Résumé
Background Primary angle-closure glaucoma (PACG) is the most common type of glaucoma in China.A screening to identify the possible angle closure is important in the prevention and treatment of PACG.Objective This study was to determine the characteristics and the optimal parameters measured by the scanning peripheral anterior chamber depth analyzer (SPAC) in the screening of occludable angle of a sample of adult Chinese population.Methods A cross-sectional study was performed in Handan from February to April in 2013.One hundred and eighty Chinese adults were enrolled with the age of 40 years and older and acceptable criteria during 5-year following-up duration of the Handan Eye Study.Routine eye examinations were carried out in all subjects under the informed consent,including visual acuity,optometry,anterior ocular segment examination under the slit lamp microscope,and then SPAC measurement and gonioscopy were performed in a dark room.Occludable angle was defined as posterior trabecular meshwork being invisible in ≥ 180° range under the static gonioscope.Occludable angle by SPAC was estimated using available central chamber depth (ACD) and a combined indicator,numerical grade was 5 or fewer and/or the categorical grade was S or P,separately.Receiver operating characteristic (ROC) curve was calculated to assess the performance of these parameters in detecting eyes with occludable angle for the population-based sample,and area under curve (AUC) was drown to compare the screening efficiencies between available ACD and combined indicator.Results In 180 subjects,occludable angles were found in 62 and open angles were in 118.Compared to the subjects with open angle,the subjects with occludable angle showed the older age (P＜0.001),more females (P＜0.05),lower visual acuity (P＜0.001),greater hyperopic diopter (P＜0.05),smaller ACD value (P＜0.001) and shorter axial length(P＜0.001).In eyes with occludable angle by using SPAC,the ACD showed an AUC of 0.832.Using a cutoff of 2.7 mm for ACD,the sensitivity and specificity were 85.48％ and 68.64％,and under the cutoff of 2.8 mm,the sensitivity and specificity was 90.32％ and 61.02％,respectively.For the combined parameters,the sensitivity and specificity was 62.90％ and 90.68％,respectively and the AUC was 0.768.Conclusions When gonioscopy is used as a reference,a cutoff of 2.8 mm ACD by SPAC shows the highest sensitivity for the screening of occludable angle in Chinese population.
Résumé
Background Early diagnosis of primary angle-closure glaucoma (PACG) and screening or case detection of high risk population have become a major challenge in the prevention and treatment of PACG.Commonly used methods for evaluation of anterior chamber depth (ACD) and anterior chamber angle nowadays have their shortcomings.Scanning peripheral anterior chamber depth analyzer (SPAC) measures ACD and evaluates the risk of angle closure.Also,SPAC is handy,objective and noninvasive.Objective This study was to evaluate the repeatability (within-rater differences) and reproducibility (between-rater differences) of SPAC to measure anterior chamber-related parameters and agreement of SPAC to estimate occludable angle between two operators.Methods A prospective cross-sectional study was designed.Thirty subjects with shallow ACD (modified van Herick grading≤ 3 and Shaffer grading≤2) aged 35 years and older,who met the inclusion criterion were enrolled as shallow anterior chamber group and 30 age-and gender-matched normal adults (modified van Herick grading≤3 and Shaffer grading≤2)from the follow-up research of the Handan Eye Study in February 2013.After an elementary eye examination,a randomly selected eye of each subject in both groups received three consecutive SPAC measurements by each of the two examiners,respectively to obtain ACD,central corneal thickness (CCT) and corneal radius of curvature (CRC).Meanwhile,the identity of occludable angle as the numerical grade was 5 or fewer and/or the categorical grade being S or P was also obtained.The repeatability of each examiner was evaluated by the repeatability limit (RL) and the reproducibility of the two examiners was evaluated by intraclass correlation coefficient (ICC).The agreement of occludable angle estimation between two operators was evaluated using Kappa coefficient.Results The RLs percentage for ACD,CCT and CRC ranged from 0.36％ to 3.29％,and 0.90％ to 4.72％ in the normal control group and shallow anterior chamber group from operator A,and those from operator B were 0.38％ to 2.55％,and 0.51％ to 3.42％.The ICCs for ACD,CCT and C RC of SPAC were 0.966,0.859,0.989 and 0.915,0.905,0.971,respectively from operator A and operator B.The Kappa coefficients for the identity of occludable angle between two operators were 1.000 and 0.520 in the normal control group and the shallow anterior chamber group,respectively.Conclusions Measurements of the three parameters provided by SPAC in normal and shallow anterior chamber subjects show a good repeatability and reproducibility.The results of identity of occludable angle from two examiners have a good agreement for normal subjects and a moderate reproducibility for subjects with shallow ACD.