|Year : 2020 | Volume
| Issue : 4 | Page : 1155-1159
Ultrasound biomicroscopy role in assessing subscleral trabeculectomy operation
Mahmoud E Abd Elkhaleq1, Hatem G Marey2, Asmaa M Ibrahim2
1 Department of Ophthalmology, Smnood General Hospital, Elgharbia, Egypt
2 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||29-Feb-2020|
|Date of Decision||15-Apr-2020|
|Date of Acceptance||25-Apr-2020|
|Date of Web Publication||24-Dec-2020|
Mahmoud E Abd Elkhaleq
Department of Ophthalmology, Smnood General Hospital, El Mahalla, Elgharbia 31951
Source of Support: None, Conflict of Interest: None
This study aimed to evaluate the role of ultrasound biomicroscopy (UBM) in assessing uneventful trabeculectomy parameters.
The recent development of the UBM device has made it possible to observe the detailed structure of the anterior segment of the eye with a noninvasive procedure.
Patients and methods
In this prospective cohort study, an analysis of UBM scanning of 30 glaucomatous eyes of 30 patients, any age, both sexes, after 1 month from uneventful subscleral trabeculectomy operation was done.
There was a negative significant correlation between bleb size (r = 0.905, P < 0.001) and intraocular pressure (IOP). There was an insignificant correlation at anterior chamber depth and IOP (P = 0.193). There was a positive significant correlation at bleb reflectivity and IOP (r = 0.836, P < 0.001). Multiple regression analysis showed that both bleb size and reflectivity affect IOP, but anterior chamber depth does not.
UBM is a good predictor of the anatomical patency of surgically created passage in post-trabeculectomy patients and well correlated with IOP.
Keywords: assessment, intraocular pressure, subscleral, trabeculectomy, ultrasound biomicroscopy
|How to cite this article:|
Abd Elkhaleq ME, Marey HG, Ibrahim AM. Ultrasound biomicroscopy role in assessing subscleral trabeculectomy operation. Menoufia Med J 2020;33:1155-9
|How to cite this URL:|
Abd Elkhaleq ME, Marey HG, Ibrahim AM. Ultrasound biomicroscopy role in assessing subscleral trabeculectomy operation. Menoufia Med J [serial online] 2020 [cited 2021 Apr 19];33:1155-9. Available from: http://www.mmj.eg.net/text.asp?2020/33/4/1155/304509
| Introduction|| |
The outcome of trabeculectomy depends mostly on the resulting intraocular pressure (IOP). The description of the morphology and the function of the bleb are usually essential to a favorable outcome. The preservation of the aqueous drainage route beneath the trabeculectomy scleral flap cannot be evaluated by conventional slit-lamp examination,,.
The recent development of the ultrasound biomicroscopy (UBM) device has made it possible to observe the detailed structure of the anterior segment of the eye with a noninvasive procedure.
In normal eyes, the main outflow resistance appears to occur at the juxtacanalicular connective tissue layer of the trabecular meshwork. This area is by-passed by the surgical procedure, allowing the passage of fluid from the anterior chamber to the intrascleral space,.
In eyes that had undergone trabeculectomy, the development of a filtering bleb was correlated with the efficiency of filtrations beneath the scleral flap. It has long been believed that the development of a filtering bleb and the microarchitecture of the connective tissue in the bleb influence the IOP during the long-term postoperative follow-up.
The use of UBM permits the detailed noninvasive observation of the inner architecture of the bleb after trabeculectomy.
This study aimed to evaluate the role of UBM in assessing uneventful trabeculectomy operation parameters (anterior chamber depth, iris profile, maximal height and the extent of the bleb, intrableb reflectivity, patency of the aqueous drainage route, and patency of the peripheral iridectomy).
| Patients and Methods|| |
In this prospective cohort study, analysis of UBM scanning of 30 glaucomatous eyes of 30 patients, any age, both sexes, after one month from uneventful subscleral trabeculectomy operation was done from to January 2018 to December 2019 after approval of Menoufia Faculty of Medicine Ethics Committee (approval number: 7/2017opht), and a written informed consent was obtained from all participants in this research.
Exclusion criteria were history of any other ocular surgery (e.g., cataract surgery and vitrectomy), any ocular injuries, and anterior segment tumors.
Complete assessment was done including first, personal history taking (age and ocular history to exclude any previous ocular surgery or ocular injuries); and second, a thorough ophthalmic examination, including visual acuity measurement using Landolt's broken ring chart, manifest refraction using the autorefractometer, evaluation of the best-corrected visual acuity, slit-lamp biomicroscopy to assess the anterior segment, IOP measurement by applanation tonometry and dilated fundus examination, and slit lamp with Volk 90 D lens to assess posterior segment.
UBM (Sonomed Escalon VuPAD UBM; 1979 Marcus Avenue C105 Lake Success, NY 11042, USA) was performed using 35–50 MHz probe, which has a lateral resolution of 50 μ, axial resolution of 25 μ, and depth of penetration of 4–5 mm. Although the image resolution provided by UBM is much higher, its depth of penetration is not as high as a conventional B-scan ultrasonography, making it unsuitable to visualize deeper structures of the eye.
UBM was used for assessing trabeculectomy operation parameters, that is, anterior chamber depth, iris profile, maximal height and the extent of the bleb, intrableb reflectivity, patency of the aqueous drainage route, and patency of the peripheral iridectomy. Then the data were collected to document the parameters of UBM after one month from trabeculectomy operation.
The examination was done with the patient in the supine position. After applying topical anesthetic to the eye, an eyecup (plastic or silicone) was placed within the palpebral fissure to create a small water bath. Either methylcellulose solution (1 or 2%) or saline is used as the coupling fluid. The water bath designed by Kapetansky is a flexible polysiloxane cup with a beveled inner edge, providing a watertight seal and using saline as a coupling fluid. The transducer should be placed within the coupling solution in such a way that the scanning beam strikes the target perpendicularly, taking care not to apply undue pressure on the eyecup. The transducer detects the signals reflected from the anterior chamber structures. While performing a quantitative assessment of the anterior chamber, the room illumination, fixation, and accommodative effort of the patient should be held constant.
Statistical analysis was done by SPSS v20 (IBM, Chicago, Illinois, USA). Normality of the variables was checked by Shapiro–Wilk test, and they were normally distributed. Qualitative data were presented as number and percentage, whereas quantitative data were presented as range, mean, and SD. Linear Pearson's correlation coefficient (r) was used for detection of correlation between two quantitative variables. Multiple regression analysis was used to show the factors affecting IOP. P value less than 0.05 was considered significant.
| Results|| |
Patients' age ranged from 52 to 71 years, with mean value 61.67 ± 5.18 years. There were 11 (36.7%) male patients and 19 (63.3%) female patients. There were 15 patients having primary open-angle glaucoma and another equal number having the primary angle-closure glaucoma [Table 1].
Anterior chamber depth ranged from 2 to 3.5 mm, with a mean value of 2.60 ± 0.36 mm. A total of 25 (83.3%) patients had patency of sclerostomy, whereas five (16.7%) patients do not have. There were 21 (70.0%) patients having straight iris profile, whereas nine (30.0%) patients have steep one. IOP ranged from 11 to 37 mmHg, with mean value 17.27 ± 7.47 mmHg. Moreover, 13 (52.0%) patients had high bleb reflectivity, whereas 12 (40.0%) patients had low. Bleb size ranged from 9 to 20.4 mm2, with a mean value of 13.87 ± 3.08 mm2 [Table 2].
|Table 2: Ultrasound biomicroscopy parameters and intraocular pressure of the studied patients (n=30)|
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There was a negative strong significant correlation between bleb size and IOP (r = 0.905, P < 0.001) [Figure 1] and [Table 3]. There was a positive weak difference at anterior chamber depth and IOP (P = 0.193) [Figure 2] and [Table 3]. There was a positive strong significant difference between bleb reflectivity and IOP (r = 0.836, P < 0.001) [Table 3]. By simple linear regression, IOP = −1.1345 × (bleb size) + 30.384.
|Figure 2: Correlation between anterior chamber depth and intraocular pressure.|
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|Table 3: Correlation between bleb size, anterior chamber depth, and bleb reflectivity and intraocular pressure|
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Multiple regression analysis showed that both bleb size and reflectivity affect IOP, but anterior chamber depth does not [Table 4].
|Table 4: Multiple regression analysis of factors affecting intraocular pressure|
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| Discussion|| |
Trabeculectomy is the most commonly used glaucoma filtering procedure. However, failure of the bleb after an interval of apparent success is a fairly common problem. Filtration surgery failure is most commonly owing to fibrosis involving episcleral-tenon-conjunctival interface. It occurs mainly by proliferation of subconjunctival fibroblasts and biosynthesis of collagen and other extracellular material.
UBM is a new investigative tool for visualization of the anterior segment of the eye with microscopic precision. It has been found to be a useful tool for evaluation of the filtering bleb. It can visualize the internal sclerostomy opening, aqueous outflow route under the scleral flap, and other bleb characteristics.
Our results agreed with the study by Thatte and Rana, who conducted a randomized interventional study of 50 eyes with more than 3 months of follow-up of primary fornix-based trabeculectomy, wherein UBM examination was undertaken to assess bleb function. UBM analysis showed well-functioning bleb in 86.0% eyes and 14.0% as failure (4% primary angle-closure glaucoma and 10% primary open-angle glaucoma). Failed cases were distinctly co-related with positive findings of 14.0% of scleral reflectivity and 12.0% route under the scleral flap. Per individual case, treatments for inner window blockers iris, vitreous, membrane, and fibrosis were provided. UBM was helpful for the assessment of bleb function, cause of bleb failure, and its management, especially with patients who showed inconclusive gonioscopy and slit-lamp procedure. They concluded that UBM is certainly useful for evaluating the anatomical patency of surgically created passage in post-trabeculectomy patients. It provided assessments of bleb function and establishing cause in case of failure.
Moreover, the study by El Salhy et al. included 33 trabeculectomy filtering blebs of 25 patients who underwent trabeculectomy with mitomycin C. There was a significant correlation between certain UBM findings (intrableb reflectivity, draining subscleral tract, bleb height, and intrableb fluid cysts) and cases with different grades of clinical functional success (P < 0.001). They concluded that 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.
Moreover, Fayed and Soliman results conducted a prospective interventional observation uncontrolled study to evaluate the relationship between filtering bleb parameters (height, extent) and the wideness of the aqueous drainage route beneath the scleral flap using UBM in patients who have undergone trabeculectomy. They found that the reflectivity inside the filtering bleb showed a significant correlation with the maximal width of the aqueous drainage route and the maximal height and the extent of the bleb. The study concluded that the internal structure of the bleb can be a more sensitive predictor of the outcome of filtering surgery.
Moreover, the study by Avitabile et al. evaluated UBM features of filtering blebs after laser suture lysis trabeculectomy to analyze whether its UBM image can predict the function (IOP). A total of 103 filtering blebs after laser suture lysis trabeculectomy were analyzed by UBM. They revealed that there was a statistically significant correlation between the UBM classification of function and the IOP control level. Both well-functioning and failed trabeculectomies could be identified by UBM. The UBM images of eyes with good IOP control are characterized by better visibility of the route under the scleral flap and a low reflectivity inside the bleb. They concluded that UBM can be a useful method to study and explain the mechanisms of filtering structures and, together with IOP control, to evaluate the bleb function.
Moreover, a study by McWhae and Crichton was conducted to determine whether UBM appearance can predict successful lowering of the IOP following trabeculectomy. A total of 46 patients who had undergone trabeculectomy 1 week to 22 years earlier were recruited. In 38 (86%) of the 44 studies, there was a positive association between the UBM grade and the clinical findings. UBM had a sensitivity of 91% in predicting a functioning bleb and a specificity of 70% in predicting a nonfunctioning bleb. They concluded that UBM is a useful adjunct to the glaucoma surgeon in the management of certain patients following trabeculectomy.
Further studies with larger sample size are needed with comparison with other techniques (e.g., slit lamp optical coherence tomography) and 3D-UBM.
| Conclusion|| |
UBM is a good predictor of the anatomical patency of surgically created passage in post-trabeculectomy patients and well correlated with IOP. Therefore, UBM is useful in assessment of bleb function. Both bleb size and reflectivity affect IOP, but anterior chamber depth does not.
The data sets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
All authors contributed in writing the manuscript. They read and approved the final manuscript.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]