Optical coherence tomography longitudinal evaluation of retinal nerve fiber layer thickness in glaucoma

Detecting glaucoma worsening using optical coherence tomography derived visual field estimates

Multiple glaucoma studies have attempted to generate visual field (VF) mean deviation (MD) estimates using cross-sectional optical coherence tomography (OCT) data. However, whether such models offer any value in detecting longitudinal VF progression is unclear. We address this by developing a machine learning (ML) model to convert OCT data to MD and assessing its ability to detect longitudinal worsening. In this study, we created a model dataset of 70,575 paired OCT/VFs to train an ML model to convert OCT to VF-MD. We created a separate progression dataset of 4,044 eyes with ≥ 5 paired OCT/VFs to assess the ability of OCT-derived MD to detect worsening. The progression dataset eyes had 2 additional unpaired VFs (≥ 7 total) to establish a "ground truth" rate of progression defined by MD slope. We used the ML model to generate longitudinal OCT-MD estimates for each OCT scan for progression dataset eyes. We calculated MD slopes after substituting/supplementing VF-MD with OCT-MD and measured the ability to detect progression. We labeled true progressors using a ground truth MD slope < 0.5 dB/year calculated from ≥ 7 VF-MD measurements. We compared the area under the curve (AUC) of MD slopes calculated using both VF-MD (with < 7 measurements) and OCT-MD. Because we found OCT-MD substitution had a statistically inferior AUC to VF-MD, we simulated the effect of reducing OCT-MD mean absolute error (MAE) on the ability to detect worsening. Our model's OCT-MD estimates had an MAE of 1.62 dB (better than that of any previously published models). However, we found the AUC of MD slopes with partial OCT-MD substitution was significantly worse than the VF-MD slope. Supplementing VF-MD with OCT-MD also did not improve AUC, regardless of MAE. We found that OCT-MD estimates needed an MAE ≤ 1.00 dB before AUC was statistically similar to VF-MD alone. Overall, our ML model converting OCT data to VF-MD had error levels lower than those published in prior work and was inferior to VF-MD data for detecting trend-based VF progression. Our data suggest that future models converting OCT data to VF-MD must achieve better prediction errors (MAE ≤ 1 dB) to be clinically valuable at detecting VF worsening.

Detecting Glaucoma Worsening Using Optical Coherence Tomography Derived Visual Field Estimates

Objective

Multiple studies have attempted to generate visual field (VF) mean deviation (MD) estimates using cross-sectional optical coherence tomography (OCT) data. However, whether such models offer any value in detecting longitudinal VF progression is unclear. We address this by developing a machine learning (ML) model to convert OCT data to MD and assessing its ability to detect longitudinal worsening.

Design

Retrospective, longitudinal study.

Participants

A model dataset of 70,575 paired OCT/VFs to train an ML model converting OCT to VF-MD. A separate progression dataset of 4,044 eyes with ≥ 5 paired OCT/VFs to assess the ability of OCT-derived MD to detect worsening. Progression dataset eyes had two additional unpaired VFs (≥ 7 total) to establish a "ground truth" rate of progression defined by MD slope.

Methods

We trained an ML model using paired VF/OCT data to estimate MD measurements for each OCT scan (OCT-MD). We used this ML model to generate longitudinal OCT-MD estimates for progression dataset eyes. We calculated MD slopes after substituting/supplementing VF-MD with OCT-MD and measured the ability to detect progression. We labeled true progressors using a ground truth MD slope <0.5 dB/year calculated from ≥ 7 VF-MD measurements. We compared the area under the curve (AUC) of MD slopes calculated using both VF-MD (with <7 measurements) and OCT-MD. Because we found OCT-MD substitution had a statistically inferior AUC to VF-MD, we simulated the effect of reducing OCT-MD mean absolute error (MAE) on the ability to detect worsening.

Main Outcome Measures

AUC.

Results

OCT-MD estimates had an MAE of 1.62 dB. AUC of MD slopes with partial OCT-MD substitution was significantly worse than the VF-MD slope. Supplementing VF-MD with OCT-MD also did not improve AUC, regardless of MAE. OCT-MD estimates needed an MAE ≤ 1.00 dB before AUC was statistically similar to VF-MD alone.

Conclusion

ML models converting OCT data to VF-MD with error levels lower than published in prior work (MAE: 1.62 dB) were inferior to VF-MD data for detecting trend-based VF progression. Models converting OCT data to VF-MD must achieve better prediction errors (MAE ≤ 1 dB) to be clinically valuable at detecting VF worsening.

Reversing Aging and Improving Health Span in Glaucoma Patients: The Next Frontier?

How to cite this article: Dada T, Mahalingam K, Bhartiya S. Reversing Aging and Improving Health Span in Glaucoma Patients: The Next Frontier? J Curr Glaucoma Pract 2024;18(3):87-93.

The Impact of Achieving Target Intraocular Pressure on Glaucomatous Retinal Nerve Fiber Layer Thinning in a Treated Clinical Population

PURPOSE

To estimate the effect of being below and above the clinician-set target intraocular pressure (IOP) on rates of glaucomatous retinal nerve fiber layer (RNFL) thinning in a treated real-world clinical population.

DESIGN

Retrospective cohort study.

METHODS

A total of 3256 eyes (1923 patients) with ≥5 reliable optical coherence tomography scans and 1 baseline visual field test were included. Linear mixed-effects modeling estimated the effects of the primary independent variables (mean target difference [measured IOP - target IOP] and mean IOP, mm Hg) on the primary dependent variable (RNFL slope, µm/y) while accounting for additional confounding variables (age, biological sex, race, baseline RNFL, baseline pachymetry, and disease severity). A spline term accounted for differential effects when above (target difference >0 mm Hg) and below (target difference ≤0 mm Hg) target pressure.

RESULTS

Eyes below and above target had significantly different mean RNFL slopes (-0.44 vs -0.71 µm/y, P < .001). Each 1 mm Hg increase above target had a 0.143 µm/y faster rate of RNFL thinning (P < .001). Separating by disease severity, suspect, mild, moderate, and advanced glaucoma had 0.135 (P = .002), 0.116 (P = .009), 0.203 (P = .02), and 0.65 (P = .22) µm/y faster rates of RNFL thinning per 1 mm Hg increase, respectively.

CONCLUSIONS

Being above the clinician-set target pressure is associated with more rapid RNFL thinning in suspect, mild, and moderate glaucoma. Faster rates of thinning were also present in advanced glaucoma, but statistical significance was limited by the lower sample size of eyes above target and the optical coherence tomography floor effect.

Comparison of Patterns of Structural Progression in Primary Open Angle Glaucoma and Pseudoexfoliation Glaucoma

PRCIS

Primary open angle glaucoma and pseudoexfoliation glaucoma showed different progression patterns of the retinal nerve fiber layer and ganglion cell-inner plexiform layer thinning in OCT-guided progression analysis.

PURPOSE

To compare the patterns of progression of retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) thinning by guided progression analysis (GPA) of optical coherence tomography (OCT) in primary open angle glaucoma (POAG) and pseudoexfoliation glaucoma (PXG).

MATERIALS AND METHODS

The progression of RNFL and GCIPL thinning was assessed by the GPA of Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA). By overlaying the acquired images of the RNFL and GCIPL thickness-change maps, the topographic patterns of progressive RNFL and GCIPL thinning were evaluated. The rates of progression of RNFL and GCIPL thinning were analyzed and compared between patients with POAG and those with PXG.

RESULTS

Of the 248 eyes of 248 patients with POAG (175 eyes of 175 patients) or PXG (73 eyes of 73 patients) enrolled, 156 POAG eyes and 48 PXG eyes were included. Progressive RNFL thinning was significantly more common in PXG than in POAG ( P =0.005). According to the RNFL progression-frequency maps, progression appeared mainly in the superotemporal and inferotemporal areas in POAG, whereas it had invaded more into the temporal area in PXG. According to the GCIPL maps, progression was most common in the inferotemporal area in both POAG and PXG. The average progression rate of GCIPL thinning was faster in PXG than in POAG ( P =0.013), and when analyzed in 2 halves (superior/inferior), the progression rate of the inferior half was faster in PXG than in POAG ( P =0.011).

CONCLUSIONS

OCT GPA showed progression patterns of RNFL and GCIPL thinning in POAG and PXG. Understanding the specific patterns of progressive RNFL and GCIPL thinning according to glaucoma type may prove helpful to glaucoma-patient treatment and monitoring.

Retinal mid-peripheral capillary free zones are enlarged in cognitively unimpaired older adults at high risk for Alzheimer's disease

BACKGROUND

Compared to standard neuro-diagnostic techniques, retinal biomarkers provide a probable low-cost and non-invasive alternative for early Alzheimer's disease (AD) risk screening. We have previously quantified the periarteriole and perivenule capillary free zones (mid-peripheral CFZs) in cognitively unimpaired (CU) young and older adults as novel metrics of retinal tissue oxygenation. There is a breakdown of the inner retinal blood barrier, pericyte loss, and capillary non-perfusion or dropout in AD leading to potential enlargement of the mid-peripheral CFZs. We hypothesized the mid-peripheral CFZs will be enlarged in CU older adults at high risk for AD compared to low-risk individuals.

METHODS

20 × 20° optical coherence tomography angiography images consisting of 512 b-scans, 512 A-scans per b-scan, 12-µm spacing between b-scans, and 5 frames averaged per each b-scan location of the central fovea and of paired major arterioles and venules with their surrounding capillaries inferior to the fovea of 57 eyes of 37 CU low-risk (mean age: 66 years) and 50 eyes of 38 CU high-risk older adults (mean age: 64 years; p = 0.24) were involved in this study. High-risk participants were defined as having at least one APOE e4 allele and a positive first-degree family history of AD while low-risk participants had neither of the two criteria. All participants had Montreal Cognitive Assessment scores ≥ 26. The mid-peripheral CFZs were computed in MATLAB and compared between the two groups.

RESULTS

The periarteriole CFZ of the high-risk group (75.8 ± 9.19 µm) was significantly larger than that of the low-risk group (71.3 ± 7.07 µm), p = 0.005, Cohen's d = 0.55. The perivenule CFZ of the high-risk group (60.4 ± 8.55 µm) was also significantly larger than that of the low-risk group (57.3 ± 6.40 µm), p = 0.034, Cohen's d = 0.42. There were no significant differences in foveal avascular zone (FAZ) size, FAZ effective diameter, and vessel density between the two groups, all p > 0.05.

CONCLUSIONS

Our results show larger mid-peripheral CFZs in CU older adults at high risk for AD, with the potential for the periarteriole CFZ to serve as a novel retinal vascular biomarker for early AD risk detection.

Neurovascular segregation of the retinal nerve fiber layer in glaucoma

The imaging data of one eye from 154 healthy and 143 glaucoma participants were acquired to evaluate the contributions of the neuronal and vascular components within the retinal nerve fiber layer (RNFL) for detecting glaucoma and modeling visual field loss through the use of optical coherence tomography (OCT) and OCT angiography. The neuronal and vascular components within the circumpapillary RNFL were independently evaluated. In healthy eyes, the neuronal component showed a stronger association with age (r = -0.52, p < 0.001) compared to measured RNFL thickness (r = -0.46, p < 0.001). Using the neuronal component alone improved detection of glaucoma (AUC: 0.890 ± 0.020) compared to measured RNFL thickness (AUC: 0.877 ± 0.021; χ2 = 5.54, p = 0.019). Inclusion of the capillary components with the sectoral neuronal component resulted in a significant improvement in glaucoma detection (AUC: 0.927 ± 0.015; χ2 = 15.34, p < 0.001). After adjusting for potential confounders, AUC increased to 0.952 ± 0.011. Results from modeling visual field loss in glaucoma eyes suggest that visual field losses associated with neuronal thinning were moderated in eyes with a larger capillary component. These findings suggest that segregation of the neurovascular components could help improve understanding of disease pathophysiology and affect disease management in glaucoma.

Evaluation of effect of covıd-19 pandemic on anatomical and functional changes and vision-related quality of life in patients with glaucoma

BACKGROUND

To evaluate anatomical and functional changes and vision-related quality of life in patients whose glaucoma follow-up was disrupted by the COVID-19 restrictions.

METHODS

This retrospective observational study included 100 patients who were followed up at the glaucoma unit. For the patients whose follow-up evaluations were postponed due to COVID-19 restrictions, visual acuity (VA), intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, visual field parameters [mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI)], and the National Institute of Ophthalmology Visual Function Scale-25 (NEI-VFQ-25) score were evaluated based on the measurements performed at the last visit before COVID-19 (V1) and at the first visit after the removal of COVID-19 restrictions (V2).

RESULTS

The mean age of the patients was 61.1 ± 13.4 years, the mean follow-up time was 11.4 ± 4.2 months, and the mean interval between the last two visits was 7.2 ± 2.7 months. In the evaluation of the last two visits, VA was lower and IOP was higher at V2, and there was progression in the MD, PSD, and VFI values (p<0.05, for all). RNFL thickness progression was seen in 13-23% of the patients. According to the NEI-VFQ-25 evaluation, except for peripheral vision and near vision, all the remaining subscale scores and the total score were lower at V2 (p<0.05, for all).

CONCLUSIONS

This study demonstrates the devastating impact of the COVID-19 pandemic on the anatomical and functional changes and vision-related quality of life together in patients with glaucoma.

False-positive classification and associated factors in segmented macular layers and retinal nerve fiber layer analysis: Spectralis OCT deviation map study

The rates, patterns and associated factors for false-positive classification of deviation maps by Cirrus optical coherence tomography (OCT) have been reported. However, research on OCT layer-by-layer deviation maps is lacking. We aimed to determine the rates and associated factors for false-positive classification of segmented macular layers and retinal nerve fiber layer (RNFL) deviation maps of Spectralis OCT, and to identify false-positive patterns on segmented macular layers deviation maps. 118 healthy eyes of 118 normal participants who had undergone Spectralis OCT imaging were included. False-positive classification was determined by the area and location of yellow or red color-coded regions on the deviation map. The false-positive rates on the deviation maps were the highest on the ganglion cell layer map, followed by the inner plexiform layer, retinal layer, and RNFL maps. More myopic/less hyperopic refractive error was a factor significantly associated with higher false-positive classification on the RNFL deviation map, and three false-positive patterns were found on the segmented macular layers deviation maps. Spectralis OCT deviation maps should be interpreted carefully to avoid misdiagnosis, especially for eyes with higher degrees of myopic refractive error on the RNFL map, for which purpose, recognizing the characteristic false-positive patterns would be helpful in clinical practice.

Agreement of Diagnostic Classification Between Structural Parameters in Pre-Perimetric and Early Perimetric Glaucoma

PRCIS

In both pre-perimetric and early perimetric glaucoma, the diagnostic agreements between optic disk, retinal nerve fiber layer, and ganglion cell-inner plexiform layer parameters based on Cirrus HD-OCT normative database classification were mostly fair, suggesting that abnormal classification in 1 anatomic area may suffice for the diagnosis of glaucoma in early stages.

PURPOSE

To evaluate the agreement of normative database diagnostic classification between optic disk, retinal nerve fiber layer (RNFL), and ganglion cell-inner plexiform layer (GCIPL) in patients with early glaucoma.

METHODS

Retrospective cross-sectional study involving 66 eyes (66 patients) with pre-perimetric and 97 eyes (97 patients) with early perimetric glaucoma. Normative database diagnostic classifications were retrieved from Cirrus HD-OCT scans of 1 eye per participant. An eye was considered abnormal if any of the optic disk, RNFL, or GCIPL was abnormal (yellow or red color-coded classification). For combined parameters, the eye had to be flagged as abnormal by both classifications, regardless of the parameters that were abnormal (global or sectorial). The agreement was assessed with Cohen's Kappa statistics.

RESULTS

The agreement between RNFL and GCIPL was fair in both pre-perimetric (κ=0.25) and perimetric glaucoma (κ=0.21). Agreements between RNFL or GCIPL and optic nerve head parameters (rim area and vertical cup-to-disk ratio; VCDR) were inconclusive due to insufficient data ( P >0.05). Combining GCIPL and rim area agreed fairly with RNFL both in pre-perimetric (κ=0.21) and perimetric glaucoma (κ=0.33). The best classification agreement (moderate) was achieved with the comparison of RNFL-rim area versus VCDR (κ=0.48 in pre-perimetric, 0.45 in perimetric glaucoma). There were no significant differences between pre-perimetric and perimetric glaucoma coefficients of classification agreement.

CONCLUSIONS

The normative database diagnostic agreements between optic disk, RNFL, and GCIPL were mostly fair in both pre-perimetric and early perimetric glaucoma. Clinicians should not wait for multiple structures to show abnormality on OCT to diagnose early glaucoma.

Wide-Field Three-Dimensional Depth-Invariant Cellular-Resolution Imaging of the Human Retina

Three-dimensional (3D) cellular-resolution imaging of the living human retina over a large field of view will bring a great impact in clinical ophthalmology, potentially finding new biomarkers for early diagnosis and improving the pathophysiological understanding of ocular diseases. While hardware-based and computational adaptive optics (AO) optical coherence tomography (OCT) have been developed to achieve cellular-resolution retinal imaging, these approaches support limited 3D imaging fields, and their high cost and intrinsic hardware complexity limit their practical utility. Here, this work demonstrates 3D depth-invariant cellular-resolution imaging of the living human retina over a 3 × 3 mm field of view using the first intrinsically phase-stable multi-MHz retinal swept-source OCT and novel computational defocus and aberration correction methods. Single-acquisition imaging of photoreceptor cells, retinal nerve fiber layer, and retinal capillaries is presented across unprecedented imaging fields. By providing wide-field 3D cellular-resolution imaging in the human retina using a standard point-scan architecture routinely used in the clinic, this platform proposes a strategy for expanded utilization of high-resolution retinal imaging in both research and clinical settings.

Progression of Early Glaucomatous Damage: Performance of Summary Statistics From Optical Coherence Tomography and Perimetry

Purpose

Performance comparison of optical coherence tomography (OCT) and visual field (VF) summary metrics for detecting glaucomatous progression.

Methods

Thirty healthy control eyes (mean deviation [MD], -1.25 ± 2.03; pattern standard deviation [PSD] , 1.78 ± 0.77) and 91 patient eyes comprised of 54 glaucoma patients and 37 glaucoma suspects (MD, -1.58 ± 1.96; PSD, 2.82 ± 1.92) with a follow-up of at least 1 year formed a group to evaluate progression with event analyses (P-Event). A subset of eyes with an additional criterion of a minimum of four tests was used for trend analyses (P-Trend) (30 healthy controls and 73 patients). For P-Event analysis, test-retest variability thresholds (lower 5th percentile) were estimated with repeat tests within a 4-month period. A P-Event eye was considered a "progressor" if the difference between follow-up and baseline tests exceeded the variability thresholds. For the P-Trend analysis, rates of change were calculated based on least-squares regression. Negative rates with significant (P < 0.05) values were considered progressing. For a reference standard, 17 patient eyes were classified as definitely progressing based on clear evidence of structural and corresponding functional progression.

Results

Isolated OCT and VF summary metrics were either inadequately sensitive or not too specific. Combinations of OCT-OCT and OCT-VF metrics markedly improved specificity to nearly 100%. A novel combination of OCT metrics (circumpapillary retinal nerve fiber layer and ganglion cell layer) showed high precision, with 13 of the 15 statistical progressors confirmed as true positives.

Conclusions

Although relying solely on metrics is not recommended for clinical purposes, in situations requiring very high specificity and precision, combinations of OCT-OCT metrics can be used.

Translational Relevance

All available OCT and VF metrics can miss eyes with progressive glaucomatous damage and/or can falsely identify progression in stable eyes.

Effects of Cataract on Retinal Nerve Fiber Layer and Ganglion Cell-Inner Plexiform Layer Thickness on Swept Source Optical Coherence Tomography

PURPOSE

To evaluate the changes in peripapillary retinal nerve fiber layer (pRNFL) thickness and macular ganglion cell-inner plexiform layer (mGC-IPL) thickness measured by swept source optical coherence tomography (SS-OCT) following cataract surgery in patients with glaucoma.

METHODS

We included 42 glaucoma eyes and 42 case-matched normal eyes that underwent cataract surgery without complications. One matching set included one glaucoma eye and one case-matched normal eye. The age, sex, and cataract subtype scores were similar for each group. Before and within 3 months of surgery, we measured the pRNFL thickness and mGCIPL thickness by SS-OCT.

RESULTS

Following cataract surgery, the image quality (IQ) of SS-OCT improved in both groups. The thickness of the pRNFL and mGC-IPL increased in the mean values and all areas, except for pRNFL from 1 to 4 o'clock in the glaucoma group and at 1 o'clock in the normal group. Posterior subcapsular cataract was related to the change in IQ following surgery. The glaucoma and normal group showed greater pRNFL thickness change due to lesser preoperative pRNFL thickness. Furthermore, the mGC-IPL thickness change was greater in the glaucoma group because of lesser preoperative mGC-IPL thickness. By contrast, the normal group demonstrated greater mGC-IPL thickness change due to higher cortical cataract scores.

CONCLUSIONS

Cataracts caused the deterioration of the IQ in SS-OCT, thereby resulting in an undermeasurement of the pRNFL and mGC-IPL thickness. Preoperative pRNFL and mGC-IPL were negatively associated with postoperative pRNFL and mGCIPL thickness change in the glaucoma and normal groups. Therefore, ophthalmologists should particularly consider the effect of cataract while diagnosing glaucoma using SS-OCT.

[Optical coherence tomography and optical coherence tomography angiography for detecting glaucoma progression. Part 1. Study methods, measurement variability and the role of age-related changes]

This paper reviews the literature on the role of optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in the diagnosis of glaucoma and considers the significance of evaluating retinal nerve fiber layer and ganglion cell complex in assessment of glaucoma progression, variability and reproducibility of the method, as well as the influence of age-related retinal changes on the results, analyzes the role of OCTA in glaucoma monitoring. Optical coherence tomography is a modern standard for glaucoma diagnosis and monitoring, and OCTA shows high potential as an auxiliary diagnostic tool.

Clinical Applications of Artificial Intelligence in Glaucoma

Ophthalmology is one of the major imaging-intensive fields of medicine and thus has potential for extensive applications of artificial intelligence (AI) to advance diagnosis, drug efficacy, and other treatment-related aspects of ocular disease. AI has made impressive progress in ophthalmology within the past few years and two autonomous AI-enabled systems have received US regulatory approvals for autonomously screening for mid-level or advanced diabetic retinopathy and macular edema. While no autonomous AI-enabled system for glaucoma screening has yet received US regulatory approval, numerous assistive AI-enabled software tools are already employed in commercialized instruments for quantifying retinal images and visual fields to augment glaucoma research and clinical practice. In this literature review (non-systematic), we provide an overview of AI applications in glaucoma, and highlight some limitations and considerations for AI integration and adoption into clinical practice.

Wide-field optical coherence tomography deviation map for early glaucoma detection

BACKGROUND/AIMS

This study aimed to establish a wide-field optical coherence tomography (OCT) deviation map obtained from swept-source OCT (SS-OCT) scans. Moreover, it also aimed to compare the diagnostic ability of this wide-field deviation map with that of the peripapillary and macular deviation maps currently being used for the detection of early glaucoma (EG).

METHODS

Four hundred eyes, including 200 healthy eyes and 200 eyes with EG were enrolled in this retrospective observational study. Patients underwent a comprehensive ocular examination, including wide-field SS-OCT (DRI-OCT Triton; Topcon, Tokyo, Japan). The individual wide-field scan was converted into a uniform template using the fovea and optic disc centres as fixed landmarks. Subsequently, the wide-field deviation map was obtained via the comparison between individual wide-field data and a normative wide-field database that had been created by combining images of healthy eyes into a uniform template in a previous study. The ability of the new wide-field deviation map to distinguish between EG and healthy eyes was assessed by comparing it with conventional deviation maps based on the area under the receiver operating characteristic curve (AUC).

RESULTS

The wide-field deviation map obtained using the normative wide-field database showed the highest diagnostic ability for the diagnosis of EG (AUC=0.980 and 961 for colour-coded pixels presenting <5% and <1%, respectively) among various deviation maps. Its AUC was significantly superior to that of most conventional deviation maps (p<0.05). The wide-field deviation map demonstrated early structural glaucomatous damage well over a wider area.

CONCLUSION

The wide-field SS-OCT deviation map exhibited good performance for distinguishing between eyes with EG and healthy eyes. The visualisation of the wider damaged area on the wide-field deviation map could be useful for the diagnosis of EG in clinical settings.

Frequency of Optical Coherence Tomography Testing to Detect Progression in Glaucoma

PRCIS

With high specificity and less variability than perimetry, more frequent testing resulted in shorter time to detect progression, though a 6-month testing interval provides a reasonable trade-off for following glaucoma patients using optical coherence tomography (OCT).

PURPOSE

To investigate the time to detect progression in glaucomatous eyes using different OCT test intervals.

MATERIALS AND METHODS

Participants with manifest glaucoma from the African Descent and Glaucoma Evaluation Study (ADAGES), a multicenter, prospective, observational cohort study, were included. A total of 2699 OCT tests from 171 glaucomatous and 149 normal eyes of 182 participants, with at least 5 tests and 2 years of follow-up, were analyzed. Computer simulations (n=10,000 eyes) were performed to estimate time to detect progression of global circumpapillary retinal nerve fiber layer thickness (cpRNFL) measured with OCT tests. Simulations were based on different testing paradigms (every 4, 6, 12, and 24 mo) and different rates of change (µm/year). Time to detect significant progression ( P <0.05) at 80% and 90% power were calculated for each paradigm and rate of cpRNFL change.

RESULTS

As expected, more frequent testing resulted in shorter time to detect progression. Although there was clear disadvantage for testing at intervals of 24 versus 12 months (~22.4% time [25 mo] increase in time to progression detection) and when testing 12 versus 6 months (~22.1% time [20 mo] increase), the improved time to detect progression was less pronounced when comparing 6 versus 4 months (~11.5% time [10 mo] reduction).

CONCLUSION

With high specificity and less variability than perimetry, a 6-month testing interval provides a reasonable trade-off for following glaucoma patients using OCT.

Research Trends and Hotspots of Retinal Optical Coherence Tomography: A 31-Year Bibliometric Analysis

The emergence of optical coherence tomography (OCT) over the past three decades has sparked great interest in retinal research. However, a comprehensive analysis of the trends and hotspots in retinal OCT research is currently lacking. We searched the publications on retinal OCT in the Web of Science database from 1991 to 2021 and performed the co-occurrence keyword analysis and co-cited reference network using bibliometric tools. A total of 25,175 publications were included. There has been a progressive increase in the number of publications. The keyword co-occurrence network revealed five clusters of hotspots: (1) thickness measurements; (2) therapies for macular degeneration and macular edema; (3) degenerative retinal diseases; (4) OCT angiography (OCTA); and (5) vitrectomy for macular hole and epiretinal membrane. The co-citation analysis displayed 26 highly credible clusters (S = 0.9387) with a well-structured network (Q = 0.879). The major trends of research were: (1) thickness measurements; (2) therapies for macular degeneration and macular edema; and (3) OCTA. Recent emerging frontiers showed a growing interest in OCTA, vessel density, choriocapillaris, central serous chorioretinopathy, Alzheimer’s disease, and deep learning. This review summarized 31 years of retinal OCT research, shedding light on the hotspots, main themes, and emerging frontiers to assist in future research.

Regression-Based Strategies to Reduce Refractive Error-Associated Glaucoma Diagnostic Bias When Using OCT and OCT Angiography

Purpose

The purpose of this study was to correct refractive error-associated bias in optical coherence tomography (OCT) and OCT angiography (OCTA) glaucoma diagnostic parameters.

Methods

OCT and OCTA imaging were obtained from participants in the Hong Kong FAMILY cohort. The Avanti/AngioVue OCT/OCTA system was used to measure the peripapillary nerve fiber layer thickness (NFLT), peripapillary nerve fiber layer plexus capillary density (NFLP-CD), macular ganglion cell complex thickness (GCCT), and macular superficial vascular complex vascular density (SVC-VD). Healthy eyes, including ones with axial ametropia, were enrolled for analysis.

Results

A total of 1346 eyes from 792 participants were divided into 4 subgroups: high myopia (<−6D), low myopia (−6D to −1D), emmetropia (−1D to 1D), and hyperopia (>1D). After accounting for age, sex, and signal strength, multivariable regression showed strong dependence in most models for NFLT, GCCT, and NFLP-CD on axial eye length (AL), spherical equivalent (SE) refraction, and apparent optic disc diameter (DD). Optical analysis indicated that AL-related transverse optical magnification variations predominated over anatomic variations and were responsible for these trends. Compared to the emmetropic group, the false positive rates were significantly (Chi-square test P < 0.003) elevated in both myopia groups for NFLT, NFLP-CD, and GCCT. Regression-based adjustment of these diagnostic parameters with AL or SE significantly (McNemar test P < 0.03) reduced the elevated false positive rates.

Conclusions

Myopic eyes are biased to have lower NFLT, GCCT, and NFLP-CD measurements. AL- and SE-based adjustments were effective in mitigating this bias.

Translational Relevance

Adoption of these adjustments into commercial OCT systems may reduce false positive rates related to refractive error.

Discrimination Between Healthy Eyes and Those With Mild Glaucoma Damage Using Hemoglobin Measurements of the Optic Nerve Head

PRCIS

The Laguna ONhE, a software that measures the hemoglobin (Hb) concentration of the optic nerve head (ONH) from fundus photographs, demonstrated good accuracy in discriminating healthy eyes from eyes with mild glaucoma.

PURPOSE

The aim was to evaluate Hb concentration of the optic nerve to distinguish between healthy eyes and eyes with mild glaucoma.

METHODS

Eyes from patients with mild primary open angle glaucoma (MD > -6 dB) (n=58) and from healthy subjects (n=64) were selected. Retinal nerve fiber layer thickness measurements of all eyes were acquired with optical coherence tomography. Optic disc photographs were also obtained, and the images were analyzed using the Laguna ONhE software, which measures the amount of Hb in 24 sectors of the ONH. The software also calculates the Glaucoma Discriminant Function (GDF), an index that expresses the chance of the ONH being compatible with glaucoma. Areas under the receiver operating characteristic curve and sensitivities at fixed specificities of 90% and 95% of each Laguna ONhE parameter were calculated.

RESULTS

The mean retinal nerve fiber layer thickness and vertical cup/disc ratio of the control and glaucoma groups were 90.0±10.6 μm versus 66.28±9.85 μm ( P <0.001) and 0.5±0.09 versus 0.65±0.09 ( P <0.001), respectively. Total Hb (67.9±4.45 vs. 62.89±4.89, P <0.001) and GDF (11.57±15.34 vs. -27.67±20.94, P <0.001) were significantly higher in the control group. The Hb concentration was also significantly higher in 21 of the 24 sectors in the control group compared with the glaucoma group ( P <0.05). The GDF had the largest areas under the receiver operating characteristic curve (0.93), with 79.3% sensitivity at a fixed specificity of 95%.

CONCLUSION

Measurements of optic nerve Hb concentration using a colorimetry photographic device demonstrated good accuracy in discriminating healthy eyes from eyes with mild glaucoma. Further studies are need to understand vascular factors implicated in the development of glaucoma.

Distinguishing Healthy From Glaucomatous Eyes With Optical Coherence Tomography Global Circumpapillary Retinal Nerve Fiber Thickness in the Bottom 5th Percentile

PRCIS

Two novel, quantitative metrics, and 1 traditional metric were able to distinguish between many, but not all healthy and glaucomatous eyes in the bottom 5th percentile of global circumpapillary retinal nerve fiber layer (cpRNFL) thickness.

PURPOSE

To test the hypothesis that objective optical coherence tomography measures can distinguish between a healthy control with global cpRNFL thickness within the lower 5% of normal and a glaucoma patient with an equivalent cpRNFL thickness.

PATIENTS AND METHODS

A total of 37 healthy eyes from over 700 normative eyes fell within the bottom 5th percentile in global cpRNFL thickness. The global cpRNFL thickness of 35 glaucomatous eyes from 188 patients fell within the same range. For the traditional methods, the global cpRNFL thickness percentile and the global ganglion cell layer (GCL) thickness percentile for the central ±8 degrees, were calculated for all 72 eyes. For the novel cpRNFL method, the normalized root mean square (RMS) difference between the cpRNFL thickness profile and the global thickness-matched normative thickness profile was calculated. For the superior-inferior (SI) GCL method, the normalized mean difference in superior and inferior GCL thickness was calculated for the central ±8 degrees.

RESULTS

The best quantitative metric, the RMS cpRNFL method, had an accuracy of 90% compared with 81% for the SI GCL and 81% for the global GCL methods. As expected, the global cpRNFL had the worst accuracy, 72%. Similarly, the RMS cpRNFL method had an area under the curve of 0.93 compared with 0.83 and 0.84 for the SI GCL and global GCL methods, respectively. The global cpRNFL method had the worst area under the curve, 0.75.

CONCLUSION

Quantitative metrics can distinguish between most of the healthy and glaucomatous eyes with low global cpRNFL thickness. However, even the most successful metric, RMS cpRNFL, missed some glaucomatous eyes.

Comparison of Retinal Nerve Fiber Layer and Ganglion Cell-Inner Plexiform Layer Thickness Values Using Spectral-Domain and Swept-Source OCT

Purpose

To compare peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell-inner plexiform layer (mGCIPL) thickness measurements obtained with spectral domain optical coherence tomography (SD-OCT) and swept-source OCT (SS-OCT) using an OCT-angiography scanning protocol, and their ability to distinguish among patients with glaucoma, glaucoma suspects (GS), and healthy controls (HC).

Methods

Cross-sectional study of 196 eyes (81 glaucoma, 48 GS, and 67 HC) of 119 participants. Participants underwent peripapillary and macular OCT with SD-OCT and SS-OCT. Parameters of interest were average and sector-wise pRNFL and mGCIPL thickness. Inter-device agreement was investigated with Bland-Altman statistics. Conversion formulas were developed with linear regression. Diagnostic performances were evaluated with area under the receiver operating characteristic curves.

Results

Both SD-OCT and SS-OCT detected a significant pRNFL and mGCIPL thinning in glaucoma patients compared to HC and GS for almost all study sectors. A strong linear relationship between the two devices was present for all quadrants/sectors (R2 ≥ 0.81, P < 0.001), except for the nasal (R2 = 0.49, P < 0.001) and temporal (R2 = 0.62, P < 0.001) pRNFL quadrants. SD-OCT and SS-OCT measurements had a proportional bias, which could be removed with conversion formulas. Overall, the two devices showed similar diagnostic abilities.

Conclusions

Thickness values obtained with SD-OCT and SS-OCT are not directly interchangeable but potentially interconvertible. Both devices have a similar ability to discriminate glaucoma patients from GS and healthy subjects.

Translational Relevance

OCT-Angiography scans can be reliably used to obtain structural metrics in glaucoma patients.

Associated Factors and Distribution of Peripapillary Retinal Nerve Fiber Layer Thickness in Children by Optical Coherence Tomography: A Population-based Study

PURPOSE

To determine the distribution of peripapillary retinal nerve fiber layer (RNFL) thickness and its association with different demographic and ocular parameters in adolescents.

METHODS

The present study is part of the second phase of the Shahroud Schoolchildren Eye cohort study, which was conducted in 2018 by re-inviting the participants in the first phase. First, preliminary ocular examinations were performed, including measurement of uncorrected and best corrected visual acuity, auto-refraction, and subjective refraction.All study participants underwent corneal imaging using Pentacam to measure central corneal thickness and corneal radius of curvature (keratometry), ocular biometry using Allegro Biograph to measure anterior chamber depth, crystalline lens thickness, and axial length, and finally OCT imaging to measure RNFL thickness as well as macular thickness and volume.

RESULTS

The data of 4963 right eyes were analyzed after applying the exclusion criteria. The mean age of the study participants was 12.41±1.72 (9 to 15) years. The mean total, superior, inferior, temporal, and nasal RNFL thicknesses were 98.93 (95% CI: 98.61-99.25), 122.84 (95% CI: 122.31-123.37), 129.17 (95% CI: 128.63-129.7), 68.02 (95% CI: 67.65-68.38), and 75.69 (95% CI: 75.3-76.07), respectively. According to the results of the multivariable regression model, macular volume (β=9.81,P=0.001] had a significant direct association, and macular thickness (β=-0.01,P=0.046) had a significant inverse association with the average RNFL thickness. In addition, axial length (β=-3.14,P<0.001), mean keratometry (β=-1.38,P<0.001], and central corneal thickness (β=-0.01,P=0.011) were significantly inversely related to the average RNFL thickness.

CONCLUSION

We report the distribution of peripapillary RNFL thickness using SD-OCT and identify macular volume, axial length, and mean keratometry as significantly associated factors in children. Our findings may serve as a database to interpret RNFL thickness results in children aged 9 to 15 years with suspected ocular disease.

Wedge Defects on Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma: Prevalence and Associated Clinical Factors

PRCIS

Among subjects with glaucoma, wedge-shaped defects on optical coherence tomography angiography (OCTA) were associated with disc hemorrhages (DH), paracentral visual field (VF) defects, increased cup-to-disc ratio (CDR), and thinner retinal nerve fiber layer (RNFL).

PURPOSE

To examine determinants of wedge defects on peripapillary OCTA in glaucoma.

MATERIALS AND METHODS

A total of 278 eyes of 186 subjects with mild to severe primary open-angle glaucoma underwent 6×6 spectral-domain OCTA imaging of the superficial peripapillary retina from 2016 to 2020 at an academic practice. Wedge defects were defined as focal microvasculature loss that extends outward from the optic nerve in an arcuate, wedge shape. Logistic regression models controlling for intereye correlation identified variables significantly associated with wedge defects. Eyes with profound microvasculature loss in both hemispheres were excluded. Candidate variables included: age, sex, race or ethnicity, diabetes, hypertension, follow-up duration, baseline untreated intraocular pressure, intraocular pressure at time of imaging, DH history, paracentral VF defects, CDR, central corneal thickness, spherical equivalent, VF mean deviation, RNFL thickness, and glaucoma stage.

RESULTS

Of 278 eyes, 126 (45.3%) had wedge defects in at least 1 hemisphere. In our multivariable logistic regression model, wedge defects were associated with DH history [odds ratio (OR): 3.19, 95% confidence interval (CI): 1.05-9.69, P=0.041], paracentral VF defects [OR: 4.38 (95% CI: 2.11-9.11), P<0.0001], larger CDR [OR: 1.27 (95% CI: 1.03-1.56), P=0.024, per 0.1 increase], and thinner RNFL [OR: 1.71 (95% CI: 1.25-2.34), P=0.0009, per 10 μm decrease].

CONCLUSION

DH history and paracentral VF defects were independently associated with wedge defects on OCTA, which was present in 45.3% of primary open-angle glaucoma patients. These findings may provide insight into glaucoma pathogenesis.

Evaluation of Macular and Retinal Ganglion Cell Count Estimates for Detecting and Staging Glaucoma

Purpose: To investigate the clinical significance of macular estimated retinal ganglion cell (mRGC) and estimated retinal ganglion cell (eRGC) in the diagnosis and staging of glaucoma.

Methods: This is a cross-section study. All enrolled subjects underwent standard automated perimetry (SAP) and optical coherence tomography (OCT) examination. Swedish Interactive Threshold Algorithm (SITA)-FAST detection strategy and 24-2, 10-2 detection programs were employed in SAP assessment. The visual-field parameters and OCT parameters were calculated according to three formulas to obtain the eRGC and mRGC1 or mRGC2. The efficiency of eRGC, mRGC1, and mRGC2 estimates for the staging of glaucoma was compared. The sensitivity and specificity of each parameter for diagnosis of glaucoma were analyzed using the receiver operating characteristic (ROC) curve.

Results: A total of 119 eyes were included in the analysis. Compared with the healthy controls, eRGC, mRGC1, and mRGC2 estimates were significantly decreased in patients with glaucoma. As glaucoma progressed, eRGC, mRGC1, and mRGC2 estimates were gradually reduced. In preperimetric glaucoma, mRGC1, mRGC2, and eRGC were reduced by 13.2, 14.5, and 18%, respectively. In the mild stage of glaucoma, mRGC1, mRGC2, and eRGC were reduced by 28, 34, and 38%, respectively. In the advanced stage of glaucoma, mRGC1, mRGC2, and eRGC were reduced by 81, 85, and 92% respectively. The proportion of retinal ganglion cell (RGC) loss in the macula was close to that outside the macula. The specificity at 95% gave a sensitivity of 95.51, 86.52, and 87.64% for eRGC, mRGC1, and mRGC2, respectively. The sensitivity of structural parameters macular ganglion cell complex thickness and retinal nerve fiber layer (RNFL) were 98.88 and 95.51%, respectively. The sensitivity of functional parameters mean deviation (24-2) and visual field index (VFI) were 80.90 and 73.03%, respectively. The area under ROC curve of mRGC1, mRGC2, and eRGC were 0.982, 0.972, and 0.995 (P < 0.0001), respectively.

Conclusion: Estimated retinal ganglion cell, mRGC1, and mRGC2 provide value to the staging of glaucoma and better diagnostic performance. Macular RGC estimatesthat integration of both structural and functional damages in macular may serve as a sensitive indicator for assessing macular damage in glaucoma and are of importance for the diagnosis and progression management of glaucoma.

Optical Coherence Tomography and Glaucoma

Early detection and monitoring are critical to the diagnosis and management of glaucoma, a progressive optic neuropathy that causes irreversible blindness. Optical coherence tomography (OCT) has become a commonly utilized imaging modality that aids in the detection and monitoring of structural glaucomatous damage. Since its inception in 1991, OCT has progressed through multiple iterations, from time-domain OCT, to spectral-domain OCT, to swept-source OCT, all of which have progressively improved the resolution and speed of scans. Even newer technological advancements and OCT applications, such as adaptive optics, visible-light OCT, and OCT-angiography, have enriched the use of OCT in the evaluation of glaucoma. This article reviews current commercial and state-of-the-art OCT technologies and analytic techniques in the context of their utility for glaucoma diagnosis and management, as well as promising future directions.

Detecting Progression in Patients With Different Clinical Presentations of Primary Open-angle Glaucoma

PRCIS

Glaucoma progression was more frequently identified by assessing retinal fiber layer thickness than by monitoring visual field (VF) loss for different baseline classifications in primary open-angle glaucoma.

PURPOSE

The aim was to compare the detection of glaucoma progression by retinal nerve fiber layer thickness (RNFLT) and VF assessments for different baseline classifications of primary open-angle glaucoma.

METHODS

This study included 194 eyes from 194 patients with a minimum of 9 follow-up visits selected from the Diagnostic Innovation in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES). Each eye was classified according to baseline clinical signs: ocular hypertension (n=39), glaucomatous optic neuropathy only (n=60), glaucomatous visual field loss only (GVF, n=39) and definite glaucoma (concurrent optic disc and VF defect, n=56). We assessed progression by performing simple linear regression on global and sectorial mean deviations values generated for RNFLT (RNFLT-MD) and VF data (VF-MD). The proportion of eyes identified as progressing (positive rate) by RNFLT-MD and by VF-MD were compared within each classification.

RESULTS

Whereas both parameters performed similarly among glaucomatous optic neuropathy only and definite glaucoma eyes, the positive rate obtained with global RNFLT-MD was significantly greater compared with global VF-MD by 33.3% and 30.8% among ocular hypertension eyes and GVF eyes, respectively. This finding was consistent in the inferotemporal sector; however, similar positive rates were obtained for both parameters in the superotemporal sector.

CONCLUSIONS

While both RNFLT and VF parameters showed comparable abilities to identify progression across the different classifications, RNFLT assessment may be better suited to monitor progression, particularly among patients with elevated intraocular pressure and those who present with only GVF defect at baseline.

Clinical Use of PanoMap for Glaucoma: Frequently Damaged Areas in Early Glaucoma

PRCIS

Recognizing the shortcomings of poor consistency of the fovea-disc relationship at different time points and comparing PanoMaps may well facilitate the understanding of the spatial relationship between parapapillary and macular areas in glaucoma.

PURPOSE

The aims of this study are to analyze the spatial distribution of the frequently damaged areas in early glaucoma, compare the patterns between nonprogressors and progressors using the combined wide-field parapapillary and macular deviation maps (PanoMap), and to evaluate the consistency of the fovea-disc relationship in PanoMap. The fovea-disc distance (FDD) and fovea-disc axis (FDA) were compared at baseline and at the last follow-up.

MATERIALS AND METHODS

In total, 118 patients with early glaucoma and a minimum follow-up period of 3 years were included in this retrospective observational study. The pattern of structural changes was evaluated by averaging the PanoMaps of the enrolled patients at baseline and last follow-up. Longitudinal comparison of the FDD and FDA was performed at baseline and the last follow-up. Patients were divided into nonprogressor (n=44) and progressor (n=74), and the patterns of glaucoma progression in PanoMaps were compared between them.

RESULTS

At baseline, the glaucomatous damage was found more frequently in the macular compared with the parapapillary area. The spatial distribution of frequently damaged areas was similar between the nonprogressor and progressor. At the last follow-up, compared with the baseline structural change on the PanoMap, the progressive structural changes extended toward the fovea at both the parapapillary and macular areas in the progressor. The FDD and FDA were significantly different between the baseline and the last follow-up.

CONCLUSIONS

The PanoMaps showed a clear spatial distribution of early glaucomatous changes, indicating that the damaged area was frequently observed in the macular area. As the consistency of the fovea-disc relationship in PanoMaps was not excellent, this aspect should be considered when interpreting the PanoMap.

A Wide-Field Optical Coherence Tomography Normative Database Considering the Fovea-Disc Relationship for Glaucoma Detection

Purpose

One purpose of this study was to collect wide-field swept-source optical coherence tomography (SS-OCT) data from healthy eyes and build a wide-filed normative database. Another purpose was to compare the glaucoma diagnostic ability of new parameters based on this normative database to the parameters that are currently in use, such as the peripapillary retinal nerve fiber layer (RNFL), macular ganglion cell-inner plexiform layer, and ganglion cell complex (GCC) thickness.

Methods

This study had 220 healthy eyes and 292 eyes with early-stage glaucoma (EG) and moderate-stage glaucoma (MG) enrolled. Using the wide-field SS-OCT images (12 × 9 mm) of healthy eyes, a wide-field normative database was constructed by transforming and combining the individual images into a uniform template using the fovea and optic disc centers as fixed landmarks. Adjustment for the disc size was conducted. With this normative database, new parameters based on the ratio of the fovea-disc distance (FDD) consisting of the fovea-disc relationship were evaluated. The glaucoma diagnostic ability was assessed based on the area under the receiver operating characteristic curve (AUC).

Results

Among the new peripapillary parameters, the RNFL of the circumference of the circle with diameter 0.8 FDD showed the highest AUC value for EG and MG, but the value was not significantly superior to that of the initial RNFL (AUC = 0.940 vs. 0.937, P = 0.631). Among the macular parameters, the GCC of the area of the circle of 1.5 FDD showed the highest AUC value for EG and MG, and the value was significantly superior to that of initial GCC (AUC = 0.929 vs. 0.919, P = 0.033). However, there was no significant difference between the initial and adjusted GCC thickness in patients included in the EG or MG groups separately.

Conclusions

A wide-field normative database was built to consider the relationship between the fovea and the optic disc. Considering this aspect, we found that the GCC analysis using a broader area presented a significantly greater glaucoma diagnostic performance for EG and MG in the macula than the initial parameter for the GCC.

Translational Relevance

Based on this wide-field normative database, the clinical use of a wide-field deviation map may help diagnose the patients with EG and MG in the future.

Risk Factors for the Structural Progression of Myopic Glaucomatous Eyes with a History of Laser Refractive Surgery

As laser refractive surgeries (LRS) have been widely performed to correct myopia, ophthalmologists easily encounter patients with glaucoma who have a history of LRS. It is well known that intraocular pressure (IOP) in eyes with glaucoma is not accurate when measured using Goldmann applanation tonometry. However, risk factors for glaucoma progression, particularly those associated with measured IOP, have rarely been studied. We analysed data for 40 patients with a history of LRS and 50 age-matched patients without a history of LRS. Structural progression was defined as significant changes in thickness in the peripapillary retinal nerve fibre layer as identified using optical coherence tomography event-based guided progression analysis. Risk factors were determined via Cox regression analysis. Disc haemorrhage (DH) was associated with glaucoma progression in both the non-LRS group and LRS group (hazard ratio (HR): 4.650, p = 0.012 and HR: 8.666, p = 0.019, respectively). However, IOP fluctuation was associated with glaucoma progression only in the LRS group (HR: 1.452, p = 0.023). Our results show that DH was a significant sign of progression in myopic glaucoma eyes. When treating patients with myopia and glaucoma, IOP fluctuation should be monitored more carefully, even if IOP seems to be well controlled.

Comparison of structural and functional tests in primary open angle glaucoma

Purpose:

To comparatively analyze the structural and functional tests used in the diagnosis and follow-up of glaucoma.

Methods:

Eighty eyes of 40 patients with primary open angle glaucoma (POAG) and 46 eyes of 23 healthy individuals were included in the study. Transient pattern electroretinography (PERG), steady-state PERG (ssPERG), computerized visual field (VF) screening, and examination of retinal nerve fiber layer (RNFL) and macular thickness on optical coherence tomography (OCT) were undertaken. The results were compared between the groups.

Results:

80 eyes belonging to 40 patients with a diagnosis of POAG (23 female, 17 male) (18 mild 22 moderate POAG) with a mean of 57.37 (±8.6) years, and 46 eyes of 23 healthy individuals (14 female, 9 male) with a mean age of 55.30 (±8.09) years were included in the study. PERG P50 and N95 and ssPERG latency revealed a significant delay in the POAG group. When the wave amplitudes were examined, they were found to be significantly lower in both PERG and sSPERG tests for the POAG group, but the results were more pronounced in ssPERG. The latency values of PERG and ssPERG tests were not significantly correlated with any of the parameters of the remaining tests. However, the amplitude values of these tests had a positive correlation with the mean deviation value and negative correlation with the pattern standard deviation value of VF. All associated parameters were significant for the amplitude value of the ssPERG test.

Conclusion:

For the proper management of glaucoma, rather than approaching damage simply as the loss of retinal ganglion cells or the neuroretinal rim, it is necessary to focus on the ongoing anatomical and functional relationship and evaluate structural and functional tests together. In addition, ssPERG test, which is not widely adopted in routine practice, provides valuable information and is significantly correlated with OCT parameters.

Time Lag Between Functional Change and Loss of Retinal Nerve Fiber Layer in Glaucoma

Purpose

It is often suggested that structural change is detectable before functional change in glaucoma. However, this may be related to the lower variability and hence narrower normative limits of structural tests. In this study, we ask whether a time lag exists between the true rates of change in structure and function, regardless of clinical detectability of those changes.

Methods

Structural equation models were used to determine whether the rate of change in function (mean linearized total deviation, AveTDLin) or structure (retinal nerve fiber layer thickness [RNFLT]) was predicted by the concurrent or previous rate for the other modality, after adjusting for its own rate in the previous time interval. Rates were calculated over 1135 pairs of consecutive visits from 318 eyes of 164 participants in the Portland Progression Project, with mean 207 days between visits.

Results

The rate of change of AveTDLin was predicted by its own rate in the previous time interval, but not by rates of RNFLT change in either the concurrent or previous time interval (both P > 0.05). Similarly, the rate of RNFLT change was not predicted by concurrent AveTDLin change after adjusting for its own previous rate. However, the rate of AveTDLin change in the previous time interval did significantly improve prediction of the current rate for RNFLT, with P = 0.005, suggesting a time lag of around six months between changes in AveTDLin and RNFLT.

Conclusions

Although RNFL thinning may be detectable sooner, true functional change appears to predict and precede thinning of the RNFL in glaucoma.

Detection of glaucoma using retinal fundus images: A comprehensive review

Content-based image analysis and computer vision techniques are used in various health-care systems to detect the diseases. The abnormalities in a human eye are detected through fundus images captured through a fundus camera. Among eye diseases, glaucoma is considered as the second leading case that can result in neurodegeneration illness. The inappropriate intraocular pressure within the human eye is reported as the main cause of this disease. There are no symptoms of glaucoma at earlier stages and if the disease remains unrectified then it can lead to complete blindness. The early diagnosis of glaucoma can prevent permanent loss of vision. Manual examination of human eye is a possible solution however it is dependant on human efforts. The automatic detection of glaucoma by using a combination of image processing, artificial intelligence and computer vision can help to prevent and detect this disease. In this review article, we aim to present a comprehensive review about the various types of glaucoma, causes of glaucoma, the details about the possible treatment, details about the publicly available image benchmarks, performance metrics, and various approaches based on digital image processing, computer vision, and deep learning. The review article presents a detailed study of various published research models that aim to detect glaucoma from low-level feature extraction to recent trends based on deep learning. The pros and cons of each approach are discussed in detail and tabular representations are used to summarize the results of each category. We report our findings and provide possible future research directions to detect glaucoma in conclusion.

A simplified combined index of structure and function for detecting and staging glaucomatous damage

Glaucomatous damage results in characteristics structural and functional changes on optical coherence tomography (OCT) imaging and standard automated perimetry (SAP) testing. The clinical utility of these measures differs based on disease severity, as they are evaluated along different measurement scales. This study therefore sought to examine if a simplified combined structure-function index (sCSFI) could improve the detection and staging of glaucomatous damage, compared to the use of average retinal nerve fiber layer thickness (RNFL) measurements from OCT and mean deviation (MD) values from SAP alone, and also an estimated retinal ganglion cell counts (eRGC) measure derived using empirical formulas described previously. Examining 577 eyes from 354 participants with perimetric glaucoma and 241 normal eyes from 138 healthy participants, we found that the sCSFI performed significantly better than average RNFL, MD and eRGC count for discriminating between glaucoma and healthy eyes (P ≤ 0.008 for all). The sCSFI also performed significantly better than RNFL and eRGC count at discriminating between different levels of visual field damage in glaucoma eyes (P < 0.001 for both). These findings highlight the clinical utility of combining structural and functional information for detecting and staging glaucomatous damage using the simplified index developed in this study.

Optical Coherence Tomography Can Be Used to Assess Glaucomatous Optic Nerve Damage in Most Eyes With High Myopia

PRECIS

It is generally assumed that optical coherence tomography (OCT) cannot be used to diagnose glaucomatous optic neuropathy (GON) in high myopes. However, this study presents evidence that there is sufficient information in OCT scans to allow for accurate diagnosis of GON in most eyes with high myopia.

PURPOSE

The purpose of this study was to test the hypothesis that glaucomatous damage can be accurately diagnosed in most high myopes via an assessment of the OCT results.

PATIENTS AND METHODS

One hundred eyes from 60 glaucoma patients or suspects, referred for OCT scans and evaluation, had corrected spherical refractive errors worse than -6 D and/or axial lengths ≥26.5 mm. An OCT specialist judged whether the eye had GON, based upon OCT circle scans of the disc and cube scans centered on the macula. A glaucoma specialist made the same judgement using all available information (eg, family history, repeat visits, intraocular pressure, 10-2 and 24-2 visual fields, OCT). A reference standard was created based upon the glaucoma specialist's classifications. In addition, the glaucoma specialist judged whether the eyes had peripapillary atrophy (PPA), epiretinal membrane (ERM), tilted disc (TD), and/or a paravascular inner retinal defect (PIRD).

RESULTS

The OCT specialist correctly identified 97 of the 100 eyes using the OCT information. In 63% of the cases, the inner circle scan alone was sufficient. For the rest, additional scans were requested. In addition, 81% of the total eyes had: PPA (79%), ERM (18%), PIRD (26%), and/or TD (48%).

CONCLUSIONS

For most eyes with high myopia, there is sufficient information in OCT scans to allow for accurate diagnosis of GON. However, the optimal use of the OCT will depend upon training to read OCT scans, which includes taking into consideration myopia related OCT artifacts and segmentation errors, as well as PPA, ERM, PIRD, and TD.

Global optical coherence tomography measures for detecting the progression of glaucoma have fundamental flaws

Objective

To understand the problems involved in using global OCT measures for detecting progression in early glaucoma.

Subjects/Methods

Eyes from 76 patients and 28 healthy controls (HC) had a least two OCT scans at least 1 year apart. To determine the 95% confidence intervals (CI), 151 eyes (49 HC and 102 patients) had at least two scans within 6 months. All eyes had 24-2 mean deviation ≥-6dB. The average (global) thicknesses of the circumpapillary retinal nerve fibre layer (cRNFL), G_ONH, and of the retinal ganglion cell layer plus inner plexiform layer (RGCLP), G_mac, were calculated. Using quantile regression, the 95% CI intervals were determined. Eyes outside the CIs were classified as “progressors.” For a reference standard (RS), four experts evaluated OCT and VF information.

Results

Compared to the RS, 31 of the 76 (40.8%) patient eyes were identified as progressors (RS-P), and 45 patient, and all 28 HC, eyes as nonprogressors (RS-NP). The metrics missed (false negative, FN) 15 (48%) (G_ONH) and 9 (29%) (G_mac) of the 31 RS-P. Further, G_ONH and/or G_mac falsely identified (false positive, FP) 10 (22.2%) of 45 patient RS-NP eyes and 7 (25%) of the 28 HC eyes as progressing. Post-hoc analysis identified three reasons (segmentation, centring, and local damage) for these errors.

Conclusions

Global metrics lead to FPs and FNs because of problems inherent in OCT scanning (segmentation and centring), and to FNs because they can miss local damage. These problems are difficult, if not impossible, to correct, and raise concerns about the advisability of using G_ONH and G_mac for detecting progression.

Risk Factors Associated with Structural Progression in Normal-Tension Glaucoma: Intraocular Pressure, Systemic Blood Pressure, and Myopia

Purpose

To determine risk factors associated with structural progression in medically treated normal-tension glaucoma (NTG).

Methods

This retrospective cohort study included 166 NTG patients (average age, 56.5 years; average mean deviation, −4.2 dB). The structural progression endpoint was determined by optical coherence tomography; significant thickness differences in the peripapillary retinal nerve fiber layer (RNFL) or macular ganglion cell inner plexiform layer (GCIPL) that exceeded baseline test-retest variability were identified with event-based guided-progression analysis. Intraocular pressure and systemic blood pressure (BP) were measured at each visit throughout the follow-up period, and the risk for progression was evaluated with Cox regression. Myopic disc features and antihypertensives were also analyzed. Tree analysis was used to determine the cutoff values and elucidate influential risk factors.

Results

Structural progression, defined as progressive peripapillary RNFL or macular GCIPL thinning, was identified in 62 eyes. Occurrence of disc hemorrhages, presence of diabetes, and lower minimum systolic BP were associated with progression (hazard ratio [HR]: 2.116, P = 0.005; HR: 1.998, P = 0.031; HR: 0.968, P = 0.005; respectively). The cutoff value derived from the tree analysis of minimum systolic BP was 108 mm Hg. The tree analysis revealed systolic and diastolic BP to be the most influential risk factors for progressive peripapillary RFNL thinning and progressive macular GCIPL thinning, respectively.

Conclusions

Low BP measured during follow-up correlated with structural progression in medically treated NTG eyes, indicating that the evaluation of hypotension is required during the management of NTG patients. The tree analysis identified BP target values that may help prevent glaucoma progression.

Comparison of the Progression of Localized Retinal Nerve Fiber Layer Defects in Red-free Fundus Photograph, En Face Structural Image, and OCT Angiography Image

PRECIS

This study demonstrated the high topographic correlation between the red-free fundus photographs and en face structural images in eyes with glaucomatous progression.

PURPOSE

The purpose of this study was to compare the progression of localized retinal nerve fiber layer (RNFL) defects in red-free fundus photographs, en face structural images, and optical coherence tomography angiography (OCTA) images.

METHODS

We performed a retrospective, comparative study on 45 glaucomatous eyes showing RNFL defect widening in red-free photography. The localized RNFL defect in the red-free photographs was termed as red-free defect. The wedge-shaped hyporeflective area radiating from the optic nerve head in the optical coherence tomography (OCT) en face structural images and OCTA images was defined as en face defect and OCTA defect, respectively. The baseline and follow-up angular parameters of each red-free defect were compared with those of en face defect and OCTA defect.

RESULTS

When the baseline angular parameters were compared, there were no significant differences between red-free defect and en face defect, and between red-free defect and OCTA defect (all, P>0.017). In addition, the follow-up angular parameters showed no difference between red-free defect and en face defect. However, the OCTA defect showed significantly greater values compared with red-free defect and en face defect with respect to the distal angular location and angular width at follow-up visit (36.78±15.10 vs. 34.10±15.09 vs. 33.40±15.05 degrees, both, P<0.001).

CONCLUSIONS

Localized RNFL defects detected in red-free photographs showed high topographic correlation with defects detected in OCT en face structural images, and this correlation was also noted in eyes with progressive glaucoma. The OCT en face structural images may be an alternative to red-free photography for identifying progressive RNFL defects in eyes with glaucoma.

Consistency between optical coherence tomography and humphrey visual field for evaluating glaucomatous defects in high myopic eyes

Background

The study is to investigate the influence of high myopia on the consistency between optical coherence tomography (OCT) and visual field in primary open-angle glaucoma (POAG).

Methods

We enrolled 37 patients with POAG with high myopia (POAG-HM group), 27 patients with POAG without high myopia (POAG group), and 29 controls with high myopia (HM group). All subjects underwent Humphrey perimetry (30–2 and 10–2 algorithms). The peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) thicknesses were measured using Cirrus HD-OCT. Spearman’s rank correlation analysis was used to determine correlations between OCT and perimetric parameters. Agreement was analyzed by cross-classification and weighted κ statistics.

Results

In POAG group, the cross-classification analysis showed strong agreement between the inferior temporal GCIPL thickness and the mean sensitivity (MS) of 10–2 algorithms (κ = 0.5447, P = 0.0048), and good agreement between the superior and inferior RNFL thicknesses and 30–2 MS (κ = 0.4407 and 0.4815; P < 0.05). In the POAG-HM group, only the inferior temporal GCIPL thickness showed good agreement with 10–2 MS (κ = 0.3155, P = 0.0289) and none of the RNFL sectors were in good agreement with the corresponding MS.

Conclusions

In POAG patients with high myopia, changes in macular measurements were in accordance with visual field defects, and RNFL thickness did not consistently decline with visual field defects due to the effects of high myopia. This study suggests that during diagnosis and follow-up of glaucoma with high myopia, more attention need to be focused on structure and functional defects in macular areas.

Can We Corroborate Peripapillary RNFL Analysis with Macular GCIPL Analysis? Our 2-Year Experience at a Single-Centre Tertiary Healthcare Hospital Using Two OCT Machines and a Review of Literature

Purpose

To determine whether macular volume and macular GCA measurements in patients are comparable to their RNFL thickness parameters.

Materials and Methods

The cross-sectional, observational study was conducted on 1380 eyes with 460 each, into three groups. Group I: patients with healthy eyes. Group II: patients diagnosed as pre-perimetric glaucoma. Group III: patients with diagnosed perimetric glaucoma. After patients were selected on the basis of inclusion and exclusion criteria, baseline standard ophthalmic examination was done by the same operator under the same settings, including SD-OCT using both the Spectralis SD-OCT and the Cirrus SD-OCT as elaborated below.

Statistical Analysis

Data were checked for normality before statistical analysis using Shapiro-Wilk test. Normally distributed continuous variables were compared using ANOVA. For all statistical tests, a p < 0.05 was taken to indicate a significant difference. Receiver operating characteristic (ROC) curves were used to define the ability RNFL and GCC parameters to distinguish perimetric and preperimetric glaucomatous eyes from control eyes.

Results

There was a statistically significant difference in the average, superior, inferior RNFL thickness and average, superior, inferior GCIPL thickness between Group I and Group II (p<0.001), between Group I and Group III (p<0.001) and also between Group II and Group III (p<0.001). The statistical significance was also reflected in their AUROCs.

Conclusion

Mean, superior, inferior GCIPL thickness along with macular volume analysis can substantiate RNFL analysis for diagnosis, serial monitoring and follow-up of glaucoma patients and suspects.

Analysis of Retinal Nerve Fibre Thickening in Progressive and Non-progressive Non-arteritic Anterior Ischaemic Optic Neuropathy Using Optical Coherence Tomography

The study aims to investigate the longitudinal changes in the circumpapillary retinal nerve fibre layer thickness (cpRNFLT) in progressive and non-progressive non-arteritic anterior ischaemic optic neuropathy (NAION). This retrospective observational case series study analysed 17 eyes with NAION. Patients sustaining any additional visual loss (additional decrease in visual acuity (VA) ≥0.2 logMAR) within two months after initial onset of symptoms were classified as having progressive NAION. Of the 17 eyes with NAION, 13 (76.5%) were diagnosed as non-progressive and 4 (23.5%) were diagnosed as progressive. Compared with control eyes, eyes with non-progressive NAION showed greater cpRNFLT in all four optic disc quadrants at the initial visit (temporal and superior: P < .001; nasal and inferior: P = .002). In contrast, compared with control eyes, eyes with progressive NAION showed greater cpRNFLT in the superior and nasal quadrants (P = .004 and 0.028, respectively), but not in the temporal and inferior quadrants. During progression, eyes with progressive NAION showed a significant increase in cpRNFLT in the inferior quadrants; furthermore, there was significant increase in cpRNFLT in the nasal sector before visual loss developed after the initial visit. Progressive NAION showed development of the disc swelling from the superior to inferior portion of optic disc via the nasal swelling, suggesting that swollen axons in one ischaemic part may lead to secondary vascular infarction in another part of the optic disc. This enlargement could constitute the earliest sign of progressive NAION.

Vulnerability Zone of Glaucoma Progression in Combined Wide-field Optical Coherence Tomography Event-based Progression Analysis

Purpose

To investigate the spatial characteristics and patterns of structural progression using the combined retinal nerve fiber layer (RNFL) and ganglion cell–inner plexiform layer event-based progression analysis feature provided by the Guided Progression Analysis (GPA) software of spectral-domain optical coherence tomography.

Methods

In this retrospective observational study, we evaluated 89 patients with open-angle glaucoma showing clinically confirmed structural progression within a minimum follow-up period of 3 years. For each eye, the RNFL and ganglion cell–inner plexiform layer GPA data were extracted from serial spectral-domain optical coherence tomography (HD-OCT 4000, Carl Zeiss Meditec, Inc., Dublin, CA) data from 2012 to 2017 (available in commercial report). A combined wide-field GPA map was merged using vascular landmark-guided superimposition of RNFL and ganglion cell–inner plexiform layer GPA event-based progression maps onto the RNFL image (resulting in the GPA PanoMaps: proposed in this study). The pattern of progressive structural changes was evaluated by comparing the baseline combined wide-field OCT deviation maps (PanoMap deviation maps: available in commercial report) and GPA PanoMaps at the time the first progression was detected and the GPA PanoMaps at the last follow-up. Spatial characteristics and patterns of glaucoma structural progression on GPA PanoMaps were evaluated.

Results

Progressive structural progression was detected most frequently at the macular vulnerability zone (MVZ), with the peripapillary and macular progression being well-correlated spatially. Compared with the baseline structural change on PanoMap, the progressive structural changes extended toward the fovea at both the peripapillary and macular areas. A spatial difference was observed between the areas where structural damage was frequently found on PanoMap (peripapillary inferoinferior sector and macular MVZ) and areas where progression was frequently found on GPA PanoMap (peripapillary and macular MVZ).

Conclusions

The patterns of progressive glaucomatous structural changes in both the peripapillary and macular areas were confirmed on the combined wide-field GPA map (GPA PanoMap). An analysis of the progression pattern using the GPA PanoMap facilitates the understanding of the spatial relation between the peripapillary and macular areas in glaucoma.

Forecasting Retinal Nerve Fiber Layer Thickness from Multimodal Temporal Data Incorporating OCT Volumes

Purpose

The purpose of this study was to develop a machine learning model to forecast future circumpapillary retinal nerve fiber layer (cpRNFL) thickness in eyes of healthy, glaucoma suspect, and glaucoma participants from multimodal temporal data.

Design

Retrospective analysis of a longitudinal clinical cohort.

Participants

Longitudinal clinical cohort of healthy, glaucoma suspect, and glaucoma participants.

Methods

The forecasting models used multimodal patient information including clinical (age and intraocular pressure), structural (cpRNFL thickness derived from scans as well as deep learning-derived OCT image features), and functional (visual field test parameters) data and the intervisit interval for prediction of cpRNFL thickness at the next visit. Four models were developed based on the number of visits used (n = 1 to 4). Longitudinal data from 1089 participants (mean observation period, 3.65±1.73 years) was used with 80% of the cohort for the development of the models. The results of our models were compared with those of a commonly adopted linear regression model, which we refer to here as linear trend-based estimation (LTBE).

Main Outcome Measures

The mean absolute difference and Pearson's correlation coefficient between the true and forecasted values of the cpRNFL in the healthy, glaucoma suspect, and glaucoma patients.

Results

The best forecasting model of cpRNFL was obtained using 3 visits and incorporated deep learning-derived OCT image features. The mean error was 1.10±0.60 μm, 1.79±1.73 μm, and 1.87±1.85 μm in eyes of healthy, glaucoma suspect, and glaucoma participants, respectively. Our method significantly outperformed the LTBE model for glaucoma suspect and glaucoma participants (P < 0.001), which showed a mean error of 1.55±1.16 μm, 2.4±2.67 μm, and 3.02±3.06 μm in the 3 groups, respectively. The Pearson's correlation coefficient between the forecasted value and the measured thickness was ρ = 0.96 (P < 0.01), ρ = 0.95 (P < 0.01), and ρ = 0.96 (P < 0.01) for the 3 groups, respectively.

Conclusions

The performance of the proposed forecasting model for cpRNFL is consistent across glaucoma suspect and glaucoma patients, which implies the robustness of the developed model against the disease state. These forecasted values may be useful to personalize patient care by determining the most appropriate intervisit schedule for timely interventions.

Discovery and clinical translation of novel glaucoma biomarkers

Glaucoma and other optic neuropathies are characterized by progressive dysfunction and loss of retinal ganglion cells and their axons. Given the high prevalence of glaucoma-related blindness and the availability of treatment options, improving the diagnosis and precise monitoring of progression in these conditions is paramount. Here we review recent progress in the development of novel biomarkers for glaucoma in the context of disease pathophysiology and we propose future steps for the field, including integration of exploratory biomarker outcomes into prospective therapeutic trials. We anticipate that, when validated, some of the novel glaucoma biomarkers discussed here will prove useful for clinical diagnosis and prediction of progression, as well as monitoring of clinical responses to standard and investigational therapies.

A framework for assessing glaucoma progression using structural and functional indices jointly

Purpose

While many tests and indices are available to identify glaucoma progression, using them in combinations may decrease overall specificity. The aim of this study was to develop a framework for assessing glaucoma progression using structural and functional indices jointly for a fixed specificity.

Methods

The study included 337 eyes of 207 patients with ocular hypertension or primary open-angle glaucoma selected from the Diagnostic Innovations in Glaucoma Study or the African Descent and Glaucoma Evaluation Study. All patients had at least 9 visits. Each visit had retinal nerve fiber layer thickness (RNFLT) and mean sensitivity from static automated perimetry (SAP MS) measured within a one-month window. Simple linear regression was applied to assess deterioration in each index for series of 5 to 9 visits. To identify progression using the two indices jointly, marginal significance levels set at a specificity of 95% were derived for two criteria: ANY (worsening on either RNFLT or SAP MS) and ALL (worsening on both RNFLT and SAP MS). Positive rate (percentage of eyes flagged as progressing) was determined individually for each index, as well as for the ANY and ALL criteria.

Results

Compared to SAP MS, RNFLT had higher positive rates (15% to 45%) for all series lengths. For the joint analyses, the positive rate was on average 12% higher for the ANY criterion compared to the ALL criterion. While RNFLT-alone had comparable positive rates and time-to-detection as the ANY criterion, each uniquely identified a subset of eyes (Kappa = 0.55 to 0.75).

Conclusions

This study provides a simple framework for assessing glaucoma progression with data from two tests jointly, without compromising specificity. This framework can be extended to include two or more parameters, can accommodate global or regional indices, and can eventually be used with novel parameters identified as predictive of glaucoma progression.

Review of Longitudinal Glaucoma Progression: 5 Years after the Shaffer Lecture

In 2013, the senior author delivered the American Academy of Ophthalmology Robert N. Shaffer Lecture entitled "Glaucoma Changes-Reality Bites." This talk focused on describing the longitudinal structure-function relationships in glaucoma progression. The study was based on a 10-year longitudinal dataset created by calibrated measurements across multiple OCT generations with corresponding visual fields (VFs). The prior held observation was that functional damage follows structural damage. The lecture posited that structure and function change at similar times, but that current measurement technology limits our ability to detect functional abnormalities and change early in glaucoma, as well as to measure structural change late in the disease. The Shaffer lecture provided evidence that structure and function change concordantly and that any apparent discordance in the relationship was due to technologic limitations to measure glaucomatous change. Furthermore, we observed 5 longitudinal relationships of concordance and discordance that can exist with structure-function interactions. Concordance: (1) structure-structure progression, (2) structure-function tipping point, (3) structural floor tipping point. Discordance: (4) functional progression in a "stable" VF with structure-function correlation, (5) functional progression with "normal" structure. In this review article, we will review longitudinal glaucoma progression studies with long-term follow-up and discuss the clinical relevance of relationships of concordance and discordance that can exist with structure-function interactions.

Progression patterns of normal-tension glaucoma groups classified by hierarchical cluster analysis

OBJECTIVES

To investigate differences in progression patterns of normal-tension glaucoma (NTG) patients in three clusters classified by hierarchical cluster analysis (HCA).

MATERIALS AND METHODS

In a retrospective study, 200 eyes of NTG patients classified by HCA in 2015 who were followed up to the current date were evaluated. Peripapillary retinal nerve fibre layer (RNFL) thicknesses were measured by Cirrus HD-OCT and progression rate was calculated by trend analysis (Guided Progression Analysis [GPA]). VF progression rate was evaluated by linear regression analysis of mean deviation (MD). Progression patterns of three clusters were compared by histograms.

RESULTS

In total, 153 eyes of 153 patients were followed up. Mean observation period was 5 years. RNFL reduction rate was -0.83 μm/year in cluster 1, which showed early glaucomatous damage in previous reports; -0.45 μm/year in cluster 2, which showed moderate glaucomatous damage; and -0.36 μm/year in cluster 3, which showed young and myopic glaucomatous damage. The progression pattern of cluster 3 showed a double-peak distribution; RNFL reduction rate was 0.11 μm/year in the non-progressive group and -1.07 μm/year in the progressive group.

CONCLUSION

The progression patterns were different among three NTG groups that were divided by HCA. In particular, the group of young and myopic eyes showed a mixture of two different patterns.

Study of correlation between stereopsis and retinal nerve fiber layer thickness in cases of glaucoma

Background

Glaucoma is an important and common optic neuropathy characterized by progressive loss of retinal ganglion cells and associated morphological changes to the optic nerve and retinal nerve fiber layer (RNFL). The most common assessment of visual function in glaucoma uses perimetric measurements of visual sensitivity. Only few studies have evaluated the binocular function in patients with glaucoma. This study was taken up to establish the correlation of RNFL thickness, in glaucoma, with near and distance stereopsis.

Methods

This pilot, cross-sectional observational study included 100 diagnosed cases of glaucoma and 100 normal participants as controls, studied over a period of one year. The records of all the participants were checked, and only established cases of glaucoma after fulfilling the inclusion and exclusion criteria were included. Analysis of the RNFL using spectral-domain optical coherence tomography was carried out. All the participants were thereafter evaluated for stereoacuity by near (at 40 inches) and distance (at 3 meter) Randot stereoacuity charts.

Results

There was a negative correlation between the RNFL thickness and the absolute value of streoacuity (-0.303 for distance versus -0.101 for near in cases and -0.308 for distance and -0.416 for near in control group), decreasing the actual functional stereoacuity, therefore the cases with lower RNFL thickness had lower stereoacuity both for distance and near, however it was statistically significant only for distance (p=0.002).

Conclusion

Functional aspects, such as stereoacuity, may also be affected in the glaucoma because of decrease in RNFL thickness. Therefore, binocular status should also be evaluated in cases of glaucoma.