Determinants of optical coherence tomography-derived minimum neuroretinal rim width in a normal Chinese population

Optic neuropathy in high myopia: Glaucoma or high myopia or both?

Due to the increasing prevalence of high myopia around the world, structural and functional damages to the optic nerve in high myopia has recently attracted much attention. Evidence has shown that high myopia is related to the development of glaucomatous or glaucoma-like optic neuropathy, and that both have many common features. These similarities often pose a diagnostic challenge that will affect the future management of glaucoma suspects in high myopia. In this review, we summarize similarities and differences in optic neuropathy arising from non-pathologic high myopia and glaucoma by considering their respective structural and functional characteristics on fundus photography, optical coherence tomography scanning, and visual field tests. These features may also help to distinguish the underlying mechanisms of the optic neuropathies and to determine management strategies for patients with high myopia and glaucoma.

Optical Coherence Tomography-Derived Measurements of the Optic Nerve Head Structure of Aboriginal and Torres Strait Islander Children

PRCIS

This study demonstrated significant differences in optic nerve head characteristics in Aboriginal and Torres Strait Islander children compared with non-Indigenous children, which has implications for glaucoma risk and diagnosis in Aboriginal and Torres Strait Islander populations.

PURPOSE

The purpose of this study was to examine the optic nerve head (ONH) characteristics of visually normal Aboriginal and Torres Strait Islander children and non-Indigenous Australian children.

MATERIALS AND METHODS

Spectral domain optical coherence tomography imaging was performed on the right eye of 95 Aboriginal and Torres Strait Islander children and 149 non-Indigenous Australian children (5-18 years). Horizontal and vertical line scans, centered on the ONH, were analyzed to determine the dimensions of the ONH (Bruch membrane opening diameter), optic cup diameter, Bruch membrane opening minimum rim width, and the peripapillary retinal nerve fiber layer thickness.

RESULTS

The vertical but not horizontal Bruch membrane opening diameter of Aboriginal and Torres Strait Islander children was significantly larger than non-Indigenous children (mean difference: 0.09 mm, P = 0.001). The horizontal (mean difference: 0.12 mm, P = 0.003) and vertical cup diameter (mean difference: 0.16 mm, P < 0.001) were also significantly larger in Aboriginal and Torres Strait Islander children, as were the horizontal and vertical cup-to-disc ratios (both P < 0.01). Aboriginal and Torres Strait Islander children also had a significantly thinner Bruch membrane opening minimum rim width in the superior, nasal, and temporal meridians (all P < 0.001). Peripapillary retinal nerve fiber layer thickness did not differ between groups.

CONCLUSIONS

Differences exist in the ONH structure between Aboriginal and Torres Strait Islander children and non-Indigenous children, which may have implications for the detection and monitoring of ocular disease in this population and highlights the need to extend this research to the adult population.

Increase in Bruch's membrane opening minimum rim width with age in healthy children: the Hong Kong Children Eye Study

BACKGROUND/AIMS

To identify normative values and determinants for Bruch's membrane opening (BMO) and the minimum rim width of BMO (BMO-MRW) among healthy children.

METHODS

A population-based cross-sectional study from the Hong Kong Children Eye Study, recruiting 1, 226 children aged 6-8 years. Spherical refractive error, axial length (AL), body mass index and intraocular pressure (IOP) were measured. The optic nerve head and the peripapillary retinal nerve fibre layer (p-RNFL) were imaged through spectral domain-optical coherence tomography, using 24 equally spaced radial B-scans. Global and sectoral BMO-MRW values, BMO area and fovea-to-BMO (FoBMO) angle were calculated. Multiple regression analysis was performed to define the determinants of BMO area and BMO-MRW in relation to demographic and ocular parameters.

RESULTS

The mean values for global BMO-MRW, BMO area and FoBMO angle among children were 345.76±54.08 µm, 2.34±0.49 mm2 and -5.45±4.36°, respectively. Global and sectoral values for BMO-MRW correlated with p-RNFL thickness (r=0.11-0.35, p<0.001). After adjusting for demographic and ocular parameters, global BMO-MRW increased with age (β=6.4, p<0.001) and greater global p-RNFL thickness (β=1.41, p<0.001), but decreased with larger BMO area (β=-47.46, p<0.001) and higher IOP (β=-1.73, p<0.001). Global BMO-MRW did not associate with AL, whereas both BMO area and FoBMO angle associated with AL (β=0.04, p=0.02 and β=0.31, p=0.03, respectively), but not with age.

CONCLUSION

We observed that BMO-MRW increases with age among children. Our results provide normative values and the determinants of BMO parameters among Chinese children.

Intravitreal Neuroglobin Mitigates Primate Experimental Glaucomatous Structural Damage in Association with Reduced Optic Nerve Microglial and Complement 3-Astrocyte Activation

Current management of glaucomatous optic neuropathy is limited to intraocular pressure control. Neuroglobin (Ngb) is an endogenous neuroprotectant expressed in neurons and astrocytes. We recently showed that exogenous intravitreal Ngb reduced inflammatory cytokines and microglial activation in a rodent model of hypoxia. We thus hypothesised that IVT-Ngb may also be neuroprotective in experimental glaucoma (EG) by mitigating optic nerve (ON) astrogliosis and microgliosis as well as structural damage. In this study using a microbead-induced model of EG in six Cynomolgus primates, optical coherence imaging showed that Ngb-treated EG eyes had significantly less thinning of the peripapillary minimum rim width, retinal nerve fibre layer thickness, and ON head cupping than untreated EG eyes. Immunohistochemistry confirmed that ON astrocytes overexpressed Ngb following Ngb treatment. A reduction in complement 3 and cleaved-caspase 3 activated microglia and astrocytes was also noted. Our findings in higher-order primates recapitulate the effects of neuroprotection by Ngb treatment in rodent EG studies and suggest that Ngb may be a potential candidate for glaucoma neuroprotection in humans.

Clinical Utility of Bruch Membrane Opening-Minimum Rim Width for Detecting Early Glaucoma in Myopic Eyes

PRCIS

Bruch membrane opening-minimum rim width (BMO-MRW) is overall a useful parameter for diagnosing early glaucoma in myopic eyes.

PURPOSE

The aim of this study was to determine the diagnostic value of BMO-MRW compared with peripapillary retinal nerve fiber layer (pRNFL) thickness for detecting early glaucoma in patients with moderate to severe myopia.

METHODS

One eye was randomly selected from each of the 253 subjects (127 normal controls, 82 with glaucoma suspect, and 44 with early glaucoma). All patients underwent visual acuity testing, refractive error assessment, slit-lamp inspection, intraocular pressure measurement, fundus photography, perimetry. BMO-MRW and pRNFL thickness data were obtained using spectral-domain optical coherence tomography. Area under the receiver operating characteristic curves (AUC) for global and sectoral thickness parameters were calculated.

RESULTS

Global analyses for the discrimination of early glaucoma in all myopic subjects showed comparable AUCs between BMO-MRW and pRNFL thickness [AUC 0.952 (95% confidence interval, 0.918-0.975) and 0.934 (95% confidence interval, 0.896-0.961), respectively, P=0.345]. However, in sectoral analysis, BMO-MRW showed significantly better diagnostic performance than pRNFL thickness except for the superotemporal sector. The AUC for discriminating early glaucoma from glaucoma suspect, BMO-MRW showed statistically better diagnostic performance in the inferotemporal, inferonasal, superonasal, and nasal sectors. When dividing the subject based on a threshold Bruch membrane opening (BMO) area of 2.5 mm2, the diagnostic power of BMO-MRW was generally lower except for the inferonasal sector in the subgroup with a large BMO area.

CONCLUSIONS

BMO-MRW was overall a useful parameter for diagnosing early glaucoma in myopic eyes. However, its diagnostic performance was decreased in myopic eyes with large BMO and there were no significant differences from pRNFL thickness.

Reduced minimum rim width of optic nerve head: a potential early marker of retinal neurodegeneration in children and adolescents with type 1 diabetes

AIMS

To determine whether early retinal neurodegenerative changes in pediatric patients with type 1 diabetes (T1D) can be detected by spectral domain-optical coherence tomography (SD-OCT) and whether such changes are associated with risk factors for T1D complications.

METHODS

A total of 147 T1D children/adolescents and 51 healthy controls underwent SD-OCT. Spherical refractive error (SRE), macular total retinal thickness (TRT), ganglion cell layer (GCL), retinal nerve fiber layer (RNFL), minimum rim width (MRW), and Bruch's membrane opening area (BMOA) were measured. Clinical and biochemical parameters were recorded at the time of SD-OCT and starting at T1D onset. Multiple regression models were calculated using SD-OCT parameters as dependent and risk factors as independent variables.

RESULTS

MRW was significantly thinner in the T1D patients (global MRW:361.58vs386.33 µm; p = 0.009), while RNFL and macular parameters were similar for both groups. MRW was inversely correlated with mean HbA1c (r ≥ -0.180, p < 0.05). Multiple regression showed that part of the variability in MRW was explained by HbA1c and BMOA (R² = 0.21; p < 0.001), independent of other cardiometabolic risk factors.

CONCLUSIONS

MRW reduction could be a potential early marker of retinal neurodegeneration detectable in pediatric patients with T1D. The association between MRW and mean HbA1c suggests that glucometabolic control may affect early retinal neurodegeneration starting in childhood.

Longitudinal assessment of optic nerve head changes using optical coherence tomography in a primate microbead model of ocular hypertension

In humans, the longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis. Previous studies assessed glaucomatous ONH cupping by measuring the anterior lamina cribrosa depth (LCD) and minimal rim width (MRW) using optical coherence tomography (OCT). In this study, we induced OHT by repeated intracameral microbead injections in 16 cynomolgus primates (10 unilateral; 6 bilateral) and assessed the structural changes of the ONH longitudinally to observe early changes. Elevated intraocular pressure (IOP) in OHT eyes was maintained for 7 months and serial OCT measurements were performed during this period. The mean IOP was significantly elevated in OHT eyes when compared to baseline and compared to the control eyes. Thinner MRW and deeper LCD values from baseline were observed in OHT eyes with the greatest changes seen between month 1 and month 2 of OHT. Both the mean and maximum IOP values were significant predictors of MRW and LCD changes, although the maximum IOP was a slightly better predictor. We believe that this model could be useful to study IOP-induced early ONH structural damage which is important for understanding glaucoma pathogenesis.

Effect of Changing Heart Rate on the Ocular Pulse and Dynamic Biomechanical Behavior of the Optic Nerve Head

Purpose

To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model.

Methods

In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates.

Results

With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate.

Conclusions

In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology.

Analysis of Neuroretinal Rim by Age, Race, and Sex Using High-Density 3-Dimensional Spectral-Domain Optical Coherence Tomography

Précis:

Neuroretinal rim minimum distance band (MDB) thickness is significantly lower in older subjects and African Americans compared with whites. It is similar in both sexes.

Purpose:

To evaluate the relationship between age, race, and sex with the neuroretinal rim using high-density spectral-domain optical coherence tomography optic nerve volume scans of normal eyes.

Methods:

A total of 256 normal subjects underwent Spectralis spectral-domain optical coherence tomography optic nerve head volume scans. One eye was randomly selected and analyzed for each subject. Using custom-designed software, the neuroretinal rim MDB thickness was calculated from volume scans, and global and quadrant neuroretinal rim thickness values were determined. The MDB is a 3-dimensional neuroretinal rim band comprised of the shortest distance between the internal limiting membrane and the termination of the retinal pigment epithelium/Bruch’s membrane complex. Multiple linear regression analysis was performed to determine the associations of age, race, and sex with neuroretinal rim MDB measurements.

Results:

The population was 57% female and 69% white with a mean age of 58.4±15.3 years. The mean MDB thickness in the normal population was 278.4±47.5 µm. For this normal population, MDB thickness decreased by 0.84 µm annually (P<0.001). African Americans had thinner MDBs compared with whites (P=0.003). Males and females had similar MDB thickness values (P=0.349).

Conclusion:

Neuroretinal rim MDB thickness measurements decreased significantly with age. African Americans had thinner MDB neuroretinal rims than whites.

The optic nerve head, lamina cribrosa, and nerve fiber layer in non-myopic and myopic children

The purpose of this study was to evaluate the optic nerve head, lamina cribrosa, retina, and choroid in school age children using spectral domain optical coherence tomography (SD-OCT) and to assess these structural parameters in relation to age, axial length, and refractive error. Healthy children, ages 11.15 ± 2.62 years (range 6-15 years, n = 53), underwent cycloplegic autorefraction, biometry, and SD-OCT imaging in both eyes. Images were analyzed using custom written programs in MATLAB, after adjustment for lateral magnification. Peripapillary retinal nerve fiber layer (RNFL) thickness, retinal and choroidal thicknesses, Bruch's membrane opening (BMO) area, minimum rim width (MRW), and anterior lamina cribrosa surface depth (ALCSD) were determined and analyzed with age, axial length, and refraction. Results show that axial length increased and refractive error became more myopic with increasing age (R2 = 0.25, β = 0.18, P < 0.0001 and R2 = 0.27, β = -0.37, P < 0.0001, respectively). Minimum foveal thickness and central 1 mm retinal thickness increased with increasing age (R2 = 0.15, β = 2.38, P < 0.01 and R2 = 0.11, β = 3.16, P < 0.05, respectively). Age-adjusted raw values for peripapillary RNFL thickness decreased with increasing axial length (R2 = 0.11, β = -3.18, P < 0.05); however, this relationship was not present when image magnification was corrected (R2 = 0.07, β = 2.72, P = 0.09). BMO area increased with myopic refractive error (R2 = 0.16, β = -0.10, P < 0.01). Age-adjusted vertical cup-to-disc ratio decreased with increasing axial length and myopic refractive error (R2 = 0.12, β = -0.05, P < 0.05 and R2 = 0.11, β = 0.03, P = 0.05, respectively). Mean MRW, mean ALCSD, and peripapillary choroidal thickness were not associated with age, axial length, or refraction. Mean MRW was significantly thinner in eyes with deeper ALCS (R2 = 0.41, β = -0.83, P < 0.0001). These findings provide normal values for retinal and optic nerve head parameters in school age children, and also suggest that ocular remodeling occurs in some structures in school age children with normal eye growth and during early stages of myopia development.

Determinants of lamina cribrosa depth in healthy Asian eyes: the Singapore Epidemiology Eye Study

AIM

To investigate the determinants of lamina cribrosa depth (LCD) in healthy eyes of Chinese and Indian Singaporean adults.

METHODS

The optic nerve head (ONH) of the right eye of 1396 subjects (628 Chinese and 768 Indian subjects) was imaged with optical coherence tomography (OCT, Spectralis, Heidelberg, Germany). LCD was defined as the distance from the Bruch's membrane opening (LCD-BMO) or the peripapillary sclera (LCD-PPS) reference plane to the laminar surface. A linear regression model was used to evaluate the relationship between the LCD and its determinants.

RESULTS

Both LCDs were significantly different between the two races (LCD-BMO: 421.95 (95% CI 365.32 to 491.79) µm in Chinese vs 430.39 (367.46-509.81) µm in Indians, p=0.021; and LCD-PPS: 353.34 (300.98-421.45) µm in Chinese vs 376.76 (313.39-459.78) µm in Indians, p<0.001). In the multivariable regression analysis, the LCD-PPS of the whole cohort was independently associated with females (β=-31.93, p<0.001), Indians subjects (β=21.39, p=0.004) (Chinese as the reference), axial length (Axl) (β=-6.68, p=0.032), retinal nerve fibre layer thickness (RNFL) (β=0.71, p=0.019), choroidal thickness (ChT) (β=0.41, p<0.001), vertical cup disc ratio (VCDR) (β=24.42, p<0.001) and disc size (β=-60.75, p=0.001). For every 1 year older in age, the LCD-PPS was deeper on average by 1.95 µm in Chinese subjects (p=0.01) but there was no association in Indians subjects (p=0.851).

CONCLUSIONS

The LCD was influenced by age, gender, race, Axl, RNFL, ChT, VCDR and disc size. This normative LCD database may facilitate a more accurate assessment of ONH cupping using OCT in Asian populations.

Diagnostic utility of neuroretinal rim thickness, measured in clock-hour sectors with HD optical coherence tomography, in preperimetric glaucoma

BACKGROUND

We evaluated the usefulness of neuroretinal rim (NRR) thicknesses, measured in clock-hour sectors with Cirrus HD optical coherence tomography, for diagnosing preperimetric glaucoma (PPG).

METHODS

This prospective study included 39 eyes of 39 patients with PPG and 39 eyes of 39 controls that were matched to patients for age and refractive error. We measured the circumpapillary retinal nerve fiber layer (cpRNFL) thickness, macular ganglion cell-inner plexiform layer (GCIPL) thickness, and optic nerve head (ONH) parameters with optical coherence tomography. The clock-hour NRR thicknesses were derived from a 360° circumferential rim thickness curve. We analyzed the area under the receiver operating characteristics curve (AUROC), cutoff values, and sensitivities at specificities of 90% and 95%.

RESULTS

The largest area under the receiver operating characteristics curves were observed for the NRR thickness at 6 o'clock (0.823), the inferior RNFL thickness (0.821), the average RNFL thickness (0.819), and the NRR thickness at 7 o'clock (0.818). The performance of the NRR thickness at 6 o'clock was comparable to the best performances of the cpRNFL, GCIPL, and ONH parameters (all p > 0.05).

CONCLUSION

The ability of the clock-hour NRR thickness assessment to diagnose PPG was comparable to the diagnostic abilities of cpRNFL, GCIPL, and ONH parameters. The best indicator of PPG was the NRR thickness parameter that was at 6 o'clock. This finding could play a role in detecting early structural changes in PPG.

Variance components for PIMD-2π estimation of the optic nerve head and consequences in clinical measurements of glaucoma

PURPOSE

To estimate the sources of variation for Pigment epithelium central limit-Inner limit of the retina Minimal Distance averaged over 2π (PIMD-2π), and further to analyse their consequences for clinical measurements of glaucoma.

METHODS

Forty subjects with early to moderate stage glaucoma were included. Three SD-OCT volumes of the optic nerve head (ONH) were captured at two occasions. Each volume was segmented three times for PIMD-2π. The magnitude of the sources of variation for PIMD-2π measurements was estimated with an analysis of variance.

RESULTS

A 95% confidence interval for mean PIMD-2π was estimated to 215 ± 12 μm (df = 38). The estimated variance for subjects was 1280 μm² . The within-subject estimated variance for occasions, volumes and segmentations was 10 μm² , 30 μm² and 40 μm² , respectively. The within-subject variances were used to model follow-up of PIMD-2π over time. A linear loss rate of 0.05 of baseline PIMD-2π/year was assumed. A significant PIMD-2π change could be detected in approximately 16-18 months with evenly spaced visits every 4 or 6 months.

CONCLUSIONS

Due to the small within-subject estimated variances, a clinically undesirable PIMD-2π change from baseline can be detected in approximately 18 months. Detection of significant PIMD-2π loss in a subject requires knowledge of normal age loss and measurement variability.

Association of Functional Loss With the Biomechanical Response of the Optic Nerve Head to Acute Transient Intraocular Pressure Elevations

Importance

The acute biomechanical response of the optic nerve head (ONH) to intraocular pressure (IOP) elevations may serve as a biomarker for the development and progression of glaucoma.

Objective

To evaluate the association between visual field loss and the biomechanical response of the ONH to acute transient IOP elevations.

Design, Setting, and Participants

In this observational study, 91 Chinese patients (23 with primary open-angle glaucoma [POAG], 45 with primary angle-closure glaucoma, and 23 without glaucoma) were recruited from September 3, 2014, through February 2, 2017. Optical coherence tomography scans of the ONH were acquired at baseline and at 2 sequential IOP elevations (0.64 N and then 0.90 N, by applying forces to the anterior sclera using an ophthalmodynamometer). In each optical coherence tomography volume, lamina cribrosa depth (LCD) and minimum rim width (MRW) were calculated. The mean deviation (MD) and the visual field index (VFI), as assessed by automated perimetry, were correlated with IOP-induced changes of LCD and MRW globally and sectorially.

Main Outcomes and Measures

The LCD, MRW, MD, and VFI.

Results

Among the 91 patients, 39 (42.9%) were women; the mean (SD) age was 65.48 (7.23) years. In POAG eyes, a greater change in LCD (anterior displacement) was associated with worse MD and VFI (R = -0.64; 95% CI, -0.97 to -0.31; P = .001; and R = -0.57; 95% CI, -0.94 to -0.19; P = .005, respectively) at the first IOP elevation, and a greater reduction in MRW was also associated with worse MD and VFI (first IOP elevation: R = -0.48; 95% CI, -0.86 to -0.09; P = .02; and R = -0.57; 95% CI, -0.94 to -0.20; P = .004, respectively; second IOP elevation: R = -0.56; 95% CI, -0.98 to -0.13; P = .01; and R = -0.60; 95% CI, -1.03 to -0.17; P = .008, respectively), after adjusting for age, sex, and baseline IOP. A correlation was found between the reduction in MRW in the inferior-temporal sector and the corresponding visual field cluster in POAG eyes at the second elevation (ρ = -0.55; 95% CI, -0.78 to -0.18; P = .006).

Conclusions and Relevance

The biomechanical response of the ONH to acute IOP elevations was associated with established visual field loss in POAG eyes, but not in primary angle-closure glaucoma eyes. This suggests that ONH biomechanics may be related to glaucoma severity in POAG and that the 2 glaucoma subgroups exhibit inherently different biomechanical properties.

Variation of Peripapillary Scleral Shape With Age

Purpose

To define the shape of the anterior surface of the peripapillary sclera (PPS) and evaluate its relationship with age and ocular determinants in a population-based Chinese cohort.

Methods

The optic nerve heads of 619 healthy Chinese subjects were imaged with spectral-domain optical coherence tomography. To assess the shape of the PPS/Bruch's membrane (BM), we measured the angle between a line parallel to the nasal anterior PPS/BM boundary and one parallel to the temporal side. A negative value indicated that the PPS/BM followed an inverted v-shaped configuration (peak pointing toward the vitreous), whereas a positive value indicated that it followed a v-shaped configuration (peak pointing toward the orbital tissues). A linear regression model was used to evaluate the relationship between the PPS angle and other ocular parameters.

Results

The mean PPS angle was 3.68° ± 6.73° and the BM angle was 9.69° ± 5.05°. The PPS angle increased on average by 0.233 deg/y. A v-shaped PPS was significantly associated with age (β = 0.087, P = 0.004), peripapillary choroidal thickness (β = -0.479, P < 0.001), lamina cribrosa depth (β = 0.307, P < 0.001), and BM angle (β = 0.487, P < 0.001) after adjusting for best corrected visual acuity, central corneal thickness, and axial length.

Conclusions

The anterior surface of PPS of an elderly adult population had a v-shaped configuration and was more pronounced with increasing age, thin peripapillary choroid, and a deep cup. Such a change in shape with age could have an impact on the biomechanical environment of the optic nerve head.

Effect of optic disc size on correlation between Bruch's membrane opening-minimum rim width and peripapillary retinal nerve fibre layer thickness

OBJECTIVES

To investigate the effect of optic disc size on correlation between Bruch's membrane opening-minimum rim width (BMO-MRW) and peripapillary retinal nerve fibre layer (RNFL) thickness from three scan circles.

METHODS

In this retrospective, observational study, non-glaucomatous eyes without visible RNFL defect or visual field loss were included. A total of 101 subjects were distributed into three groups based on disc size: group 1 (n = 26), small disc (disc area < 1.63 mm²); group 2 (n = 40), regular size disc (disc area: 1.63~2.43 mm²); and group 3 (n = 35), large disc (disc area > 2.43 mm²). All patients underwent standard ophthalmic examinations including confocal scanning laser tomography and spectral-domain optical coherence tomography.

RESULTS

Global BMO-MRW was the thickest in group 1 (314.96 ± 60.38 μm, BMO area: 1.72 ± 0.45 mm²), followed by that in group 2 (259.03 ± 40.04 μm, BMO area: 2.29 ± 0.31 mm²). It was the thinnest in group 3 (236.74 ± 31.21 μm, BMO area: 2.91 ± 0.31 mm²; p < 0.001, Kruskal-Wallis test). Correlation between global BMO-MRW value and RNFL thickness was the strongest in group 3 (Spearman's rho = 0.656), followed by that in group 2 (rho = 0.572). It was the weakest in group 1 (rho = 0.147). There was no significant difference in global RNFL thickness by disc size from either the 3.5 mm, 4.1 mm, or 4.7 mm diameter scan circles (all p > 0.05).

CONCLUSIONS

Correlation between BMO-MRW values and RNFL thickness differed significantly according to disc size. Thus, when we assess BMO-MRW in relation to RNFL thickness, disc size may need to be taken into consideration.

Diagnostic criteria for detection of retinal nerve fibre layer thickness and neuroretinal rim width abnormalities in glaucoma

Background/aims

Although measurements of the Bruch’s membrane opening minimum rim width (BMO-MRW) and retinal nerve fibre layer thickness (RNFLT) with optical coherence tomography (OCT) have been widely adopted in the diagnostic evaluation of glaucoma, there is no consensus on the diagnostic criteria to define BMO-MRW and RNFLT abnormalities. This study investigated the sensitivities and specificities of different diagnostic criteria based on the OCT classification reports for detection of glaucoma.

Methods

340 eyes of 137 patients with glaucoma and 87 healthy individuals, all with axial length ≤26mm, had global and sectoral BMO-MRW and RNFLT measured with Spectralis OCT (Heidelberg Engineering). Six diagnostic criteria were examined: global measurement below the fifth or the first percentile; ≥1 sector measurement below the fifth or the first percentile; superotemporal and/or inferotemporal measurement below the fifth or the first percentile. The sensitivities and specificities of BMO-MRW/RNFLT assessment for detection of glaucoma (eyes with visual field (VF) defects) were compared.

Results

Among the six criteria examined, superotemporal and/or inferotemporal measurement below the fifth percentile showed the highest sensitivities and specificities for glaucoma detection. Abnormal superotemporal and/or inferotemporal RNFLT attained a higher sensitivity than abnormal superotemporal and/or inferotemporal BMO-MRW to detect mild glaucoma (mean VF MD: −3.32±1.59 dB) (97.9% and 88.4%, respectively, p=0.006), and glaucoma (mean VF MD: −9.36±8.31 dB) (98.4% and 93.6%, respectively, p=0.006), at the same specificity (96.1%).

Conclusions

Superotemporal and/or inferotemporal RNFLT/MRW below the fifth percentile yield the best diagnostic performance for glaucoma detection with RNFLT attains higher sensitivities than MRW at the same specificity in eyes without high myopia.

Factors Influencing Central Lamina Cribrosa Depth: A Multicenter Study

Purpose

To quantify the influence of ocular and demographic factors on central laminar depth (LD) in healthy participants.

Methods

A total of 362 normal subjects underwent optical coherence tomography (OCT) enhanced depth imaging of the optic nerve head (ONH) with a 24 radial B-scan pattern aligned to the fovea–to–Bruch's membrane opening (BMO) axis. BMO, anterior lamina, anterior scleral canal opening (ASCO), Bruch's membrane (BM), and the peripapillary scleral surface were manually segmented. The extent of laminar segmentation was quantified within 72 ASCO subsectors. Central LD was quantified relative to four reference planes: BMO, ASCO, BM, and scleral. The effects of age, sex, ethnicity, IOP, BMO area, ASCO area, and axial length on LD were assessed.

Results

Laminar visibility was most consistent within the central ASCO (median 89%, range, 69%–95%). LD_BMO and LD_BM were significantly shallower in eyes with greater age, BMO area, and axial length and in females. LD_ASCO was shallower in eyes with greater ASCO area and axial length and in European and Hispanic descent compared to African descent eyes. LD_Sclera behaved similarly, but was not associated with axial length. BMO and ASCO area were not different between African descent and European descent eyes.

Conclusions

Central LD was deeper in African descent eyes and influenced least by age, axial length, and sex, but more by ASCO area, when measured relative to the ASCO and sclera. However, the magnitude of these effects for all four reference planes was small, and their clinical importance in the detection of glaucoma and its progression remains to be determined.

Influence of uveitis on Bruch's membrane opening minimum rim width and retinal nerve fibre layer thickness measurements

BACKGROUND/AIMS

To assess the impact of papillary leakage and active inflammation on optical coherence tomography (OCT)-based retinal nerve fibre layer thickness (RNFLT) and Bruch's membrane opening minimum rim width (BMO-MRW) measurements in uveitic eyes with and without secondary glaucoma.

METHODS

Prospective, single-centre analysis of patients with uveitis. All patients included received a fluorescein angiography examination and an OCT scan measuring the BMO-MRW and the RNFLT in three concentric peripapillary ring scans.

RESULTS

Overall, 95 eyes of 56 patients were enrolled. Papillary leakage and active inflammation were present in 39 (41%) and 57 (60%) eyes, respectively. Twenty-one eyes were classified as glaucomatous; 10 of those glaucomatous eyes showed papillary leakage. Both BMO-MRW and RNFLT measurements were significantly increased in eyes with papillary leakage (BMO-MRW: p=0.0001; RNFLT: first to third ring (p<0.0001)). Active inflammation led to a significantly thickened RNFLT (first ring: p=0.0026; second ring: p=0.0009; third ring: p=0.0002) while only a trend towards increased values could be observed in the BMO-MRW measurements (p=0.3063). Glaucomatous eyes with papillary leakage demonstrated significantly higher values on both BMO-MRW and RNFLT measurements than glaucomatous eyes without leakage (BMO-MRW: p=0.0159; RNFLT: first ring: p=0.0062; second ring: p=0.0037; third ring: p=0.0197). No significant difference could be observed between glaucomatous eyes with leakage and non-glaucomatous eyes without leakage (BMO-MRW: p=0.4132; RNFLT: first ring: p=0.5412; second ring: p=0.3208; third ring: p=0.1164).

CONCLUSIONS

The OCT scanning parameters BMO-MRW and RNFLT were significantly influenced by papillary leakage in uveitic eyes with and without glaucoma. RNFLT values were also significantly increased while active inflammation was present. In patients with uveitis, these OCT-based imaging tools should be interpreted with caution, especially in those with papillary leakage or active inflammation.

Anatomical Characterization of an Optic Disc Notch Using SD-OCT in Glaucoma

PURPOSE

To characterize anatomical dimensions of a disc notch using novel methods using spectral domain optical coherence tomography (SD-OCT).

PARTICIPANTS

All age- and severity-matched glaucoma patients with disc notch (defined as complete loss of neural rim with no residual rim between disc and cup) seen from 2014 to 2015 who underwent enhanced depth imaging with SD-OCT (Cirrus HD-OCT version 6.5, Carl Zeiss, USA) were included for this retrospective observational study.

METHODS

Using known dimensions of the 200 * 200 optic disc cube (6 * 6 mm), the notch width was calculated from the margins of the notch on either side using ImageJ software. The height was calculated from the lowest margin of the cup to the lowest point of the defect on the optic disc. These were compared with the quadrant retinal nerve fiber layer (qRNFT) and sectoral retinal nerve fiber layer (sRNFLT) thickness in notch and the sector 2 clock hours adjacent to the notch region (SaRNFLT).

RESULTS

The height and width of the notch in 31 eyes of 27 patients were 2.6 ± 0.48 mm and 2.23 ± 0.31 mm. The RNFL thickness in the same sector as that of the notch was 41 ± 21.06 µm while the adjacent two sectors measured 62 ± 26.5 and 64 ± 26.5 µm on either sides of the sector of the notch. The difference between the sRNFLT and s_aRNFLT ranged from -9 to 67 and -13 to 50 µm, respectively. This difference was significantly associated with height of the notch (R² = 20.8, p = 0.01).

CONCLUSION

Automated analysis of a notch and RNFL thickness in that sector can help in precise glaucoma monitoring in the region of interest.

The Relationship Between Bruch's Membrane Opening-Minimum Rim Width and Retinal Nerve Fiber Layer Thickness and a New Index Using a Neural Network

PURPOSE

We evaluate the relationship between Bruch's membrane opening minimum rim width (BMO-MRW) and peripapillary retinal nerve fiber layer thickness (pRNFLT) and develop a new parameter combining BMO-MRW and pRNFLT using a neural network to maximize their compensatory values.

METHODS

A total of 402 subjects were divided into two groups: 273 (validation group) and 129 (neural net training) subjects. Linear quadratic and broken-stick regression models were used to explore the relationship between BMO-MRW and pRNFLT. A multilayer neural network was used to create a combined parameter, and diagnostic performances were compared using area under the receiver operating characteristic curves (AUROCs).

RESULTS

Regression analyses between BMO-MRW and pRNFLT revealed that the broken-stick model afforded the best fit. Globally, the tipping point was a BMO-MRW of 226.5 μm. BMO-MRW and pRNFLT were correlated significantly with visual field. When differentiating normal from glaucoma subjects, the neural network exhibited the largest AUROC. When differentiating normal from early glaucoma subjects, the overall diagnostic performance decreased, but the neural network still exhibited the largest AUROC.

CONCLUSIONS

The optimal relationship between BMO-MRW and pRNFLT was revealed using the broken-stick model. Considerable BMO-MRW thinning preceded pRNFLT thinning. The neural network significantly improved diagnostic power by combining BMO-MRW and pRNFLT.

TRANSLATIONAL RELEVANCE

A combined index featuring BMO-MRW and pRNFLT data can aid clinical decision-making, particularly when individual parameters yield confusing results. Our neural network effectively combines information from separate parameters.

Diagnostic accuracy of macular ganglion cell-inner plexiform layer thickness for glaucoma detection in a population-based study: Comparison with optic nerve head imaging parameters

Aims

To determine the diagnostic performance of macular ganglion cell-inner plexiform layer (GCIPL) thickness measured by spectral-domain optical coherence tomography (SD-OCT) for glaucoma detection in a Chinese population in comparison with optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters measured by both SD-OCT and Heidelberg Retina Tomography 3 (HRT-3).

Methods

Adults aged 40 to 80 years were recruited from the population-based study (n = 3353, response rate 72.8%). Macular cube 200x200 scan was performed with Cirrus SD-OCT (version 6.0, Carl Zeiss Meditec Inc, Dublin, CA) for GCIPL thickness measurement. ONH and RNFL imaging was performed with Cirrus SD-OCT and HRT-3 (Heidelberg Engineering, Heidelberg, Germany). Glaucoma was defined according to International Society for Geographical and Epidemiological Ophthalmology criteria.

Results

In total, 86 eyes of 60 subjects with glaucoma and 1709 eyes of 1001 non-glaucoma participants were included. The best performing parameters for Cirrus SD-OCT GCIPL, Cirrus SD-OCT ONH and HRT-3 were minimum GCIPL thickness (Area under receiver-operating curve [AUC] = 0.89, 95% CI 0.83–0.95), vertical cup-disc ratio (CDR) (AUC = 0.94, 0.91–0.98) and vertical CDR (AUC = 0.86, 0.81–0.92), respectively. At 85% specificity, vertical CDR measured using Cirrus OCT ONH scan showed the highest sensitivity (88.64%, 95% CI 75.4–96.2) compared to minimum GCIPL thickness with sensitivity of 60.53% (95% CI 46.4–73.0) (p<0.001). Inferior RNFL thickness (AUC = 0.84, 95% CI 0.91–0.97) measured by Cirrus SD-OCT was also superior to Cirrus SD-OCT GCIPL (p<0.007).

Conclusions

The diagnostic performance of macular GCIPL scan is inferior compared to vertical CDR measured by Cirrus OCT ONH scan. Cirrus OCT ONH scan showed the best ability in detecting glaucoma in a Chinese population, suggesting it could be a good glaucoma screening tool in an Asian population.

Structure-Function Relationships in Perimetric Glaucoma: Comparison of Minimum-Rim Width and Retinal Nerve Fiber Layer Parameters

Purpose

To test the hypotheses that: (1) structure–function (SF) relationships between visual fields (VF) and Bruch's membrane opening-based minimum rim width (BMO-MRW) measurements are superior to those for peripapillary retinal nerve fiber layer (pRNFL) in perimetric glaucoma; (2) BMO-MRW measurements may extend the utility of structural measurement across the range of glaucoma severity; and (3) to estimate the influence of Bruch's membrane opening (BMO) size on BMO-MRW measurements.

Methods

One hundred eight perimetric glaucoma eyes (68 patients) with good quality spectral-domain optical coherence tomography images of the optic disc and pRNFL, and reliable VF within 6 months were recruited. Relationship of global and sectoral BMO-MRW and pRNFL thickness with corresponding VF parameters and the influence of normalizing BMO-MRW (on BMO circumference, nBMO-MRW) on SF relationships were investigated. Broken-stick models were used to compare the point at which pRNFL and BMO-MRW parameters reached their measurement floor.

Results

The median (interquartile range) of VF mean deviation was −5.9 (−12.6 to −3.6) dB. Spearman correlation coefficients between pRNFL, BMO-MRW, and nBMO-MRW measures and corresponding VF cluster average deviations ranged between 0.55 to 0.80, 0.35 to 0.66, and 0.38 to 0.65, respectively. Bruch's membrane opening–MRW parameters demonstrated weaker SF relationships compared with pRNFL globally and in temporal, temporal-superior, and nasal-inferior sectors (P < 0.03). Normalization of BMO-MRW did not significantly influence SF relationships.

Conclusions

Structure–function relationships were somewhat weaker with BMO-MRW parameters compared with pRNFL in eyes with perimetric glaucoma. Bruch's membrane opening–MRW normalization did not significantly change SF relationships in this group of eyes with mild departures from average BMO size.

Determinants and Characteristics of Bruch's Membrane Opening and Bruch's Membrane Opening-Minimum Rim Width in a Normal Japanese Population

Purpose

To identify determinants of Bruch's membrane opening (BMO), and BMO-minimum rim width (BMO-MRW) and circumpapillary retinal nerve fiber layer thickness (RNFLT) centered on BMO center and characterize these parameters in a normal Japanese population.

Methods

Spectral-domain optical coherence tomography images of optic nerve head and circumpapillary and macular retina were obtained in 258 eyes of 258 normal Japanese with mean (standard deviation) age of 51.7 (18.2) years. BMO area, BMO-MRW, RNFLT (measured with a 3.5-mm-diameter circle scan) were all acquired and analyzed relative to the eye-specific fovea to BMO (FoBMO) axis. One randomly selected eye of each subject was analyzed. Multiple regression analysis was used to identify determinants to the parameters.

Results

BMO area, global BMO-MRW, RNFLT, and FoBMO angle averaged 2.06 (0.45) mm2, 305.5 (50.0) μm, 101.8 (9.6) μm, and -7.8° (3.8°), respectively. There was a modest correlation between global BMO-MRW and RNFLT (r = 0.337; P < 0.001), while the sectorwise correlations were highest in the superior-temporal sector (r = 0.500; P < 0.001) and lowest in the nasal sector (r = 0.117; P = 0.063). Global BMO-MRW and RNFLT declined with age at -1.04 μm/y (P < 0.001) and -0.12 μm/y (P = 0.001), and the former correlated negatively (P = 0.001) and the latter positively (P < 0.001) with BMO area after adjustment for other factors (R2 = 0.191 and 0.272, respectively). BMO area correlated positively with axial length (P = 0.023) and negatively with age (P < 0.001) (R2 = 0.157).

Conclusions

BMO-MRW and RNFLT declined with age with a difference between them in their relationship to BMO area. BMO area positively correlated with axial length and negatively with age.

Comparing optical coherence tomography radial and cube scan patterns for measuring Bruch’s membrane opening minimum rim width (BMO-MRW) in glaucoma and healthy eyes: cross-sectional and longitudinal analysis

Aim

To compare the cube and radial scan patterns of the spectral domain optical coherence tomography (SD-OCT) for quantifying the Bruch’s membrane opening minimum rim width (BMO-MRW).

Methods

Sixty healthy eyes and 189 glaucomatous eyes were included. The optic nerve head cube and radial pattern scans were acquired using Spectralis SD-OCT. BMO-MRWs were automatically delineated using the San Diego Automated Layer Segmentation Algorithm. The BMO-MRW diagnostic accuracy for glaucoma detection and rates of change derived from the two scan patterns were compared.

Results

There was a significant difference between the baseline global BMO-MRW measurements of cube and radial scans for healthy (301.9±57.8 µm and 334.7±61.8 µm, respectively, p<0.003) and glaucoma eyes (181.2±63.0 µm and 210.2±67.2 µm, respectively, p<0.001). The area under the receiver operating characteristic curve for differentiating between healthy and glaucoma eyes was 0.90 for both the radial scan-based and cube scan-based BMO-MRW. No significant difference in the rate of BMO-MRW change (mean follow-up years) by scan pattern was found among both healthy (cube: −1.47 µm/year, radial: −1.53 µm/year; p=0.48) (1.6 years) and glaucoma eyes (cube: −2.37 µm/year, radial: −2.28 µm/year; p=0.45) (2.6 years).

Conclusion

Although the cube scan-based BMO-MRW was significantly smaller than the radial scan-based BMO-MRW, we found no significant difference between the two scan patterns for detecting glaucoma, identifying BMO location and measuring the rate of BMO-MRW change. These results suggest that although BMO-MRW estimates are not interchangeable, both scan patterns can be used for monitoring BMO-MRW changes over time.

Comprehensive Three-Dimensional Analysis of the Neuroretinal Rim in Glaucoma Using High-Density Spectral-Domain Optical Coherence Tomography Volume Scans

Purpose

To describe spectral-domain optical coherence tomography (OCT) methods for quantifying neuroretinal rim tissue in glaucoma and to compare these methods to the traditional retinal nerve fiber layer thickness diagnostic parameter.

Methods

Neuroretinal rim parameters derived from three-dimensional (3D) volume scans were compared with the two-dimensional (2D) Spectralis retinal nerve fiber layer (RNFL) thickness scans for diagnostic capability. This study analyzed one eye per patient of 104 glaucoma patients and 58 healthy subjects. The shortest distances between the cup surface and the OCT-based disc margin were automatically calculated to determine the thickness and area of the minimum distance band (MDB) neuroretinal rim parameter. Traditional 150-μm reference surface–based rim parameters (volume, area, and thickness) were also calculated. The diagnostic capabilities of these five parameters were compared with RNFL thickness using the area under the receiver operating characteristic (AUROC) curves.

Results

The MDB thickness had significantly higher diagnostic capability than the RNFL thickness in the nasal (0.913 vs. 0.818, P = 0.004) and temporal (0.922 vs. 0.858, P = 0.026) quadrants and the inferonasal (0.950 vs. 0.897, P = 0.011) and superonasal (0.933 vs. 0.868, P = 0.012) sectors. The MDB area and the three neuroretinal rim parameters based on the 150-μm reference surface had diagnostic capabilities similar to RNFL thickness.

Conclusions

The 3D MDB thickness had a high diagnostic capability for glaucoma and may be of significant clinical utility. It had higher diagnostic capability than the RNFL thickness in the nasal and temporal quadrants and the inferonasal and superonasal sectors.

Effect of acute intraocular pressure elevation on the minimum rim width in normal, ocular hypertensive and glaucoma eyes

BACKGROUND

To estimate and compare changes in the Bruch's membrane opening-minimum rim width (BMO-MRW) and area in normal, ocular hypertensive and glaucoma eyes following acute elevations in intraocular pressure (IOP).

METHODS

The optic nerve heads (ONHs) of 104 subjects (31 normals, 20 ocular hypertension (OHT) and 53 with primary glaucoma) were imaged using Spectral-domain optical coherence tomography (OCT; Spectralis, Heidelberg Engineering, Germany). IOP was raised twice by applying a force (0.64 n then 0.9 n) to the anterior sclera using an ophthalmo-dynamometer. After each IOP increment, IOP was held constant, measured with a Tonopen (AVIA applanation tonometer, Reichert, Depew, New York, USA), and ONH was rescanned with OCT. In each OCT volume, BMO-MRW and area were calculated and at each IOP increment.

RESULTS

The baseline MRW was significantly smaller in glaucoma subjects (174.3±54.3 µm) compared with normal (287.4±42.2 µm, p<0.001) and OHT subjects (255.4±45.3 µm, p<0.001). MRW of glaucoma subjects was significantly thinner at the first and second IOP elevations than that at baseline (both p<0.01), but no significant change was noted in normal and OHT subjects. There was no significant change of BMO area at acute IOP elevations from baseline in all diagnoses (all p>0.05).

CONCLUSION

Acute IOP elevation leads to compression of the nerve fibre layers of neuroretinal rim in glaucoma subjects only without changing ONH size. This suggests that the neural and connective tissues at ONH level in glaucoma subjects are more susceptible to acute IOP episodes than OHT or normal controls.

A Digital Staining Algorithm for Optical Coherence Tomography Images of the Optic Nerve Head

Purpose

To digitally stain spectral-domain optical coherence tomography (OCT) images of the optic nerve head (ONH), and highlight either connective or neural tissues.

Methods

OCT volumes of the ONH were acquired from one eye of 10 healthy subjects. We processed all volumes with adaptive compensation to remove shadows and enhance deep tissue visibility. For each ONH, we identified the four most dissimilar pixel-intensity histograms, each of which was assumed to represent a tissue group. These four histograms formed a vector basis on which we ‘projected' each OCT volume in order to generate four digitally stained volumes P1 to P4. Digital staining was also verified using a digital phantom, and compared with k-means clustering for three and four clusters.

Results

Digital staining was able to isolate three regions of interest from the proposed phantom. For the ONH, the digitally stained images P1 highlighted mostly connective tissues, as demonstrated through an excellent contrast increase across the anterior lamina cribrosa boundary (3.6 ± 0.6 times). P2 highlighted the nerve fiber layer and the prelamina, P3 the remaining layers of the retina, and P4 the image background. Further, digital staining was able to separate ONH tissue layers that were not well separated by k-means clustering.

Conclusion

We have described an algorithm that can digitally stain connective and neural tissues in OCT images of the ONH.

Translational Relevance

Because connective and neural tissues are considerably altered in glaucoma, digital staining of the ONH tissues may be of interest in the clinical management of this pathology.

Diagnostic Performance of a Novel Three-Dimensional Neuroretinal Rim Parameter for Glaucoma Using High-Density Volume Scans

PURPOSE

To evaluate the diagnostic performance of a 3-dimensional (3D) neuroretinal rim parameter, the minimum distance band (MDB), using optical coherence tomography (OCT) high-density volume scans for open-angle glaucoma.

DESIGN

Reliability analysis.

METHODS

setting: Institutional.

STUDY POPULATION

Total of 163 patients (105 glaucoma and 58 healthy subjects).

OBSERVATION PROCEDURES

One eye of each patient was included. MDB and retinal nerve fiber layer (RNFL) thickness values were determined for 4 quadrants and 4 sectors using a spectral-domain OCT device.

MAIN OUTCOME MEASURES

Area under the receiver operating characteristic curve (AUROC) values, sensitivities, specificities, and positive and negative predictive values.

RESULTS

The best AUROC values of 3D MDB thickness for glaucoma and early glaucoma were for the overall globe (0.969, 0.952), followed by the inferior quadrant (0.966, 0.949) and inferior-temporal sector (0.966, 0.944), and then followed by the superior-temporal sector (0.964, 0.932) and superior quadrant (0.962, 0.924). All 3D MDB thickness AUROC values were higher than those of 2D RNFL thickness. Pairwise comparisons showed that the diagnostic performance of the 3D MDB parameter was significantly better than 2D RNFL thickness only for the nasal quadrant and inferior-nasal and superior-nasal sectors (P = .023-.049). Combining 3D MDB with 2D RNFL parameters provided significantly better diagnostic performance (AUROC 0.984) than most single MDB parameters and all single RNFL parameters.

CONCLUSIONS

Compared with the 2D RNFL thickness parameter, the 3D MDB neuroretinal rim thickness parameter had uniformly equal or better diagnostic performance for glaucoma in all regions and was significantly better in the nasal region.

Optical coherence tomography platforms and parameters for glaucoma diagnosis and progression

PURPOSE OF REVIEW

Optical coherence tomography (OCT) aids in the diagnosis and long-term monitoring of various ocular diseases, including glaucoma. Initially, the retinal nerve fiber layer was the only OCT structural parameter used in glaucoma. Subsequent research has resulted in more retinal and optic nerve head parameters. In addition, OCT is being investigated for its ability to assess ocular hemodynamics. This review summarizes these spectral domain-optical coherence tomography (SDOCT) parameters in the context of glaucoma.

RECENT FINDINGS

Several new SDOCT retinal nerve fiber layer, optic nerve head, and macular parameters with good glaucoma diagnostic ability have been added to existing ones recently. The combination of SDOCT and Doppler or angiography has also resulted in hemodynamic parameters that may prove to be useful in the functional assessment in glaucoma.

SUMMARY

OCT technology is advancing not only as a tool for structural assessment, but also as a multimodality tool to assess both structure and function to enhance our understanding of glaucoma, and ultimately clinical decisions.

Spectral-Domain Optical Coherence Tomography-Derived Characteristics of Bruch Membrane Opening in a Young Adult Australian Population

PURPOSE

To characterize and quantify Bruch membrane opening (BMO)-based optic nerve head (ONH) parameters in a large, young and healthy, predominantly white population.

DESIGN

Cross-sectional study and reliability analysis.

METHODS

The ONH of 1344 predominantly white subjects were imaged with spectral-domain optical coherence tomography (SD-OCT). A customized script, coded in Matlab, was used to manually segment and measure multiple BMO-based parameters of the ONH. Measurements were compared to those obtained with confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph; HRT). Regression analysis was performed to assess the relationship between BMO parameters and other ocular and demographic variables.

RESULTS

Mean BMO disc and neuroretinal rim (NRR) areas ranged from 0.94 to 4.06 mm(2) (mean 1.77 ± 0.38 mm(2)) and 0.94 to 3.99 mm(2) (mean 1.56 ± 0.31 mm(2)), respectively. When compared to the equivalent HRT measurements, SD-OCT-derived measures differed significantly for all comparable ONH parameters (P < .001). The limits of agreement computed from Bland-Altman plots comparing SD-OCT and HRT measurements showed suboptimal agreement between the techniques. Linear regression analysis demonstrated an effect of ethnicity, axial length, and refractive error on BMO-based parameters.

CONCLUSIONS

We have quantified BMO-based parameters in a large cohort of young adults using SD-OCT. These data will be informative in constructing normative profiles for clinical and research purposes in glaucoma diagnosis and management.