Comparison of diamond and metal blade for scleral flap dissection in Trabeculectomy, using an anterior segment optical coherence tomography

Abstract

Purpose : To evaluate and compare the characteristics of the filtering bleb and scleral flap in trabeculectomy, created with a diamond or metal blade, using an anterior segment optical coherence tomography (AS-OCT).

Methods : We enrolled patients after a first trabeculectomy, in which the scleral flap was created using a diamond or metal blade, and continued follow up in our clinic by a glaucoma specialist. An AS-OCT was done at least 6 months post operation and analyzed for bleb height, bleb-wall thickness and para-scleral drainage route in the anterior and posterior parts of the scleral flap. Operative success was defined as IOP reduction of 30% and bellow 18 mmHg, addition of medication was considered as qualified success.

Results : 32 eyes (of 30 patients) were evaluated, 18 in the diamond blade group (DB) and 14 in the metal blade (MB) group. Success rate was 94.44% and 71.43%, respectively. Preoperative IOP was 23.33±7.09 [range 12-38 mmHg] in the DB group and 23.43±4.97 [range 16-36 mmHg] in the MB group. A mean IOP reduction at last follow up was 11.56±7.42 and 10.43±5.35 mmHg, respectively, with a lower medication rate in the DB group: 0.7 vs 1.7.
AS-OCT analysis showed a mean bleb height and bleb wall thickness of 843.33±357.37 and 685.11±259.35µm in the DB group compared to 651.29±284.17 and 519.5±237.61µm in the MB group, respectively, with p<0.05 for bleb wall thickness.

Conclusions : Higher success rate, IOP and medication reduction was seen with a diamond blade used for the scleral flap in trabeculectomy. This may be attributed to a thicker bleb wall associated with higher filtration rate.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Anterior segment OCT of 3 patients: A) Horizontal scan of patient#1 at the anterior part of the scleral flap, illustrating the parameters measured in the study: bleb wall thickness, para-scleral cavity height, total bleb height. B) Horizontal scan of patient#1 just posterior to the end of the scleral flap measuring the posterior bleb cavity, posterior bleb wall thickness and posterior total bleb height. C+D) Horizontal scans of patient#2 at the anterior scleral flap and just posterior to it, in a flat and scarred bleb. E) Vertical scan of a filtering bleb in patient#3. The sign * marks the posterior bleb cavity.