Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-Source Optical Coherence Tomography Study

Assessment interocular symmetry of peripapillary vessel density in young myopes with optical coherence tomographic angiography

PURPOSE

The purpose of our study was to evaluate the interocular symmetry and distribution of peripapillary vessel density in young myopic eyes.

METHODS

A cross-sectional observational study was designed. A total of 174 eyes of 87 young myopic patients were recruited in this study. According to spherical equivalent (SE), 48 eyes were classified as mild myopia with a mean SE of - 2.12D (SD 0.66D), 66 as moderate myopia with a mean SE of - 4.50D (SD 0.87D), and 60 as high myopia with a mean SE of - 7.39D (SD 1.30D). Optical coherence tomography angiography (OCTA) was used to measure the vessel density. The distribution and interocular symmetry of peripapillary vessel densities were analyzed.

RESULTS

The vessel densities in the whole image, peripapillary, superior and inferior sectors were significantly lower in the high myopia group than in the mild or moderate myopia group (All P < 0.001), and the density in the nasal sector was significantly lower in the high myopia group than in the mild group. And most interesting, the vessel densities in the inside disc and temporal sector showed no difference among the three myopic groups (All P > 0.05). By Pearson correlation analysis, the vessel densities in the whole image, peripapillary, superior, inferior and nasal sectors were negatively correlated with axial length (AL) and SE (All P < 0.001), but vessel densities in the inside disc and temporal sector did not show this correlation (All P > 0.05). Interocular symmetry was observed in all the vascular parameters through paired-samples t-tests (All P > 0.05), intraclass correlation coefficient (ICC) and Pearson correlation analysis (All P < 0.001).

CONCLUSION

The density of radial peripapillary capillaries decreased in the myopic eye with axial elongation, and optical vascular parameters showed significant interocular symmetry among young myopic eyes.

Ganglion Cell Complex Analysis: Correlations with Retinal Nerve Fiber Layer on Optical Coherence Tomography

The aim of this review is to analyze the correlations between the changes in the ganglion cell complex (GCC) and the retinal nerve fiber layer (RNFL) on optical coherence tomography in different possible situations, especially in eyes with glaucoma. For glaucoma evaluation, several studies have suggested that in the early stages, GCC analysis, especially the thickness of the infero and that of the inferotemporal GCC layers, is a more sensitive examination than circumpapillary RNFL (pRNFL). In the moderate stages of glaucoma, inferior pRNFL thinning is better correlated with the disease than in advanced cases. Another strategy for glaucoma detection is to find any asymmetry of the ganglion cell-inner plexiform layers (GCIPL) between the two macular hemifields, because this finding is a valuable indicator for preperimetric glaucoma, better than the RNFL thickness or the absolute thickness parameters of GCIPL. In preperimetric and suspected glaucoma, GCC and pRNFL have better specificity and are superior to the visual field. In advanced stages, pRNFL and later, GCC reach the floor effect. Therefore, in this stage, it is more useful to evaluate the visual field for monitoring the progression of glaucoma. In conclusion, GCC and pRNFL are parameters that can be used for glaucoma diagnosis and monitoring of the progression of the disease, with each having a higher accuracy depending on the stage of the disease.

Evaluation of vessel density in healthy subjects with family history of glaucoma

OBJECTIVES

To investigate whether any microvascular changes are present in optic disc, peripapillary or maculary regions in healthy subjects with a family history of glaucoma.

METHODS

A total of 82 healthy subjects including 42 first-degree relatives of primary open-angle glaucoma (POAG) and 40 controls were enroled in this cross-sectional study. Global and sectoral vessel density (VD) measurements excluding large vessels, retina nerve fibre layer (RNFL) and macula ganglion cell (mGCC) thicknesses were obtained from a combined optical coherence tomography-angiography (OCT-A) and spectral-domain OCT system. Effect size (ES) was used for evaluating the magnitude of the statistically significant difference. Area under receiver operating characteristic curves (AUCs) were used to examine the ability of parameters to differentiate first-degree relatives to controls.

RESULTS

There was no significant difference in RNFL and mGCC thicknesses between groups. Although lower VD measurements in optic disc, peripapillary region, and macula were observed in the first-degree relatives, statistically significant mean difference (3.13 ± 0.87, p = 0.001) and large ES (0.80) were in only lower nasal sector of peripapillary region. Inter-eye asymmetry of supero-nasal VD was also statistically higher (3.74 ± 2.55 vs 1.89 ± 1.64) with a large ES in the first-degree relatives (p < 0.001, ES = 0.86). AUC for differentiating first-degree relatives from controls was highest for inter-eye asymmetry of supero-nasal sector VD (0.74, p < 0.001), followed by lower nasal sector VD (0.72, p < 0.001).

CONCLUSION

Compared to controls, first-degree relatives of patients with POAG were found to have significantly greater inter-eye asymmetry in supero-nasal peripapillary VD and less VD in the lower nasal peripapillary region.

Interleaved Optical Coherence Tomography: Clinical and Laboratory Biomarkers in Patients with Diabetic Macular Edema

(1) Background: The global burden of diabetes mellitus (DM) has been estimated to reach 600 million patients worldwide by 2040. Approximately 200 million people will develop diabetic retinopathy within this time frame. Diabetic macular edema (DME) is a severe, vision-threatening complication that can develop at any stage of diabetic retinopathy, and it represents the main cause of vision loss in patients with DM. Its harmful consequences on visual function could be prevented with timely recognition and treatment. (2) Methods: This study assessed the clinical (demographic characteristics, diabetic evolution, and systemic vascular complications); laboratory (glycated hemoglobin, metabolic parameters, capillary oxygen saturation, and renal function); ophthalmologic exam; and spectral-domain optical coherence tomography (SD–OCT) (macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, temporal inner, inferior outer, superior outer, nasal outer, and temporal outer thicknesses, disruption of the ellipsoid zone, and disruption of the inner retinal layers (DRIL) parameters in three groups of individuals: healthy controls (HC), patients with DME and type 1 DM (T1DM—group A), and patients with DME and type 2 DM (T2DM—group B) to identify novel correlations between them that would open a path to new pathogenetic hypotheses and, implicitly, to the identification of new therapeutic methods, as part of a tailored treatment within the concept of precision medicine. (3) Results: The duration of DM was significantly longer in group A as compared with group B, as were the prevalence of smoking and systemic vascular complications. Capillary oxygen saturation and estimated glomerular filtration rates were significantly lower, and serum creatinine levels were significantly higher in group A as compared to group B. Regarding the OCT findings, DME had a predominantly eccentric pattern, and the right eye was more severely affected in both groups of patients. Significantly higher values were obtained in group B as compared to group A for the following OCT biomarkers: macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, inferior outer and nasal outer thickness. The disruption of the ellipsoid zone was significantly more prevalent within group A, whereas the overall disruption of the retinal inner layers (DRIL) was identified significantly more frequently in group B. (4) Conclusions: Whereas systemic and laboratory biomarkers were more severely affected in patients with DME and T1DM, the OCT quantitative biomarkers revealed significantly higher values in patients with DME and T2DM.

Hemiretinal Asymmetry in Peripapillary Vessel Density in Healthy, Glaucoma Suspect, and Glaucoma Eyes

PURPOSE

To investigate hemiretinal asymmetry in radial peripapillary capillary vessel area density (VAD) of healthy, glaucoma suspect, and glaucoma eyes of varying severity and its diagnostic utility for glaucoma.

DESIGN

Population-based, cross-sectional study.

METHODS

Optic disc scans (6 × 6 mm) were collected on optical coherence tomography angiography (OCTA) to obtain VAD and on optical coherence tomography (OCT) to measure circumpapillary retinal nerve fiber layer (RNFL) thickness. Hemiretinal difference in VAD (hdVAD) was defined as the absolute difference between superior and inferior hemiretinal VAD. Age-adjusted multivariable linear regression of hdVAD on glaucoma severity was performed. Areas under curves (AUCs) were calculated from predicted probabilities generated by multiple logistic regression of glaucoma severity on age-adjusted single and combined parameters.

RESULTS

A total of 1,043 eyes of 1,043 participants (587 healthy, 270 suspect, 67 mild, 54 moderate, 65 severe glaucoma) were included. After age adjustment, mean hdVAD was similar between healthy and suspect (P = .225), higher in mild vs suspect (P < .001), and higher in moderate vs mild (P = .018), but lower in severe vs moderate (P = .001). AUCs of hdVAD were highest for discriminating mild (0.685) and moderate (0.681) glaucoma from healthy. Combining hdVAD and global RNFL (gRNFL) yielded the highest AUCs of all parameters for mild (0.818) and any POAG (0.859) and resulted in significantly better diagnostic accuracy than either hdVAD or gRNFL alone (P < .05 for all comparisons).

CONCLUSIONS

hdVAD is higher in early glaucoma and may help with early detection when damage is focal, but its diagnostic ability appears less robust in advanced glaucoma when damage is diffuse.

Circumpapillary optical coherence tomography angiography differences in perimetrically affected and unaffected hemispheres in primary open-angle glaucoma and the preperimetric fellow eye

Purpose

Evaluation of circumpapillary vessel density (VD) and perfusion density (PD) on optical coherence tomography angiography (OCTa) in mild-moderate glaucoma patients having unilateral visual field defects, with their fellow eyes and controls.

Methods

Both eyes of 24 patients having a definitive nasal step or arcuate scotoma in one hemisphere of one eye only, and 24 controls, underwent OCTa.

Results

In eyes with a superior field defect, the superior/inferior quadrant ratios, (SQ/IQ) of 3 mm scan of VD and PD were significantly higher in eyes with a superior arcuate scotoma than fellow eyes (P = 0.03,0.02) as also controls, (P = 0.004,0.001). The mean percentage loss of inferior quadrant VD between control to fellow eyes, and superior nasal step eyes were similar, 20.19%/19.57% respectively, P = 0.85, while a loss in arcuate scotoma eyes was 38.81% (P = 0.001). The percentage decrease in inferior quadrant PD in fellow eyes was 14.70%, superior nasal step 23.39%, and an arcuate scotoma 34.74% (P = 0.02). Eyes with a superior nasal step had significantly lower VD and PD absolute values in the inferior quadrant OCTa in 3 mm and 6 mm circle scan only as compared to control eyes, VD, P = 0.03,0.04/PD, P = 0.008,0.02. Fellow eyes of superior field defects had significantly lower VD and PD absolute values in the inferior quadrant in 3 mm and 6 mm circle scan as compared to control eyes, VD, P = 0.006,0.04/PD, P = 0.01,0.03. Eyes with an isolated inferior field defect in only one eye, showed a significant decrease in both VD and PD in all quadrants as compared to fellow eyes and control eyes. A significant positive correlation was found between VD and RNFL thickness in peripapillary superior unaffected quadrants in eyes with superior field defects and inferior unaffected quadrants in inferior defects (P = 0.001 and 0.01).

Conclusion

There was a statistically significant increasing SQ/IQ ratio and percentage loss of vascular parameters from control to fellow eyes, those with a superior nasal step, and those with a superior arcuate scotoma. Inferior VFDs appeared to be associated with a more generalized circulatory loss. The asymmetry between hemispheres and between eyes could be used as a biomarker for early glaucomatous neuropathy.

Evaluation of Asymmetry in Right and Left Eyes of Normal Individuals Using Extracted Features from Optical Coherence Tomography and Fundus Images

BACKGROUND

Asymmetry analysis of retinal layers in right and left eyes can be a valuable tool for early diagnoses of retinal diseases. To determine the limits of the normal interocular asymmetry in retinal layers around macula, thickness measurements are obtained with optical coherence tomography (OCT).

METHODS

For this purpose, after segmentation of intraretinal layer in threedimensional OCT data and calculating the midmacular point, the TM of each layer is obtained in 9 sectors in concentric circles around the macula. To compare corresponding sectors in the right and left eyes, the TMs of the left and right images are registered by alignment of retinal raphe (i.e. diskfovea axes). Since the retinal raphe of macular OCTs is not calculable due to limited region size, the TMs are registered by first aligning corresponding retinal raphe of fundus images and then registration of the OCTs to aligned fundus images. To analyze the asymmetry in each retinal layer, the mean and standard deviation of thickness in 9 sectors of 11 layers are calculated in 50 normal individuals.

RESULTS

The results demonstrate that some sectors of retinal layers have signifcant asymmetry with P < 0.05 in normal population. In this base, the tolerance limits for normal individuals are calculated.

CONCLUSION

This article shows that normal population does not have identical retinal information in both eyes, and without considering this reality, normal asymmetry in information gathered from both eyes might be interpreted as retinal disorders.

Macular imaging with optical coherence tomography in glaucoma

With the advent of spectral-domain optical coherence tomography, imaging of the posterior segment of the eye can be carried out rapidly at multiple anatomical locations, including the optic nerve head, circumpapillary retinal nerve fiber layer, and macula. There is now ample evidence to support the role of spectral-domain optical coherence tomography imaging of the macula for detection of early glaucoma. Macular spectral-domain optical coherence tomography measurements demonstrate high reproducibility, and evidence on its utility for detection of glaucoma progression is accumulating. We present a comprehensive review of macular spectral-domain optical coherence tomography imaging emerging as an essential diagnostic tool in glaucoma.

Ability of Macular Inner Retinal Layer Thickness Asymmetry Evaluated by Optical Coherence Tomography to Detect Preperimetric Glaucoma

Purpose

We assessed the ability to detect preperimetric glaucoma (PPG) based on asymmetry in the thickness of the macular inner retinal layers measured by spectral-domain optical coherence tomography.

Methods

We studied 45 normal eyes and 50 PPG eyes retrospectively. Three-dimensional optical coherence tomography macular area scans were used to obtain the thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer/inner plexiform layer (GCL/IPL), and ganglion cell complex (GCC). We calculated the thickness differences between the upper and lower macular hemispheres for the corresponding superpixels, then evaluated the mean absolute value of the thickness differences and the number of superpixels in which the thickness difference was greater than X µm, where X is an integer number from 1 to 10. Areas under the receiver operating characteristic curves (AUCs) for their PPG diagnostic performances were compared to the average thickness measurements of the total and hemiretinal sectors. X was determined at the maximum AUC value.

Results

The AUC for the mean absolute value of the difference in GCL/IPL thickness (0.923) was higher than the difference in RNFL and GCC thickness (0.710 and 0.905, respectively). The AUC for the number of superpixels in which the GCL/IPL thickness difference was greater than 8 µm (X = 8) was 0.914. The ability to diagnose PPG using these GCL/IPL parameters was statistically higher than for total or superior and inferior hemiretinal GCL/IPL thicknesses.

Conclusions

Asymmetry in the thickness of the GCL/IPL shows good PPG diagnostic performance.

Translational Relevance

This approach would be useful in the early detection of glaucoma.

Bilateral asymmetry improved accuracy when assessing glaucomatous vision-related quality of life impairment

Bilateral asymmetry has been used in optical coherence tomography tests to find early damage to the optic nerve. However, limited studies have quantitatively evaluated bilateral asymmetry in electrophysiological disorders in patients with glaucoma. The aim of the study was to evaluate bilateral asymmetry in pattern visual evoked potentials (PVEPs) and conventional clinical markers as well as its potential use in detecting glaucomatous impairment. After investigating 60 glaucomatous patients (120 eyes) and 65 age and sex-matched normal control subjects (130 eyes) using uni- and multivariable analysis, we found that vision-related quality of life (VRQOL) impairment was significantly associated with larger bilateral asymmetry index (BAI) of clinical markers. Rasch-calibrated National Eye Institute Visual Function Questionnaire-25 scores were significantly associated with the BAI in PVEPs latency in 15 minutes check size (β = -0.478, 95% confidence interval [CI], -0.708 to -0.248, P < .001) and the BAI in visual field mean deviation (β = -0.249, 95% CI, -0.454 to -0.044, P = .018) according to multivariable analysis. Bilateral asymmetry in objective and subjective functional measurements was quantitatively associated with glaucomatous VRQOL impairment. This finding may help bridge the gap in understanding between patients and clinicians, and increase awareness of how glaucomatous neuropathic progression may interfere with patients' daily life.

Intereye and intraeye asymmetry analysis of retinal microvascular and neural structure parameters for diagnosis of primary open-angle glaucoma

PURPOSE

To investigate the diagnostic values of intereye or intraeye asymmetry of retinal perfused vessel density and neural structure parameters for detection of glaucoma.

METHODS

In total, 152 healthy subjects and 72 bilateral primary open-angle glaucoma (POAG) patients were enrolled. Total POAG group contains all glaucoma patients. Early to moderate POAG group contains patients whose binocular mean defect values were larger than -12 dB. The retinal perfused vessel densities were acquired using optic coherence tomography angiography. The neural structure parameters include RNFL, GCC thickness and its derivative indices like focal loss volume percentage (FLV%) and global loss volume percentage (GLV%). Intereye asymmetry equaled to the absolute difference of parameters between paired eyes. Intraeye asymmetry was defined as absolute difference between the inferior and superior hemisphere values from one random selected eye. The areas under the receiver operating characteristic curves (AUROCs) were calculated to evaluate diagnostic ability.

RESULTS

From pairwise comparison analysis of ROC curves, the intereye asymmetric parameters with the largest diagnostic accuracy were FLV and GLV% (AUROC = 0.944), which were significantly superior to the intereye asymmetry of perfused vessel density in peripapillary area and parafoveal area (P < 0.05). Particularly, the intereye asymmetry of FLV% (AUROC = 0.926) and GLV% (AUROC = 0.950) showed excellent diagnostic precision for detecting early to moderate glaucoma patients. However, the intraeye asymmetry of microvascular parameters and neural structure parameters showed fair diagnostic ability for identifying POAG patients.

CONCLUSIONS

The intereye asymmetry of neural structure parameters, particularly the FLV% and GLV%, outperformed the microvascular parameters for identifying POAG patients.

Intraocular retinal thickness asymmetry in early stage of primary open angle glaucoma and normal tension glaucoma

AIM

To investigate the intraocular retinal thickness asymmetry of peripapillary retinal nerve fiber layer (pRNFL) and macular layers measured by spectral-domain optical coherence tomography (SD-OCT) in patients with early stage of primary open angle glaucoma (POAG) and normal tension glaucoma (NTG).

METHODS

A total of 117 patients with early stage of glaucoma (54 patients with POAG and 63 patients with NTG) and 32 normal subjects were recruited for the study. The pRNFL thickness, total macular layer (TML) thickness, and isolated inner macular layer (IML) thickness were measured by SD-OCT. Hemisphere TML thickness asymmetry measured by the posterior pole asymmetry scan was evaluated. Thickness differences of pRNFL and IML between superior and inferior quadrants were calculated. Asymmetry indices (AIs) of the pRNFL, TML and isolated IML were also computed. Areas under the receiver-operating characteristic curves (AROCs) were generated to determine the diagnostic capabilities of different parameters.

RESULTS

Intraocular pRNFL thickness differences and AIs between the superior and inferior quadrants were significantly different between normal and NTG groups (P=0.009 and P<0.001, respectively). Intraocular pRNFL thickness differences and AIs between the temporal-superior and temporal-inferior sectors were also significantly different between normal and NTG groups (P=0.035 and P<0.001, respectively). The thickness differences and AIs of TML between superior and inferior hemispheres were significantly different between normal and NTG groups (P=0.001 and P=0.001, respectively) and between normal and POAG groups (P=0.032 and P=0.020, respectively). The thickness differences and AIs of macular ganglion cell layer (mGCL) between superior and inferior quadrants were significantly different between normal and NTG groups (P=0.013 and P=0.004, respectively), and between NTG and POAG groups (P=0.015 and P=0.012, respectively). The thickness difference of TML between superior and inferior hemispheres showed the highest diagnostic capability for early NTG eyes (AROC=0.832).

CONCLUSION

Intraocular retinal thickness asymmetry in pRNFL, TML and mGCL are found in early stage of NTG. Hemisphere TML thickness asymmetry is also found in POAG eyes. Asymmetry analysis of retinal thickness can be an adjunctive modality for early detection of glaucoma.

Inter-eye Asymmetry of Optical Coherence Tomography Angiography Vessel Density in Bilateral Glaucoma, Glaucoma Suspect, and Healthy Eyes

PURPOSE

To investigate inter-eye retinal vessel density asymmetry in healthy, glaucoma suspect, and mild-to-moderate glaucoma subjects, and its potential utility for early detection of glaucomatous damage.

DESIGN

Cross-sectional study.

METHODS

In 153 subjects including 55 healthy, 32 glaucoma suspect, and 66 glaucoma subjects enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS), vessel density was obtained from optical coherence tomography angiography (OCT-A) macular and optic nerve head scans. Thickness of peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (mGCC) was measured with spectral-domain optical coherence tomography (SD-OCT) scans. Inter-eye asymmetry was calculated by taking the absolute value of difference in vessel density and thickness between the right and left eyes.

RESULTS

Inter-eye retinal vessel density asymmetry parameters were significantly different among the 3 groups. Glaucoma suspects had significantly higher peripapillary and macular inter-eye vessel density asymmetries compared to healthy groups in univariate (1.1% vs 2.0%, P = .014 and 1.2% vs 2.5%, P = .027, respectively) and multivariate analyses (P = .007 and P = .038, respectively). No significant differences in asymmetry of thickness parameters were found between glaucoma suspect and healthy groups (all P > .718). However, significant differences in asymmetry of thickness parameters between glaucoma suspects and glaucoma patients (P < .01) were found for all parameters.

CONCLUSION

Inter-eye vessel density asymmetry can be quantified by OCT-A measurement. Glaucoma suspects have significantly greater vessel density asymmetry than healthy eyes. Longitudinal studies are needed to better characterize the relationship of vessel density asymmetry with the development and progression of glaucoma.

Microstructural visual pathway abnormalities in patients with primary glaucoma: 3 T diffusion kurtosis imaging study

AIM

To evaluate microstructural visual pathway damage in patients with primary glaucoma (PG) by using 3 T diffusion kurtosis imaging (DKI).

MATERIALS AND METHODS

The study was approved by the ethics committee, and all participants provided written informed consent. Ten patients with PG were examined. Twenty healthy individuals served as control subjects. DKI was performed with a GE Silent 3 T magnetic resonance imaging (MRI) unit. Mean diffusivity (MD), fractional anisotropy (FA), and mean kurtosis (MK) maps were automatically created. Mean MK, MD, and FA values were calculated for each part of the visual pathway.

RESULTS

No abnormalities in the shape and signal intensity were observed along the entire visual pathway in patients and the control group on the conventional MRI. Higher MD, and lower MK and FA were observed in the optic nerves (ON), lateral geniculate nucleus (LGN), optic radiations (OR), and visual cortex (VCx) of PG patients, as compared with control subjects. A significantly higher MD was observed in the ON (p<0.01), and significantly lower FA was observed in OR (p<0.05). Additionally, significantly lower MK was observed in the ON, LGN, and VCx, except for OR (p<0.01). Changes of DKI parameters in the ON were the most distinct.

CONCLUSION

Glaucoma is a complex neurological disease that affects the entire visual pathway. MK derived from DKI would be a better biomarkers than FA and MD in detecting microstructural damage.