Effect of Trabeculectomy on OCT Measurements of the Optic Nerve Head Neuroretinal Rim Tissue

Progressive Changes in the Neuroretinal Rim and Retinal Nerve Fiber Layer in Glaucoma: Impact of Baseline Values and Floor Effects

PURPOSE

To determine whether more severe baseline damage impedes measurement of minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness (RNFLT) change in glaucoma patients because of a floor effect.

DESIGN

Prospective, longitudinal cohort study in a hospital-based setting.

PARTICIPANTS

The study included patients with open-angle glaucoma and healthy control subjects. Participants had at least 5 years of follow-up with OCT every 6 months.

METHODS

Baseline global and sectorial MRW and RNFLT values were classified as within normal limits, borderline, or outside normal limits based on reference normative values. Regression analysis was used to determine the magnitude and significance of MRW and RNFLT change. Additionally, the follow-up period for each participant was divided into 2 equal halves (first and second periods) to determine whether there was attenuation of MRW and RNFLT change with follow-up time.

MAIN OUTCOME MEASURES

Rates of global and sectoral MRW and RNFLT changes (slopes).

RESULTS

A total of 97 patients with glaucoma (median age, 70.3 years) and 42 healthy subjects (median age, 64.8 years) were followed for a median of 6.9 years and 7.0 years, respectively. The median mean deviation of the visual field in glaucoma patients was -4.30 decibels (dB) (interquartile range, -7.81 to -2.06 dB; range, -20.68 to 1.37 dB). Statistically significant changes in global and sectoral MRW and RNFLT were detected across all baseline classifications; however, there was a tendency for less change with increasing baseline damage. In glaucoma patients, RNFLT slopes, but not MRW slopes, were significantly more positive (less change) in the second period compared with the first. There were also no differences in MRW or RNFLT slopes in the first and second periods in healthy subjects.

CONCLUSIONS

Significant MRW and RNFLT changes were detected at all levels of baseline damage. However, an attenuation in the rate of RNFLT change compared with MRW indicates an earlier floor effect in RNFLT measurements globally and in equivalent sectors. Because the axonal component of these measurements should be equivalent, our results suggest important differences in tissue remodeling at the level of the optic nerve head and peripapillary retina.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Postoperative RNFL-Changes after Successful Trabeculectomy: 2-Year Outcomes

BACKGROUND

The most important tool in glaucoma therapy is to lower the intraocular pressure to slow down the apoptosis of retinal ganglion cells. Trabeculectomy (TE) is considered the gold standard in glaucoma surgery. The aim of this study was to analyse the postoperative changes in retinal nerve fibre layer (RNFL) using optical coherence tomography (OCT) after TE.

MATERIAL AND METHODS

We examined 40 patients naïve to prior glaucoma surgery retrospectively, who received a TE for medically uncontrolled primary open-angle glaucoma (POAG). Intraocular pressure (IOP), IOP-lowering medication, mean deviation of perimetry, visual acuity and peripapillary RNFL-thickness using OCT were evaluated during the first 24 month after TE.

RESULTS

In total 40 eyes from 40 patients were treated with TE. Mean IOP decreased from 25.0 ± 0,9 to 13.9 ± 0.6 (p < 0.01), and the mean number of IOP-lowering eye drops from 3.3 ± 0.2 to 0.5 ± 0.2 (p < 0.01). Visual acuity and mean deviation in perimetry remained stable while mean global RNFL-thickness decreased from 67.8 ± 2.9 to 63.7 ± 2.9 (p < 0.01) and 63.4 ± 2.9 µm (p < 0.01) 12 and 24 months after TE.

CONCLUSION

The TE is an effective method to reduce the IOD and the amount of IOP-lowering medication. Nevertheless, a significant further loss in RNFL thickness was observed in the first 12 months after TE. Thus, RNFL changes seem to stabilise only after a protracted period.

Clinical Factors Associated With Long-Term OCT Variability in Glaucoma

PURPOSE

To examine clinical factors associated with long-term optical coherence tomography (OCT)-measured retinal nerve fiber layer thickness (RNFLT) variability in glaucoma.

STUDY DESIGN

Retrospective cohort study.

METHODS

Glaucoma eyes from Diagnostic Innovations in Glaucoma Study (DIGS)/the African Descent and Glaucoma Evaluation Study (ADAGES) with ≥2-years and 4-visit follow-up were included. RNFLT variability was calculated per visit as the absolute error of optic nerve head RNFLT residuals across longitudinal follow-up. Clinical factors examined included general demographics, baseline ocular measurements, prior and intervening cataract extraction (CE) or glaucoma surgery, scan quality, baseline RNFLT and RNFLT thinning rate, follow-up duration, and visit/testing frequency. Three multivariable linear mixed models (full model, baseline model, and parsimonious model) were fit to evaluate the effects of clinical factors on RNFLT variability, with 10-fold cross-validation to estimate real-world model performance.

RESULTS

A total of 1140 eyes (634 patients) were included. The overall mean (95% CI) RNFLT variability was 1.51(1.45, 1.58) µm. Across different models, African American race (β [standard error {SE} = 0.18 [0.06]), intervening CE (β [SE] = 0.52 [0.07]), intervening glaucoma surgeries (β [SE] = 0.15 [0.03]), and more positive RNFLT thinning rate (β [SE] = 0.06 [0.02] per 1 µm/y more positive) showed consistent association with greater RNFLT variability, whereas more frequent visits/testing (β [SE] = -0.11[0.05] per 1 visit/y higher) was associated with smaller RNFLT variability (P < .05 for all).

CONCLUSIONS

Relevant clinical factors affecting long-term RNFLT variability in glaucoma were identified. These data enhance the evaluation of longitudinal structural change. Increasing the testing frequency, especially in eyes at risk for higher measurement variability, and resetting of baseline imaging after intervening procedures may help to more reliably detect OCT progression.

[Biomechanics of the lamina cribrosa: A determining factor in glaucomatous neuropathy. A review of the literature]

Glaucoma is a chronic optic neuropathy characterized by progressive sclero-laminar remodeling. The main factor at the origin of these deformations is the intraocular pressure (IOP), the effect of which varies according to the biomechanical properties of the individual lamina cribrosa (LC). In this environment, the LC represents a malleable zone of weakness within a rigid corneoscleral shell. It is a dynamic structure whose movements play a key role in the pathogenesis of glaucoma: displacing it posteriorly, in addition to contributing to the characteristic appearance of glaucomatous cupping, would increase constriction on the nerve fibers and the laminar capillaries. Often incorrectly considered permanent in adults, these deformations have a certain degree of reversibility, which is currently better characterized thanks to progress in imaging techniques. The occurrence of anterior displacement and laminar thickening following a reduction in IOP could thus constitute a good prognostic factor by reducing mechanical stress on this region. These changes would tend to reduce laminar pore tortuosity and shear forces, which are probably key mechanisms of axonal loss in glaucoma.

Two Year Functional and Structural Changes-A Comparison between Trabeculectomy and XEN Microstent Implantation Using Spectral Domain Optical Coherence Tomography

The aim of this study was to analyze retinal nerve fiber layer (RNFL) thickness after trabeculectomy (TE) versus XEN microstent implantation (XEN) in primary open-angle glaucoma (POAG) cases naïve to prior incisional glaucoma surgery. We examined 119 consecutive glaucoma patients retrospectively, who received a TE or XEN for medically uncontrolled POAG. Intraocular pressure (IOP), amount of IOP-lowering medication, mean deviation of standard automated perimetry and peripapillary RNFL thickness were evaluated during the first 24 months after surgery. Fifty eyes were treated with TE and 69 eyes with XEN. Mean IOP decreased from 25.1 ± 0.8 to 13.3 ± 0.6 mm Hg (p < 0.01) and mean number of IOP-lowering eye drops from 3.2 ± 0.2 to 0.4 ± 0.1 (p < 0.01) 24 months after TE. In 69 eyes undergoing XEN, mean IOP dropped from 24.8 ± 0.6 to 15.0 ± 0.4 mm Hg (p < 0.01) and medication from 3.0 ± 0.1 to 0.6 ± 0.1 (p < 0.01) during the 24 months follow-up. Mean deviation of standard automated perimetry remained stable in TE (8.5 ± 0.7 to 8.1 ± 0.8 dB; p = 0.54) and XEN group (11,0 ± 0.5 to 11.5 ± 0.5 dB; p = 0.12) after 24 months, while mean RNFL thickness further deteriorated in the TE (−2.28 ± 0.65 µm/year) and XEN (−0.68 ± 0.34 µm/year) group. Postoperative RNFL loss develops after TE and XEN despite effective and significant lowering of IOP and amount of IOP-lowering medication. RNFL loss was more pronounced in the first year after glaucoma surgery.

Intra-Operative Mounted Optical Coherence Tomography Findings Following Reversal of Optic Nerve Head Cupping in Childhood Glaucoma

PURPOSE

To examine the structural changes occurring in the optic nerve head (ONH) and macula in infants with childhood glaucoma and clinically observed ONH cupping reversal following intraocular pressure (IOP)-reducing glaucoma surgery, as captured by intra-operative spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Retrospective observational case series from an ongoing prospective cohort study.

METHODS

Included were 18 eyes of 14 patients with childhood glaucoma. All eyes had SD-OCT imaging pre- and post-glaucoma intervention and clinically identified ONH cupping reversal. Patients with poor quality images or persistent optic nerve swelling following IOP reduction were excluded. Outcome measurements included IOP, cup-to-disc ratio, axial length and SD-OCT measurements of the peripapillary retinal nerve fiber layer (pRNFL), transverse horizontal diameter of Bruch membrane opening (BMO-D), cup depth, and macula.

RESULTS

Mean age at surgery was 1.14±0.93 years and mean interval between pre- and post-operative imaging was 127 days (range 35-595). Following intervention, mean IOP reduction was 45%, accompanied by significant reductions in the cup-to-disc ratio (0.30±0.12, p<0.001), axial length (0.43±0.28mm, p<0.001) and cup depth (46%, p<0.001). Mean global pRNFL thickness pre- vs. post-treatment was 93.1±14.7µm vs. 93.1±17.1µm, respectively, p=1.0. There was no significant difference in pre- and post-treatment global or sectoral pRNFL, 3mm macular total and segmented retinal layer volumes, or the BMO-D.

CONCLUSIONS

Clinical ONH cupping reversal after IOP-lowering surgery was associated with axial length reduction and decrease in cup depth, but no significant change in the pRNFL or macular volume measures. ONH cupping reversal likely marks stabilization but any pre-intervention ONH damage persists.

Changes in optic nerve head and macula optical coherence tomography angiography parameters before and after trabeculectomy

Purpose

To evaluate the effects of lowering intraocular pressure (IOP) on foveal avascular zone (FAZ), peripapillary and macular vessel density (VD) by optical coherence tomography angiography (OCTA) in patients with open angle glaucoma after trabeculectomy.

Study design

Prospective study

Methods

Twenty eyes of 20 patients with primary open angle glaucoma (POAG) or exfoliation glaucoma (EG) who were followed up to six months and underwent trabeculectomy were included in our study. OCTA, AngioVue (Optovue Inc.) software was used to analyse the FAZ, peripapillary VD, macular superficial capillary plexus (SCP) and deep capillary plexus (DCP) VD. The parameters of the preoperative and postoperative controls were compared statistically.

Results

Twelve of the patients (60%) had POAG and eight (40%) had EG. Mean IOP measured was 22.4±2.4 mmHg preoperatively and 14.9±2.4 mmHg in the postoperative sixth month (p <0.001). There were no significant changes in OCTA optic disc and macular SCP VD values at the end of the sixth month. In macular DCP parameters; whole image VD (WI-VD), foveal VD (F-VD), parafoveal VD (PAF-VD) and perifoveal VD (PEF-VD) values increased statistically (p=0.003; p=0.026; p=0.006; p=0.004). There was a statistically significant decrease in FAZ area (FAZ-A) and FAZ perimeter (FAZ-P); and a significant increase was found in foveal density values (FD) (p=0.026; p=0.049; p=0.005).

Conclusions

We found that reducing IOP by trabeculectomy did not affect the microcirculation of the peripapillary region and macular SCP, while there was a significant increase in the DCP parameters of the macular region.

Optical coherence tomographic angiography study of perfusion recovery after surgical lowering of intraocular pressure

We investigated the time and location of retinal perfusion recovery after surgical intraocular pressure (IOP) lowering in glaucoma by using optical coherent tomography angiography (OCTA). Seventeen patients were analyzed. The 4.5 × 4.5-mm OCTA scans centered on the disc were performed preoperatively and postoperatively at 6 weeks, 3 months, and 6 months. The peripapillary retinal nerve fiber layer (NFL) thickness, NFL plexus capillary density (NFLP-CD) and visual field (VF) were measured overall and in 8 corresponding sectors. The low-perfusion area (LPA) was used to assess the cumulative area where local NFLP-CD was significantly below normal. At 6 months, the average IOP decreased 5.3 mmHg (P = 0.004), LPA decreased by 15% (P = 0.005), and NFLP-CD improved by 12% (P < 0.001). The NFL thickness and VF mean deviation didn’t change significantly at any time point. Among the sectors with significant preoperative NFLP-CD loss, the recovery at 6 months was greatest in sectors with minimal preoperative NFL thinning (P < 0.001). In conclusion, surgical IOP lowering may improve NFLP capillary perfusion after 6 months. The perfusion recovery tended to occur in areas with minimal NFL thinning at baseline. OCTA parameters may have potential usefulness as pharmacodynamic biomarkers for glaucoma therapy.

Factors Associated with Increased Neuroretinal Rim Thickness Measured Based on Bruch's Membrane Opening-Minimum Rim Width after Trabeculectomy

Purpose: To investigate the factors associated with an increase in the neuroretinal rim (NRR) thickness measured based on Bruch’s membrane opening-minimum rim width (BMO-MRW) after trabeculectomy in patients with primary open-angle glaucoma (POAG). Methods: We analyzed the BMO-MRW using spectral-domain optical coherence tomography (SD-OCT) of patients with POAG who underwent a trabeculectomy for uncontrolled intraocular pressure (IOP) despite maximal IOP reduction treatment. The BMO-MRW was measured before and after trabeculectomy in patients with POAG. Demographic and systemic factors, ocular factors, pre- and post-operative IOP, and visual field parameters were collected, together with SD-OCT measurements. A regression analysis was performed to investigate the factors that affected the change in the BMO-MRW after the trabeculectomy. Results: Forty-four eyes of 44 patients were included in the analysis. The IOP significantly decreased from a preoperative 27.0 mmHg to a postoperative 10.5 mmHg. The mean interval between the trabeculectomy and the date of post-operative SD-OCT measurement was 3.3 months. The global and sectoral BMO-MRW significantly increased after trabeculectomy, whereas the peripapillary retinal nerve fiber layer thickness did not show a difference between before and after the trabeculectomy. Younger age and a greater reduction in the IOP after the trabeculectomy were significantly associated with the increase in the BMO-MRW after trabeculectomy. Conclusions: The NRR thickness measured based on the BMO-MRW increased with decreasing IOP after trabeculectomy, and the increase in the BMO-MRW was associated with the young age of the patients and greater reduction in the IOP after trabeculectomy. Biomechanically, these suggest that the NRR comprises cells and substances that sensitively respond to changes in the IOP and age.

Functional Monitoring after Trabeculectomy or XEN Microstent Implantation Using Spectral Domain Optical Coherence Tomography and Visual Field Indices-A Retrospective Comparative Cohort Study

Simple Summary

Primary open-angle glaucoma leads to a loss of retinal ganglion cells and a reduction in the retinal nerve fiber layer thickness, consequently leading to the development and growth of visual field defects. In its final stages, this results in visual loss and irreversible blindness if not treated adequately. A reduction in the intraocular pressure by means of medication and/or surgery is the only known treatment option for slowing, or at best, arresting disease progression. This study demonstrates that trabeculectomy and XEN microstent implantation are nearly equally effective techniques for reducing intraocular pressure and stabilizing visual acuity and pre-developed visual field defects over a follow-up period of 24 months after surgery. However, further analysis using spectral domain optical coherence tomography revealed that disease progression occurs in terms of further retinal nerve fiber layer loss after both trabeculectomy and XEN microstent implantation.

Abstract

The aim of this study was to compare the efficacy of trabeculectomy (TE), single XEN microstent implantation (solo XEN) or combined XEN implantation and cataract surgery (combined XEN) in primary open-angle glaucoma cases, naïve to prior surgical treatment, using a monocentric retrospective comparative cohort study. Intraocular pressure (IOP) and the number of IOP-lowering drugs (Meds) were monitored during the first 24 months after surgery. Further disease progression was monitored using peripapillary retinal nerve fiber layer (RNFL) thickness examinations using spectral domain optical coherence tomography (OCT) as well as visual acuity (VA) and visual field (VF) tests. In the TE group (52 eyes), the mean IOP decreased from 24.9 ± 5.9 to 13.9 ± 4.2 mmHg (p < 0.001) and Meds decreased from 3.2 ± 1.2 to 0.5 ± 1.1 (p < 0.001). In the solo XEN (38 eyes) and the combined XEN groups, the mean IOP decreased from 24.1 ± 4.7 to 15.7 ± 3.0 mmHg (p < 0.001) and 25.4 ± 5.6 to 14.7 ± 3.2 mmHg (p < 0.001), while Meds decreased from 3.3 ± 0.8 to 0.8 ± 1.2 (p < 0.001) and 2.7 ± 1.2 to 0.4 ± 1.0 (p < 0.001), respectively. The VF and VA indices showed no sign of further deterioration, the RNFL thickness further decreased in all treatment groups after surgery. TE and XEN led to comparable reductions in IOP and Meds. Although the VA and VF indices remained unaltered, the RNFL thickness continuously decreased in all treatment groups during the 24-month follow-up.

Long-Term Follow-Up After Successful Trabeculectomy: A Case Report of Reversal of Cupping and Recovery of Visual Field Progression

Glaucoma is one of the leading causes of blindness worldwide, and reduction of intraocular pressure (IOP) is the only available evidence-based treatment that reduces visual field deterioration in glaucoma. We present a representative case of structural recovery and recovery of visual field progression after successful trabeculectomy (TLE) with long-term follow-up. A 35-year-old woman with glaucoma visited our hospital in 2008. The IOP in her right eye was 11 mmHg at the first visit, and subsequently increased to values in the high teens to 20 mmHg despite treatment with anti-glaucoma eye drops. During this period, the progression of this eye's visual field deterioration was fast (mean deviation [MD] slope = -0.63 dB/year) and the optic disc cupping was advanced. In the seven-year period after successful TLE in 2014, the IOP declined to between 8 and 12 mmHg without any anti-glaucoma medication. During the first two years after TLE, the MD values were poorer than those before TLE. However, by 2020, MD values improved gradually to a state better than that before the surgery (MD slope during this period was +0.75 dB/year). The appearance of the optic disc was monitored using fundus photography, which showed optic disc morphological changes during topical glaucoma medication before and after TLE. In particular, a remarkable reversal of optic disc cupping enlargement started at two weeks after TLE, and the optic disc shape in 2021 was similar to that in 2008. Minimally invasive glaucoma surgeries are often preferred; however, our findings suggest that successful TLE followed by long-term rigorous IOP control can result in structural recoveries. Additionally, despite the deterioration in visual field in the early years after TLE, in the long term, it may settle down to the same level before the surgery with recovery of visual field progression, which may be a part of functional recovery.