The development of a reference database with the Topcon 3D OCT-1 Maestro

Glaucoma Detection Using Optical Coherence Tomography: Reviewing the Pitfalls of Comparison to Normative Data

PRCIS

Optical coherence tomography is essential in managing glaucoma. This review describes various artifacts that originate from using a normative database to compare the individual's scans. This is a review paper regarding artifacts in optical coherence tomography imaging for glaucoma arising from using a normative database as a reference for healthy retinal nerve fiber layer and ganglion cell layer.

Agreement and precision of wide and cube scan measurements between swept-source and spectral-domain OCT in normal and glaucoma eyes

This study aimed to evaluate agreement of Wide scan measurements from swept-source optical coherence tomography (SS-OCT) Triton and spectral-domain OCT (SD-OCT) Maestro in normal/glaucoma eyes, and to assess the precision of measurements from Wide and Cube scans of both devices. Three Triton and three Maestro operator/device configurations were created by pairing three operators, with study eye and testing order randomized. Three scans were captured for Wide (12 mm × 9 mm), Macular Cube (7 mm × 7 mm-Triton; 6 mm × 6 mm-Maestro), and Optic Disc Cube (6 mm × 6 mm) scans for 25 normal eyes and 25 glaucoma eyes. Parameter measurements included circumpapillary retinal nerve fiber layer(cpRNFL), ganglion cell layer + inner plexiform layer (GCL+), and ganglion cell complex (GCL++). A two-way random effect analysis of variance model was used to estimate the repeatability and reproducibility; agreement was evaluated by Bland-Altman analysis and Deming regression. The precision estimates were low, indicating high precision, for all thickness measurements with the majority of the limits < 5 µm for the macula and < 10 µm for the optic disc. Precision of the Wide and Cube scans were comparable. Excellent agreement between the two devices was found for Wide scans, with the mean difference < 3 µm across all measurements (cpRNFL < 3 µm, GCL+  < 2 µm, GCL ++  < 1 µm), indicating interoperability. A single Wide scan covering the peripapillary and macular regions may be useful for glaucoma diagnosis and management.

Normative Data for Macular Thickness and Volume for Optical Coherence Tomography in a Diabetic Population without Maculopathies

PURPOSE

The purpose was to establish normative data for the macular thicknesses and volume using spectral-domain optical coherence tomography (SD-OCT) in a diabetic population without maculopathies for use as a reference in diabetic retinopathy (DR) and diabetic macular edema screening programs.

METHODS

This was an observational study nested in a cohort of diabetics from a telemedicine DR screening program. Each patient underwent SD-OCT centered on the fovea. Macular thickness and volume were described and compared using the built-in normative database of the device. Quantile regression models for the 97.5% percentile were fitted to evaluate the predictors of macular thickness and volume.

RESULTS

A total of 3410 eyes (mean age, 62.25 (SD, 0.22) years) were included. Mean (SD) central subfield thickness (CST) was 238.2 (23.7) µm, while center thickness (CT), average thickness (AT), and macular volume (MV) were 205.4 (31.6) µm, 263.9 (14.3) µm, and 7.46 (0.40) mm3, respectively. Para- and perifoveal thicknesses were clinically and statistically significantly thinner in our population than in the normative reference database. The 97.5% percentile of the thickness of all sectors was increased in males and in the para- and perifovea among those with DR.

CONCLUSIONS

All ETDRS sectors were thinner in patients with diabetes than in the reference population, except for the CST, which was the most stable parameter that only changed with sex. The upper cutoff limit to detect diabetic macular edema (DME) was different from that of the reference population and was influenced by conditions related to diabetes, such as DR. Therefore, specific normative data for diabetic patients should be used for the screening and diagnosis of DME using SD-OCT.

Toward a Real-world Optical Coherence Tomography Reference Database: Optometric Practices as a Source of Healthy Eyes

SIGNIFICANCE

The reports from optical coherence tomography (OCT) instruments depend on a reference database (RDB) of healthy eyes. Although these RDBs tend to be relatively small, they are time consuming and expensive to obtain. A larger RDB should improve our ability to screen for diseases such as glaucoma.

PURPOSE

To explore the feasibility of developing a large RDB from OCT scans obtained by optometrists as part of their pre-test gathering of information, we tested the hypothesis that these scans are of sufficient quality for an RDB and contain a relatively low base rate of glaucoma and other pathologies (OPs).

METHODS

Optical coherence tomography widefield (12 × 9 mm) scans from 400 eyes of 400 patients were randomly selected from a data set of more than 49,000 scans obtained from four optometry sites. Based on a commercial OCT report and a previously validated reading center method, two OCT graders categorized eyes as unacceptable to use for RDB, healthy (H), optic neuropathy consistent with glaucoma (ON-G), glaucoma suspect, or OPs.

RESULTS

Overall, 29 (7.25%) of the eyes were graded unacceptable. Of the remaining 371 eyes, 352 (94.9%) were graded H. Although, for one site, 7.4% of the eligible eyes were graded ON-G, the average for the other three sites was 1.4%. Adjustments of the reading center criteria resulted in exclusion of more than half of these ON-G and OP eyes.

CONCLUSIONS

The OCT scans obtained from optometry practices as part of their pre-test regimen are of sufficient quality for an RDB and contain a relatively low base rate of glaucoma and OPs. With the suggested exclusion criteria, the scans from optometry practices that are primarily involved in refraction and medical screening services should yield a large, real-world RDB with improved specificity and a base rate of glaucoma and/or OPs comparable with existing RDB.

Agreement and Precision of Wide and Cube Scan Measurements between Swept-source and Spectral-domain OCT in Normal and Glaucoma Eyes

This study aimed to evaluate agreement of Wide scan measurements from swept-source optical coherence tomography(SS-OCT) Triton and spectral-domain OCT(SD-OCT) Maestro in normal/glaucoma eyes, and to assess the precision of measurements from Wide and Cube scans of both devices. Three Triton and three Maestro operator/device configurations were created by pairing three operators, with study eye and testing order randomized. Three scans were captured for Wide (12mm×9mm), Macular Cube (7mmx7mm-Triton; 6mmx6mm-Maestro), and Optic Disc Cube (6mmx6mm) scans for 25 normal eyes and 25 glaucoma eyes. Thickness of circumpapillary retinal nerve fiber layer(cpRNFL), ganglion cell layer+inner plexiform layer(GCL+), and ganglion cell complex(GCL++) was obtained from each scan. A two-way random effect analysis of variance model was used to estimate the repeatability and reproducibility; agreement was evaluated by Bland-Altman analysis and Deming regression. Precision limit estimates were low: <5µm for macular and <10µm for optic disc parameters. Precision for Wide and Cube scans of both devices were comparablein both groups. Excellent agreement between the two devices was found for Wide scans, with the mean difference<3µm across all measurements (cpRNFL<3µm, GCL+<2µm, GCL++<1µm), indicating interoperability. A single Wide scan covering the peripapillary and macular regions may be useful for glaucoma management.

Accurate C/D ratio estimation with elliptical fitting for OCT image based on joint segmentation and detection network

Proper estimation of the cup-to-disc ratio (C/D ratio) plays a significant role in ophthalmic examinations, and it is urgent to improve the efficiency of C/D ratio automatic measurement. Therefore, we propose a new method for measuring the C/D ratio of OCTs in normal subjects. Firstly, the end-to-end deep convolution network is used to segment and detect the inner limiting membrane (ILM) and the two Bruch's membrane opening (BMO) terminations. Then, we introduce an ellipse fitting technique to post-process the edge of the optic disc. Finally, the proposed method is evaluated on 41 normal subjects using the optic-disc-area scanning mode of three machines: BV1000, Topcon 3D OCT-1, and Nidek ARK-1. In addition, pairwise correlation analyses are carried out to compare the C/D ratio measurement method of BV1000 to existing commercial OCT machines as well as other state-of-the-art methods. The correlation coefficient between the C/D ratio calculated by BV1000 and the C/D ratio calculated by manual annotation is 0.84, which indicates that the proposed method has a strong correlation with the results of manual annotation by ophthalmologists. Moreover, in comparison between BV1000, Topcon and Nidek in practical screening among normal subjects, the proportion of the C/D ratio less than 0.6 calculated by BV1000 accounts for 96.34%, which is the closest to the clinical statistics among the three OCT machines. The above experimental results and analysis show that the proposed method performs well in cup and disc detection and C/D ratio measurement, and compared with the existing commercial OCT equipment, the C/D ratio measurement results are relatively close to reality, which has certain clinical application value.

How Can We Diagnose Ocular Surface Squamous Neoplasia With Optical Coherence Tomography?

AIM

We aimed to evaluate the effectiveness of optical coherence tomography (OCT) in the differential diagnosis of anterior segment diseases such as ocular surface squamous neoplasia (OSSN) and pterygium.

METHODS

Patients who were pre-diagnosed with either OSSN (21) or pterygium (19) between January 2020 and November 2022 were included in this retrospective study. Anterior segment photographs and anterior segment optical coherence tomography (AS-OCT) measurements were obtained from each patient. Excisional or incisional biopsy materials underwent pathological evaluation.

RESULTS

Preoperative AS-OCT images of the patients with OSSN showed similarities with histopathological specimens. Both ocular and pathological specimens appeared to have a thicker epithelial layer with a distinct change from healthy to neoplastic epithelium. Preoperative AS-OCT images of individuals with pterygium were also comparable with histopathological samples. Both pathological and AS-OCT images of the pterygium patients showed a normal thickness epithelium and a thickened subepithelial layer under the epithelium. The mean epithelial thickness measured with AS-OCT in OSSN patients was found to be 295.3 ± 111.3 µm, while it was 80.7 ± 43.4 µm in pterygium patients. The difference was statistically significant (P<0.001). The receiver operating characteristic (ROC) curve analysis revealed a cut-off value of 97 µm for the differential diagnosis of OSSN from pterygium, with a sensitivity of 100% and specificity of 94.7%.

CONCLUSIONS

AS-OCT can be used as a noninvasive diagnostic tool for the evaluation of ocular surface lesions. Its ability to distinguish between OSSN and pterygium is demonstrated by the statistically significant difference in epithelial thickness and the significant morphological association with histopathological findings.

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.

Optical Coherence Tomography Retinal Nerve Fibre Layer and Ganglion Cell Complex Measurements in Normal Southern Nigerian Eyes

Introduction Glaucoma is the leading cause of irreversible blindness worldwide. It is more severe in people with African heritage, and intraocular pressure remains the only modifiable risk factor in managing glaucoma. Attempts to improve the diagnosis and monitoring of glaucoma are ongoing. One of those attempts is the development of optical coherence tomography (OCT). However, there is a theoretical possibility of a delayed or wrong diagnosis of glaucoma using the OCT because of racial, age, and sex differences in the RNFL (retina nerve fibre layer), GCL (ganglion cell layer), and GCL+IPL (ganglion cell layer and inner plexiform layer) thickness. Objective This study aims to provide the measurements of RNFL, GCL, and GCL+IPL in normal eyes of southern Nigerian patients and specifically to evaluate the relationship of these measurements to gender, age, intra-eye variability, and the Topcon SD-OCT normative database. Method Three hundred and four eyes of 152 patients who had normal OCT scans using the 6x6 RNFL (four sectors) and Macula scans of the Topcon OCT-1 3D Maestro OCT machine were included for analysis. Parametric tests were used to interrogate the relationship between normally distributed parameters and gender, age, and the Topcon reference database. Non-parametric tests were used for non-normally distributed data. Results The male-to-female ratio was 1:1, and ages ranged between 18 and 71 for both genders. The average RNFL values were 111.49 ± 10.44 (right eye - RE) and 111.96 ± 9.66 (left eye - LE). For the GCL, average values were 66.23 ± 4.4 (RE) and 66.34 ± 4.19 (LE). GCL+IPL values were 104.02 ± 6.71 (RE) and 103.89 ± 6.66 (LE). There was no difference between genders (X² = 56.467; df = 46; p = 0.160), and RNFL, GCL, and GCL+IPL values showed a significant reduction as the age of the respondents increased. There was a significant difference between RNFL, GCL, and GCL+IPL values and the Topcon reference database, p < 0.001. Conclusion Significant differences exist between the Southern Nigerian eyes' RNFL, GCL, and GCL+ IPL values and the Topcon OCT-1 3D Maestro reference database. While randomised control trials and extensive multi-centre studies have not been conducted to determine the possible effects of these differences between measured values and reference databases of the OCTs, they need to be considered while diagnosing and managing glaucoma with the OCT.

Deep Learning-Based Glaucoma Screening Using Regional RNFL Thickness in Fundus Photography

Since glaucoma is a progressive and irreversible optic neuropathy, accurate screening and/or early diagnosis is critical in preventing permanent vision loss. Recently, optical coherence tomography (OCT) has become an accurate diagnostic tool to observe and extract the thickness of the retinal nerve fiber layer (RNFL), which closely reflects the nerve damage caused by glaucoma. However, OCT is less accessible than fundus photography due to higher cost and expertise required for operation. Though widely used, fundus photography is effective for early glaucoma detection only when used by experts with extensive training. Here, we introduce a deep learning-based approach to predict the RNFL thickness around optic disc regions in fundus photography for glaucoma screening. The proposed deep learning model is based on a convolutional neural network (CNN) and utilizes images taken with fundus photography and with RNFL thickness measured with OCT for model training and validation. Using a dataset acquired from normal tension glaucoma (NTG) patients, the trained model can estimate RNFL thicknesses in 12 optic disc regions from fundus photos. Using intuitive thickness labels to identify localized damage of the optic nerve head and then estimating regional RNFL thicknesses from fundus images, we determine that screening for glaucoma could achieve 92% sensitivity and 86.9% specificity. Receiver operating characteristic (ROC) analysis results for specificity of 80% demonstrate that use of the localized mean over superior and inferior regions reaches 90.7% sensitivity, whereas 71.2% sensitivity is reached using the global RNFL thicknesses for specificity at 80%. This demonstrates that the new approach of using regional RNFL thicknesses in fundus images holds good promise as a potential screening technique for early stage of glaucoma.

Retinal and circumpapillary nerve fiber layer thickness and associated factors in children

OBJECTIVE

To evaluate the distribution of macula and circumpapillary retina nerve fiber layer (cpRNFL) thickness and other associated factors among grade-1 primary school children in Lhasa using spectral-domain optical coherence tomography (SD-OCT).

METHODOLOGY

OCT assessment was conducted on 1856 grade-1 students from 7 primary schools in Lhasa, Tibet following a successful random stratified sampling of the students. Each child underwent comprehensive general and ocular examinations as well as an SD-OCT detection (12 × 9 mm, 3D wide scan mode, Topcon 3D OCT-1) to assess the thickness of the macula, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex (GCC), and cpRNFL. Multivariate and correlation analyses were performed to evaluate the association of the demographic and ocular variables.

RESULTS

The average age of the 1762 (94.43%) students who underwent OCT assessment was 6.83 ± 0.46 years. Among them, 984 (53.02%) were boys. The number of students who had macular, cpRNFL, and optic disc scans completed and with adequate image quality were 1412 (82.2%), 1277 (74.4%), and 1243 (72.4%), respectively. The average macula full retinal thickness (FRT), GCIPL, GCC, and cpRNFL thickness of the students was 279.19 ± 10.61 μm, 76.41 ± 4.70 μm, 108.15 ± 6.15  μm, and 112.33 ± 13.5 μm, respectively. Multivariate regression and correlation analysis further revealed that boys and girls had significant differences in their average cpRNFL thickness. Moreover, GCC and GCIPL thickness was negatively correlated with IOP but positively correlated with the body mass index. The thickness of all the layers of the macula and cpRNFL were positively correlated with spherical equivalent. Further to this, the average macular FRT, GCIPL, and GCC thicknesses were positively correlated with cpRNFL global thickness.

CONCLUSION

This study describes the normal distribution of macular retina, cpRNFL, and optic disc parameters in grade-1 Tibetan children in Lhasa. It contributes to the establishment of a normative ophthalmology database of Tibetan children, and advances the ability of OCT in ophthalmic disorder diagnosis during long-term monitoring in plateau.

Genetic variation affects morphological retinal phenotypes extracted from UK Biobank optical coherence tomography images

Optical Coherence Tomography (OCT) enables non-invasive imaging of the retina and is used to diagnose and manage ophthalmic diseases including glaucoma. We present the first large-scale genome-wide association study of inner retinal morphology using phenotypes derived from OCT images of 31,434 UK Biobank participants. We identify 46 loci associated with thickness of the retinal nerve fibre layer or ganglion cell inner plexiform layer. Only one of these loci has been associated with glaucoma, and despite its clear role as a biomarker for the disease, Mendelian randomisation does not support inner retinal thickness being on the same genetic causal pathway as glaucoma. We extracted overall retinal thickness at the fovea, representative of foveal hypoplasia, with which three of the 46 SNPs were associated. We additionally associate these three loci with visual acuity. In contrast to the Mendelian causes of severe foveal hypoplasia, our results suggest a spectrum of foveal hypoplasia, in part genetically determined, with consequences on visual function.

Ageing and glaucoma progression of the retinal nerve fibre layer using spectral-domain optical coherence tomography analysis

PURPOSE

To compare the effects of ageing and glaucoma progression on the thickness of the circumpapillary retinal nerve fibre layer (cpRNFL) and to evaluate the performance of a set of optical coherence tomography (OCT) progression analyses.

METHODS

The cpRNFL was measured twice by OCT at each of two visits made 10 years apart in 69 healthy individuals and 49 glaucoma patients. Both visits also included Humphrey 24-2 SITA standard testing. The change in cpRNFL thickness was analysed by linear regression, and a sub-analysis was performed on glaucoma patients with a perimetric mean deviation better than -10 dB at the first visit. The proportion of individuals whose OCT progression analyses indicated progression was also evaluated for the same groups.

RESULTS

The average cpRNFL thickness deteriorated by a mean of -0.16 μm/year in the healthy cohort, increased by 0.03 μm/year in the glaucoma cohort, and deteriorated by -0.24 μm/year in eyes with less severe glaucoma; there were no statistically significant differences between the groups. For 17 (30%) of 56 healthy individuals, at least one of the three different OCT progression analyses incorrectly indicated progression.

CONCLUSIONS

No significant differences in change of cpRNFL thickness between visits were found when comparing healthy subjects with glaucoma patients. Also, further cpRNFL thinning was not observed in glaucomatous eyes in which at least one-third of the visual field had been lost. The OCT progression analyses generated a relatively high proportion of false positives. Using OCT for glaucoma follow-up may not be entirely straightforward.

Optic disc morphometry using spectral domain optical coherence tomography in a Nigerian population

PURPOSE

To assess morphological optic disc dimensions using spectral-domain optical coherence tomography (OCT) in a Nigerian population.

MATERIALS AND METHOD

Good quality SD-OCT scans of the optic disc of 147 eyes of 88 participants were selected, enrolled, and retrospectively reviewed. All subjects had optic nerve head and retinal nerve fibre layer OCT imaging, as well as analysis, done using the Topcon 3D OCT-1 Maestro®. The age, sex, and some OCT-generated optic disc dimensions namely disc area (DA), vertical disc diameter (VDD), horizontal disc diameter (HDD) were retrieved from the database and analyzed.

RESULTS

The mean age of the study subjects was 52.6±20.9 years with a range of 8-90 years; male to female ratio was 1:1.3. The right eye and left eye accounted for 75 and 72 of the 147 scans respectively. The mean DA, VDD, and HDD were 2.54 ± 0.48 mm2, 1926.5 ± 189.6 μm and 1673.9 ± 173.9 μm, respectively. Males had significantly larger DA than females (2.56 ± 0.53 mm2 vs 2.51 ± 0.44 mm2, p = 0.043). The mean DA and VDD of eyes of subjects aged 21-40 years were significantly higher compared to subjects aged 60 years and more (p = 0.008 and 0.001, respectively).

CONCLUSION

The mean optic disc area and diameters are larger than those reported in similar studies involving blacks and other races. The mean disc area reduces with increasing age.

Profiles of Ganglion Cell-Inner Plexiform Layer Thickness in a Multi-Ethnic Asian Population: The Singapore Epidemiology of Eye Diseases Study

PURPOSE

To examine the normative profile and determinants of macular ganglion cell-inner plexiform layer (GCIPL) thickness based on spectral-domain OCT (SD-OCT) in a nonglaucoma, multi-ethnic Asian population.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Ethnic Chinese, Malay, and Indian adults aged ≥40 years recruited from the Singapore Epidemiology of Eye Diseases Study.

METHODS

All participants underwent standardized examinations. The GCIPL thickness was measured using Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA). Participants with glaucoma or poor-quality scans were excluded. Eye-specific data were used. Associations of ocular and systemic factors with GCIPL thickness parameters were investigated using multivariable linear regression with generalized estimating equation models to account for correlation between both eyes.

MAIN OUTCOME MEASURES

GCIPL thickness.

RESULTS

A total of 4464 participants (7520 eyes) consisting of 1625 Chinese, 1212 Malay, and 1627 Indian adults contributed to this analysis. Average GCIPL thickness was 82.6±6.1 μm in Chinese, 81.5±6.8 μm in Malays, and 78.0±6.9 μm in Indians (P < 0.001 by analysis of variance). The 5th percentile limit of average GCIPL thickness was 72 μm in Chinese, 70 μm in Malays, and 67 μm in Indians. In multivariable analysis adjusting for age, gender, axial length, presence of cataract, OCT signal strength, disc area, hypertension, diabetes, and hyperlipidemia, eyes of Indians were observed to have 3.43 μm thinner GCIPL on average compared with Chinese (P < 0.001) and 3.36 μm thinner GCIPL compared with Malays (P < 0.001). In addition, older age (per decade; β = -2.51), female (β = -1.57), longer axial length (per mm; β = -1.54), and presence of chronic kidney disease (β = -1.49) were significantly associated with thinner average GCIPL (all P ≤ 0.008). Larger optic disc area (per mm²; β = 0.78; P < 0.001) was associated with thicker GCIPL. These factors were consistently observed to be significant for superior and inferior hemisphere GCIPL thickness.

CONCLUSIONS

GCIPL thickness profiles were significantly thinner in Indians compared with Chinese and Malays. Our findings further highlight the need of a more refined, ethnic-specific normative database for GCIPL thickness, which in turn may improve the detection and diagnosis of glaucoma in Asians.

Peripapillary retinal nerve fibre layer thinning in genetic generalized epilepsy

PURPOSE

The purpose of this study was to compare the peripapillary retinal nerve fibre layer (RNFL) between patients with genetic generalized epilepsy (GGE) and healthy controls.

METHODS

This prospective observational study was conducted on adults aged 18-60 years. The study group comprised 26 consecutive patients who met the inclusion criteria and 26 healthy age- and sex-matched healthy adults. Peripapillary RNFL thickness was measured by spectral domain optical coherence tomography.

RESULTS

The average peripapillary RNFL thickness was significantly thinner for GGE patients (98.61 μm) than for healthy controls (104.77 μm) (p = 0.016). Similar results were obtained for the left eye. The peripapillary RFNL thickness of all quadrants was lower for GGE patients than for healthy controls, but it was significant only in the superior (p = 0.009) and inferior (p = 0.024) quadrants for both eyes.

CONCLUSIONS

Our results suggest that the peripapillary RNFL is significantly thinner in GGE patients than in healthy participants. We concluded that this microstructural feature might be an intrinsic feature of GGE.