Repeatability and reproducibility of macular thickness measurements using fourier domain optical coherence tomography

Retinal Nerve Fiber Layer Changes in Patients With Chronic Obstructive Pulmonary Disease Compared to Healthy Controls: A Meta-analysis

BACKGROUND AND OBJECTIVE

This study investigated changes in retinal nerve fiber layers (RNFL) in patients diagnosed with chronic obstructive pulmonary disease (COPD) compared to healthy control patients, using optical coherence tomography.

METHODS

PubMed, Cochrane Library, and Google Scholar databases were systematically searched for published articles comparing RNFL between patients with COPD and healthy controls. Standardized mean difference (SMD) with 95% confidence interval (CI) was computed to compare continuous variables.

RESULTS

Average RNFL thickness was significantly reduced in COPD patients compared to healthy controls (SMD = -0.31, 95% CI = -0.48 to -0.14, P = 0.0004, I2 = 0%). Average RNFL thickness did not differ significantly between patients with mild/moderate COPD and healthy controls (SMD = -0.17, 95% CI = -0.39 to 0.04, P = 0.12, I2 = 2%), while a statistically significant reduction in average RNFL thickness was noticed in patients with severe COPD compared to healthy controls (SMD = -0.72, 95% CI = -1.23 to -0.21, P = 0.006, I2 = 83%). Average RNFL thickness was significantly higher in patients with mild/moderate COPD compared to patients with severe COPD (SMD = 0.69, 95% CI = 0.29 to 1.09, P = 0.0008, I2 = 66%).

CONCLUSIONS

This meta-analysis showed that RNFL thickness was decreased in patients with COPD compared to healthy controls. Patients diagnosed with severe COPD seem to be more affected and have thinner RNFL. [Ophthalmic Surg Lasers Imaging Retina 2024;55:XX-XX.].

Evaluation of amblyopic eyes with optical coherence tomography angiography and electrophysiological tests

Purpose

To investigate the structural and functional changes of the retina and optic nerve in amblyopia.

Methods

Eighteen patients with unilateral anisometropic amblyopia and 27 age-matched healthy controls were involved in this study. All patients underwent optical coherence tomography angiography (OCTA), pattern visual evoked potential (pVEP), and flash electroretinogram (fERG).

Results

There was no statistically significant difference in terms of the foveal avascular zone (FAZ), perifoveal superficial density, whole superficial density, parafoveal deep density, perifoveal deep density among the eyes (P > 0 0.05). Significant differences were found only in superficial capillary plexus (SCP) vessel density in whole (P = 0.029) and parafoveal (P = 0.008) image. In electrophysiological tests, while VEP latencies of the amblyopic eyes increased compared to nonamblyopic eyes and controls (P = 0.027), VEP amplitudes decreased in amblyopic and nonamblyopic eyes compared to controls (P = 0.01), amplitudes of the rod (P = 0.027) and cones (P < 0.001) also decreased in amblyopic eyes compared to nonamblyopic and healthy eyes. When we assessed the correlation between the parameters of OCTA and electrophysiological test, only a significant correlation was found between parafoveal SCP vessel density and VEP amplitudes (r = 0.341).

Conclusion

We found a significant decrease only in SCP vessel density of the OCTA parameters in amblyopic eyes compared to healthy eyes. We detected a significant relationship between parafoveal SCP vessel density and VEP parameters, which might be associated with the underlying pathophysiology of the amblyopia.

Effects of a high level of illumination before sleep at night on chorioretinal thickness and ocular biometry

The choroid is affected by many factors. One of the factors, change in illumination has been suggested to influence choroidal thickness. However, the effects of bright light before sleep at night on the human eye are not well established. The purpose of this study was to investigate the effects of a high level of illumination in the evening on ocular measurements. Twenty-seven men with myopia spent seven consecutive nights in the sleep laboratory. During the first two nights, subjects were exposed to light at 150 lux between 20:00 and midnight. Then, for five consecutive nights, they were exposed to ambient light at 1000 lux between 20:00 and midnight. Ocular parameters and their diurnal variations were compared between the two periods and the effects of a high level of illumination were analyzed. After subjects were exposed to 1000 lux of illumination, axial length increased with borderline significance (p = 0.064). Macular volume and retinal thickness did not change. However, subfoveal choroidal thickness after exposure to 1000 lux of illumination (245.37 ± 52.84 μm) was significantly lower than that after 150 lux of illumination (268.00 ± 57.10 μm), (p < 0.001). Significant diurnal variations were found in mean keratometry (p = 0.039), intraocular pressure (IOP, p = 0.003), ocular perfusion pressure (OPP, p < 0.0001), macular volume (p = 0.019), and subfoveal choroidal thickness (p < 0.0001). A high level of illumination had significant effects on only IOP and OPP (p = 0.027 and 0.017, respectively). Bright light exposure before sleep at an intensity as high as 1000 lux reduced subfoveal choroidal thickness in healthy young men. In conclusion, diurnal variation in choroidal thickness can be affected by bright light exposure before sleep.

Retinal structural changes in systemic arterial hypertension: an OCT study

PURPOSE

To assess retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and macular thickness changes in young adults with systemic arterial hypertension.

METHODS

This study included 80 young patients (age 23.8 ± 2.8 years) with systemic hypertension (sHT) without any known systemic or ocular disease and 80 age-matched (23.5 ± 2.1 years) healthy controls. Retinal nerve fiber layer thickness, macular thickness, and GCC thickness were measured with spectral-domain optical coherence tomography.

RESULTS

Mean disease duration was 3.45 ± 1.48 years (range 2-10). Differences in intraocular pressure, body mass index, axial length, and spherical equivalent between the groups were insignificant (p&gt;0.05). The differences in RNFL thickness did not differ between the groups. Patients with sHT had significantly lower central macular thickness (p = 0.037), inner superior macular thickness (p = 0.045), and outer temporal superior and outer temporal inferior GCC (p&lt;0.001 for both). The RNFL thickness did not differ significantly in all quadrants between the groups (p&gt;0.05). Systolic and diastolic blood pressure were significantly correlated with inner temporal superior and inner temporal inferior GCC thickness in a negative manner (p&lt;0.05 for all).

CONCLUSIONS

Ganglion cell complex thickness decrease is possibly a better retinal marker for hypertensive changes with respect to RNFL and macular thickness.

Ophthalmic imaging

INTRODUCTION OR BACKGROUND

The last two decades have seen a revolution in ophthalmic imaging. In this review we present an overview of the breadth of ophthalmic imaging modalities in use today and describe how the role of ophthalmic imaging has changed from documenting abnormalities visible on clinical examination to the detection of clinically silent abnormalities which can lead to an earlier and more precise diagnosis.

SOURCES OF DATA

This review is based on published literature in the fields of ophthalmic imaging and with focus on most commonly used imaging modalities.

AREAS OF AGREEMENT

New imaging techniques enable non-invasive evaluation of ocular structures at a resolution of a few micrometres. This has led to a re-evaluation of diagnostic criteria for ocular disease, which were previously defined by clinical findings without significant reference to imaging.

AREAS OF CONTROVERSY

Lack of formal training and clinical guidelines regarding use of new imaging techniques in diagnosing and monitoring various ocular conditions. Lack of large normative databases and interchangeability issues between different commercial machines can hinder the detection of disease progression.

GROWING POINTS

Imaging devices are being constantly refined with improved image capture and image analysis tools.

AREAS TIMELY FOR DEVELOPING RESEARCH

Clinical applications of new techniques and devices have yet to be determined using systematic scientific research methods.

Optical Coherence Tomography (OCT) Device Independent Intraretinal Layer Segmentation

PURPOSE

To develop and test an algorithm to segment intraretinal layers irrespectively of the actual Optical Coherence Tomography (OCT) device used.

METHODS

The developed algorithm is based on the graph theory optimization. The algorithm's performance was evaluated against that of three expert graders for unsigned boundary position difference and thickness measurement of a retinal layer group in 50 and 41 B-scans, respectively. Reproducibility of the algorithm was tested in 30 C-scans of 10 healthy subjects each with the Spectralis and the Stratus OCT. Comparability between different devices was evaluated in 84 C-scans (volume or radial scans) obtained from 21 healthy subjects, two scans per subject with the Spectralis OCT, and one scan per subject each with the Stratus OCT and the RTVue-100 OCT. Each C-scan was segmented and the mean thickness for each retinal layer in sections of the early treatment of diabetic retinopathy study (ETDRS) grid was measured.

RESULTS

The algorithm was able to segment up to 11 intraretinal layers. Measurements with the algorithm were within the 95% confidence interval of a single grader and the difference was smaller than the interindividual difference between the expert graders themselves. The cross-device examination of ETDRS-grid related layer thicknesses highly agreed between the three OCT devices. The algorithm correctly segmented a C-scan of a patient with X-linked retinitis pigmentosa.

CONCLUSIONS

The segmentation software provides device-independent, reliable, and reproducible analysis of intraretinal layers, similar to what is obtained from expert graders.

TRANSLATIONAL RELEVANCE

Potential application of the software includes routine clinical practice and multicenter clinical trials.

The morpho-functional evaluation of retina in amblyopia

PURPOSE

To investigate the morphological or functional differences of retina in amblyopia.

MATERIALS AND METHODS

Forty-one patients with unilateral strabismic, anisometropic or combined amblyopia were included in the study. A control group was composed of 16 normal children. All participants were tested with optical coherence tomography (OCT) and pattern electroretinography (PERG). The findings from amblyopic and nonamblyopic eyes were compared among the amblyopic groups. Also, amblyopic and nonamblyopic eyes were compared with the healthy control eyes.

RESULTS

No significant difference was found in OCT parameters for amblyopic and nonamblyopic eyes among the amblyopic groups (p > 0.05). In the combined and anisometropic groups, ganglion cell complex (GCC) was found to be significantly increased in both amblyopic and nonamblyopic eyes compared to the control group (p < 0.05). In strabismic amblyopia, significant reduction in GCC thickness and increase in foveal thickness were found, compared to nonamblyopic eyes (p = 0.019, p = 0.08). There were no significant differences in PERG amplitude and latency between the amblyopic and the nonamblyopic eyes in amblyopic groups (p > 0.05). PERG amplitude in amblyopic eyes was found to be significantly decreased compared with that in normal eyes (p < 0.05). When the nonamblyopic eyes were compared with the control group, only the anisometropic amblyopia group demonstrated significant reduction in amplitude and prolongation in latency (p = 0.002, p = 0.026).

CONCLUSION

We found no significant differences in morphological and functional measures among amblyopic groups. However, we detected significant differences in the retinal function and morphology of both amblyopic and nonamblyopic eyes compared with healthy control eyes.

Comparison of central macular thickness between two spectral-domain optical coherence tomography in elderly non-mydriatic eyes

AIM

To compare central macular thickness (CMT) measurements obtained by two spectral-domain optical coherence tomography (SD-OCT) exams, and to evaluate measurement reproducibility and agreement between these two exams, and to investigate the relationship between CMT and possible influencing factors such as age, sex, eye (OD/OS), and operators in elderly non-mydriatic eyes.

METHODS

Seventy-two normal subjects were included. Every subject underwent CMT measurement twice using one of two SD-OCT (OSE-2000, Moptim, Shenzhen, China & 3-D OCT-1000, Topcon, Tokyo, Japan) instruments respectively where we randomly chose one eye in each patient for the test; these exams were performed by two operators over an hour period with a brief rest between sessions. Comparison of the OSE-2000 and 3-D OCT-1000 CMT measurements was based on paired-t test. The mean difference between the CMT measurements was calculated. General linear model analyzed the relationships among eye (OD/OS), operator, sex, and CMT values using age as co-variant. All tests were considered statistically significant at P<0.05. The main outcome measures included CMT.

RESULTS

When evaluated with general linear model analysis, CMT measurements were found to have high reproducibility across the two instruments between the two operators for the OSE-2000 single line scan and 3-D OCT-1000 macular scans (P=0.731; P=0.443). There was statistically significant difference in CMT values between the two instruments (P<0.001) and the mean difference was -46.83µm at 95% confidence limits (-49.15,-44.51). Age was positively correlated with CMT (beta coefficient = 0.516, P=0.001; beta coefficient = 0.453, P=0.009) and sex was correlated with CMT from the OSE-2000 (P=0.021) but not with the 3-D OCT-1000 (P=0.056). According to the actual thickness measurements, the CMT of the male was thicker than the female's but there was no statistical difference. There was interaction between sex and eye in OSE-2000 and not in 3-D OCT-1000 (P=0.02; P=0.374). No significant correlation was found between CMT and the influencing factor of eye in both of the instruments (P=0.884; P=0.492).

CONCLUSION

Reproducibility of CMT measurement using the two SD-OCTs is excellent in normal eyes according to the operator factor analysis. OSE-2000 has a different posterior retinal boundary of CMT measurement, which results in the CMT value differences, compared with the 3-D OCT-1000. Age is positively correlated with CMT measurement while sex is correlated with CMT in the OSE-2000 but not in the 3-D OCT-1000 and eye (OD/OS) had no correlation with CMT values. Mydriatic drops may not be necessary for CMT measurement using high scan rate SD-OCT in normal eyes in dark room.

Macular thickness by age and gender in healthy eyes using spectral domain optical coherence tomography

Purpose

To determine normal macular thickness and its variation by age and gender in healthy eyes using spectral-domain optical coherence tomography (SD-OCT).

Methods

In this cross-sectional analysis, two hundred and twenty eyes of 220 healthy subjects underwent raster scanning using Topcon SD-OCT system, at the Department of Ophthalmology, Dow University of Health Sciences and Civil Hospital Karachi, Pakistan. Macular thickness from all 9 regions of the ETDRS map was documented for each subject. Variations in macular thickness measurements by age and gender were determined.

Results

The 220 subjects had a mean age of 45.3 years (16–80 years). Using the ETDRS map, foveal thickness for all subjects was measured to be 229±20.46 µm. Mean macular thickness for all subjects was 262.8±13.34 µm. Male gender was associated with greater foveal (p<0.0001) and mean macular (p<0.0001) thickness compared to females. There was no association of mean macular thickness (r² = 0.01; p>0.05) and foveal thickness (r² = 0.00004; p>0.05) with age.

Conclusion

We have provided normative data for macular thickness using Topcon SD-OCT system. Our results are comparable to some and vary from other reports using the similar OCT system. Our results suggest that male gender is associated with greater macular thickness, while macular thickness has no association with age in healthy eyes. This is the first normative data for macular thickness from Pakistan; benchmark for diagnosing and monitoring macular pathologies. The values obtained in this study may be useful for comparison with other populations, other SD-OCT systems and future imaging technologies.

SDOCT imaging to identify macular pathology in patients diagnosed with diabetic maculopathy by a digital photographic retinal screening programme

Introduction

Diabetic macular edema (DME) is an important cause of vision loss. England has a national systematic photographic retinal screening programme to identify patients with diabetic eye disease. Grading retinal photographs according to this national protocol identifies surrogate markers for DME. We audited a care pathway using a spectral-domain optical coherence tomography (SDOCT) clinic to identify macular pathology in this subset of patients.

Methods

A prospective audit was performed of patients referred from screening with mild to moderate non-proliferative diabetic retinopathy (R1) and surrogate markers for diabetic macular edema (M1) attending an SDOCT clinic. The SDOCT images were graded by an ophthalmologist as SDOCT positive, borderline or negative. SDOCT positive patients were referred to the medical retina clinic. SDOCT negative and borderline patients were further reviewed in the SDOCT clinic in 6 months.

Results

From a registered screening population of 17 551 patients with diabetes mellitus, 311 patients met the inclusion criteria between (March 2008 and September 2009). We analyzed images from 311 patients’ SDOCT clinic episodes. There were 131 SDOCT negative and 12 borderline patients booked for revisit in the OCT clinic. Twenty-four were referred back to photographic screening for a variety of reasons. A total of 144 were referred to ophthalmology with OCT evidence of definite macular pathology requiring review by an ophthalmologist.

Discussion

This analysis shows that patients with diabetes, mild to moderate non-proliferative diabetic retinopathy (R1) and evidence of diabetic maculopathy on non-stereoscopic retinal photographs (M1) have a 42.1% chance of having no macular edema on SDOCT imaging as defined by standard OCT definitions of DME when graded by a retinal specialist. SDOCT imaging is a useful adjunct to colour fundus photography in screening for referable diabetic maculopathy in our screening population.

Automated layer segmentation of macular OCT images using dual-scale gradient information

A novel automated boundary segmentation algorithm is proposed for fast and reliable quantification of nine intra-retinal boundaries in optical coherence tomography (OCT) images. The algorithm employs a two-step segmentation schema based on gradient information in dual scales, utilizing local and complementary global gradient information simultaneously. A shortest path search is applied to optimize the edge selection. The segmentation algorithm was validated with independent manual segmentation and a reproducibility study. It demonstrates high accuracy and reproducibility in segmenting normal 3D OCT volumes. The execution time is about 16 seconds per volume (480x512x128 voxels). The algorithm shows potential for quantifying images from diseased retinas as well.