Purpose:
To compare ultrasound biomicroscopy (UBM) and slit lamp optical coherence tomography (SL-OCT) for imaging filtering blebs.
Methods:
Radial scans through the center of 25 post-trabeculectomy blebs of 21 patients (mean age 64.3±14.2 yrs, 13 (62%) women) were obtained using UBM and SL-OCT. The mean time after trabeculectomy was 47.9 months (range, 11 days to 24 years). A single experienced observer compared and measured the following morphologic features of blebs: bleb wall conjunctival thickness, subconjunctival cystic spaces, bleb height from the bleb wall to episclera, presence of conjunctival microcysts, internal ostium width and scleral tunnel width. The blebs were classified as successful, partially successful, or failed based on the clinical appearance, intraocular pressure, and number of medications.
Results:
UBM and SL-OCT data are presented in the table. An acceptable UBM image of one large bleb could not be obtained due to patient discomfort. SL-OCT could not image bleb height in 2 eyes or measure the internal ostium in 7 eyes due to poor penetration.
Conclusions:
SL-OCT is fast, safe and does not require supine positioning. It is superior to UBM at demonstrating intraconjunctival morphology and subconjunctival cystic spaces. However, it is limited for detecting deeper structures such as the scleral flap and internal ostium. Both UBM and SL-OCT show correlation between bleb success and bleb height. There is also a correlation between bleb success and the presence of conjunctival microcysts.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment