Analysis of Bleb Morphology after Trabeculectomy with MMC 0.02% with Anterior Segment Spectralis Domain Optical Coherence Tomography (SD-OCT)

Abstract

Purpose: : To correlate the clinical morphologic appearance of filtering blebs in the early postoperative period with anterior segment Spectral-Domain Optical Coherence Tomography (SD-OCT, Spectralis^R, Heidelberg Engineering Inc.) images.

Methods: : 30 eyes of 30 patients (age 66±8 years) consecutively scheduled for trabeculectomy with MMC 0.02% were enrolled. Preoperative mean intraocular pressure was 20.1±6.3 mmHg under topical therapy. The filtering blebs were evaluated clinically according to a grading system and with SD-OCT on day 1, at 1,2,3,4 weeks and at 3 months following surgery. Bleb wall thickness and bleb cavity height were analyzed with horizontal and vertical SD-OCT-scans. Pre- and postoperative differences were analysed with the paired samples t-test.

Results: : 19 eyes (63%) had successful filtering blebs after 3 months without any further intervention. Intraocular pressure was 10±4.9 mmHg. Mean thickness of the bleb wall was 549±186 µm horizontally and 564±206 µm vertically, the height of the bleb cavity was 289±252 µm horizontally and 306±278 µm vertically. 9 filtering blebs (30%) showed early encapsulation (3 after 3 weeks, 6 after 4 weeks). Mean intraocular pressure at that time was 21±3 mmHg. Mean thickness of the bleb wall was 260±107 µm and 218±114µm and mean height of the bleb cavity was 1030±283 µm and 1167±342 µm in horizontal and vertical scans. After a needling procedure mean IOP was 14±7.6 mmHg at 3 months with diffuse filtering blebs. With SD-OCT the tendency towards encapsulation was already seen 1 week prior to clinical manifestation. Bleb wall measurements were 262±54 µm and 142±78 µm, cavity measurements 783±168 µm and 875±139 µm horizontally and vertically then. 2 patients (7%) showed early scarring and needed a revision.

Conclusions: : Anterior segment SD-OCT allows a non-invasive, high-resolution analysis of the clinically invisible deeper regions of the filtering bleb. Encapsulation and scarring are seen earlier compared to the observed clinical appearance. This might be of benefit in the management of the postoperative period after trabeculectomy.

Clinical Trial: : http://www.clinicaltrials.gov NCT01391676

Keywords: wound healing • clinical (human) or epidemiologic studies: outcomes/complications • imaging/image analysis: clinical