Evaluation of computerized image analysis system for quantification of posterior capsular opacification / 国际眼科杂志(Guoji Yanke Zazhi)

ABSTRACT

AIM: To set up and evaluate a computerized image scoring system for quantification of posterior capsular opacification (PCO) that is independent of examinee.METHODS: The PCO model was made in rabbits. Following dilation of the pupil (＞6.5mm), standardized digital images of the PCO were obtained using slit-lamp photographic system(digital camera, computer included). PCO was scored by evaluating retroillumination photograghs. The PCO score was calculated by the formula PCO score=∑ (OD×AI in CR)×2 +∑(OD×AI in OR), in which OD is opacity density (class 0 to 4),AI is the opacity area fraction, CR is the central region (diameter=3mm), OR is the outer region (3-6mm ring region).To evaluate the reliability of the scoring system, 6 examiners scored the pictures of 5 same eyes (interindividual reliability),and one examiner scored the pictures of 5 eyes on five different days (intraindividual reliability).RESULTS: The PCO scoring system was very reliable. With PCO score range from 0 to 1.5, the interindividual reliability showed standard deviation between 0.05-0.087. Kruskal-Wallis analysis showed no significant difference (H=0.314,P=0.9726). The intraindividual reliability showed standard deviation between 0.041-0.067, no significant difference either (H =0.613, P =0.9616).CONCLUSION: This PCO quantification analysis system evaluates the central area (diameter=6mm) of posterior capsule which is larger than visual acuity or other objective testing. The system revealed high reliability and insignificant investigator-dependent difference. With 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.