Trabeculectomy for normal tension glaucoma: outcomes using the Moorfields Safer Surgery technique

"Long-term safety and efficacy of injection mitomycin C(MMC) versus sponge application in trabeculectomies"

AIMS

To compare the long-term safety and efficacy of subconjunctival injection mitomycin C(MMC) with conventional sponge applied MMC during trabeculectomy.

METHODS AND MATERIAL

Retrospective analysis of 98 eyes of 90 patients who underwent trabeculectomy with Mitomycin C were divided into two groups, group 1- sponge (n = 52) and group 2- Injection(n = 46). Follow-up data were collected on day one, day 15, one month, three months, six months, one year, two years and three years. Data from baseline and follow-up visits were analyzed and compared to study the significant difference in intraocular pressure (IOP), number of antiglaucoma medications (AGM) and best corrected visual acuity (BCVA) . P-value of <0.05 was considered statistically significant.

RESULTS

Mean preop IOP was 34.61 ± 13.3 mmHg in group one and 33.07 ± 9.6 mmHg in group two, which reduced to 11.43 ± 3.2 and 11.59 ± 3.2 mmHg at three years (p < 0.001 in both groups) with no significant difference between the groups. Mean number of preoperative AGM was 2.28 ± 0.8 and 2.42 ± 0.7 in group one and two respectively which reduced to 1.19 ± 1.1(p = 0.405) and 0.88 ± 0.9(p = 0.001) at three years. Complete and overall success rates (complete + qualified) were 59.3% and 78.9% in group one and 60.9% and 80.4% in group two at three years. No statistically significant difference was found in complication rates, post-operative interventions, and final visual outcome in both groups.

CONCLUSIONS

Subconjunctival Injection MMC was a safe and effective alternative to sponge application with comparable long term surgical outcomes.

Long-term efficacy and safety of XEN-45 gel stent implantation in patients with normal-tension glaucoma

BACKGROUND

Minimally invasive bleb surgery using the XEN-45 gel stent has not been established for the treatment of normal-tension glaucoma (NTG). The main objective of this study was to evaluate the long-term treatment efficacy and safety of XEN-45 in eyes with uncontrolled NTG.

METHODS

A retrospective analysis of patients with NTG who underwent XEN-45 gel stent implantation at university hospital Tuebingen between 2016 and 2021. The primary outcome measure was surgical success after three years defined as lowering of intraocular pressure (IOP) of ≥ 20%, with target IOP between 6 and 15 mmHg. Success was complete without and qualified irrespective of topical antiglaucoma medication use. The need for further glaucoma surgery, except for needling, was regarded as a failure. The secondary outcome measures included changes in mean IOP, number of antiglaucoma medications, and needling and complication rates.

RESULTS

Twenty-eight eyes from 23 patients were included in the final analysis. Complete and qualified success rates were 56.5% and 75% after three years, respectively. Mean postoperative IOP ± standard deviation decreased significantly after three years from 19.3 ± 2.0 mmHg at baseline to 13.7 ± 4.2 mmHg (n = 22; p < 0.0001). The median number of antiglaucoma medications decreased from 2 (range 0-4) to 0 after three years (range 0-3; p < 0.0001). Sixteen eyes (57%) required a median of 1 (range 1-3) needling procedures. One eye required further glaucoma surgery. No sight-threatening complications were observed.

CONCLUSION

The XEN-45 stent is effective and safe for the long-term treatment of NTG. However, needling was frequently required to improve outcomes.

Long-Term Surgical Outcomes of Glaucoma Drainage Implants in Eyes with Preoperative Intraocular Pressure Less than 19 mmHg

Background

This retrospective review reports on patients who underwent glaucoma drainage implant (GDI) surgery and had baseline intraocular pressure (IOP) of ≤18 mmHg with at least one year of follow-up.

Methods

Clinical data of 67 eyes of 67 patients were collected from patients' charts, and the outcomes of GDI were evaluated until 7 years. GDI failure was defined as IOP reduction of less than 20% from the baseline at two consecutive visits three months after surgery, decline to no light perception, or if additional glaucoma surgery was performed.

Results

The average age was 65.9 ± 13.2 years. Most cases were male (52.2%), White (53.7%), and had primary open-angle glaucoma (62.7%). Forty-four eyes had prior glaucoma surgery (68.6%) and 46 (68.6%) had severe glaucoma. Though postoperative (postop) IOP changes were insignificant, the average postop number of medications dropped from 2.4 ± 1.4 to 1.9 ± 1.2 medications two years after surgery (p = 0.0451). Postop complications (23.9%) included GDI exposure (7.5%), inflammation (4.5%), shallow anterior chamber (4.5%), and strabismus (1.5%). Hypotony was observed in 4 eyes (5.9%), none of which developed hypotony maculopathy. The cumulative one-year failure rate was 56.7%, most of which were due to failure to lower IOP.

Conclusion

In patients with baseline IOP ≤18 mmHg who had GDI surgery, though the change in IOP was not statistically significant, the number of medications dropped and visual field progression slowed in a subset of patients with adequate perimetric data. Due to a relatively high rate of complications and limited effectiveness in lowering IOP, GDI should be cautiously used in these eyes.

Trabeculectomy: Does It Have a Future?

The trabeculectomy (TRAB) procedure has undergone various modifications to increase the long-term surgical success and safety profiles. The main issues with TRAB include short and long-term complications, that are more common with the concomitant use of anti-fibrotic agents. While many surgeons have predicted the demise of trabeculectomy amidst newer non-penetrating glaucoma surgeries, it is still the gold standard procedure for patients with an advanced or rapidly progressing disease and for those patients who need very low intraocular pressures. This review article is unique in summarizing the evolution of trabeculectomy and its efficacy compared to neoteric shunt procedures while trying to predict if trabeculectomy has a future in the modern surgical world. We have compared the outcomes and complications of trabeculectomy to all the surgical procedures available to date and have tried to evolve an algorithm to help surgeons to decide on their preferred technique.

Trabeculectomy With Antimetabolite Agents for Normal Tension Glaucoma: A Systematic Review and Meta-Analysis

Background

Evidence regarding the impact on visual field (VF), intraocular pressure (IOP), and antiglaucoma medications from trabeculectomy with antimetabolites for normal tension glaucoma (NTG) is conflicting because of insufficient study sample sizes. The aim of this study is to systematically assess VF progression rate, IOP control and antiglaucoma medication use after trabeculectomy with antimetabolites for progressing NTG.

Methods

We searched published articles on PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials from database inception to March 21, 2022. We selected studies that reported VF data before and after trabeculectomy with antimetabolite agents for NTG. We followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guidelines. Data were extracted by 2 independent reviewers, and a random-effects model was employed for the meta-analysis. Study outcomes were VF progression rates measured using the pooled mean deviation (MD) slope, changes in antiglaucoma medications, and IOP. Subgroup analyses of the MD slope according to mean age (over or under 65 years), baseline MD (over or under –12 dB), and baseline IOP (over or under 15 mmHg) were performed to determine the results’ robustness.

Results

We included 7 retrospective observational studies (Japan: 6 studies, United States: 1 study) comprising a total of 166 eyes. Mean preoperative VF MD slopes ranged from –0.52 to –1.05 dB/year. The meta-analysis demonstrated significant MD slope improvement after trabeculectomy (pooled mean difference: 0.54 dB/year, 95% CI: 0.40 to 0.67, I² = 9%). Mean age, baseline MD, and baseline IOP subgroup analyses revealed MD slope results were consistent with those of the main analyses. The mean IOP (pooled mean difference: –5.54 mmHg, 95% CI: –6.02 to –5.06, I² = 0%) and mean number of antiglaucoma medications (pooled mean difference: –1.75, 95% CI: –2.97 to –0.53, I² = 98%) significantly decreased after trabeculectomy. The most frequently reported early complications after trabeculectomy were hypotony, hyphema, and shallow anterior chamber.

Conclusion

This systematic review and meta-analysis indicated that trabeculectomy with antimetabolites is beneficial for progressing NTG; it preserves visual function by alleviating the MD slope and reducing antiglaucoma medication use. However, several post-trabeculectomy complications should be monitored.

One-Year Randomized Comparison of Safety and Efficacy of Trabeculectomy with Mitomycin C Sub-Tenon Injection versus Mitomycin C-Infused Sponges

PURPOSE

To compare the safety and efficacy of sub-Tenon injection of mitomycin C (MMC) with application of MMC-infused sponges during trabeculectomy.

DESIGN

Single-center randomized clinical trial.

PARTICIPANTS

A total of 56 eyes of 49 patients with open-angle glaucoma were included in this clinical trial.

METHODS

In this single-center randomized clinical trial, 56 eyes of 49 patients underwent trabeculectomy with MMC for primary open-angle glaucoma. Patients were randomized into 2 groups. The injection group received a sub-Tenon injection of 0.15 ml of 0.01% MMC diluted with preservative free lidocaine 2% (n = 27). In the sponges group, sponges soaked in 0.02% MMC were applied under the Tenon's capsule and the scleral flap for 2 minutes (n = 29). Intraocular pressure, endothelial cell count, best-corrected visual acuity, and number of intraocular pressure (IOP)-lowering medications were assessed before surgery and 1 week; 1, 3, and 6 months; and 1 year after surgery. Complete success was defined as IOP of 14 mmHg or less without medication. Bleb morphologic features were assessed using the Indiana Bleb Appearance Grading Scale bleb grading system.

MAIN OUTCOME MEASURES

Intraocular pressure reduction was the primary outcome. Bleb morphologic features and endothelial cell counts (ECCs) were secondary outcomes.

RESULTS

Mean IOP in the sponges group decreased from 30.5 ± 7.4 mmHg at baseline to 12.6 ± 5.9 mmHg at 1 year (P < 0.001); in the injection group, IOP decreased from 29.3 ± 6.8 mmHg at baseline to 12.7 ± 4.3 mmHg at 1 year (P < 0.001). No difference in IOP between the 2 groups was noted at any visit (P < 0.001). Surgical success was 81.5% and 82.8% in the injection and sponges groups, respectively, at 1 year. Mean ECC values were unchanged from baseline to 1 year after surgery for both groups (P = 0.444). Complication rates were similar in the 2 groups. Bleb morphologic features showed differences in the appearance and grading of the blebs between the 2 groups at 1 year, showing larger extent, lower height, and less vascularization in the injection group.

CONCLUSIONS

Sub-Tenon injection of MMC during trabeculectomy seems to be as safe and as efficacious as conventional application of MMC with sponges at 1 year after surgery. Bleb morphologic features show notable differences that may suggest a better long-term outcome.

Effective treatment of a normal-tension glaucoma patient with bilateral ab externo XEN Gel Stent implantation

Purpose

To provide the first report of effective use of bilateral XEN Gel Stent implantation using an ab externo open-conjunctival approach designed to improve bleb function and meet the uniquely low intraocular pressure requirements of a Japanese patient with normal-tension glaucoma refractory to topical medical therapy.

Observations

A 54-year-old phakic Japanese woman with severe normal-tension glaucoma on maximally tolerated medical therapy of four topical agents presented with above-goal intraocular pressures and new medication intolerances. She underwent bilateral ab externo open-conjunctival XEN Gel Stent implantation with tenectomy and sub-Tenon's injection of 40μg of mitomycin-C, which resulted in reduction of intraocular pressures by 41.2 and 28.6% to 10 and 10 mmHg in the right and left eyes, respectively at the most recent visit. Postoperatively, a diffuse filtering bleb with good morphology developed in both eyes. The procedure has so far allowed for complete cessation of all four topical medications for up to eight months following surgery without any serious complications.

Conclusions

This case illustrates the potential of Xen Gel Stent implantation through an ab externo, open-conjunctival approach to be an effective, simple alternative to trabeculectomy to meet the unique low-pressure requirements of normal-tension glaucoma patients with practical and safety benefits of a micro-invasive approach.

Normal tension glaucoma in Asia: Epidemiology, pathogenesis, diagnosis, and management

Normal tension glaucoma (NTG) has similar optic neuropathy as primary open-angle glaucoma (POAG), but intraocular pressure (IOP) is within the normal range. Compared with high-pressure POAG, the development of NTG is possibly a consequence of a complex interaction of several ocular and systemic factors. Recent data have shown higher translaminar pressure gradient due to impaired cerebrospinal fluid dynamics may account for the pathogenic mechanism. Insufficient blood supply and vascular dysregulation may also be the cause of the disease. In clinical evaluation, NTG is a diagnosis by excluding other nonglaucomatous optic neuropathies. NTG is characterized by larger and deeper optic-disc cupping, more central visual field defects and a higher incidence of disc hemorrhage compared with POAG. In clinical practice, controlling IOP as low as possible (with medication, laser trabeculoplasty, or surgery) is the key to manage NTG patients. In addition to IOP reduction, the control of systemic risk factors or improving ocular perfusion may be beneficial therapies. NTG is more prevalent in Asia than in the Western countries. Due to increasing old population and underdiagnoses in the clinical settings, NTG became a great challenge for ophthalmologist in Asia. Therefore, the aim of this article is to focus on the epidemiology, to update pathogenesis, diagnosis, and management for NTG.

The Tenons' Layer Reposition Approach of Trabeculectomy: A Longitudinal Case Series of a Mixed Group of Glaucoma Patients

SYNOPSIS

This 1-year prospective study demonstrated that the Tenon's layer reposition approach of trabeculectomy could achieve zero leakage rate, minimal rate of transient hypotony without compromising the surgical outcome.

PURPOSE

The purpose of this study was to investigate the effectiveness and safety of a Tenon's layer reposition approach of trabeculectomy.

METHODS

A prospective, noncomparative case series of 30 eyes of 30 Chinese patients with mixed types of glaucoma who underwent fornix-based trabeculectomy combined with intraoperative mitomycin C application. During the conjunctival flap closure, the Tenons' layer was identified, separated, and anchored on to the sclera surface with 8/0 vicryl, followed by conjunctival closure with 10/0 nylon as a separate layer. All patients were followed up for 1 year. Assessment including intraocular pressure (IOP), vertical cup-disc ratio measurement, best-corrected visual acuity, and visual field examination were performed before and after the operation. Qualified and complete success was defined as IOP of ≤21 mm Hg in 2 consecutive visits with or without medication, respectively. Outcomes were evaluated using scattered plot and Kaplan-Meier survival curve.

RESULTS

Twenty-one eyes (70%) and 28 eyes (93.3%) achieved complete and partial success at 1 year, respectively. There was a significant reduction of IOP (28.5±9.6 to 15.5±2.6 mm Hg, P<0.001) and medication use (4.4±0.9 to 0.8±1.2 bottles/eye, P<0.001). There were no significant changes in best-corrected visual acuity, vertical cup-disc ratio, and visual field indices. No wound leak was identified throughout the study. The procedure did not induce significant astigmatic change. Other postoperative complications, including 2 eyes (6.7%) with transient hypotony and 1 eye (3.3%) required cataract surgery, were of relatively low rate.

CONCLUSION

The Tenon's layer reposition approach of performing trabeculectomy is a safe and efficacious procedure for Chinese subjects with different types of glaucoma.

Effectiveness of trabeculectomy with mitomycin C for glaucomatous eyes with low intraocular pressure on treatment eye drops

PURPOSE

To examine the efficacy and safety of current trabeculectomy with mitomycin C in Japan for glaucomatous eyes with low intraocular pressure (IOP).

METHODS

Two hundred ninety-four eyes of 294 patients with IOP ≤21 mmHg before surgery were studied; all patients were participants in the Collaborative Bleb-related Infection Incidence and Treatment Study (CBIITS), a multicentre, prospective, cohort study conducted at 34 ophthalmological institutions throughout Japan. All eyes had an intraocular pressure ≤ 21 mmHg and had undergone trabeculectomy alone or phacotrabeculectomy. Two success criteria were used: Criterion A comprised 20% reduction of baseline IOP and Criterion B comprised 30% reduction of baseline IOP. The primary outcome was the success rate for each of these criteria.

RESULTS

The qualified success rates were 87.3% for Criterion A and 42.0% for Criterion B at 5 years. Mean IOP was significantly reduced, from 16.7 ± 2.7 to 11.6 ± 4.0 mmHg at 5 years after trabeculectomy (p < 0.0001); the number of anti-glaucoma medications significantly decreased from 2.7 ± 1.1 to 1.0 ± 1.2 (p < 0.0001) at 5 years after the surgery. Three or more trabeculectomies, and needling were related to increased risk of failure. Incidences of postoperative hyphema, infection, shallow anterior chamber and bleb leakage were 2.4%, 2.4%, 2.0% and 3.4%, respectively.

CONCLUSIONS

This study showed that trabeculectomy with mitomycin C is an effective procedure with few surgical complications for reducing IOP in patients, even if preoperative IOP was within the normal range.

Ocular hypotony: A comprehensive review

Ocular hypotony is an infrequent, yet potentially vision-threatening, entity. The list of differential causes is extensive, involving any condition that may compromise aqueous humor dynamics or the integrity of the globe and sometimes following medical treatments or procedures. Depending on the cause and the clinical impact, treatment options aim to correct the underlying pathology and to reestablish anatomical integrity, as well as visual function. We review the pathophysiology, clinical presentation, different causes, and associated therapeutic options of ocular hypotony.

ReGAE 12: preventing glaucoma blindness in the Caribbean through implementation of the Moorfields Safer Surgery System and skills transfer from the UK to Trinidad and Tobago

Objective

The objective of the study was to present evidence of successful skills transfer of the Moorfields Safer Surgery System (MSSS) from the UK to Trinidad and Tobago and the safety and efficacy of this technique.

Methods

Hospital-based retrospective, consecutive, non-comparative case series study of 33 eyes (24 African-Caribbean patients; 16 male patients) with primary open-angle glaucoma undergoing trabeculectomy + mitomycin C (MSSS) by a single surgeon with UK Glaucoma Fellowship training. The clinical outcome measures included intraocular pressure (IOP), bleb morphology, postsurgical interventions, postoperative complications, and best-corrected visual acuity (BCVA) at the final follow-up.

Results

All patients were self-identified as African-Caribbean. The median age was 56 years (range 34-79 years). The mean preoperative IOP on maximum tolerated medical treatment was 22.4 mmHg (SD=5.9 mmHg). With or without medication, IOP was ≤21 mmHg in 92.6% at 1 year and 87.5% at 5 years. At 1 year, IOP was ≤18 mmHg in 78%, ≤15 mmHg in 73% and ≤14 mmHg in 52%. Removal of scleral flap releasable suture(s) was performed in 84%, 5-fluorouracil injection(s) in 88% and bleb needling revision in 38%. The most common complication was early transient bleb leak (52%). No patient developed endophthalmitis, hypotony maculopathy, suprachoroidal hemorrhage, or malignant glaucoma. At the final follow-up, 91% had excellent or satisfactory bleb morphology, and 73% had equal or better BCVA.

Conclusion

Skills transfer between different geographical and economic regions contributes to the prevention of avoidable blindness through disease control - one of the core strategies of the World Health Organization's Vision 2020 initiative. In the Caribbean (Trinidad and Tobago), the MSSS was utilized by a surgeon with Glaucoma Fellowship training and achieved outcomes similar to best-published data. This success can be reproduced in other geographic locations.

Outcome of Primary Nonpenetrating Deep Sclerectomy in Patients with Steroid-Induced Glaucoma

Purpose

To evaluate the outcome of primary nonpenetrating deep sclerectomy (NPDS) in patients with steroid-induced glaucoma.

Methods

This was a retrospective interventional clinical study that included 60 eyes of 60 steroid-induced glaucoma patients that had undergone NPDS. Patients were followed up for 4 years. Data from the records was retrieved as regards corrected distance visual acuity (CDVA), intraocular pressure (IOP), visual field mean defect (dB), and number of antiglaucoma medications needed if any. Complete success of the surgical outcome was considered an IOP ≤ 21 mmHg with no antiglaucoma medications. Qualified success was considered an IOP ≤ 21 mmHg using antiglaucoma medications.

Results

The mean age was 21.2 ± 8.5 years (ranged from 12 to 35 years). At 48 months, mean IOP was 13.6 ± 2.8 mmHg (range 11-23 mmHg). This represented 60% reduction of mean IOP from preoperative levels. One case had YAG laser goniopuncture. Three cases required needling followed by ab interno revision. Using ANOVA test, there was a statistically significant difference between preoperative and postoperative mean IOP values (P = 0.032). Twelve, 16, and 20 patients required topical antiglaucoma medications at 24, 26, and 48 months postoperative, respectively.

Conclusion

Primary nonpenetrating deep sclerectomy is a safe and an effective method of treating eyes with steroid-induced glaucoma. No major complications were encountered. After 4 years of follow-up, complete success rate was 56.7% and qualified success rate was 70%.

Long-term results of deep sclerectomy in normal-tension glaucoma

PURPOSE

To study the long-term outcome of deep sclerectomy with and without mitomycin-C (MMC) in patients with normal-tension glaucoma (NTG).

METHODS

We prospectively analysed consecutive patients randomized to surgery performed either with (MMC group) or without (non-MMC) MMC. Surgery was considered totally successful if, after surgery, the preoperative intra-ocular pressure (IOP) level was reduced by 25% without medication, and a qualified success if medication was required to achieve the same limits.

RESULTS

A total of 37 patients were enrolled, 15 in the MMC and 22 in the non-MMC group. The median (range) follow-up was 7.9 (1.0-9.0) years, with a drop-out of three (8%) patients. The preoperative IOP was 15 (11-21) mmHg in the MMC and 15 (10-19) mmHg in the non-MMC group. At the last 6- to 9-year follow-up, IOP was significantly reduced to 9 (2-13) mmHg (p = 0.002) and 10 (5-13) mmHg (p < 0.001). The overall (groups combined) complete and qualified success rates were 50% and 71%, with no significant difference between groups (p = 0.48 and p = 0.25). Goniopuncture was performed in 87% and 100% of eyes in the MMC and non-MMC groups (p = 0.14). Needling with MMC injection was performed 0 (0-1) times in the MMC group and 0.5 (0-4) times in the non-MMC group (p = 0.056). We encountered no cases of hyphema, shallow anterior chamber, hypotony maculopathy, choroidal effusion, late bleb leakage, blebitis, endophthalmitis or malignant glaucoma.

CONCLUSION

In NTG, long-term significant IOP reduction can be achieved with deep sclerectomy with a low incidence of sight-threatening complications.

Posterior Surgical Revision of Failed Fornix-based Trabeculectomy

PURPOSE

To evaluate outcomes after revision of failed fornix-based trabeculectomy using a posterior conjunctival incision and mitomycin C.

METHODS

Cases were identified using Current Procedural Terminology codes. Information from clinical records was analyzed retrospectively. Complete success was defined as intraocular pressure (IOP) ≤16 mm Hg with no glaucoma medications and IOP reduction of >20% from preoperative levels. Qualified success was defined as IOP≤16 with or without medications and IOP reduction of >20%. Secondary outcomes included IOP, number of glaucoma medications used, visual acuity, and complications.

RESULTS

Sixty eyes of 56 patients underwent surgical revision of failed trabeculectomy. The complete success rate at 1 year was 43.7%, declining to 41.7% at 2 years and all time points up to 5 years; qualified success rates were 68.9% at 1 year and at all subsequent time points. Mean IOP declined from 21.2±7.7 (SD) mm Hg preoperatively to 10.9±4.3 mm Hg at 1 year, to 10.5±3.8 mm Hg at 2 years, and to 9.9±4.6 mm Hg at 3 years. The mean number of glaucoma medications used fell from 2.5±0.5 preoperatively to 1.0±0.4 at 1 year, 0.9±0.4 at 2 years, and 0.9±0.4 at 3 years. Complications included bleb leak in 3 eyes (5.0%), hypotony with choroidal detachment in 3 eyes (5.0%) and hyphema in 1 eye (1.7%). Eight eyes required additional glaucoma surgery.

CONCLUSIONS

Surgical bleb revision with mitomycin C using a posterior incision in cases of failed fornix-based trabeculectomy can provide effective control of IOP. This conjunctiva-sparing procedure should be considered as a viable alternative to a tube shunt or repeat trabeculectomy.

[Revision after filtration surgery]

BACKGROUND

In contrast to all other glaucoma surgeries, filtration surgery is associated with biomicroscopically visible wound healing, which enables the surgeon to perform revision surgeries if necessary.

OBJECTIVES

The aim of this review is to provide general considerations and to give a structured overview about bleb revisions after trabeculectomy.

MATERIALS AND METHODS

The different revision techniques are explained in detail and in the context of perioperative management.

RESULTS

Preoperative preparation and modifications of the surgical techniques reduce the incidence of postoperative revisions. The site of the fibrosis defines the revision technique (bleb needling, needle revision, bleb revision with reopening). The increased percolation rate of aqueous humor in postoperative hypotony contributes to fibrosis and may lead to maculopathy, choroidal effusion, and suprachoroidal hemorrhage.

DISCUSSION

Discontinuing administration of local medication and pretreatment with steroids without preservative for at least one week prior to surgery increase surgical success of trabeculectomy and reduce the incidence of postoperative revisions. Postoperative management after filtration surgery should be performed after consulting the surgeon. The primary endpoint of trabeculectomy is an intraocular pressure between 8 and 12 mm Hg without local antiglaucomatous medication. In postoperative hypotony revisions should be done earlier and based on the pathological findings.

In Vivo 3-Dimensional Strain Mapping of the Optic Nerve Head Following Intraocular Pressure Lowering by Trabeculectomy

PURPOSE

To map the 3-dimensional (3D) strain of the optic nerve head (ONH) in vivo after intraocular pressure (IOP) lowering by trabeculectomy (TE) and to establish associations between ONH strain and retinal sensitivity.

DESIGN

Observational case series.

PARTICIPANTS

Nine patients with primary open-angle glaucoma (POAG) and 3 normal controls.

METHODS

The ONHs of 9 subjects with POAG (pre-TE IOP: 25.3±13.9 mmHg; post-TE IOP: 11.8±8.6 mmHg) were imaged (1 eye per subject) using optical coherence tomography (OCT) (Heidelberg Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany) before (<21 days) and after (<50 days) TE. The imaging protocol was repeated for 3 controls in whom IOP was not altered. In each post-TE OCT volume, 4 tissues were manually segmented (prelamina, choroid, sclera, and lamina cribrosa [LC]). For each ONH, a 3D tracking algorithm was applied to both post- and pre-TE OCT volumes to extract IOP-induced 3D displacements at segmented nodes. Displacements were filtered, smoothed, and processed to extract 3D strain relief (the amount of tissue deformation relieved after TE). Strain relief was compared with measures of retinal sensitivity from visual field testing.

MAIN OUTCOME MEASURES

Three-dimensional ONH displacements and strain relief.

RESULTS

On average, strain relief (averaged or effective component) in the glaucoma ONHs (8.6%) due to TE was higher than that measured in the normal controls (1.07%). We found no associations between the magnitude of IOP decrease and the LC strain relief (P > 0.05), suggesting biomechanical variability across subjects. The LC displaced posteriorly, anteriorly, or not at all. Furthermore, we found linear associations between retinal sensitivity and LC effective strain relief (P < 0.001; high strain relief associated with low retinal sensitivity).

CONCLUSIONS

We demonstrate that ONH displacements and strains can be measured in vivo and that TE can relieve ONH strains. Our data suggest a wide variability in ONH biomechanics in the subjects examined in this study. We further demonstrate associations between LC effective strain relief and retinal sensitivity.