[Evaluation of the filtering bleb using ultrasound biomicroscopy]

The significance of ultrasound biomicroscopy in the objective assessment of post-trabeculectomy bleb success

PURPOSE

To compare clinical characteristics and ultrasound biomicroscopy (UBM) measurements of cases with functional and non-functional blebs, and to identify potential risk factors capable of affecting UBM parameters.

METHODS

Thirty-one patients aged 40-79 were included. Following trabeculectomy, cases were divided into two groups as those with functional bleb (Group 1, n = 20) and those with non-functional bleb (Group 2, n = 11). UBM was performed.

RESULTS

In Group 1 compared to Group 2, lower postoperative intraocular pressure (IOP) (12.1 ± 1.7 vs 27.2 ± 3.2 mmHg, p < 0.001), greater bleb height (1.0 ± 0.2 vs 0.5 ± 0.3 mm, p < 0.001), greater scleral route visibility [16/20 (80%) vs 4/11 (36.4%), p = 0.023] and lower bleb reflectivity (1.8 ± 0.2 vs 2.4 ± 0.4, p = 0.015) were observed. In Group 1, as postoperative IOP decreased, bleb height and scleral route visibility increased (r = -0.387, p = 0.029 for bleb height; r = -0.374, p = 0.033 for scleral route), and bleb reflectivity decreased (r = 0.359, p = 0.042). In Group 1, as duration of preoperative antiglaucoma drug use increased, bleb reflectivity increased (r = 0.348, p = 0.046). Preoperative IOP and number of preoperative antiglaucoma drug use had no effect on UBM parameters in groups (p > 0.05).

CONCLUSION

UBM is useful in assessing bleb success. Lower bleb reflectivity, greater bleb height and greater scleral route visibility indicate that the bleb is functional. To the best of our knowledge, this is the first study investigating effects of preoperative IOP, number and duration of preoperative antiglaucoma drug use on UBM parameters. In cases with functional bleb, duration of preoperative drug use affects only bleb reflectivity, while postoperative IOP affects bleb height, scleral route visibility and bleb reflectivity.

Functional evaluation of the filtering bleb by ultrasound biomicroscopy after trabeculectomy with mitomycin C

AIM

To study the role of ultrasound biomicroscopy (UBM) in the assessment of the bleb function after trabeculectomy with mitomycin C (MMC).

METHODS

This was a cross-sectional study including all cases had undergone trabeculectomy with MMC 0.2 mg/mL for 3min. Participants were recruited from the follow-up cases at Department of Ophthalmology, Tanta University in the period from August 2015 to August 2016. Full history taking and ophthalmological examination were performed. Intraocular pressure (IOP) was measured using Goldmann applanation tonometry and the history of prescribed postoperative antiglaucoma medications was recorded. Accordingly, the trabeculectomy blebs were divided clinically into successful blebs when the IOP post-operative was ≤18 mm Hg without medications. Scanning examination of the filtering bleb using UBM examination was performed at the period from 2 to 36mo after trabeculectomy (13.6±9.7mo).

RESULTS

This study included 33 trabeculectomy filtering blebs of 25 patients (9 males and 16 females). The mean age of patients was 53.2±14.2y (range 25-71y). We had 20 eyes with complete success, 9 eyes with qualified success, and 4 eyes with failure after trabeculectomy with MMC. The blebs were classified into successful blebs (IOP ≤18 mm Hg without antiglaucoma medications), others were classified into qualified successful and failed blebs. There was a significant correlation between certain UBM findings (intra-bleb reflectivity, draining sub-scleral tract, bleb height, and intrableb fluid cysts) and cases with different grades of clinical functional success (P<0.01).

CONCLUSION

UBM is an objective tool in the functional assessment of the post-trabeculectomy filtering bleb through a significant correlation between certain UBM parameters and the different grades of clinical functional success.

Use of Ultrasound Biomicroscopy to Predict Long-Term Outcome of Sub-Tenon Needle Revision of Failed Trabeculectomy Blebs: A Pilot Study

Purpose.

To evaluate the role of ultrasound biomicroscopy (UBM) in predicting the long-term outcome of sub-Tenon needling revision of failed trabeculectomy blebs.

Methods.

Adult patients with a failed trabeculectomy bleb and unsatisfactory intraocular pressure (IOP) control were recruited. The aqueous flow under the partial thickness scleral flap was looked for and the blebs classified on UBM as scleral route patent (SRP) or scleral route occluded (SRO). All blebs underwent needling revision with injection of 5 mg/0.1 mL 5-fluorouracil. Survival of the revision procedure at the end of 2 years follow-up with regards to the baseline UBM characterization of the bleb was noted. Successful outcome was defined as IOP <22.0 mmHg and/or 30% reduction of baseline IOP with or without medication.

Results.

A total of 13 eyes had SRP and 5 eyes had SRO blebs on UBM. Only SRP blebs survived the needling procedure by the end of 2 years. Of the 13 SRP blebs, 10 blebs survived (76.9%). Needling had failed in all 5 SRO blebs. The overall success rate was 55.6 % at 2 years. There was no difference in age, IOP, and time from initial trabeculectomy between the failed and successful group. The outcome correlated significantly to the patency of the scleral route assessed by UBM (p=0.07).

Conclusions.

Ultrasound biomicroscopy characterization of failed blebs appears to help in predicting the outcome of needle revision. In SRO blebs, it may be better to plan a full bleb revision rather than needling alone. Ultrasound biomicroscopy may help in avoiding an unnecessary needling procedure in SRO blebs where it is likely to fail.

The effects of phacoemulsification on intraocular pressure and ultrasound biomicroscopic image of filtering bleb in eyes with cataract and functioning filtering blebs

AIM

To evaluate the effects of phacoemulsification on intraocular pressure (IOP) and ultrasound biomicroscope (UBM) images of filtering bleb in eyes with cataract and a previous functioning filtering bleb.

METHODS

The IOPs and UBM images of filtering bleb of 24 patients (27 eyes) who underwent phacoemulsification after successful trabeculectomy were recorded at each follow-up examination and at the 12 months after phacoemulsification, respectively. Preoperative IOP and two parameters of the UBM images, including visibility of a route under the scleral flap and reflectivity inside the bleb were evaluated for an association with postoperative success rate using Kaplan-Meier survival analysis.

RESULTS

The mean IOP increased 5.50, 3.85, 3.11, 3.05, 2.79, and 2.58 mmHg after 1 day, 1 week, 1, 3, 6, and 12 months, and it was significantly higher than the preoperative IOP (P=0.000, 0.000, 0.000, 0.000, 0.000, and 0.000 respectively). There was no statistically significant difference in visibility of the route under the scleral flap and reflectivity inside the bleb before and after phacoemulsification (P=0.398, 0.096). An IOP greater than 10 mmHg, a bleb with an invisible route under the scleral flap and stronger intrableb reflectivity before phacoemulsification were associated with postoperative antiglaucomatous failure (P=0.025, 0.000, and 0.000 respectively).

CONCLUSIONS

Phacoemulsification significantly increased IOP, but had less effect on intrableb features in UBM image. Eyes with higher IOP, invisible route under scleral flap and stronger intrableb reflectivity in UBM image before phacoemulsification had greater postoperative antiglaucomatous failure.

UBM-guided chamber angle surgery for glaucoma management: an experimental study

PURPOSE

The aim of this experimental study was to investigate the potential of ultrasound bimicroscopy (UBM)-guided chamber angle surgery as an alternative or supplement to gonioscopy and intraocular microendoscopy for intraoperative control.

METHODS

In 15 porcine cadaver eyes, mechanical goniopuncture or punctual Er:YAG laser trabecular ablation was performed without operating microscope or gonioscopy, but with real-life ultrasound biomicroscopy monitoring with a 50 MHz transducer. Intraoperative localization of the microsurgical instruments and tissue-instrument contact were qualitatively evaluated.

RESULTS

The instruments could be clearly visualized within the chamber angle and disturbing artefacts were only minimal when using mechanically fixed instruments in slow motion. Topographic localization, tissue contact, and penetration depth of the instruments entering the scleral were well illustrated as far as the technical resolution limits of UBM would allow.

CONCLUSIONS

UBM can be used intraoperatively to monitor the correct manoeuvring of microsurgical instruments in selected ab interno procedures. Some adaptations and further modifications of the technique presented here will be necessary before UBM-guided surgery can be considered for clinical use in humans.

Ultrasound biomicroscopy and its value in predicting the long term outcome of viscocanalostomy

AIMS

To examine whether the early postoperative morphology at the site of sclerectomy, as visualised by ultrasound biomicroscopy (UBM), is an indicator of the mechanisms that lower intraocular pressure (IOP) and/or predictors of the long term outcome of viscocanalostomy.

METHODS

15 eyes of 14 patients with medically uncontrolled open angle glaucoma and no history of surgery underwent viscocanalostomy according to Stegmann's technique. Ultrasound biomicroscopy was performed during the first month after surgery. The following parameters were assessed: dimensions of the intrascleral "lake," presence of a filtering bleb, presence of a subconjunctival cavity or a suprachoroidal hypoechoic area, and the thickness of the residual trabeculocorneal membrane. A complete ophthalmological examination was performed the day before and the day after surgery. Follow up visits were scheduled 1 week, 4 weeks, 6 months, and 12 months after surgery.

RESULTS

At 1 year successful control of IOP (<20 mm Hg) was achieved without further manipulation or medication in six of 15 eyes. The size of the intrascleral "lake" (average 0.62 mm(3)) did not correlate with later IOP; however, a visible route under the scleral flap and accidental perforation of the trabeculocorneal membrane were associated with long term lowering of IOP. Normal thickness of the trabeculocorneal membrane (0.10-0.15 mm) was indicative of IOP control with and without medication. When UBM showed an early collapse of the intrascleral cavity, control of IOP was not achieved. Other UBM findings did not predict long term function.

CONCLUSION

In accordance with previous studies, the authors found that UBM examination is a useful method to evaluate outflow mechanisms after glaucoma surgery. This study shows that UBM imaging of external filtration during the early postoperative period can be used to predict the success of viscocanalostomy. However, to establish conclusively what parameters of UBM predict successful viscocanalostomy a larger number of patients must be studied.

Ultrasound biomicroscopic patterns after glaucoma surgery in congenital glaucoma

OBJECTIVE

This study aimed to demonstrate specific morphologic patterns in congenital glaucoma after various surgical procedures by means of ultrasound biomicroscopy (UBM) and to investigate correlations between UBM morphology and the effectiveness of glaucoma surgery in reducing intraocular pressure.

DESIGN

Observational case series.

PARTICIPANTS AND INTERVENTIONS

Thirty four eyes of 18 consecutive patients, not older than 18 years, with congenital glaucoma and with a history of previous antiglaucomatous surgery underwent UBM examination of the anterior chamber angle in the treatment area and in an untreated region.

MAIN OUTCOME MEASURES

The morphology of the anterior chamber angle region and the tissue reflectivity were analyzed.

RESULTS

Specific UBM patterns of the anterior chamber angle in congenital glaucoma were observed after goniotomy, trabeculotomy, trabeculectomy, deep sclerectomy, and cyclodialysis. In the first months after surgery, a limited correlation was found between morphology and the success of filtering surgery. Adhesions of the iris or the ciliary processes to the trabeculectomy cleft were detected in 19 of 25 eyes after filtering procedures.

CONCLUSIONS

In cases of cloudy cornea and unknown previous glaucoma surgery, UBM can be used to identify the type and localization of previous surgery in congenital glaucoma, thus assisting surgical planning for subsequent glaucoma management. The correlation between UBM morphology and the effectiveness of filtering surgery is less convincing than previously demonstrated in adults, possibly underlining the importance of individual nonsurgical factors for prognosis in congenital glaucoma.