Referenced scans improve the repeatability of optical coherence tomography angiography measurements in normal and glaucoma eyes

Peripapillary vessel density in healthy people, primary open-angle glaucoma, and normal-tension glaucoma

OBJECTIVE

To compare peripapillary vessel density using optical coherence tomography angiography (OCT-A) in eyes of healthy people, primary open-angle glaucoma (POAG), and normal-tension glaucoma (NTG).

METHODS

Thirty patients with POAG, 27 patients with NTG, and 29 healthy individuals in the control group were assessed. Capillary vessels in peripapillary retinal nerve fiber layer (RNFL) represented by whole image RPC (radial peripapillary capillary) density in an AngioDisc scan 4.5 × 4.5 mm centered on the optic disc, and ONH morphological variables (disc area, rim area, cup to disc area ratio (CDR)), and average peripapillary RNFL thickness were measured.

RESULTS

Differences in mean RPC, RNFL, disc area, rim area, and CDR between the groups were statistically significant (P < 0.05). The difference in RNFL thickness and rim area was not significant between NTG and healthy groups, while RPC and CDR showed a statistically significant difference between all pairs. The vessel density in the POAG group was 8.25% and 11.7% lower compared to the NTG and healthy groups, respectively; while the mean difference was less (2.97%) for the NTG and healthy group. In the POAG group, 67.2% of the variation in RPC can be explained by a model containing CDR and RNFL thickness, and in normal eyes 38.8% of the changes using a model containing RNFL.

CONCLUSION

The peripapillary vessel density is reduced in both types of glaucoma. The vessel density in NTG was significantly lower than in the healthy eyes, despite the lack of significant difference in RNFL thickness and neuroretinal rim area between them.

Nicotinamide Prevents Retinal Vascular Dropout in a Rat Model of Ocular Hypertension and Supports Ocular Blood Supply in Glaucoma Patients

Purpose

To investigate whether nicotinamide (NAM) modulates retinal vasculature in glaucoma.

Methods

This was a prospective controlled clinical trial investigating animal and human histopathology. Participants included normotensive and ocular hypertensive rats, postmortem human ocular tissue, glaucoma patients (n = 90), and healthy controls (n = 30). The study utilized histopathology, computer-assisted retinal vasculature analysis, optical coherence tomography angiography (OCTA), and NAM treatment. The main outcome measures included retinal vascular parameters in rats as assessed by AngioTool; retinal vasculature integrity in rats and humans as assessed by histopathology, antibody-staining, and ImageJ-based measurements; and retinal perfusion density (PD) and flux index in humans as assessed by OCTA.

Results

A number of vessel parameters were altered in ocular hypertension/glaucoma compared to healthy controls. NAM treatment improved the retinal vasculature in ocular hypertensive rats, with an increase in mean vessel area, percentage area covered by vessels, total vessel length, total junctions, and junction density as assessed by AngioTool (all P < 0.05); vessel wall integrity as assessed by VE-cadherin antibody staining was also improved (P < 0.01). In humans, as assessed by OCTA, increases in PD in the optic nerve head and macula complete image (0.7%, P = 0.04 and 1.0%, P = 0.002, respectively) in healthy controls, and an increase in the temporal quadrant of the macula (0.7%, P = 0.02) in glaucoma patients was seen after NAM treatment.

Conclusions

NAM can prevent retinal vascular damage in an animal model of glaucoma. After NAM treatment, glaucoma patients and healthy controls demonstrated a small increase in retinal vessel parameters as assessed by OCTA.

Precision (repeatability and reproducibility) of papillary and peripapillary vascular density measurements using optical coherence tomography angiography in children

Importance

Optical coherence tomography angiography (OCTA) has been widely applied into children, however, few studies have assessed the repeatability and reproducibility of papillary and peripapillary VD in healthy children.

Objective

To assess the precision of papillary and peripapillary vascular density (VD) measurements using optical coherence tomography angiography (OCTA) and analyze the effects of the signal strength index (SSI) and axial length (AL) on precision estimates.

Design setting and participants

This was a prospective observational study. Seventy-eight children aged 6-16 years underwent 4.5 × 4.5 mm OCTA (RTVue XR Avanti) disc scans: two scans by one examiner (repeatability) and two additional scans by another examiner (reproducibility). Within-subject standard deviation (Sw), test-retest reproducibility (TRT), within-subject coefficient of variation (CoV), intraclass correlation coefficient (ICC), and Bland-Altman analysis were performed.

Main outcomes and measures

In repeatability measurement, the fluctuation ranges (minimum to maximum) of VD between intraexaminer A/B in Sw, TRT, CoV, and ICC were (1.05-2.17)% / (1.16-2.32)%, (2.9-6)% / (3.21-6.44)%, (1.9-4.47)% / (2.08-5)%, and (0.588-0.783)% / (0.633-0.803)%, respectively. In reproducibility measurement, the fluctuation ranges of VD in Sw, TRT, CoV, and ICC were 1.11-2.13%, 3.07-5.91%, 1.99-4.41%, and 0.644-0.777%, respectively. VD was negatively correlated with SSI in most sectors of the peripapillary (e.g., inferior nasal, temporal inferior, temporal superior, superior temporal, and superior nasal). AL was positively correlated with inferior temporal VD and negatively correlated with superior nasal VD.

Conclusion and relevance

Optical coherence tomography angiography showed moderate-to-good repeatability and reproducibility for papillary and peripapillary perfusion measurements in healthy children. The SSI value affects most of the peripapillary VD, while AL affects only the temporal inferior and nasal superior peripapillary VD.

Optical Microangiography and Progressive Ganglion Cell-Inner Plexiform Layer Loss in Primary Open-Angle Glaucoma

PURPOSE

To evaluate the association between optical microangiography (OMAG) measurements and progressive ganglion cell-inner plexiform layer (GCIPL) loss in patients with primary open-angle glaucoma (POAG).

DESIGN

Prospective case series.

METHODS

Sixty-three eyes of 38 patients with POAG were studied for ≥2 years and with ≥ 3 optical coherence tomography examinations. Only those hemifields with mild to moderate functional damage at baseline (106 hemifields) were included in the analysis. OMAG imaging was performed at the baseline visit. The effects of clinical parameters (age, gender, central corneal thickness, presence of disc hemorrhage, and mean and fluctuation of intraocular pressure), baseline mean deviation, retinal nerve fiber layer, and GCIPL thickness and baseline OMAG measurements (peripapillary and macular perfusion density [PD] and vessel density [VD]) on the rate of change of GCIPL thickness were evaluated using linear mixed models.

RESULTS

Average (± standard deviation) mean deviation, quadrant retinal nerve fiber layer, and sector GCIPL thickness of the analyzed hemifields respectively at baseline were -5.2 ± 2.8 dB, 94.5 ± 20.0 µm, and 72.4 ± 8.7 µm, respectively. Peripapillary PD and VD in the quadrant were 43.1% ± 7.0% and 17.0 ± 2.6 mm/mm², respectively. Macular PD and VD in the quadrant were 37.2% ± 6.9% and 15.1 ± 2.6 mm/mm², respectively. Rate of sector GCIPL change was -0.97 ± 0.15 µm per year. Multivariate mixed models showed that lower peripapillary PD (coefficient 0.04, P = .01) and VD (coefficient 0.09, P = .05) were significantly associated with a faster rate of GCIPL loss.

CONCLUSIONS

Lower baseline peripapillary OMAG measurements were significantly associated with a faster rate of GCIPL loss in patients with mild to moderate POAG.

Optical Microangiography and Progressive Retinal Nerve Fiber Layer Loss in Primary Open Angle Glaucoma

PURPOSE

To evaluate the association between optical microangiography (OMAG) measurements and progressive retinal nerve fiber layer (RNFL) loss in primary open angle glaucoma (POAG).

DESIGN

Prospective case series.

METHODS

Sixty-four eyes of 40 patients with POAG (108 quadrants) with mild to moderate functional damage were longitudinally studied for at least 2 years and with a minimum of 3 optical coherence tomography examinations. OMAG imaging was performed at the baseline visit. Effect of clinical parameters (age, sex, presence of systemic diseases, central corneal thickness, presence of disc hemorrhage, and mean and fluctuation of intraocular pressure during follow-up), baseline hemifield mean deviation, baseline quadrant optical coherence tomography RNFL and ganglion cell inner plexiform layer thickness), and OMAG (peripapillary and macular perfusion density [PD] and vessel density [VD]) on the rate of RNFL change was evaluated using linear mixed models.

RESULTS

Average (±SD) mean deviation, RNFL, and ganglion cell inner plexiform layer thickness of the analyzed quadrants at baseline were -5.5 ± 2.9 dB, 96.5 ± 17.9 µm, and 73.8 ± 8.6 µm, respectively. Peripapillary PD and VD in the quadrant were 44.6% ± 5.9% and 17.5 ± 2.2 mm/mm², respectively. Rate of quadrant RNFL change was -1.8 ± 0.6 µm/y. Multivariate mixed models showed that lower peripapillary PD (coefficient = 0.08, P = .01) and lower VD (coefficient = 0.21, P = .02) were significantly associated with a faster rate of RNFL loss.

CONCLUSIONS

Lower baseline peripapillary PD and VD measured using OMAG were significantly associated with a faster rate of RNFL loss in POAG. OMAG imaging provides useful information about the risk of glaucoma progression and the rate of disease worsening.

Fixation stability and deviation in optical coherence tomography angiography using soft contact lens correction in myopes

To compare fixation deviation and stability with soft contact lens correction and device built-in auto-focus system during optical coherence tomography angiography (OCTA). This observational study measured OCTA metrics first with contact lens correction, followed by removal of contact lenses, using the device auto-focus system at a University Optometry Clinic, Hong Kong. All participants were habitual soft contact lens wearers with either low or high myopia. OCTA measurements were obtained using a spectral domain OCTA. Fixation deviation was distance (in pixels) of the fovea to the center of the OCTA measurement grid. Fixation stability was test–retest repeatability (TRR) and coefficient of variation (CV) of fixation deviation from three consecutive OCTA measurements. OCTA metrics included vessel length density (VD), perfusion density (PD), and foveal avascular zone (FAZ) area. Averaged OCTA metrics were calculated from three measurements and compared between the two correction methods. The mean ± SD spherical equivalent of 74 eyes from 74 myopes measured was − 1.94D ± 0.75D in low myopes (n = 37) and − 7.97D ± 1.31D in high myopes (n = 37). When corrected with contact lenses, visual acuities of high myopes (median [IQR], − 0.06 [0.08] logMAR) and low myopes (− 0.02 ± 0.08 logMAR) were similar (P = 0.060), and with similar fixation deviation (5.0 ± 2.2 pixels vs 5.3 [3.6] pixels; P = 0.689). High myopes had poorer fixation stability than low myopes (TRR: 10.2 pixels vs 7.5 pixels; CV: 65% vs 54%, respectively). The worst fixation stability occurred when high myopes were corrected using the auto-focus system (TRR: 12.5 pixels, CV: 72%). The difference in VD and PD was within 1 mm⁻¹ and 1%, respectively. The FAZ area was similar. Difference in OCTA metrics was small in each refractive group (< 1 mm⁻¹ in VD, and < 2% in PD). High myopes had more stable fixation when corrected when wearing contact lenses. Subjects with good contact lens corrected visual acuity should wear their contact lenses during OCTA measurements.