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

Diagnostic Performance for Detection of Glaucomatous Structural Damage Using Pixelwise Analysis of Retinal Thickness Measurements

Purpose

To compare the diagnostic accuracy of thickness measurements of individual and combined macular retinal layers to discriminate 188 glaucomatous and 148 glaucoma suspect eyes from 362 healthy control (HC) eyes on a pixel-by-pixel basis.

Methods

For this retrospective study, we manually corrected the segmentations of posterior pole optical coherence tomography (OCT) scans to determine the thickness of the nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), the ganglion cell complex (GCC), and the total neural retina (TR). For each eye, the total number of pixels with thickness values less than the fifth percentile of the HC distribution was used to create a receiver operating characteristic (ROC) curve for each layer and for layer combinations.

Results

Using total abnormal pixel count criteria to discriminate glaucoma from HC eyes, the individual layers with the highest area under the ROC curve (AUC) were the NFL and GCL; IPL performance was significantly lower (P < 0.05). GCC had a significant higher AUC (94.3%) than individual the AUC of the NFL (92.3%) (P = 0.0231) but not higher than AUC of the GCL (93.4%) (P = 0.3487). The highest AUC (95.4%) and sensitivity (85.1%) at 95% specificity was found for the Boolean combination of NFL or GCL. The highest AUC is not significantly higher (P = 0.0882) than the AUC of the GCC but the highest sensitivity is significantly higher than the sensitivity of the GCC. This pattern was similar for discriminating between suspect and HC eyes (P = 0.0356).

Conclusions

Using pixel-based methods, the diagnostic accuracy of NFL and GCL exceeded that of IPL and TR. GCC had equivalent performance as NFL and GCL. The specific spatial locations within the posterior pole that exhibit best performance vary depending on which layer is being assessed. Recognizing this dependency highlights the importance of considering multiple layers independently, as they offer complementary information for effective and comprehensive diagnosis.

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.

Real-Time Risk Score for Glaucoma Mass Screening by Spectral Domain Optical Coherence Tomography: Development and Validation

Purpose

To develop and validate a risk score assessable in real-time using only retinal thickness-related values measured by spectral domain optical coherence tomography alone for use in population-based glaucoma mass screenings.

Methods

A total of 7572 participants (aged 35-74 years) underwent spectral domain optical coherence tomography examination annually between 2016 to 2021 in a population-based setting. We selected 284 glaucoma cases and 284 controls, matched by age and sex, from 11,487 scans in 2016. We conducted multivariable logistic regression with backward stepwise selection of retinal thickness-related variables to develop the diagnostic models. The developed risk scores were applied to all participants in 2018 (9720 eyes), and we randomly selected 723 scans for validation. Additional validation using the Humphrey field analyzer was conducted on 129 eyes in 2020. We assessed the models using sensitivity, specificity, the area under the receiver operating characteristic curve and positive and negative predictive values.

Results

The best-predicting model achieved an area under the receiver operating characteristic curve of 0.97 (95% confidence interval, 0.96-0.98) with a sensitivity of 0.93 and specificity of 0.91. The validation dataset showed a positive predictive value of 90.8% for high-risk scorers, corresponding to 6.2% of the population, and negative predictive value of 88.2% for low-risk scorers, corresponding to 85.2%. Sensitivity and specificity for glaucoma diagnosis were 0.85 and 0.91, when we set the risk score cut-off at 90 points out of 100.

Conclusions

This risk score could be used as a valid index for glaucoma screening in a population-based setting.

Translational Relevance

The score is feasible by installing a simple computer application on an existing spectral domain optical coherence tomography and will help to improve the accuracy and efficiency of glaucoma screening.

Reference Database of Inner Retinal Layer Thickness and Thickness Asymmetry in Healthy Thai Adults as Measured by the Spectralis Spectral-Domain Optical Coherence Tomography

INTRODUCTION

The study aimed to determine a reference database of the thickness and intraocular thickness asymmetry of total retina, retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) in healthy Thai subjects measured by the Spectralis spectral-domain optical coherence tomography.

METHODS

This cross-sectional study recruited the healthy subjects age ≥18 years, having spherical refraction within ±6 diopters and cylindrical refraction ±3 diopters, from a hospital's personnel and the people visiting the ophthalmology department. Only 1 eye of each subject was randomly selected for an analysis. Macular images were obtained using posterior pole thickness scan protocol over a 24° × 24° area at the center of the fovea. The automated retinal thickness segmentation values of total retina and three inner retinal layers were calculated for the mean and the mean intraocular thickness difference between superior and inferior retinal hemispheres. The influence of age, gender, and axial length on thickness and thickness asymmetry of individualized retinal layer was evaluated.

RESULTS

252 subjects were included in study with a mean (SD) age of 46.7 (15.8) years, and 120 (47.6%) were males. According to the Early Treatment Diabetic Retinopathy Study map, the inner ring area was the thickest location of the total retina (range; 326.0-341.5 µm), GCL (range; 47.7-52.7 µm), and IPL (range; 39.9-42.1 µm), whereas the thickest location of RNFL was at the outer ring area (range; 18.8-47.5 µm). For posterior pole intraocular thickness asymmetry, the greatest mean ± SD difference was observed for total retina (9.0 ± 2.2 µm), followed by RNFL (9.9 ± 3.2 µm) and GCL (2.7 ± 0.6 µm), and the lowest mean difference was noted for IPL (2.4 ± 0.5 µm). The thickness and thickness asymmetry of each retinal layer were variably influenced by age, gender, and axial length; however, these factors had a minimal influence on the thickness asymmetry maps of GCL and RNFL.

CONCLUSION

The reference database of the macular thickness and thickness asymmetry from this study would be beneficial in determining physiologic variations of the OCT parameters in the healthy Thai population.

Overexpression of BMP4 protects retinal ganglion cells in a mouse model of experimental glaucoma

PURPOSE

Activation of bone morphogenetic protein (BMP) 4 signaling promotes the survival of retinal ganglion cell (RGC) after acute injury. Chordin-like 1 (CHRDL1) is an endogenous BMP antagonist. In this study, we researched whether CHRDL1 was involved in BMP4 signaling and regulation of RGC degeneration in a mouse model of glaucoma.

METHODS

Magnetic microbeads were intracameral injected to induce experimental glaucoma in a mouse model. A recombinant adeno-associated virus (rAAV) system was designed for overexpression of BMP4 or CHRDL1 in mouse retina. Immunohistochemistry and hematoxylin-eosin (HE) stains were performed to identify changes in retinal morphology. Electroretinogram (ERG) recordings were used to assess changes in visual function.

RESULTS

The mRNA expression levels of Bmp4 and its downstream BMPRIa, small mothers against decapentaplegic 1 (Smad1), were significantly upregulated in retinas with glaucoma. RGC survival was significantly enhanced in the beads + AAV-BMP4 group and significantly reduced in the beads + AAV-CHRDL1 group, compared with the beads + AAV-EGFP group. Similar results were observed in retinal explant culture in vitro. Consistent with these findings, the photopic negative response (PhNR)responses in ERG, which indicate RGC function, were restored in mice overexpressing BMP4, whereas a-wave and b-wave responses were not. Activation of CHRLD1 inhibited Smad1/5/8 phosphorylation and exacerbated RGC damage. The expression of Glial fibrillary acidic protein (GFAP) was decreased significantly in beads + AAV-BMP4 group.

CONCLUSIONS

BMP4 promoted RGC survival and visual function in an experimental glaucoma model. Activation of CHRDL1 exaggerated RGC degeneration by inhibiting the BMP4/Smad1/5/8 pathway. The mechanism of BMP4/Smad1/5/8 pathway may be related to the inhibition of glial cell activation. Our studies suggested that BMP4 and CHRLD1 might serve as therapeutic targets in glaucoma.