Analysis of Bleb Morphology After Trabeculectomy with Anterior Segment Optical Coherence Tomography

TITLE: Analysis of bleb morphology after trabeculectomy with anterior segment optical coherence tomography. PURPOSE: To describe the use of Anterior segment optical coherence tomography (AS OCT ) in imaging of trabeculectomy bleb to find out the morphology and internal structure, and correlate its internal characteristics with the function of the bleb. METHODS: Observational case-series study.60 eyes of 53 patient who attended glaucoma OPD during a period of March to May 2013 ,who had previously undergone trabeculectomy Surgery/combined surgery ,with a minimum post operative period of 2 months were included. Bleb morphology clinically noted with slit lamp. Blebs were classified as Filtering (Successful) or Nonfiltering (Failed) depending upon the IOP. Bleb was considered as Filtering bleb if last recorded IOP without any antiglaucoma medication is <18mm Hg if the initial IOP WAS >18mm Hg with or without antiglaucoma medications, 20% reduction in initial IOP if pre operative IOP was <18mmhg without antiglaucoma medications. Blebs were analyzed with Visante AS OCT vertical, horizontal, oblique sections for bleb wall thickness, height of internal fluid-filled cavity,supra scleral fluid space, micro cystic spaces in bleb wall, visible drainage route under the scleral flap. RESULTS: Images were obtained of 60 blebs. 48 blebs were filtering and 12 were non filtering. The mean preoperative IOP in filtering blebs was 24.31±7.88 mm Hg, and in non filtering blebs were 17.92±6.62 mm Hg. Mean post operative IOP was 11.92± 3.03in filtering and 18.25±6.62 in nonfiltering blebs. % reduction in IOP was 35± 26.24 % in filtering and 6.5±6.76 % in non filtering blebs. AS OCT showed mean bleb wall thickness in filtering blebs is0.70±0.26mm, and in non filtering blebs 0.44±0.24mm.Mean height of internal fluid filled cavity in filtering blebs 0.48±0.29mm, in non filtering blebs is 0.22±0.22m .Supra -scleral fluid space was seen in 43(90%) filtering blebs average size 0.27±0.17mm and only in 5 case of non filtering blebs, average size 0.12±0.20mm. Micro cystic spaces in the bleb wall were present in 33/48 cases of filtering blebs, with an average number being 1.46±1.37 and was present in 2/12 of non filtering blebs, average number of cysts being 0.25±0.62. Route under the scleral flap was present in 44 cases (92%) of filtering blebs and 6 cases (50%) in non filtering blebs. CONCLUSION: Anterior segment optical coherence tomography (AS OCT) is a promising tool to image trabeculectomy blebs. The different patterns of intra bleb morphology identified by AS OCT were related to the bleb function. The filtering blebs exhibited a large internal fluid filled cavity, thicker bleb walls with more number of micro cysts. Introduction Trabeculectomy has been widely applied as treatment of choice in medically uncontrolled glaucoma patients1. The outcome of this surgery depends on the formation of a functioning shunt, termed the filtration bleb, to enable egress of aqueous from the eye. Bleb morphology after trabeculectomy is an important clinical parameter; it is an indicator of bleb function. A careful slit-lamp examination and colour photography which are non invasive, easy is important in evaluation of bleb function. Two major objective bleb grading systems, including the Indiana Bleb Appearance Grading Scale (IBAGS) and the Moorfields Bleb Grading System (MBGS) have been introduced for clinical evaluation and classification of filtering blebs 2,3 However, bleb evaluation merely based on slit-lamp examination has its own limitations; because of the subjective nature of these methods and the internal morphology of filtering blebs, which could play an important part in determining surgical outcome, cannot be evaluated under slit lamp. Ultrasound biomicroscopy, confocal microscopy, conventional retinal optical coherence tomography (OCT), and time-domain anterior segment AS OCT , are used for analyzing internal bleb characteristics. Ultrasound biomicroscopy and confocal microscopy needs Address for Correspondance: Little Flower Hospital, Angamaly 683 572. Email: [email protected] Devika.K DO, Girija. K MS, Sindhu. S DO