Optical Coherence Tomography Angiography and Visual Field Progression in Primary Angle Closure Glaucoma

The Role of Optical Coherence Tomography Angiography in Glaucoma

Glaucoma is the leading cause of irreversible vision loss and comprises a group of chronic optic neuropathies characterized by progressive retinal ganglion cell (RGC) loss. Various etiologies, including impaired blood supply to the optic nerve, have been implicated for glaucoma pathogenesis. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality for visualizing the ophthalmic microvasculature. Using blood flow as an intrinsic contrast agent, it distinguishes blood vessels from the surrounding tissue. Vessel density (VD) is mainly used as a metric for quantifying the ophthalmic microvasculature. The key anatomic regions for OCTA in glaucoma are the optic nerve head area including the peripapillary region, and the macular region. Specifically, VD of the superficial peripapillary and superficial macular microvasculature is reduced in glaucoma patients compared to unaffected subjects, and VD correlates with functional deficits measured by visual field (VF). This renders OCTA similar in diagnostic capabilities compared to structural retinal nerve fiber layer (RNFL) thickness measurements, especially in early glaucoma. Furthermore, in cases where RNFL thickness measurements are limited due to artifact or floor effect, OCTA technology can be used to evaluate and monitor glaucoma, such as in eyes with high myopia and eyes with advanced glaucoma. However, the clinical utility of OCTA in glaucoma management is limited due to the prevalence of imaging artifacts. Overall, OCTA can play a complementary role in structural OCT imaging and VF testing to aid in the diagnosis and monitoring of glaucoma.

Long-term prognosis of acute primary angle closure in an east asian cohort

PURPOSE

To provide an updated analysis of the long-term outcomes of patients with acute primary angle closure (APAC) and to investigate the risk factors for visual field (VF) loss progression.

STUDY DESIGN

Retrospective, clinical cohort study METHODS: One hundred and forty-six APAC patients with a minimum of 1-year follow-up were included. The presenting features and the treatment utilized were recorded. The visual and intraocular pressure (IOP) outcomes were analyzed. The main outcome measures were the proportion of blindness and IOP at the final visit. A subset of patients with sufficient VF results was divided into a stable and progressive group based on mean deviation (MD) loss rate. Univariate and multivariate logistic regression analyses were performed to identify predictors of progression.

RESULTS

Nine patients (6.2%) were blind, and 76.0% (111/146) had final decimal visual acuity greater than or equal to 0.5. All patients had normal final IOP, and 65.1% (95/146) were medication-free. 64.4% (94/146) underwent cataract surgery at a median 4 months after their APAC attack. The use of topical hypotensive medications (OR = 8.029, P = 0.012) was the only significant predictor of fast MD loss in the multivariate regression.

CONCLUSIONS

The long-term outcomes of APAC in recent years have been more promising. All patients maintained normal IOP several years following their APAC attack, and fewer than half required hypotensive agents. The incidence of blindness was low. These findings suggest that current practice patterns in the management of APAC are beneficial.

Morphological and vascular evidence of glaucomatous damage in myopic guinea pigs with scleral crosslinking

Guinea pigs are often used as models for myopia studies. However, the imaging structure and vasculature of the optic nerve head (ONH) in guinea pigs are tentative. This study investigated morphological parameters and vascular characteristics of the ONH in guinea pigs with form deprivation (FD) myopia before and after scleral crosslinking (CXL), using optical coherence tomography (OCT) and OCT angiography (OCTA). Refractive error, axial length (AL), intraocular pressure (IOP), and OCT-based structural parameters of the ONH were measured at baseline and 3 weeks after the FD + CXL procedure in guinea pigs. The 88 guinea pigs analysed in this study were aged 3 (n = 29), 4 (n = 51), and 5 (n = 8) weeks. The IOP, AL, average and vertical cup-to-disc ratio (C/D), circumpapillary retinal nerve fibre layer, disc area, and cup volume increased at 3 weeks compared to baseline values (all p < 0.001). The refractive error and rim area decreased at 3 weeks compared to baseline values (all p < 0.001). After adjustment for age, IOP was correlated positively with average C/D (p = 0.039) and negatively with rim area (p = 0.009). The severity of blood signal defects was positively associated with the average C/D at 3 weeks (p = 0.027). These findings may facilitate further research on myopia using guinea pigs.

Optical Coherence Tomography Angiography (OCTA) Differences in Vessel Perfusion Density and Flux Index of the Optic Nerve and Peri-Papillary Area in Healthy, Glaucoma Suspect and Glaucomatous Eyes

Purpose

To assess the ability of vascular perfusion parameters determined by optical coherence tomography angiography (OCTA) to detect and monitor glaucoma.

Methods

This prospective study included healthy, glaucoma suspect and glaucomatous eyes. All eyes underwent comprehensive glaucoma examination, including visual field tests and ocular imaging scans by OCTA. Parameters measured included retinal nerve fiber layer (RNFL) thickness, ganglion cell analysis (GCA), vascular perfusion density (VPD) and flux index (FI) of the optic nerve and peri-papillary area. Ocular parameters in healthy, glaucoma suspect, and glaucomatous eyes were compared by generalized estimating equations (GEE) with adjustments for age, with their relationships analyzed by Pearson's correlation coefficient. Rates of change per year were compared in glaucomatous eyes with and without glaucoma progression.

Results

This study enrolled 238 eyes, including 56 healthy, 79 glaucoma suspect, and 103 glaucomatous eyes. After adjustments for age, the average VPD (45.40 ± 0.19% vs 45.05 ± 0.22% vs 42.89 ± 0.32%, p < 0.001) and FI (0.4210 ± 0.0055 vs 0.4105 ± 0.0039 vs 0.3801 ± 0.0048, p < 0.001) in these three groups differed significantly. Average VPD in the glaucoma group was inversely associated with the severity of glaucoma, being 43.99 ± 0.32%, 42.63 ± 0.43% and 39.27 ± 0.48% in eyes with early, moderate and severe glaucoma, respectively (p < 0.001). Average VPD, as well as VPD in the superior and inferior quadrants correlated well with both OCT determined RNFL and visual field parameters. The decreases per year in both superior (-0.012 vs -0.001, p = 0.002) and inferior (-0.008 vs -0.003, p = 0.007) FI were significantly greater in glaucomatous eyes with than without glaucoma progression.

Conclusion

Both VPD and FI as measured by OCTA are promising ocular parameters that can distinguish between normal and glaucomatous eyes. VPD is sensitive in comparing eyes at different glaucoma stages, whereas FI can detect rates of glaucoma progression.

Trial Registration

Thai Clinical Trial Registry, TCTR20181031002.

Relatively anterior lens position in primary angle-closure glaucoma eyes with long axial length

Purpose

To evaluate the refractive status and ocular biometric parameters in primary angle-closure glaucoma (PACG) eyes with different axial lengths (ALs).

Methods

In total, 742 Chinese PACG subjects with complete ophthalmic examinations were enrolled. The refractive status was categorized as myopia (spherical equivalent [SE] ≤-0.5 D), emmetropia (-0.5 D < SE < +0.5 D), and hyperopia (SE ≥+0.5 D), whereas the AL was divided into short (AL <22.5 mm), regular (22.5 ≤ AL <23.5 mm), and long (AL ≥23.5 mm). The refractive status and ocular biometric parameters were compared among different AL groups.

Results

The mean AL of the PACG eyes was 22.53 ± 0.84 mm (range: 19.68-25.57 mm). The refractive status was significantly different among different AL groups (P < 0.001). Also, 92.6% of hyperopic PACG eyes showed AL <23.5 mm, and 19.0% of myopic PACG eyes showed AL ≥23.5 mm. The SE showed significant differences among different AL groups only in the hyperopic subjects (P = 0.012). The AL was significantly longer in myopic eyes (P < 0.001). The PACG eyes with longer AL exhibited lower keratometry, longer central anterior chamber depth and corneal diameter, and lens position and relative lens position closer to the anterior (P < 0.001).

Conclusion

Axial hyperopia was common in PACG eyes, and axial myopia was not uncommon. Relatively anterior lens position could explain the occurrence of PACG in the eyes with long AL.

A comprehensive update on the use of optical coherence tomography angiography in glaucoma

PURPOSE

The primary purpose of this review is to provide a comprehensive summary on the technical principles of OCTA and to enumerate vascular parameters being explicated for glaucoma diagnosis and progression with emphasis on recent studies. In addition, the authors also summarize the future clinical potentials of OCTA in glaucoma and enumerate the limitations of this imaging modality in the present-day scenario.

METHODS

The index study is a narrative review on OCTA in glaucoma. The authors searched the PubMed database using the key phrases ''optical coherence tomography angiography" AND "glaucoma,'' AND/OR "vascular parameters" AND/OR "ocular perfusion." Being a relatively recent development in ocular imaging, studies in which OCTA imaging had been used for glaucoma evaluation since 2012 were included until March 2022. The literature search included original studies and previous review articles, while case reports were excluded. Preliminary search was based on relevant articles with search keywords in the title and abstract. The second screening was performed by reading the full text of the literature.

RESULTS

Recent studies indicate reduction in microcirculation in glaucomatous eyes compared to the normal subjects. The area of interest for glaucoma evaluation using OCTA varies among the different studies. Based on the literature reviewed here, (1) OCTA parameters measured in the peripapillary; ONH and macular area have been shown to differentiate between glaucoma and normal eyes with a discriminatory power comparable to OCT parameters used routinely in clinics, (2) monitoring of peripapillary and macular vessel density may provide important information to the evaluation of glaucoma progression and prediction of rates of disease worsening, (3) studies suggest strong correlation between the OCTA parameters, the OCT parameters and visual function, measured by visual field testing, in glaucomatous eyes, (4) future prospects of OCTA in glaucoma evaluations using AI predicting structural and functional features and prognosis based on early vascular findings would open up scope for early detection of high-risk suspects and fast progressors in glaucoma.

CONCLUSION

OCTA can be useful in quantifying vascular parameters in the optic disc, peripapillary and the macular regions for glaucoma evaluation. OCTA shows potential to become a part of everyday glaucoma management.

Longitudinal Structure-Function Relationship between Macular Vessel Density and Thickness and Central Visual Field in Early Glaucoma

PURPOSE

To investigate the relationship of longitudinal changes in macular vessel density (VD) from OCT angiography and in ganglion cell complex (GCC) from OCT with central visual field (VF) in eyes with early glaucoma.

DESIGN

Observational cohort.

PARTICIPANTS

A total of 95 eyes, 37 preperimetric and 58 with early glaucoma (24-2 VF mean deviation [MD] ≥ -6 decibels), with an average follow-up of 3.8 years and 5.3 visits, were included.

METHODS

Whole-image VD (wiVD) and whole-image GCC (wiGCC) and parafoveal scans, as well as localized regions of interest (LROIs), hemiretinae of whole images, and superior, inferior, temporal, and nasal sectors of parafoveal maps, were matched with central VF locations. Age-adjusted rates of change of VD, GCC, mean sensitivity of VF locations, and 10-2 VF MD were calculated using linear mixed-effect models. Normalized rates of change were calculated for comparison of change rates in wiVD and wiGCC.

MAIN OUTCOME MEASURES

Structure-function (SF) correlations of VD and GCC with central VF measurement change rates and comparison of different correlations of SF relationships after bootstrapping the difference of the correlation coefficients.

RESULTS

Vessel density loss and GCC thinning demonstrated significant correlations with central VF damage, globally and with most LROIs. The SF correlation (r, 95% confidence interval [CI]) between wiVD and 10-2 VF MD change rates was 0.42 [0.24, 0.58], whereas it was 0.27 [0.08, 0.45] between wiGCC and 10-2 VF MD changes rates (all P < 0.05). In contrast to GCC thinning, VD loss in the parafoveal sectors demonstrated significant correlations with central VF damage in inferior and temporal sectors. Differences in the relationship of SF with central VF damage were not significant between VD loss and GCC thinning. The mean (95% CI) normalized change rates of wiVD (-7.40 [-7.71 to 7.09] %/year) was faster than that of wiGCC (-2.39 [-2.94 to 1.84] %/year) (P < 0.05).

CONCLUSIONS

Rates of VD loss and GCC thinning are associated with central VF loss over time. Assessment of both macular VD and GCC thickness should be considered for evaluation of glaucoma progression.

Association of Initial Optical Coherence Tomography Angiography Vessel Density Loss With Faster Visual Field Loss in Glaucoma

IMPORTANCE

Rapid vessel density loss during an initial follow-up period may be associated with the rates of visual field loss over time.

OBJECTIVES

To evaluate the association between the rate of vessel density loss during initial follow-up and the rate of visual field loss during an extended follow-up period in patients suspected of having glaucoma and patients with primary open-angle glaucoma.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study assessed 124 eyes (86 with primary open-angle glaucoma and 38 suspected of having glaucoma) of 82 patients who were followed up at a tertiary glaucoma center for a mean of 4.0 years (95% CI, 3.9-4.1 years) from January 1, 2015, to February 29, 2020. Data analysis for the current study was undertaken in March 2021.

MAIN OUTCOMES AND MEASURES

The rate of vessel density loss was derived from macular whole-image vessel density values from 3 optical coherence tomography angiography scans early during the study. The rate of visual field loss was calculated from visual field mean deviation during the entire follow-up period after the first optical coherence tomography angiography visit. Linear mixed-effects models were used to estimate rates of change.

RESULTS

A total of 124 eyes from 82 patients (mean [SD] age, 69.2 [10.9] years; 41 female [50.0%] and 41 male [50.0%]; and 20 African American [24.4%], 10 Asian [12.2%], 50 White [61.0%], and 2 other race or ethnicity [2.4%]) were assessed. The annual rate of vessel density change was -0.80% (95% CI, -0.88% to -0.72%) during a mean initial follow-up of 2.1 years (95% CI, 1.9-2.3 years). Eyes with annual rates of vessel density loss of -0.75% or greater (n = 62) were categorized as fast progressors, and eyes with annual rates of less than -0.75% (n = 62) were categorized as slow progressors. The annual rate of visual field loss was -0.15 dB (95% CI, -0.29 to -0.01 dB) for the slow optical coherence tomography angiography progressors and -0.43 dB (95% CI, -0.58 to -0.29 dB) for the fast optical coherence tomography angiography progressors (difference, -0.28 dB; 95% CI, -0.48 to -0.08 dB; P = .006). The fast optical coherence tomography angiography progressor group was associated with the faster overall rate of visual field loss in a multivariable model after adjusting to include concurrent visual field mean deviation rate (-0.17 dB; 95% CI, -0.33 to -0.01 dB; P = .04).

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that faster vessel density loss during an initial follow-up period was associated with faster concurrent and subsequent rates of visual field loss during an extended period.

Beneficial effect of mindfulness based stress reduction on optic disc perfusion in primary open angle glaucoma: A randomized controlled trial

Background and aim

Glaucoma is one of the leading causes of visual impairment worldwide. Next to intraocular pressure (IOP), vascular factors play a major role in glaucoma. Mindfulness-based stress reduction (MBSR) has been shown to reduce the IOP, normalize the stress biomarkers, modulate gene expression, and also improve the quality of life. This study was aimed to assess the effect of MBSR in optic disc perfusion of patients with primary open angle glaucoma (POAG).

Experimental procedure

POAG patients with controlled IOP (<21 mmHg) were randomised in to intervention group (n = 30) and control group (n = 30). Both the groups continued their routine glaucoma medications while the intervention group practiced 45 min of MBSR every day in addition. IOP and optic disc perfusion using OCT-Angiography were recorded at baseline and at 6 weeks for both the groups.

Results

The mean age of the participants were 53.23 ± 8.4yr in intervention and 50.23 ± 7.3yr in the control group (p = 0.06). All the baseline parameters were comparable in both groups. After MBSR, in the intervention group there was a significant reduction of IOP (p=0.001), increase in circum-papillary vessel density in superior quadrant (15.8%-17.4%, p=0.02) and nasal quadrant (14.2%-16.5%, p=0.01), increase in circum papillary vascular perfusion, in superior quadrant (38.9%-41.1%, p<0.001), in temporal quadrant (42.2%-44.5%, p<0.001), in inferior quadrant (40.1%-43.8%, p<0.001), and in nasal quadrant (40.6%-42.8%, p<0.001). There was also a significant increase in Flux Index after 6weeks (0.38-0.40, p<0.001).

Conclusion

MBSR can reduce barotrauma and improve optic disc perfusion in POAG patients and serve as a useful adjunct to the standard medical therapy.

Association Between Diabetes, Diabetic Retinopathy, and Glaucoma

PURPOSE OF REVIEW

The strength of the relationship between diabetes, diabetic retinopathy (DR), and glaucoma remains controversial. We review evidence supporting and refuting this association and explore mechanistic pathological and treatment relationships linking these diseases.

RECENT FINDINGS

While studies have shown diabetes/DR may increase the risk for glaucoma, this remains inconsistently demonstrated. Diabetes/DR may contribute toward glaucomatous optic neuropathy indirectly (either by increasing intraocular pressure or vasculopathy) or through direct damage to the optic nerve. However, certain elements of diabetes may slow glaucoma progression, and diabetic treatment may concurrently be beneficial in glaucoma management. Diabetes plays a significant role in poor outcomes after glaucoma surgery. While the relationship between diabetes/DR and glaucoma remains controversial, multiple mechanistic links connecting pathophysiology and management of diabetes, DR, and glaucoma have been made. However, a deeper understanding of the causes of disease association is needed.