Imaging of Trabeculectomy Blebs Using Anterior Segment Optical Coherence Tomography
Received 26 January 2006; accepted 31 May 2006. published online 27 October 2006.
Objective
To image trabeculectomy blebs using anterior segment optical coherence tomography (AS-OCT).
Design
Prospective cross-sectional study.
Participants
Fifty-five patients who had previously undergone trabeculectomy surgery.
Methods
All blebs were imaged with a prototype of the AS-OCT. Standardized color monophotographs of blebs were also obtained. Blebs were assessed for the following qualitative features: bleb height, thickness of the conjunctiva in the bleb wall, presence of cystic spaces within the bleb wall, apposition of the scleral flap to underlying sclera, and patency of the internal ostium.
Main Outcome Measures
For blebs with preoperative intraocular pressure (IOP) > 18 mmHg with or without ocular hypotensive medication, success was defined as last recorded IOP≤18 mmHg without topical glaucoma medication. For blebs with preoperative IOP≤18 mmHg with ocular hypotensive medication, success was defined last recorded IOP≤18 mmHg with cessation of ocular hypotensive medication. For blebs with preoperative IOP≤18 mmHg without ocular hypotensive medication, a 20% drop in IOP with no ocular hypotensive medication was accepted as success.
Results
Seventy-eight blebs in eyes of 55 patients were imaged. There were 32 (58.2%) men and the mean age was 68.9±11.5 years. Fifty-seven (73.1%) blebs were classified as successful. Anterior segment optical coherence tomography identified the following bleb characteristics: total bleb height, bleb cavity, bleb wall thickness, tangential and radial dimensions, scleral flap thickness, and patency of the internal ostium. The majority of successful blebs displayed thickening of the bleb wall. Failed blebs were mostly low and were characterized by ostial occlusion, apposition of conjunctiva-episclera to sclera or apposition of the scleral flap to its bed. Thickening of the bleb wall was typically absent.
Conclusions
AS-OCT is a promising tool to image trabeculectomy blebs. It was able to demonstrate features of bleb morphology not visible with the slit lamp.
Correspondence to Dr Tin Aung, Glaucoma Department, Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751.
Manuscript no. 2006-107.
Supported by a grant from the National University of Singapore. Carl Zeiss Meditec, Dublin, California, loaned the anterior segment optical coherence tomograph for this study and provided technical support.
Drs Smith, See, and Aung have received financial support for travel to conferences from Carl Zeiss Meditec.
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