Scanning laser 'en face' retinal imaging of epiretinal membranes

The role of near-infrared reflectance imaging in retinal disease: A systematic review

Near-infrared reflectance (NIR) retinal imaging aids in a better visualization of structures at the level of outer retina, retinal pigment epithelium, and choroid. It has multiple advantages, including easy acquisition in association with structural spectral domain optical coherence tomography, more comfort for patients, and enhanced contrast and spatial resolution. It helps in the diagnosis of chorioretinal diseases that present with minimal funduscopic findings and can be used to follow up many chorioretinal conditions. We describe the chorioretinal NIR imaging appearance and the clinical role of NIR imaging in ocular inflammatory disease, vascular and acquired disease, degenerative disease, tumors, associated systemic condition, toxic and traumatic disease, optic nerve head conditions, and physiological findings.

CLINICAL APPLICATION OF MULTICOLOR IMAGING IN CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To characterize features of central serous chorioretinopathy (CSC) using multicolor (MC) imaging and to compare the efficacy of using MC imaging and traditional color fundus photography (CFP) for detecting features of CSC.

METHODS

A retrospective review of 75 eyes of 69 participants with CSC from the Eye Center of the Renmin Hospital of Wuhan University. The patients underwent same-day CFP, fundus fluorescein angiography (FFA), spectral domain optical coherence tomography (SD-OCT), and MC imaging (including infrared reflectance (IR), green reflectance (GR), blue reflectance (BR), combined standard MC image, and green-blue-enhanced image). Positive CSC lesions were evaluated using FFA and SD-OCT. Features in images of CFP, standard MC, green-blue-enhanced, IR, GR, and BR were analyzed and calculated.

RESULTS

Among the 75 eyes of 69 patients, 75 eyes with subretinal fluid (SRF) and retinal pigment epithelial (RPE) leakage point, and 43 eyes with RPE damage were observed by FFA and SD-OCT. The detection rate of SRF was significantly higher with the standard MC image (92.0%), green-blue-enhanced image (92.0%), IR (88.0%), and GR (88.0%) than that with CFP (66.7%) (P < 0.05). Blue reflectance (45.3%) was associated with lower rate of SRF detection compared to CFP (P < 0.05). The standard MC image (84.0%), green-blue-enhanced image (84.0%), IR (78.7%), and GR (80%) delineated the boundaries of SRF more effectively than CFP (44%). The abnormal areas corresponding to RPE leakage points on FFA were observed with the standard MC image, green-blue-enhanced image, and IR at detection rates of 90.7, 82.7, and 90.7%, respectively, which were significantly higher than with CFP (29.3%) (P < 0.05). However, the detection rates of the abnormalities corresponding to leakage on FFA were lower with GR (5.3%) and BR (1.3%) than those with CFP (P < 0.05). Areas of RPE damage on FFA were observed at the same locations with the standard MC image, green-blue-enhanced image, and IR at detection rates of 97.7, 93.0, and 95.3%, respectively, which were significantly higher than with CFP (41.9%) (P < 0.05). Compared with CFP, the detectable rates of RPE damage on GR (14.0%) and BR (9.3%) were lower (P < 0.05).

CONCLUSION

As an adjunct to SD-OCT, the MC image can delineate the extent or boundaries of SRF more effectively than CFP. As an adjunct to FFA, the MC image can identify foci of leakage more effectively than CFP. The MC image, particularly the IR channel, can identify areas of RPE damage more effectively than CFP. Therefore, the MC image may be a useful adjunct to FFA and OCT for detecting or monitoring CSC.

Preoperative imaging optimized for epiretinal membrane surgery

Background

To compare imaging modalities for visualizing primary epiretinal membrane (ERM) with each other and with intraoperative digital images (IDI) after blue staining.

Methods

The records of consecutive patients operated for primary ERM over a 12-month period were retrospectively reviewed. Preoperative imaging included color fundus photography (CFP), En Face spectral-domain optical coherence tomography (OCT), 45° infrared- (IR) and blue-reflectance (BR) scanning laser ophthalmoscopy. All images were qualitatively analyzed and scored from 0–4 according to the ability to visualize ERM details (0 = no visible ERM or vessel contraction, 1 = vessel contraction, 2 = retinal folds, 3 = ERM limits, 4 = elevated ERM edge). The preoperative ERM morphology was then compared to that seen on the IDI acquired after 1-min blue dye staining when available.

Results

Seventy eyes were included. The highest score for ERM visualization was obtained on BR and En Face OCT. A score of 3 or 4 was obtained in 68.5%, 62.1%, 17.9% and 13.6% of cases on En Face OCT, BR, CFP and IR images, respectively. IDI were available for 20 eyes, and showed a similar ERM morphology compared to preoperative images in most cases: a negative staining pattern corresponded to a plaque on En face OCT in 91% of eyes. However, IDI failed to show the ERM edges in 37.5% of cases.

Conclusion

ERM morphology was better visualized preoperatively by BR and En Face OCT, in a similar way to the IDI after staining. Future intraoperative visualization systems could integrate both imaging modalities overlaid with the IDI for guiding ERM removal instead of staining.

COMPARISON OF RETINAL PATHOLOGY VISUALIZATION IN MULTISPECTRAL SCANNING LASER IMAGING

PURPOSE

To compare retinal pathology visualization in multispectral scanning laser ophthalmoscope imaging between the Spectralis and Optos devices.

METHODS

This retrospective cross-sectional study included 42 eyes from 30 patients with age-related macular degeneration (19 eyes), diabetic retinopathy (10 eyes), and epiretinal membrane (13 eyes). All patients underwent retinal imaging with a color fundus camera (broad-spectrum white light), the Spectralis HRA-2 system (3-color monochromatic lasers), and the Optos P200 system (2-color monochromatic lasers). The Optos image was cropped to a similar size as the Spectralis image. Seven masked graders marked retinal pathologies in each image within a 5 × 5 grid that included the macula.

RESULTS

The average area with detected retinal pathology in all eyes was larger in the Spectralis images compared with Optos images (32.4% larger, P < 0.0001), mainly because of better visualization of epiretinal membrane and retinal hemorrhage. The average detection rate of age-related macular degeneration and diabetic retinopathy pathologies was similar across the three modalities, whereas epiretinal membrane detection rate was significantly higher in the Spectralis images.

CONCLUSION

Spectralis tricolor multispectral scanning laser ophthalmoscope imaging had higher rate of pathology detection primarily because of better epiretinal membrane and retinal hemorrhage visualization compared with Optos bicolor multispectral scanning laser ophthalmoscope imaging.

IDENTIFICATION OF POSTERIOR SEGMENT PATHOLOGY WITH EN FACE RETINAL IMAGING USING MULTICOLOR CONFOCAL SCANNING LASER OPHTHALMOSCOPY

PURPOSE

To assess posterior segment findings on multicolor confocal scanning laser ophthalmoscopy by correlation with spectral domain optical coherence tomography (SD-OCT) and to quantify agreement between these imaging modalities.

METHODS

Retrospective review of 159 eyes of 96 consecutive patients who underwent concurrent imaging with multicolor confocal scanning laser ophthalmoscopy and SD-OCT. Positive percent agreement and negative percent agreement were calculated for each finding identified on infrared, green, blue, and multicolor reflectance images using SD-OCT as a comparator.

RESULTS

Infrared reflectance best detected outer retinal and choroidal findings such as choroidal lesions, retinal pigment epithelium atrophy, peripapillary atrophy, and drusen (positive percent agreement 100, 92, 92, and 67%, respectively). Inner retinal changes including epiretinal membrane, lamellar macular hole, and inner retinal alterations were best detected on blue reflectance (positive percent agreement 94, 50, and 100%, respectively). Composite multicolor reflectance most effectively detected conditions with retinal elevation, including pigment epithelial detachment, intraretinal fluid, and subretinal fluid (positive percent agreement 65, 49, and 54%, respectively). Multicolor confocal scanning laser ophthalmoscopy detected intraretinal and subretinal hemorrhages, which were not detected on SD-OCT (negative percent agreement 87 and 97%, respectively).

CONCLUSION

Multicolor confocal scanning laser ophthalmoscopy is capable of identifying posterior segment pathology at various anatomical depths and may be a useful adjunct to SD-OCT for detecting or monitoring certain retinal conditions.

Comparison of MultiColor fundus imaging and colour fundus photography in the evaluation of epiretinal membrane

PURPOSE

To compare MultiColor fundus imaging (MC) and colour fundus photography (CFP) for the evaluation of epiretinal membrane (ERM).

METHODS

In this retrospective study, 192 eyes (181 patients) that underwent vitrectomy for ERM were imaged using Spectralis optical coherence tomography (for MC) and AFC-210 digital camera (for CFP) 1 week before vitrectomy. Two investigators independently determined the rate of delineability and ERM area for each modality.

RESULTS

The intergrader agreement rates for delineability were very high for both image modalities. The rate of delineability of ERM (%) was higher for MC than for CFP, for both investigators [70.8% versus 52.6% and 73.4% versus 53.6% (both p -)]. Epiretinal membrane (ERM) area measurement showed high agreement between investigators for MC (p = 0.466) but differed significantly between the investigators for CFP (p -). The ERM area determined on MC was significantly wider than that on CFP for both investigators (p - for investigator 1 and p - for investigator 2).

CONCLUSION

The ERM area is more clearly detectable and widely demarcated in MC than in CFP images. MultiColor imaging (MC) may be more sensitive and accurate for early detection of ERM and ERM area measurement.

Clinical application of multicolor optical coherence tomography in the diagnosis of retinal pathologies

Objective:

To assess the clinical application of multicolor optical coherence tomography (OCT) using confocal scanning laser ophthalmoscopy (cSLO) in different retinal pathologies.

Methods:

This observational study was conducted at the Layton Rahmatullah Benevolent Trust (LRBT), Free Base Eye Hospital, Karachi, from April 2018 to June 2018. It includes 36 patients suffering from different retinal pathologies including diabetic retinopathy, age related macular degeneration, and vitreomacular interface disorders using multicolor optical coherence tomography as a screening tool.

Results:

It was found that automated eye tracking system of this new version tool enables ophthalmologists to take high-resolution cSLO reflectance images. The light scatter can be avoided with the use of confocal optics. Appearances of pigment changes and hemorrhages were some of the differences found when compared to the conventional CFP. About 20% in AMD, 37.5% with diabetes and 100% patients with vitreomacular interface disorders could have be easily missed by CFP.

Conclusions:

Multicolor OCT can provide information and figures far more authoritatively than the conventional CFP, which is highly affected by media opacities. To interpret Multicolor OCT ophthalmologists should be watchful with plenty of understanding.

Clinical application of multicolour scanning laser imaging in diabetic retinopathy

To compare the visualization of the lesions of diabetic retinopathy (DR) using multicolour scanning laser imaging (MSLI) and conventional colour fundus photography (CFP). The paired images of diabetic patients who underwent same-day MSLI and CFP examinations were reviewed. Combined multicolour (MC) images were acquired simultaneously using three laser wavelengths: blue reflectance (BR, λ = 488 nm), green reflectance (GR, λ = 518 nm) and infrared reflectance (IR, λ = 820 nm). The number of positive DR lesions was calculated using fundus fluorescein angiography as the reference standard. The visibility of the microaneurysms (Mas) was graded using a scale, and the number of Mas for each method was counted by two masked readers. Eighty eyes of 42 diabetic patients were included. The average grading score for Mas visualization was significantly higher with MC (1.50 ± 0.71) and GR (1.55 ± 0.69) than with CFP (0.95 ± 0.81). The average number of Mas was also significantly higher with MC (11.41 ± 14.02) and GR (11.93 ± 13.43) than with CFP (6.43 ± 9.39). The number of positive Mas, diabetic macular edema (DME) and epiretinal membranes (ERM) were significantly higher with MC than CFP (P < 0.05), while the numbers of cotton wool spots, haemorrhages, hard exudates, venous beading and abnormal new vessels were not significantly different (P > 0.05). Mas and ERM were most effectively detected on GR images, and an elevated greenish shift was clearly visualized in patients with DME on the MC images. MSLI can effectively visualize Mas and other pathological lesions of DR compared with CFP. MSLI with superior resolution may be a useful complement for DME and ERM detection.

VISUALIZATION OF MACULAR PUCKER BY MULTICOLOR SCANNING LASER IMAGING

PURPOSE

To compare the visualization of the epiretinal membrane (ERM) using multicolor imaging (MCI) (Heidelberg Engineering, Carlsbad, CA) and conventional white light flood color fundus photography (FP) (Topcon).

METHODS

The paired images of patients with ERM who underwent same-day MCI and FP examinations were reviewed. Visibility of the ERM was graded using a scale (0: not visible, 1: barely visible, and 2: clearly visible) by masked readers, and surface folds were counted to quantify the membrane visibility for each method. Images from individual color channels in MCI (green, blue, and infrared) were also graded using the same method to further investigate MCI images.

RESULTS

Forty-eight eyes of 42 patients were included. The average ERM visibility score was 1.8 ± 0.37 for MCI and 1.01 ± 0.63 for FP (P < 0.001). The number of the surface folds detected per quadrant was signifi8cantly higher in MCI than that in FP (6.79 ± 3.32 vs. 2.85 ± 2.81, P < 0.001). The ERM was graded with similar scores on the two modalities in 43.8% of the eyes; in 56.2%, the ERM was better visualized on MCI than that on FP. Conventional FP failed to detect ERM in 11.4% of eyes when the mean central retinal thickness was <413 microns. Analysis of laser color reflectance revealed that green reflectance provided better detection of surface folds (5.54 ± 2.12) compared to blue reflectance (4.2 ± 2.34) and infrared reflectance (1.2 ± 0.9).

CONCLUSION

Multicolor scanning laser imaging provides superior ERM detection and delineation of surface folds than conventional FP, primarily due to the green channel present in the combination-pseudocolor image in MCI.

Characterization of Artifacts Associated With Multicolor Confocal Scanning Laser Ophthalmoscopy

BACKGROUND AND OBJECTIVE

To characterize the appearance of three types of artifacts observed on multicolor confocal scanning laser ophthalmoscopy (cSLO).

PATIENTS AND METHODS

Retrospective review of 159 eyes of 96 consecutive patients from the Duke Eye Center who underwent multicolor cSLO with spectral-domain optical coherence tomography (SD-OCT). Infrared (IR), green, blue, and multicolor reflectance images were evaluated for artifacts with corresponding SD-OCT scans available for reference.

RESULTS

Multicolor cSLO artifacts were detected in 23.3% (37 of 159) of eyes and comprised three main patterns: spot, wisp, and net. Only three instances of these artifacts were detected on IR reflectance versus 34, 37, and 35 instances on green, blue, and multicolor reflectance, respectively. Artifacts were observed in 0% of eyes with clear lenses, 27.7% of eyes with cataracts, and in 20.8% of eyes with posterior chamber intraocular lenses.

CONCLUSION

Awareness of spot, wisp, and net artifacts when interpreting multicolor cSLO images may facilitate the identification of true retinal pathology. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:810-815.].

Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography

Purpose

This article reports a method for en face optical coherence tomography (OCT) imaging and quantitative assessment of alterations in both thickness and reflectance of individual retinal layers at different stages of diabetic retinopathy (DR).

Methods

High-density OCT raster volume scans were acquired in 29 diabetic subjects divided into no DR (NDR) or non-proliferative DR (NPDR) groups and 22 control subjects (CNTL). A customized image segmentation method identified eight retinal layer interfaces and generated en face thickness maps and reflectance images for nerve fiber layer (NFL), ganglion cell and inner plexiform layers (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE). Mean thickness and intensity values were calculated in nine macular subfields for each retinal layer.

Results

En face thickness maps and reflectance images of retinal layers in CNTL subjects corresponded to normal retinal anatomy. Total retinal thickness correlated negatively with age in nasal subfields (R ≤−0.31; P ≤ 0.03, N = 51). In NDR subjects, NFL and OPL thickness were decreased (P = 0.05), and ONL thickness was increased (P = 0.04) compared to CNTL. In NPDR subjects, GCLIPL thickness was increased in perifoveal subfields (P< 0.05) and INL intensity was higher in all macular subfields (P = 0.04) compared to CNTL.

Conclusions

Depth and spatially resolved retinal thickness and reflectance measurements are potential biomarkers for assessment and monitoring of DR.

Glaucoma: the retina and beyond

Over 60 million people worldwide are diagnosed with glaucomatous optic neuropathy, which is estimated to be responsible for 8.4 million cases of irreversible blindness globally. Glaucoma is associated with characteristic damage to the optic nerve and patterns of visual field loss which principally involves the loss of retinal ganglion cells (RGCs). At present, intraocular pressure (IOP) presents the only modifiable risk factor for glaucoma, although RGC and vision loss can continue in patients despite well-controlled IOP. This, coupled with the present inability to diagnose glaucoma until relatively late in the disease process, has led to intense investigations towards the development of novel techniques for the early diagnosis of disease. This review outlines our current understanding of the potential mechanisms underlying RGC and axonal loss in glaucoma. Similarities between glaucoma and other neurodegenerative diseases of the central nervous system are drawn before an overview of recent developments in techniques for monitoring RGC health is provided, including recent progress towards the development of RGC specific contrast agents. The review concludes by discussing techniques to assess glaucomatous changes in the brain using MRI and the clinical relevance of glaucomatous-associated changes in the visual centres of the brain.

A Review on Recent Developments for Detection of Diabetic Retinopathy

Diabetic retinopathy is caused by the retinal micro vasculature which may be formed as a result of diabetes mellitus. Blindness may appear as a result of unchecked and severe cases of diabetic retinopathy. Manual inspection of fundus images to check morphological changes in microaneurysms, exudates, blood vessels, hemorrhages, and macula is a very time-consuming and tedious work. It can be made easily with the help of computer-aided system and intervariability for the observer. In this paper, several techniques for detecting microaneurysms, hemorrhages, and exudates are discussed for ultimate detection of nonproliferative diabetic retinopathy. Blood vessels detection techniques are also discussed for the diagnosis of proliferative diabetic retinopathy. Furthermore, the paper elaborates a discussion on the experiments accessed by authors for the detection of diabetic retinopathy. This work will be helpful for the researchers and technical persons who want to utilize the ongoing research in this area.

Enface Thickness Mapping and Reflectance Imaging of Retinal Layers in Diabetic Retinopathy

Purpose

To present a method for image segmentation and generation of enface thickness maps and reflectance images of retinal layers in healthy and diabetic retinopathy (DR) subjects.

Methods

High density spectral domain optical coherence tomography (SDOCT) images were acquired in 10 healthy and 4 DR subjects. Customized image analysis software identified 5 retinal cell layer interfaces and generated thickness maps and reflectance images of the total retina (TR), inner retina (IR), outer retina (OR), and the inner segment ellipsoid (ISe) band. Thickness maps in DR subjects were compared to those of healthy subjects by generating deviation maps which displayed retinal locations with thickness below, within, and above the normal 95% confidence interval.

Results

In healthy subjects, TR and IR thickness maps displayed the foveal depression and increased thickness in the parafoveal region. OR and ISe thickness maps showed increased thickness at the fovea, consistent with normal retinal anatomy. In DR subjects, thickening and thinning in localized regions were demonstrated on TR, IR, OR, and ISe thickness maps, corresponding to retinal edema and atrophy, respectively. TR and OR reflectance images showed reduced reflectivity in regions of increased thickness. Hard exudates appeared as hyper-reflective spots in IR reflectance images and casted shadows on the deeper OR and ISe reflectance images. The ISe reflectance image clearly showed the presence of focal laser scars.

Conclusions

Enface thickness mapping and reflectance imaging of retinal layers is a potentially useful method for quantifying the spatial and axial extent of pathologies due to DR.