Abstract
Purpose :
A portable and inexpensive spectral-domain OCT (SD-OCT) has been designed to improve the cost-effectiveness of glaucoma diagnosis. We performed a transversal, prospective study to evaluate the diagnostic accuracy of a portable OCT iVue to detect glaucoma and to compare this accuracy with a full size SD-OCT (the Cirrus OCT).
Methods :
The study population consisted of 146 eyes of 146 patients, 113 were healthy subjects and 33 had glaucoma. Patients were included if visual acuity was 20/40, with two reliable and reproducible visual field tests, and good quality OCT images (Cirrus and iVue) obtained within 6 months.The parameters measured, with both OCTs, and compared were: global, superior and inferior retinal thickness of the nerve fiber layer (RNFL), the area and volume of the disk, cup/disk ratio and rim area. T test and Kruskal Wallis test were used to compare these parameters from the two instruments. Sensitivity, specificity, positive and negative predictive values of each parameter were also calculated and compared from both SD-OCT. To analyze the diagnostic precision, the area under the ROC curve (AUC) was calculated. To compare sensitivity and specificity the McNemar's test was used.
Results :
Cirrus and iVue identified significant differences between normal subjects and glaucoma patients in RNFL thickness and disk parameters. No statistically significant differences were found in sensitivity, specificity and predictive values of RNFL parameters between instruments. Sensitivity and specificity for average RNFL thickness were 0.67(0.49-0.82) vs. 0.71(0.53-0.85) and 0.9(0.81-0.95) vs. 0.87(0.78-0.93) for Cirrus and iVue, respectively. AUC for RNFL thickness tended to be slightly superior for Cirrus (average thickness AUC= 0.892) than for iVue (average thickness AUC= 0.869), with no significant differences. There were no significant differences in sensitivity of vertical cup/disk ratio between Cirrus (0.68 (0.49-0.82)) vs. iVue (0.71 (0.53-0.85)), but specificity resulted significantly higher for iVue (0.95 (0.88-0.98)) than for Cirrus (0.79 (0.68-0.86)).
Conclusions :
Both instruments were able to classify normal and glaucoma patients with high accuracy. RNFL parameters of Cirrus OCT tended to offer higher AUC values than iVue RNFL parameters. iVue vertical cup/disk ratio showed significantly higher specificity than Cirrus vertical cup/disk ratio.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.