Comparison of localized retinal nerve fiber layer defects in highly myopic, myopic, and non-myopic patients with normal-tension glaucoma: a retrospective cross-sectional study

Progress in clinical characteristics of high myopia with primary open-angle glaucoma

High myopia (HM) is a significant risk factor for the occurrence and progression of primary open-angle glaucoma (POAG). Identification with POAG in the HM population is an emergent challenge. Patients with HM have a significantly higher probability of complicating POAG than those without HM. When HM is associated with POAG, the changes to the fundus caused by both of them are confused with each other, making the diagnosis of early glaucoma difficult. This article reviews available researches on HM with POAG, summarizing the characteristics of the fundus structure such as epidemiology, intraocular pressure, optic disc, ganglion cell layer, retinal nerve fiber layer, vascular density, and visual field.

Discriminating Diseases Mimicking Normal-Tension Glaucoma (NTG) from NTG

Background/Objectives: The aim of this study was to identify the most reliable ocular exam and establish a threshold for deciding whether to perform neuroimaging in order to screen for diverse diseases other than normal-tension glaucoma (NTG). A retrospective, observational, comparative study was used. Methods: In total, 106 individuals with atypical features of NTG who underwent glaucoma assessments and contrast-enhanced MRI of the brain or orbit were included. The criteria for atypical NTG included the following: (1) unilateral normal-tension glaucoma, (2) visual field (VF) damage inconsistent with optic disc appearance, (3) fast VF progression, (4) worsening of visual acuity, (5) optic disc pallor, (6) scotoma restricted by a vertical line, and (7) central scotoma. Glaucoma evaluations included measurements of visual acuity, intraocular pressure, central corneal thickness, axial length, cup-disc ratio, retinal nerve fiber layer (RNFL) thickness, ganglion cell-inner plexiform layer (GCIPL) thickness, mean deviation (MD), and visual field index (VFI). Statistical analyses involved independent t-tests, receiver operating characteristic (ROC) curves, and area under the curve (AUC) in order to differentiate neuro-ophthalmological conditions from NTG, compare the diagnostic power of each factor, and determine the cut-off value. Results: Relatively fewer diagnoses of non-glaucomatous diseases were associated with unilateral NTG, the worsening of VA, and central scotoma. Factors such as rapid visual field progression, optic disc pallor, and scotoma restricted by a vertical line had a relatively higher diagnostic rate of non-glaucomatous diseases. There were significant differences in average RNFL and GCIPL thicknesses at the nasal quadrant between NTG and NTG-mimicking conditions. Only the GCIPL thickness at the nasal quadrant had reliable power for discriminating between neuro-ophthalmological disease and NTG. For the GCIPL thickness at the nasal quadrant, the AUC was 0.659, and the cut-off value was 65.75. Conclusions: When deciding whether to proceed with imaging, such as carrying out an MRI test, for NTG patients with atypical NTG characteristics, it would be advisable to consider the nasal sector cut-off value of GCIPL thickness.

How is eyeball growth associated with optic nerve head shape and glaucoma? The Lamina cribrosa/Bruch's membrane opening offset theory

The optic nerve head (ONH) is a complex structure wherein the axons of the retinal ganglion cells extrude from the eyeball through three openings: 1) the Bruch's membrane opening (BMO) in the retinal layer, 2) the anterior scleral canal opening in the anterior scleral layer, and 3) the lamina cribrosa (LC). Eyeball expansion during growth induces an offset among openings, since the expansion affects the inner retinal and outer scleral layers differently: the posterior polar retinal structure is preserved by the preferential growth in the equatorial region, whereas no such regional difference is observed in the scleral layer. The various modes and extents of eyeball expansion result in diverse directionality and amount of offset among openings, which causes diverse ONH morphology in adults, especially in myopia. In this review, we summarize the ONH changes that occur during myopic axial elongation. These changes were observed prospectively in our previous studies, wherein LC shift and subsequent offset from the BMO center could be predicted by tracing the central retinal vascular trunk position. This offset induces the formation of γ-zone parapapillary atrophy or externally oblique border tissue. As a presumptive site of glaucomatous damage, the LC/BMO offset may render the LC pores in the opposite direction more vulnerable. To support such speculation, we also summarize the relationship between LC/BMO offset and glaucomatous damage. Indeed, LC/BMO offset is not only the cause of diverse ONH morphology in adults, but is also, potentially, an important clinical marker for assessment of glaucoma.

Structure-function relationship in glaucoma: Optical coherence tomography en face imaging vs. red-free fundus photography

BACKGROUND/OBJECTIVES

To analyse retinal nerve fibre layer (RNFL) defect measurements obtained from red-free fundus photography and optical coherence tomography (OCT) en face imaging, respectively, and to compare them for the strength of the structure-function association.

SUBJECTS/METHODS

Two hundred and fifty-six glaucomatous eyes of 256 patients with localized RNFL defect on red-free fundus photography were enrolled. A subgroup analysis included 81 highly myopic eyes (≤ -6.0 dioptres). Angular width of RNFL defect was compared between red-free fundus photography (i.e., red-free RNFL defect) and OCT en face imaging (i.e., en face RNFL defect). The correlation between angular width of each RNFL defect and functional outcomes, reported as mean deviation (MD) and pattern standard deviation (PSD), were assessed and compared.

RESULTS

The angular width of en face RNFL defect was measured smaller than that of red-free RNFL defect in 91.0% eyes (mean difference, 19.98°). The association of en face RNFL defect with MD and PSD was stronger (R2 = 0.311 and R2 = 0.372, respectively) than that of red-free RNFL defect with MD and PSD (R2 = 0.162 and R2 = 0.137, respectively) (P < 0.05 for all). Especially in highly myopic eyes, the association of en face RNFL defect with MD and PSD was much stronger (R2 = 0.503 and R2 = 0.555, respectively) than that of red-free RNFL defect with MD and PSD (R2 = 0.216 and R2 = 0.166, respectively) (P < 0.05 for all).

CONCLUSIONS

En face RNFL defect showed a higher correlation with severity of visual field loss than did red-free RNFL defect. The same dynamic was observed for highly myopic eyes.

Effect of myopia on the progression of normal tension glaucoma

PURPOSE

Identify risk factors of progression in treated normal-tension glaucoma (NTG) in highly myopic and non-highly myopic eyes.

METHODS

This retrospective, observational case series study included 42 highly myopic glaucoma (HMG, <-6D) eyes and 39 non-highly myopic glaucoma (NHG,≧-6D) eyes. Glaucoma progression was determined by serial visual field data. Univariate and multivariate logistic regression method were used to detect associations between potential risk factors and glaucoma progression.

RESULTS

Among 81 eyes from 81 normal-tension glaucoma patients (mean follow-up, 3.10 years), 20 of 42 eye (45.24%) in the HMG and 14 of 39 eyes (35.90%) in the NHG showed progression. The HMG group had larger optic disc tilt ratio (p = 0.007) and thinner inferior macular thickness (P = 0.03) than the NHG group. Changes in the linear regression values for MD for each group were as follows: -0.652 dB/year for the HMG and -0.717 dB/year for the NHG (P = 0.298). Basal pattern standard deviation (PSD) (OR: 1.55, p = 0.016) and post treatment IOP (OR = 1.54, p = 0.043) were risk factors for visual field progression in normal tension glaucoma patients. In subgroup analysis of HMG patients, PSD (OR: 2.77, p = 0.017) was a risk factor for visual field progression.

CONCLUSION

Reduction IOP was postulated to be contributing in the prevention of visual field progression, especially in highly myopic NTG patients with large basal pattern standard deviation.

Optic Disc Morphology and Paracentral Scotoma in Patients with Open-Angle Glaucoma and Myopia

This study's aim was to investigate the association between optic disc morphology and the occurrence of paracentral scotoma in eyes with open-angle glaucoma (OAG) and myopia. Two-hundred and eleven myopic eyes with OAG were classified into three groups according to the location of visual field (VF) defect (99 paracentral scotoma, 65 peripheral scotoma, and 47 no VF defect). Optic disc morphology was assessed based on the tilt ratio and eccentricity of the central retinal vessel trunk (CRVT). Clinical characteristics of the three groups were compared, and factors affecting the occurrence of paracentral scotoma were determined. Eyes with paracentral scotoma had a higher tilt ratio than the other groups (ps ≤ 0.04). Multiple linear regression showed that a nasal location of CRVT (p < 0.001), longer axial length (p = 0.001), and lower VF mean deviation (p = 0.021) were significantly associated with higher tilt ratio. In logistic regression analysis, tilt ratio was the only factor that was significantly associated with the occurrence of paracentral scotoma (odds ratio = 7.12, p = 0.032). In conclusion, the optic disc tilt ratio increased with nasal shift of CRVT, longer axial length, and lower VF mean deviation. Higher optic disc tilt was significantly associated with the occurrence of paracentral scotoma in eyes with OAG and myopia.

Cluster Formation for Analyses of Glaucomatous Visual Field Defects in Central 10-2 Visual Field in Normal Tension Glaucoma Eyes

Purpose

To develop a cluster system to analyze the retinal sensitivity loss of 68 test points in the central 10 degrees of standard automated perimetry (SAP) in eyes with normal tension glaucoma (NTG).

Patients and Methods

Patients with NTG who met the following criteria were included: visual acuity ≥0.7, SAP-derived mean deviation ≥−15 dB, and pattern deviation probability plots with at least one point with a probability of <0.5% and/or two or more contiguous points with a probability of <1% that did not cross the horizontal meridian in the central 12 points of the 24-2 test points. SAP with the Swedish Interactive Threshold Algorithm Standard (SITA-S) 10-2 program (10-2) was performed within 6 months of the SITA-S 24-2. The averaged total deviation (TD) for each of the 68 test points in the 10-2 was calculated. Hierarchical cluster analyses were performed based on the deviation of the TDs of the test points, and a dendrogram was created. The number of clusters was determined following the Sturges’ rule.

Results

One hundred and twenty-six eyes of 126 patients (61.9±11.4 years) were studied. Hierarchical cluster analysis of the TD values statistically obtained a dendrogram that divided the 68 test points into 7 clusters. Of these 7 clusters, 21 points belonging to the clusters in the papillomacular region included cluster 5. Cluster 5 was distributed above and below the horizontal meridian, which does not agree with the course of the retinal nerve fiber layer (RNFL).

Conclusion

The hierarchical cluster analysis of the TD values stratified the 68 test points of the 10-2 into seven clusters. Considering the course of the RNFL, cluster 5 was divided into clusters of 5a and 5b, and consequently eight clusters were considered to be appropriate for detecting glaucomatous visual field defects in the central 10 degrees in NTG eyes.

Relationship Between Macular Ganglion Cell Thickness and Ocular Elongation as Measured by Axial Length and Retinal Artery Position

Purpose

We recently reported on the usefulness of retinal artery trajectory in estimating the magnitude of retinal stretch due to myopia. The purpose of the present study was to elucidate the relationship between the peripapillary retinal artery angle (PRAA) and thickness of the macular ganglion cell–inner plexiform layer (GCIPL).

Methods

This r included 138 healthy eyes of 79 subjects older than 20 years of age without any known eye disease. GCIPL thickness was separated into eight sectors according to quadrant and eccentricity from the fovea. The PRAA was calculated as the angle between the superior and inferior retinal arteries. Relationships between whole GCIPL thickness (average and sectorial) and the values of PRAA and axial length (AL) were investigated using a linear mixed model.

Results

Average GCIPL thickness in the whole scanned area decreased significantly with narrowing of the PRAA with and without adjusting for AL. Sectorized macular GCIPL thickness also decreased significantly, with narrowing of the PRAA in seven out of the eight with the adjustment of AL, the exception being the inferior peripheral temporal sector.

Conclusions

Macular GCIPL thickness decreased significantly with narrowing of the PRAA on average and in seven out of eight sectors.

Angular Location of Retinal Nerve Fiber Layer Defect: Association With Myopia and Open-Angle Glaucoma

Purpose

To compare retinal nerve fiber layer (RNFL) defects' angle measurements determined from the center of the optic disc and Bruch's membrane opening (BMO), as a function of myopia and open-angle glaucoma (OAG) subtypes.

Methods

In total, 118 patients with OAG were grouped by axial length (AL; high myopia, AL >26 mm; mild to moderate myopia, 24 ≤ AL ≤26 mm; nonmyopia, AL <24 mm) and OAG subtype (normal-tension glaucoma [NTG], high-tension glaucoma [HTG]). The disc and BMO centers were determined by a merged image of red-free fundus photography and spectral-domain optical coherence tomography. The angular location of the RNFL defect close to the fovea (angle α) was measured from the disc center and BMO center, respectively (angle αdisc and angle αBMO). The difference between angle αdisc and αBMO (Δα), as well as the RNFL defect width (angle γ), was evaluated.

Results

Angle αdisc was smaller in myopic eyes and correlated significantly with AL (P = 0.001), whereas it did not differ among OAG subgroups. Angle αBMO and angle γ were not different in the myopic and OAG subgroups. The Δ α was larger for eyes with higher degree of myopia and had significant correlation with AL (P < 0.001) and was larger in NTG eyes than in HTG eyes (P = 0.023).

Conclusions

The angular location of the RNFL defect measured from the disc center, but not from the BMO center, was closer to the fovea for glaucomatous eyes with higher values of AL. The present study may facilitate understanding of the characteristic locational pattern of the RNFL defect in myopic glaucomatous eyes.

Longitudinal Macular Ganglion Cell-Inner Plexiform Layer Measurements to Detect Glaucoma Progression in High Myopia

PURPOSE

To investigate whether progressive macular ganglion cell-inner plexiform layer (GCIPL) and peripapillary retinal nerve fiber layer (RNFL) thinning are predictive for detecting visual field (VF) progression in eyes with high myopia.

DESIGN

Cohort study.

METHODS

A total of 104 primary open-angle glaucoma (POAG) eyes with high myopia and 104 age- and VF severity-matched POAG eyes without high myopia (mean follow-up, 5.4 years) were included. High myopia was defined as a spherical equivalent <-6.0 diopters or axial length >26.5 mm. Progressive GCIPL, RNFL, and VF deterioration were determined by Guided Progression Analysis (GPA) in optical coherence tomography and standard automated perimetry. The risk of VF progression was evaluated using Cox proportional hazard models.

RESULTS

Highly myopic eyes with progressive GCIPL thinning had a significantly higher risk of developing VF progression after adjusting for the baseline intraocular pressure (HR 4.00; P = .001) or peak intraocular pressure (HR 3.11; P = .011) in the multivariable Cox proportional hazard model, whereas highly myopic eyes with progressive RNFL thinning were not significantly associated with VF progression. In eyes without high myopia, both progressive GCIPL (HR 4.67 or 3.62; P = .008 or .037, respectively) and RNFL (HR 6.60 or 3.97; P = .001 or .016, respectively) thinning were associated with a significantly higher risk of developing VF progression after adjusting for the baseline or peak intraocular pressure.

CONCLUSIONS

Monitoring macular GCIPL thickness was effective for predicting glaucoma progression regardless of the presence of high myopia.

The severity of visual field defect and the defective angles of localized retinal nerve fiber layer using a novel approach

BACKGROUND/PURPOSE

A modified novel analytical method for evaluating photographic retinal nerve fiber layer defect (RNFLD) was developed for the purpose of estimating the severity of early glaucomatous eyes. This new method was then compared with the original method, as described below, in relation to the visual field defect severity.

METHODS

The clinical records of 47 glaucomatous eyes with qualified photographs were obtained from a prior retrospective study. The reference point of the angle was set at the center of the optic disc center (COD group) and the central vessel trunk (COV group). Angle α was the angular width between the fovea and the proximity of RNFLD, while angle β (+c) was the sum of the angular width(s) of localized RNFLD. The correlation between the visual field parameters and the angles of RNFLD in the above two groups were analyzed.

RESULTS

There were significant differences in angle α (p = 0.001) and angle β (+c) (p = 0.016) between the two groups. Angle β (+c) showed significant correlation with MD (p = 0.012), PSD (p = 0.035), VFI (p = 0.042) and MD (p = 0.016), PSD (p = 0.035), VFI (p = 0.031) in the COD and COV group, respectively. No correlation was found between angle α and the presence of central scotoma in both groups.

CONCLUSION

Our novel method was more convenient in a clinical setting and noninferior to the original method.

Topographic Relationship with a Retinal Nerve Fiber Layer Defect Differs between β-Zone and γ-Zone Parapapillary Atrophy

Introduction

γ-Zone parapapillary atrophy (PPA), an associated feature in myopic tilted optic disc, is considered to be relevant with glaucomatous optic nerve damage in myopic eyes. This study determines the topographic relationship of γ-zone PPA with a retinal nerve fiber layer defect.

Purpose

To determine the topographic relationship of γ-zone PPA with a RNFL defect and to compare it with that of β-zone PPA.

Design

Cross-sectional, observational study. Participants. Eighty-nine eyes from 89 patients with primary open-angle glaucoma who had β-zone PPA (n = 49) or γ-zone PPA (n = 40) and a single localized RNFL defect.

Methods

PPA was classified according to the presence or absence of Bruch's membrane on the PPA bed in spectral-domain optical coherence tomography. The angular location of the point of maximum radial extent of PPA (PMRE) and the RNFL defect was measured with the fovea-disc axis set at 0° in color and red-free fundus photographs. Main Outcome Measures. Angular distance between the RNFL defect and the PMRE.

Results

There was no significant intergroup difference in the extent of the RNFL defect (P=0.920). The angular distance between the RNFL defect and the PMRE was significantly greater in γ-zone than β-zone PPA (26.49 ± 17.27° vs. 60.31 ± 17.12°, P < 0.001). The angular location of the PMRE was significantly correlated with the location of the RNFL defect in the β-zone group (r = 0.822, P < 0.001) but not in the γ-zone group. The RNFL defect was mostly located near the edge of γ-zone PPA in the γ-zone group (10.56 ± 9.47°).

Conclusions

An RNFL defect was observed near the edge of PPA in eyes with γ-zone PPA, in contrast to it being close to the PMRE in eyes with β-zone PPA.

Evaluation of Peripapillary Choroidal Microvasculature to Detect Glaucomatous Damage in Eyes With High Myopia

PRECIS

Parapapillary choroidal microvasculature dropout (MvD), as observed by optical coherence tomography (OCT) angiography, was useful to detect glaucomatous damage in highly myopic eyes with unreliable OCT results due to segmentation errors.

PURPOSE

The purpose of this study was to evaluate the usefulness of optical coherence tomography angiography (OCTA) imaging of the peripapillary choroidal microvasculature in detecting glaucomatous damage in highly myopic eyes, in cases where evaluating the thickness of the retinal nerve fiber layer (RNFL) is unreliable due to OCT segmentation errors.

MATERIALS AND METHODS

Forty-five highly myopic eyes with primary open-angle glaucoma (POAG) with an axial length >26.5 mm, and 15 age-matched and axial length-matched 15 control eyes were included in this cross-sectional observational study. All participants had a segmentation error in OCT circumpapillary RNFL scanning. The peripapillary choroidal microvasculature was evaluated on en-face images obtained using swept-source OCTA. MvD was defined as a focal sectoral capillary dropout with no visible microvascular network identified in the choroidal layer. The topographic correlation between the MvD and a hemifield visual field (VF) defect was assessed using κ statistics. The MvD size was assessed by measuring both its area and circumferential extent.

RESULTS

Choroidal MvD was observed in 44 of the 45 (97.8%) POAG eyes with high myopia, while none of the control eyes showed a choroidal MvD. There was an excellent topographic relationship between the choroidal MvD and the hemifield VF defect (κ=0.863, P<0.001). The area (R=0.2619, P=0.0006) and circumferential extent (R=0.3088, P=0.0002) of the MvD have significantly associated with the VF mean deviation.

CONCLUSIONS

Choroidal MvDs were observed in most of the highly myopic POAG eyes and were topographically correlated with the location of glaucomatous VF defects despite unreliable OCT RNFL thickness measurements. Using OCTA to investigate the choroidal microvasculature may facilitate diagnoses of glaucoma in highly myopic eyes.

Defective angles of localized retinal nerve fiber layer reflect the severity of visual field defect- a cross-sectional analysis

Background

In order to detect glaucomatous optic nerve damages early on and evaluate the severity of glaucoma, a previously developed analytic method based on photographic retinal nerve fiber layer (RNFL) angle defect was proposed. However, the correlation between these defective angles and the severity of visual field defect has not been verified. This study aimed to confirm the correlation described above.

Methods

We reviewed a total of 227 glaucomatous eyes (38 enrolled, 189 excluded) during an interval of 5 years. The angles of all eyes were measured on RNFL photograph, of which angle α is the angular width between the macula center and the proximity of RNFL defect, and angle β (+c) is the sum of angular width(s) of localized RNFL defect. The severity of visual field defect was determined by mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI). Correlation analysis was performed on angle α and angle β (+c) with the presence of central scotoma and visual field defect parameters, respectively.

Results

Angle β (+c) showed significant correlation with MD (P = 0.007), PSD (P = 0.02), VFI (P = 0.03), and average RNFL thickness (P = 0.03). No correlation was found between angle α and the presence of central scotoma.

Conclusions

In conclusion, measuring the angular width of localized RNFL defect is a viable method for determining the severity of visual field defect.

Diagnostic ability of vessel density measured by spectral-domain optical coherence tomography angiography for glaucoma in patients with high myopia

Although early glaucoma detection is important to prevent visual loss due to disease progression, its clinical diagnosis in highly myopic eyes is still difficult. Many studies using optical coherence tomography (OCT) angiography (OCTA) reported decreased vessel density (VD) in glaucomatous eyes compared to normal eyes. We evaluated the diagnostic ability of peripapillary VD and macular VD measured by OCTA, comparing them with conventional valuables such as peripapillary retinal nerve fibre layer (RNFL) thickness and macular ganglion cell-inner plexiform layer (GCIPL) thickness measured by OCT. We also calculated the average VD ratio (VDR) (average outer macular VD/average inner macular VD), superior VDR (superior outer macular VD/average inner macular VD), and inferior VDR (inferior outer macular VD/average inner macular VD). Totally, 169 eyes from 169 subjects were enrolled. Among OCTA measurements, the best diagnostic parameters were average VDR (AUROC: 0.852 and 0.909) and inferior VDR (AUROC: 0.820 and 0.941) in nonhighly and highly myopic eyes, respectively. Inferior VDR showed better diagnostic ability than most of the other OCT measurements including peripapillary RNFL thickness and macular GCIPL thickness in highly myopic eyes. Accordingly, OCTA measurements can be useful for diagnosing glaucoma in highly myopic eyes, especially when using calculated indices such as average VDR or inferior VDR.

Positional Change of Optic Nerve Head Vasculature during Axial Elongation as Evidence of Lamina Cribrosa Shifting: Boramae Myopia Cohort Study Report 2

PURPOSE

To investigate the positional change of central retinal vasculature and vascular trunk to deduce the change in the lamina cribrosa (LC) during axial elongation.

DESIGN

Prospective cohort study.

PARTICIPANTS

Twenty-three healthy myopic children (46 eyes).

METHODS

Participants had undergone a full ophthalmologic examination and axial length measurement every 6 months for 2 years. Using spectral-domain OCT, circle scans centered around the optic disc in the glaucoma progression analysis mode, which enabled capturing of the same positions throughout the entire study period, and enhanced depth imaging of the deep optic nerve head complex were performed. Infrared imaging of the circle scans was used to measure the changes in the angles between the first and final visits. The angle between the major superior and inferior retinal arteries was measured along the circle scan twice: from the center of the circle scan and from the central retinal vascular trunk, respectively. The positional change of the retinal vascular trunk also was measured.

MAIN OUTCOME MEASURES

Change in vascular angle and position of vascular trunk with axial elongation and associated factors.

RESULTS

The vascular angle measured from the center of the circle scan did not change (P = 0.247), whereas the angle measured from the central retinal arterial trunk decreased with axial elongation (P < 0.001). A generalized estimating equation analysis revealed that the factors associated with angle decrease were axial elongation (P = 0.004) and vascular trunk dragging (P < 0.001). The extent of vascular trunk dragging was associated with axial elongation (P < 0.001) and increased border length with marginal significance (P = 0.053), but the extent of dragging could not be explained fully by their combination. The major directionality of dragging was mostly to the nasal side of the optic disc, with large variations among participants.

CONCLUSIONS

During axial elongation, the retinal vasculature at the posterior pole was unchanged, whereas the position of the central vascular trunk was dragged nasally. Because the central retinal vascular trunk is embedded in the LC, its dragging indicates nasal shifting of the LC, which could explain the vulnerability of myopic eyes to glaucomatous optic neuropathy.

Relationship between retinal artery trajectory and axial length in Japanese school students

PURPOSE

The trajectories of the supratemporal and infratemporal retinal arteries are associated with the position of the nerve fiber layer defects of glaucomatous eyes. However, no reports have thus far been published on changes in the retinal artery trajectory (RA trajectory) along with growth. Thus, the purpose of this study was to investigate the differences in the RA trajectories of elementary and junior high school students and the associations with axial length (AL).

STUDY DESIGN

Prospective cross-sectional observational study.

METHODS

In total, 122 right eyes of healthy elementary school students (61 boys, 61 girls) and 170 right eyes of healthy junior high school students (83 boys, 87 girls) were studied. The AL was measured and color fundus photographs were taken, and used for the analysis. The RA trajectory was plotted in the color fundus photographs and fitted to a second-degree polynomial equation, [Formula: see text], using ImageJ. The coefficient "a" represented the steepness of the trajectories. The differences in the RA trajectories and ALs of elementary and junior high school students were determined using the Mann-Whitney test. The association between the RA trajectory and AL was determined using the Spearman rank correlation.

RESULTS

The AL and the RA trajectory of the junior high school students were significantly greater than those of the elementary school students (P < 0.001). The RA trajectory was significantly associated with the AL in both elementary (r = 0.26, P = 0.005) and junior high (r = 0.32, P < 0.001) school students.

CONCLUSIONS

Junior high school students have a longer AL and narrower RA trajectory than do elementary school students. A longer AL is associated with a narrower RA trajectory in both elementary and junior high school students.

Predicting the risk of parafoveal scotoma in myopic normal tension glaucoma: role of optic disc tilt and rotation

PurposeThe purpose of the study was to evaluate the factors associated with development of parafoveal scotoma in early myopic normal tension glaucoma (NTG).Patients and methodsNinety-nine myopic NTG patients with mean deviation (MD) >-6.0 decibels (dB) were enrolled. Parafoveal scotoma was defined as a visual field (VF) defect within 10° of fixation with at least one point at P<1% lying at the four innermost central points. Systemic factors, optic disc characteristics including tilt ratio, rotation degree, β-zone parapapillary atrophy, disc hemorrhage, and peripapillary retinal nerve fiber layer and macular ganglion cell-inner plexiform layer (mGCIPL) thickness parameters using optical coherence tomography were evaluated. Logistic regression analysis was performed to identify factors associated with the development of parafoveal scotoma.ResultsThe mean spherical equivalent refractive error and MD were -6.07±2.83 diopters and -3.29±1.70 dB, respectively. Among 99 eyes, 42 (42.42%) showed parafoveal scotoma. Eyes with parafoveal scotoma had greater disc tilt, lesser disc rotation, lower MD, thinner minimum mGCIPL, and a higher proportion of VF defect in the superior hemifield than eyes without parafoveal scotoma. Multivariate logistic regression showed that all these parameters were significantly associated with development of parafoveal scotoma (P=0.047, P=0.011, P=0.032, P=0.010, and P=0.001, respectively).ConclusionIn addition to the previously reported risk factors, optic disc characteristics, such as tilt ratio and optic disc rotation, were also significantly associated with development of parafoveal scotoma in patients with myopic NTG.

Optic Nerve Sheath as a Novel Mechanical Load on the Globe in Ocular Duction

Purpose

The optic nerve (ON) sheath's role in limiting duction has been previously unappreciated. This study employed magnetic resonance imaging (MRI) to demonstrate this constraint on adduction.

Methods

High-resolution, surface coil axial MRI was obtained in 11 normal adults, 14 subjects with esotropia (ET) having normal axial length (AL) < 25.8 mm, 13 myopic subjects with ET and mean AL 29.3 ± 3.3 (SD) mm, and 7 subjects with exotropia (XT). Gaze angles and ON lengths were measured for scans employing eccentric lateral fixation in which an ON became completely straightened.

Results

In all groups, ON straightening occurred only in the adducting, not abducting, eye. Adduction at ON straightening was 26.0 ± 8.8° in normal subjects, not significantly different from XT at 22.2 ± 11.8°. However, there was significant increase in comparable adduction in ET to 36.3 ± 9.3°, and in myopic ET to 33.6 ± 10.7° (P < 0.04). Optic nerve length at straightening was 27.6 ± 2.7 mm in normals, not significantly different from 28.2 ± 2.8 mm in ET and 27.8 ± 2.7 mm in XT. In myopic ET, ON length at straightening was significantly reduced to 24.0 ± 2.9 mm (P < 0.002) and was associated with globe retraction in adduction, suggesting ON tethering.

Conclusions

Large adduction may exhaust length redundancy in the normally sinuous ON and sheath, so that additional adduction must stretch the sheath and retract or deform the globe. These mechanical effects are most significant in ET with axial myopia, but may also exert traction on the posterior sclera absent strabismus or myopia. Tethering by the ON sheath in adduction is an important, novel mechanical load on the globe.

Update on the Prevalence, Etiology, Diagnosis, and Monitoring of Normal-Tension Glaucoma

Glaucoma is a leading cause of blindness worldwide. Normal-tension glaucoma (NTG) is a type of open-angle glaucoma with intraocular pressure measurements always 21 mm Hg or less. A controversy surrounding NTG is the question of whether it should be regarded as a disease within the spectrum of primary open-angle glaucoma or as a distinctive disease entity. Nonetheless, NTG does have distinctive features compared with primary open-angle glaucoma: intraocular pressure-independent risk factors for development of NTG, characteristic patterns of structural and functional damage, and a unique disease course. This review provides an overview and update on the current issues surrounding the prevalence, etiology, diagnosis, and monitoring of NTG.