical significance by Kruskal-Wallis nonparameter analysis. (H= 0.314, p value = 0.972618). the standerd difference of intraindividual reliability test was 0.041-0.067, there was no statistical significance by Kruskal-Wallis nonparameter analysis either. (H = 0.613, p value = 0.961617 ).Experiment 2: Comparision of two methods for the quantification of posterior capsular opacificationThere was direct relativity between the lens epitheliul cells counting in the equator of the capsular bag and the PCO score of the same after cataract model image gained from PCO-CAAS software, r =0.84236Experiment3: The Effect of Continuous circular capsulorehxis and hydrodisection on the Posterior capsular opacificationIn group 1, the lens epithelial cells counting was 32.65±5.71, the PCO score of the after catarct images was 0.8996±0.2878; in group 2, the lens epithelial cells counting was 21.61±5.83, the PCO score of the after catarct images was 0.4406±0.2623, there was statistically significant fifference between the two groups.ConclusionsExperiment 1: Set up and evaluation of computerized image analysis system for quantification of posterior capsule opacificationThis PCO quanitification analysis system evaluates the central area (diameter=6mm) of posterior capsule which is larger than does visual acuity or other objective testing. The system revealed high reliability and insignificant investigatord ependent difference.Using a standardized photographic setup, systematic errors by the photographic technique were not relevant. This system was proved to be an easy and useful tool to accurately evaluate PCO.Experiment 2: Comparision of two methods for the quantification of posterior capsular opacificationBy comparing with lens epithelial cells counting, which was widely used as an quantification method to evaluate posterior capsular opacification, the PCO-CAAS software was proved to be an easy and useful tool to accurately evaluate PCO, and can be used in vivo.Experiment3: The Effect of Continuous circular capsulorehxis and hydrodisection on the Posterior capsular opacificationBoth the lens epithelial cells counting and the PCO Score indicated that CCC and hydradissection can prevent the formation of PCO and reduce the PCO severity.
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