Although OCT can improve your diagnostic accuracy for myriad conditions, complete posterior vitreous detachment (PVD) may not be one of them, according to new research. A team of investigators recently found macular OCT is effective when diagnosing attached vitreous if the premacular bursa or posterior vitreous cortex is visible, but it may need ultrasound as a supplemental tool to accurately diagnose complete PVD.

“We were inspired to do this study because any time we use new technology, we need to first figure out how accurate our technology is for measuring what we want to measure,” says the study’s lead author Eileen Hwang, MD, PhD, assistant professor at the University of Utah. “There have been many studies correlating the appearance of vitreomacular adhesion on OCT with clinical outcomes, but very few studies evaluating the accuracy of OCT for assessing the status of the vitreous. When we looked at preoperative OCT compared with the surgeon’s findings during vitrectomy, we found that when we see vitreomacular adhesion on OCT, we can confidently say that the vitreous is attached. However, when we don’t see any vitreous structures on OCT, sometimes the vitreous is attached and sometimes there is a complete posterior vitreous detachment.”

Dr. Hwang and her team enrolled 175 eyes of 175 patients who had preoperative OCT within 90 days of vitectomy. The patients’ average age was 65, and the group included 111 females and 64 males.

The investigators reviewed the suspect PVD findings on the preoperative macular OCT scans and compared them with the actual PVD found during vitrectomy. Attached vitreous was identified on OCT by visualizing the posterior vitreous cortex or the premacular bursa. Complete PVD was identified by the absence of these findings and was considered a positive outcome.

Of the 38 eyes graded as complete PVD on OCT, 20 eyes were found to have pre-existing PVD at the time of surgery (true positives), and 18 eyes had attached vitreous at the time of surgery (false positives). Of the 137 eyes graded as attached vitreous on OCT, 129 eyes were true negatives and eight eyes had pre-existing PVD at the time of surgery (false negatives).

The sensitivity of OCT for detecting complete PVD was 71% and the specificity was 88%. The positive predictive value of an OCT scan showing complete PVD was just 53%, while the negative predictive value of an OCT scan showing attached vitreous was much higher at 94%.