Correlation of Retinal Nerve Fiber Layer Thickness and Axial Length on Fourier Domain Optical Coherence Tomography

Superficial Retinal Vessel Density and Foveal Avascular Zone in Myopic Anisometropia: An OCTA-Based Study in Young Chinese Children

This retrospective study investigated superficial retinal vessel density (SRVLD) and foveal avascular zone (FAZ) area using optical coherence tomography angiography (OCTA) in children with myopic anisometropia. We included 84 eyes of 42 individuals with myopic anisometropia and no posterior segment abnormalities. All eyes underwent OCTA. Individual SRVLD and FAZ area were measured on OCTA. Using a paired t-test, we compared the interocular difference between the fellow eyes for all the measurements. SRVLD was significantly higher in the relatively more myopic eyes than in the fellow eyes in the whole population and in patients with an interocular difference of >1.5 D (p = 003 and 0.01, respectively). In patients with an interocular difference of ≤1.5 D in spherical equivalent refraction, only the nasal sector showed higher SRVLD in the less myopic eyes. SRVLD in the whole image and parafoveal sector was significantly lower in the dominant eye (paired t-test, p = 003 and 0.03, respectively), while other locations showed no difference. The area, perimeter, and circularity index in FAZ parameters showed no difference. SRVLD showed no significant differences between the two types of eyes, with an interocular difference of ≤1.5 D but increased in the relatively more myopic eyes than in the fellow eyes in children with myopic anisometropia, with an interocular difference of >1.5 D. Increasing SRVLD may show a compensatory increase to maintain retinal function and thus maintain normal visual function in the relatively more myopic fellow eyes. As the study to use patients as self-control with OCTA analysis in both eyes, this study provides some reference value for further interpretation of the pathogenesis of anisometropia.

Determinants of macular ganglion cell-inner plexiform layer thickness in normal Chinese adults

Background

Demographic, systemic and ocular factors may impact macular ganglion cell–inner plexiform layer (GCIPL) thickness measurements. This study aimed to investigate the influences of multiple potential determinants of macular GCIPL thickness in normal Chinese adults.

Methods

This was a retrospective study conducted on 225 normal eyes from 225 healthy Chinese adults. GCIPL thickness were obtained using Cirrus high-definition optical coherence tomography (OCT). The age, gender, laterality, spherical equivalent (SE) refractive error, intraocular pressure (IOP), axial length (AL), central cornea thickness (CCT), circumpapillary retinal nerve fibre layer (pRNFL) thickness and OCT signal strength were recorded and their respective effect on GCIPL thickness parameters were evaluated.

Results

The mean (± SD) average, minimum, superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal GCIPL thickness was 84.56 ± 5.36, 81.32 ± 5.58, 83.08 ± 5.37, 85.70 ± 5.95, 87.15 ± 6.26, 85.07 ± 6.11, 82.46 ± 5.76, and 83.88 ± 5.59 μm, respectively. Determinants of thinner GCIPL thickness were older age (P = 0.001–0.117; effects enhanced if age over 40 years), thinner pRNFL (all P < 0.001), and weaker signal strength (all P < 0.001). No significant difference was found between males and females (P = 0.069–0.842), and between right eyes and the left eyes (P = 0.160–0.875) except that of superonasal GCIPL thickness (P < 0.001). There was no significant correlation between GCIPL thickness and SE, IOP, CCT, and AL (P = 0.135–0.968).

Conclusions

Individual determinants associated with thinner GCIPL thickness were older age (particularly over 40 years of age), thinner pRNFL, and weaker OCT signal strength. This is relevant in comprehensively understanding the normative data and differentiating normal aging from abnormalities.

The Role of Multimodal Approach in the Assessment of Glaucomatous Damage in High Myopes

Purpose

To compare the optic disc structure and peripapillary retinal function between high myopes with and without glaucoma and to address the differential role of papillary optical coherence tomography angiography (OCT-A) and circumpapillary microperimetry (cpMP) on the diagnosis and prognosis of this patients.

Patients and Methods

It is a cross-sectional study including 30 high myopic patients (60 eyes), divided into 15 with (GG) and 15 without glaucoma (NGG). Demographic and clinical data were collected from patient records. Papillary structure (peripapillary retinal nerve fiber layer thickness, ppRNFLTs) and vascularization (small vessel densities, SVD´s) were assessed with SD-OCT (RTVue XR Avanti, with AngioVue system, Optovue^®). cpMP was carried out with the MP-3 microperimeter (Nidek^®).

Results

The GG were older, had lower best-corrected visual acuities and higher intraocular pressures and axial lengths (p<0.001). The GG showed lower values in all ppRNFLTs (p<0.05), lower values in all SVDs (p<0.001), except the SVD-inside disc (p=0.638) and lower retinal sensitivities within all cpMPs (p<0.001). The adjusted analysis computing the best two parameters per exam revealed that the anatomical model including the ppRNFLT-inferior and ppRNFLT-temporal and the vascular model including SVD-inferior and SVD-superior had the best discrimination power between groups, with cross-validated AUROCs of 0.9599 and 0.9921, respectively.

Conclusion

Despite the apparent superiority of the papillary vascular study, a multimodal approach including the papillary anatomic and circumpapillary microperimetric assessments can be the new way on the diagnosis and prognosis of glaucoma in high myopia.

Birth Weight Is a Significant Predictor of Retinal Nerve Fiber Layer Thickness at 36 Weeks Postmenstrual Age in Preterm Infants

PURPOSE

To assess retinal nerve fiber layer (RNFL) thickness in preterm infants.

DESIGN

Prospective observational study.

METHODS

We imaged 83 awake infants (159 eyes) at 36 ± 1 weeks postmenstrual age (defined as the time elapsed between the first day of the last maternal menstrual period and the time at imaging) using a handheld optical coherence tomography (OCT) system at the bedside. Blinded graders semi-automatically segmented RNFL in the papillomacular bundle (-15 to +15° relative to the fovea-optic nerve axis). We correlated RNFL thickness and 7 characteristics of interest (sex, race, ethnicity, gestational age, birth weight, stage of retinopathy at prematurity, and presence of pre-plus or plus disease) via univariable and multivariable regressions.

RESULTS

RNFL was 3.4 μm thicker in the right eyes than in the left eyes (P < .001). Among 7 characteristics, birth weight was the only independent predictor of RNFL thickness (P < .001). A 250-g increase in birth weight was associated with 5.2 μm (95% confidence interval: 3.3-7.0) increase in RNFL thickness. Compared with very preterm infants, extremely preterm infants had thinner RNFL (58.0 ± 10.7 μm vs 63.4 ± 10.7 μm, P = .03), but the statistical significance disappeared after adjustment for birth weight (P = .25). RNFL thickness was 11.2 μm thinner in extremely low birth weight infants than in very low birth weight infants (55.5 ± 8.3 μm vs. 66.7 ± 10.2 μm; P < .001). The difference remained statistically significant after adjustment for gestational age.

CONCLUSION

Birth weight is a significant independent predictor of RNFL thickness near birth, implying that the retinal ganglion cells reserve is affected by intrauterine processes that affect birth weight.

Altered visual functions, macular ganglion cell and papillary retinal nerve fiber layer thickness in early-treated adult PKU patients

Purpose

Retinal changes are poorly described in early treated phenylketonuria (ETPKU). We aimed to investigate possible visual functional and ocular microstructural changes in adult patients with ETPKU. Optical coherence tomography (OCT) and its angiography (OCTA) data from patients with PKU were compared to healthy controls.

Methods

In this prospective, monocentric, cross-sectional, case-control study 50 patients with ETPKU and 50 healthy subjects were evaluated with OCT and OCTA. Measurements were performed on right eyes. The following visual function parameters were studied: best corrected visual acuity (BCVA), spherical equivalent (SE), contrast sensitivity and near stereoacuity; microstructural parameters: retinal nerve fiber layer thickness (RNFLT), ganglion cell layer (GCC) thickness, focal loss of volume (FLV), global loss of volume (GLV), peripapillary, papillary vessel density (VD), ocular axial length (AL) and intraocular pressure (IOP).

Results

Among functional tests there were significant differences in contrast sensitivity at 1.5 (p < 0.001), 6 (p < 0.013), 12 (p < 0.001), 18 (p < 0.003) cycles per degree, in near stereoacuity (Titmus Wirt circles, p < 0.001) and in best corrected visual acuity (BCVA, p < 0.001). A statistically significant, moderate positive linear correlation was observed between BCVA and average Phe levels over the last ten years (β = 0.49, p < 0.001). The average (p < 0.001), superior (p < 0.001) inferior GCC (p < 0.001), the FLV (p < 0.003), GLV (p < 0.001) and the average RNFLT (p < 0.004) values of the PKU group were significantly lower than the controls. The serum phenylalanine level (Phe) in the PKU group negatively correlated with inferior (−0.32, p < 0.007), superior (r = −0.26, p < 0.028) and average (−0.29 p < 0.014) RNFL and with AL (−0.32, p < 0.026). In AL we detected a significant difference (p < 0.04) between the good and suboptimal dietary controlled group. There was no significant difference between the ETPKU and control group in the measured vessel density parameters and in IOP.

Conclusions

Our results suggest that functional and ocular microstructural defects are present in patients with PKU, and some of them may depend on dietary control. The mechanism is unclear, but the correlation indicates the importance of strict dietary control in terms of preservation of retinal functions.

Local Macular Thickness Relationships between 2 OCT Devices

PURPOSE

To compare local ganglion cell-inner plexiform layer (GCIPL) thickness measurements between 2 OCT devices and to explore factors that may influence the difference in measurements.

DESIGN

Cross-sectional study.

PARTICIPANTS

Sixty-nine glaucoma eyes (63 patients) with evidence of central damage or mean deviation (MD) of -6.0 dB or worse on a 24-2 visual field (VF).

METHODS

Cirrus and Spectralis OCT macular volume scans were exported, data from the central 20° of both OCT devices were centered and aligned, and 50 × 50 arrays of 0.4° × 0.4° superpixels were created. We estimated nonparametric (Spearman's) correlations and used Bland-Altman plots to compare GCIPL thickness measurements between the two OCTs at the superpixel level. Factors that may have influenced the differences between thickness measurements between the two devices were explored with linear mixed models.

MAIN OUTCOME MEASURES

Pooled and individual-eye Spearman's correlation and agreement between thickness measurements from the two devices.

RESULTS

The median 24-2 VF MD was -6.8 dB (interquartile range [IQR], -4.9 to -12.3 dB). The overall pooled Spearman's correlation between the two devices for all superpixels and eyes was 0.97 (P < 0.001). The median within-eye correlation coefficient was 0.72 (IQR, 0.59-0.79). Bland-Altman plots demonstrated a systematic bias in most individual eyes, with Spectralis GCIPL measurements becoming larger than Cirrus measurements with increasing superpixel thickness. The average superpixel thickness and distance to the fovea influenced the thickness difference between the two devices in multivariate models (P < 0.001).

CONCLUSIONS

Local macular thickness measurements from the Spectralis and Cirrus devices are highly correlated, but not interchangeable. Differences in thickness measurements between the two devices are influenced by the location of superpixels and their thickness.

Relationship between preoperative high intraocular pressure and retinal nerve fibre layer thinning after glaucoma surgery

Recent reports show varying results regarding peripapillary retinal nerve fibre layer (RNFL) thickness after intraocular pressure (IOP)-lowering glaucoma surgery. We hypothesised that different levels of the preoperative IOP influence RNFL thickness. A total of 60 patients (60 eyes) with glaucoma, who underwent glaucoma surgery and had a stable postoperative mean IOP < 22 mmHg, were enrolled. The RNFL thickness was measured using spectral domain optical coherence tomography, before and at 3–6 months after surgery. The preoperative peak IOP, 37.4 ± 10.8 mmHg, decreased to a postoperative mean IOP of 14.8 ± 3.5 mmHg (p < 0.001). The average RNFL thickness was significantly reduced from 75.6 ± 17.7 μm to 70.2 ± 15.8 μm (p < 0.001). In subgroup analyses, only patients with a preoperative peak IOP ≥ median value (37 mmHg) exhibited significant RNFL thinning (9.7 ± 6.6 μm, p < 0.001) associated with a higher preoperative peak IOP (r = 0.475, p = 0.008). The RNFL thinning was evident for a few months after glaucoma surgery in patients with a higher preoperative peak IOP, although the postoperative IOP was stable.

Additive Role of Optical Coherence Tomography Angiography Vessel Density Measurements in Glaucoma Diagnoses

Purpose

This study compared the glaucoma diagnostic abilities of optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). In addition, the possibility of enhancing diagnostic capability by combining the two modalities was investigated.

Methods

A total of 131 healthy eyes and 113 glaucomatous eyes were imaged by both OCT and OCTA. In OCT, glaucoma was defined as when the color of the superior or inferior quadrant of the peripapillary retinal nerve fiber layer thickness map was yellow (borderline, <5%) or red (outside normal limits, <1%). In OCTA, glaucoma was determined using the cut-off value of the superior or inferior peripapillary vessel density, calculated after receiver operating characteristic curve analysis. Sensitivity and specificity were determined by OCT alone, by OCTA alone, or by OCT and OCTA combined.

Results

The sensitivity of OCT (86.7%) was better than that of OCTA (74.3%), whereas the specificity of OCTA (87.0%) was better than that of OCT (67.9%). When these two modalities were combined, both sensitivity and specificity were enhanced (90.3% and 92.4%, respectively). Among the 131 eyes, 32 were misdiagnosed as glaucomatous by OCT but accurately diagnosed as normal by OCTA. These eyes were myopic, with a longer axial length and a thinner and temporally displaced peak of peripapillary retinal nerve fiber layer thickness, causing the false positive result in OCT.

Conclusions

When OCTA was combined with OCT, the specificity of glaucoma diagnoses were enhanced. OCTA may compensate for the shortcomings of OCT in the diagnosis of glaucoma.

Optical coherence tomography angiography of superficial retinal vessel density and foveal avascular zone in myopic children

Purpose

To assess the superficial retinal vessel density (SRVD) and foveal avascular zone (FAZ) in myopic children using optical coherence tomography angiography (OCTA).

Methods

174 eyes of 89 subjects with myopia and 101 eyes of 54 age-matched, emmetropic volunteers (control group) were enrolled in this study. The mean age of the subjects and controls was 13.9 (SD ± 2.3) and 13.1 (SD ± 2.4), respectively. Myopia was defined as spherical equivalent <– 1.0 diopter. Emmetropic subjects were defined as having spherical equivalent from + 0.5 to − 0.5 diopter. The mean axial length (AL) in myopic patients was 24.58 mm (SD ± 1.22) and 22.88 mm (SD ± 0.65) in the controls. Every patient underwent a complete ophthalmological examination and OCTA, using AngioVue (Optovue). The FAZ area and superficial retinal vessel density, including whole SRVD, fovea SRVD and parafovea SRVD, were analyzed. Foveal thickness (FT) and parafoveal thickness (PFT) were also taken into consideration.

Results

Whole SRVD, parafovea SRVD and PFT were significantly higher in controls than in the myopic subjects (p < 0.001, p = 0.007, p < 0.01, respectively). The FAZ area was significantly larger in the myopic group compared to the controls (p = 0.010). Fovea SRVD and FT did not differ significantly between the groups (p = 0.740, p = 0.795 respectively). In overall subjects we found significant correlation between axial length and all the investigative parameters: age, FAZ area, whole SRVD, parafovea SRVD, fovea SRVD, PFT, FT (p < 0.001, p = 0.014, p = 0.008, p < 0.005, p = 0.014, p = 0.010, p = 0.024, respectively). Analyzing only myopic group we confirmed that AL was significantly correlated with age, whole SRVD and parafovea SRVD (p < 0.001, p = 0.014, p = 0.009, respectively). Similarly, in this group the spherical equivalent also correlated with age, whole SRVD and parafovea SRVD (p < 0.001, p = 0.007, p = 0.005, respectively). Such correlations were not confirmed in the non–myopic group.

Conclusions

Our results suggest that superficial retinal vessel density is decreased and FAZ area is enlarged in the entire group of the myopic children compared to emmetropic subjects. Longitudinal observation of these young patients is needed to determine the relevance of the microvascular alterations in future.

The relationship between age, axial length and retinal nerve fiber layer thickness in the normal elderly population in Taiwan: The Chiayi eye study in Taiwan

AIMS

To interpret how the thickness of the peripapillary retinal nerve fiber layer (RNFL) changes with increasing age, axial length, or anterior chamber depth as measured by spectral domain optical coherence tomography (OCT) in the normal elderly population in Taiwan.

METHODS

A total of 82 volunteers (143 eyes) were enrolled. Generalized estimating equations were used to evaluate the correlation.

RESULTS

The RNFL was significantly thinner in the superonasal (p = 0.004), inferotemporal (p = 0.046), and temporolower (p = 0.009) segments with age. The same trend was also observed in the superotemporal (p = 0.330) segment, although it was not statistically significant. The global RNFL thickness decreased by 4.97 μm per decade (β = -0.497; p = 0.021), and thinning was significant in the superonasal (-9.90 μm per decade, p < 0.001) and temporolower (-6.78 μm per decade, p < 0.001) segments; the same trend showed borderline significance in the superotemporal (-6.96 μm per decade, p = 0.073) and inferotemporal (-7.23 μm per decade, p = 0.059) segments. In eyes with longer axial length, the RNFLs significantly decreased in the non-temporal segments. Global RNFL thickness decreased by 3.086 μm for each additional millimeter of axial length (β = -3.086; p < 0.001).

CONCLUSIONS

Changes in RNFL thickness were correlated with age in the superonasal, superotemporal, inferotemporal, and temporolower segments, and were correlated with axial length in the non-temporal segments. Anterior chamber depth was not correlated with RNFL thickness.