FP1425: Structural and Functional Correlation of Bleb Post Trabeculectomy

Dr.Nancy Sehdev, Dr. Suhas Haldipurkar, Dr. Vijay Shetty, Dr. (Mrs.) Dhamankar PR, Dr. Ravneet Chadha

Presenting author: Dr Nancy Sehdev
Chief author: Dr. Rita Dhamankar

Co-authors:Dr. Suhas Haldipurkar ,: Dr. Vijay Shetty

Financial Disclosure

None

Introduction

Bleb morphology is an important clinical parameter as an indicator for bleb function. Imaging techniques like ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) have been used to study bleb morphology(1).

 Advantages of  AS-OCT are that it produces higher resolution images with non-invasive and non contact approach(2,3).

 Need for study

There have been limited studies that have used imaging to identify features of blebs early in their development after trabeculectomy , that may predict success of these blebs in the long term using imaging techniques like AS-OCT.

 Aim of study

To correlate internal bleb morphology and bleb wall features on AS-OCT with bleb function(intraocular pressure)at  1 month, 3 months,6 months post-operatively.

 Objectives of study

  1. To study the bleb morphology using AS-OCT in early postoperative period.
  2. To correlate bleb wall thickness, bleb wall reflectivity, and bleb pattern on AS-OCT with intraocular pressure.

Inclusion criteria  

All consenting patients who were  diagnosed to have Primary open angle glaucoma or Primary angle closure glaucoma or Secondary glaucoma and  who underwent trabeculectomy surgery were included in the study.

 Exclusion criteria

Re-trabeculectomy cases and cases with history of  surgery involving conjunctival dissection eg-pterygium surgery,retinal surgery involving 360o peritomy were exluded from the study.

 Study design: It was a  Prospective cohort study

 Study duration: Enrolment of patients was done over a period of twelve months  and they were followed up at 1,3 ,6 months after surgery.

Method     

All blebs were imaged by AS‑OCT (Optovue) using a standardized protocol. Patients were asked to look      down, and the upper lid was gently elevated to expose the bleb as much as possible, taking care to avoid exerting any pressure on the globe or bleb. Vertical scans were taken through the bleb and scan at the   maximum point of elevation on the bleb was used to assess the parameters.

Can delete photographs

Bleb parameters assessed were

1.Bleb wall reflectivity– Bleb wall reflectivity was classified as uniform reflectivity or multiform reflectivity depending on presence or absence of hyper‑reflective areas in the bleb wall itself.

In uniform reflectivity there were no fluid filled hyporeflective spaces in the subconjunctival space. It was seen as smooth, hyperreflective wall.

In multiform reflective wall there was presence of small multiple fluid filled spaces seen as hyporeflective areas in the conjunctiva or bleb wall.

2.Bleb wall thickness-It is defined as the distance between the first reflective signal from the conjunctiva to the top of the subconjunctival fluid space, or the suprascleral fluid space if the former is not present.

As bleb wall thickness may vary along the scan, only the minimum distance was measured.

3.Bleb pattern– Three types of bleb patterns were noted-Diffuse, cystic and non functioning.

a) Cystic blebs were composed of a large subconjunctival hyporeflective space with multiloculated fluid collections of varying size and intensity. The blebs were covered by a thin layer of conjunctiva.

b) Non functioning blebs/ encapsulated bleb-were characterized by the absence of subconjunctival fluid collection and high intrableb reflectivity.

c) Diffuse filtering blebs were characterised by multiple subconjunctival signal void areas corresponding to pockets of fluid collections and low to moderate intrableb reflectivity.

Results– 42 eyes of 38 patients were enrolled. Mean age was 55.3 years. Females and males were 11 and 27% respectively

Graph was plotted to shows correlation between bleb height and intra-ocular pressure at 1, 3, 6 months. X axis on left side shows intra-ocular pressure and on right side shows bleb height. Follow-up visits are plotted on Y-axis.  A positive correlation between intra-ocular pressure and bleb height was obtained-1µ increase in bleb height leads to 0.02 mmHg reduction in intra-ocular pressure with significant p value of 0.004 and 95% confidence intervals.

Also, with each increase in month, IOP reduces by 0.37mmHg(p < 0.001,95% Confidence interval=-0.56 to -0.18)

Also, in 15 of our patients, change in bleb pattern from multiform to uniform was noted with rise in IOP during follow-ups. Intervention in terms of 5-Flourouracil injection was done and reversal of reflectivity was noted with better control of IOP.

 Discussion 

Predictors of functioning bleb(as evidenced clinically by controlled IOP) on AS-OCT-

  1. Multiform reflectivity
  2. Diffuse pattern of bleb
  3. Progressive increase in bleb height with follow-ups

Also,  internal bleb morphology visualised on AS- OCT provide a new perspective towards understanding the different surgical outcomes after trabeculectomy.

Observation of bleb by  AS-OCT is a useful way to proceed any intervention after trabeculectomy.

Clinical significance derived

AS-OCT can be used as an efficient tool to decide on managing a bleb successfully, by identifying the AS-OCT picture for different stages of bleb healing. Eg- identifying early failure and giving subconjunctival  5-fluorouracil injection which helps in salvaging a failing bleb. Similarly, needling a bleb that is encysting will open up the bleb.

References

  1. 1. Sacu S, Rainer G, Findl O, Georgopoulos M, Vass C. Correlation between the early morphological appearance of filering blebs and outcome of trabeculectomy with Mitomycin C. J Glaucoma 2003;12:430‑5.
  2. Allingham RR, Damji KF, Freedman SF et al. Editors. SHEILDS. Textbook of Glaucoma.6th ed. Lippincott Williams & Wilkins: 2012
  3. Khamar MB, Soni SR, Mehta SV, Srivastava S, Vasavada VA. Morphology of functioning trabeculectomy blebs using anterior segment optical coherence tomography. Indian J Ophthalmol 2014;62:711-4.

 

          

FP18 : Effect of Ocular Torsion on the Followability of Isnt Rule By the Rnfl Using SD -OCT
FP774 : Estimation of Intraocular Pressure (Iop) Lowering Effect of Selective Laser Trabeculoplasty (SLT).

Leave a comment