Infrared Scanning Laser Ophthalmoscope Research Articles

Accuracy and Time Comparison Between Side-by-Side and Artificial Intelligence Overlayed Images.

The purpose of this study was to evaluate the accuracy and the time to find a lesion, taken in different platforms, color fundus photographs and infrared scanning laser ophthalmoscope images, using the traditional side-by-side (SBS) colocalization technique to an artificial intelligence (AI)-assisted technique. Fifty-three pathological lesions were studied in 11 eyes. Images were aligned using SBS and AI overlaid methods. The location of each color fundus lesion on the corresponding infrared scanning laser ophthalmoscope image was analyzed twice, one time for each method, on different days, for two specialists, in random order. The outcomes for each method were measured and recorded by an independent observer. The colocalization AI method was superior to the conventional in accuracy and time (P < .001), with a mean time to colocalize 37% faster. The error rate using AI was 0% compared with 18% in SBS measurements. AI permitted a more accurate and faster colocalization of pathologic lesions than the conventional method. [Ophthalmic Surg Lasers Imaging Retina 2023;54:108-113.].

Artificial Intelligence for Automated Overlay of Fundus Camera and Scanning Laser Ophthalmoscope Images.

PurposeThe purpose of this study was to evaluate the ability to align two types of retinal images taken on different platforms; color fundus (CF) photographs and infrared scanning laser ophthalmoscope (IR SLO) images using mathematical warping and artificial intelligence (AI).MethodsWe collected 109 matched pairs of CF and IR SLO images. An AI algorithm utilizing two separate networks was developed. A style transfer network (STN) was used to segment vessel structures. A registration network was used to align the segmented images to each. Neither network used a ground truth dataset. A conventional image warping algorithm was used as a control. Software displayed image pairs as a 5 × 5 checkerboard grid composed of alternating subimages. This technique permitted vessel alignment determination by human observers and 5 masked graders evaluated alignment by the AI and conventional warping in 25 fields for each image.ResultsOur new AI method was superior to conventional warping at generating vessel alignment as judged by masked human graders (P < 0.0001). The average number of good/excellent matches increased from 90.5% to 94.4% with AI method.ConclusionsAI permitted a more accurate overlay of CF and IR SLO images than conventional mathematical warping. This is a first step toward developing an AI that could allow overlay of all types of fundus images by utilizing vascular landmarks.Translational RelevanceThe ability to align and overlay imaging data from multiple instruments and manufacturers will permit better analysis of this complex data helping understand disease and predict treatment.

Postnatal maturation of the fovea in Macaca mulatta using optical coherence tomography

Changes in the foveal anatomy during infancy are an important component in early development of spatial vision. The present longitudinal study in rhesus monkeys was undertaken to characterize the postnatal maturation of the fovea. Starting at four weeks after birth, the retinas of the left eyes of sixteen infant monkeys were imaged using spectral domain optical coherence tomography (SD OCT). Retinal scans were repeated every 30 days during the first year of life and every 60 days thereafter. Volume scans through the fovea were registered, scaled using a three surface schematic eye, and analyzed to measure foveal pit parameters. The individual layers of the retina were manually segmented and thicknesses were measured over a transverse distance of 1250 microns from the center of the foveal pit. Based on infrared scanning laser ophthalmoscope (IR SLO) images acquired with the SD OCT system, there were significant changes in the extent of the retina scanned as the eyes matured. Using a three-surface schematic eye, the length of each scan could be computed and was validated using image registration (R2 = 0.88, slope = 1.003, p < 0.05). Over the first 18 months of life, the mean retinal thickness at the pit center had increased by 21.4% with a corresponding 20.3% decrease in pit depth. The major changes occurred within the first 120 days, but did not stabilize until a year after birth. In Macaca mulatta infants, the primary anatomical maturation of the fovea occurs within the first few months of life, as determined by longitudinal data from SD OCT measurements. The timelines for maturation of the fovea correspond well with the normal development of the lateral geniculate nucleus, cortical neurophysiology, and spatial resolution in monkeys.

A novel method for segmentation of Infrared Scanning Laser Ophthalmoscope (IR-SLO) images of retina.

Retinal vessel segmentation forms an essential element of automatic retinal disease screening systems. The development of multimodal imaging system with IR-SLO and OCT could help in studying the early stages of retinal disease. The advantages of IR-SLO to examine the alterations in the structure of retina and direct correlation with OCT can be useful for assessment of various diseases. This paper presents an automatic method for segmentation of IR-SLO fundus images based on the combination of morphological filters and image enhancement techniques. As a first step, the retinal vessels are contrasted using morphological filters followed by background exclusion using Contrast Limited Adaptive Histogram Equalization (CLAHE) and Bilateral filtering. The final segmentation is obtained by using Isodata technique. Our approach was tested on a set of 26 IR-SLO images and results were compared to two set of gold standard images. The performance of the proposed method was evaluated in terms of sensitivity, specificity and accuracy. The system has an average accuracy of 0.90 for both the sets.

Pseudodrusen Subtypes as Delineated by Multimodal Imaging of the Fundus

To subclassify pseudodrusen based on their appearance in multimodal imaging. Retrospective, observational series. The color fundus photographs and infrared scanning laser ophthalmoscope (IR-SLO) images of patients with pseudodrusen were evaluated along with spectral-domain optical coherence tomography (SD OCT) by masked readers. Distinct types of pseudodrusen could be differentiated. There were 140 eyes of 93 patients with a mean age of 82.4 years. Multimodal imaging analysis showed 3 subtypes of pseudodrusen. One principal type was an orderly array of whitish discrete accumulations principally located in the perifovea, termed dot pseudodrusen. They appeared as hyporeflective spots, often with a target configuration, in IR-SLO images. The second type was interconnected bands of yellowish-white material forming a reticular pattern, called ribbon pseudodrusen, which were located in the perifovea. This subtype was faintly hyporeflective in IR-SLO imaging. Dot pseudodrusen were detected more commonly with IR-SLO imaging than in color photography (P= .014) and ribbon pseudodrusen were seen more frequently in color than in IR-SLO images (P < .001). An uncommon third type of pseudodrusen, yellow-white globules primarily located peripheral to the perifoveal region, appeared hyper-reflective in IR-SLO and were called peripheral pseudodrusen. All 3 types were seen as subretinal drusenoid deposits by SD OCT. Pseudodrusen may be classified into at least 3 categories, each with optimal methods of detection and only 1 that formed a reticular pattern. These findings suggest pseudodrusen could contain differing constituents and therefore may vary in conferred risk for progression to advanced age-related macular disease.

Feasibility of a Method for En Face Imaging of Photoreceptor Cell Integrity

To report a method for en face imaging of the photoreceptor inner and outer segment junction by spectral-domain optical coherence tomography (SD OCT) and to describe findings in normal subjects and patients with various retinal diseases. Observational case series. SD OCT images were acquired from 6 normal subjects (mean age, 44 ± 11 years) and from 5 subjects with retinal diseases (mean age, 66 ± 22 years). A customized high-density SD OCT volume scan was acquired on the retina. SD OCT B-scan images were segmented automatically to extract intensity data along the inner and outer segment junction. Data obtained from the raster B-scans were combined to generate an inner and outer segment en face image in a 4.4 × 4.4-mm retinal area centered on the fovea. The foveal-to-parafoveal mean intensity ratio was measured, and repeatability was determined. An infrared scanning laser ophthalmoscope image was acquired and was cropped to provide a field of view similar to the inner and outer segment en face image. Inner and outer segment en face images generated in normal subjects provided clear visualization of the retinal vasculature, matching the vascular network observed in the infrared scanning laser ophthalmoscope image. In normal subjects, the foveal-to-parafoveal mean intensity ratio was 0.88 ± 0.06, and repeatability of measurements was, on average, 7%. In macular hole, a dark circular region was observed in the inner and outer segment en face image, indicative of photoreceptor cell loss. In age-related macular degeneration, the en face image displayed nonuniform texture corresponding to topographic variations in the inner and outer segment junction. In central serous retinopathy, areas of lower intensity were visible on the en face image corresponding to regions of prior neurosensory elevation. In cystoid macular edema, reduced intensity was present in the inner and outer segment en face image in areas with increased retinal thickness. In diabetic retinopathy, the inner and outer segment en face image displayed regions of reduced intensity resulting from edema, laser scars, or both. Detection of intensity abnormalities in the inner and outer segment en face image is useful for monitoring the integrity of photoreceptor cells in the course of disease progression and therapeutic intervention.

ISSUES IN QUANTIFYING ATROPHIC MACULAR DISEASE USING RETINAL AUTOFLUORESCENCE

In Brief Purpose: To demonstrate the potential and limits of autofluorescence imaging in identifying and delineating areas of atrophy. Methods: Fundus photographs and infrared scanning laser ophthalmoscope (SLO) imaging, SLO macular perimetry, and SLO autofluorescence imaging results were compared for two patients with geographic atrophy (GA) from age-related macular degeneration, one patient with pigmentary alteration of the retina, and two patients with Stargardt disease. The main outcome measure in this case series was the presence of reduced autofluorescence. Results: Drusen may become undetectable during autofluorescence imaging for some patients, allowing simple identification of areas of GA with areas of reduced autofluorescence. In other patients, drusen themselves have decreased autofluorescence, despite having intact retinal function in the retina overlying them. Some patients may have areas of reduced autofluorescence that persist for many years, without evidence of the development of atrophy. In Stargardt disease, decreased autofluorescence can easily detect and delineate areas of scotoma. Areas with mottled autofluorescence may have overlying function, but the function may not be adequate to support a fixation locus in that area. Conclusions: Using decreased autofluorescence to delineate areas of atrophy may be helpful in atrophic macular disorders. For GA, correlation with fundus photographs or macular perimetry findings may be necessary to differentiate between drusen and atrophy. For Stargardt disease, the nature of areas of decreased autofluorescence may help explain visual function of those areas. A reduction in retinal autofluorescence is a valuable tool for delineating areas of atrophy in age–related macular degeneration and Shargardt disease.

ISSUES IN QUANTIFYING ATROPHIC MACULAR DISEASE USING RETINAL AUTOFLUORESCENCE

To demonstrate the potential and limits of autofluorescence imaging in identifying and delineating areas of atrophy. Fundus photographs and infrared scanning laser ophthalmoscope (SLO) imaging, SLO macular perimetry, and SLO autofluorescence imaging results were compared for two patients with geographic atrophy (GA) from age-related macular degeneration, one patient with pigmentary alteration of the retina, and two patients with Stargardt disease. The main outcome measure in this case series was the presence of reduced autofluorescence. Drusen may become undetectable during autofluorescence imaging for some patients, allowing simple identification of areas of GA with areas of reduced autofluorescence. In other patients, drusen themselves have decreased autofluorescence, despite having intact retinal function in the retina overlying them. Some patients may have areas of reduced autofluorescence that persist for many years, without evidence of the development of atrophy. In Stargardt disease, decreased autofluorescence can easily detect and delineate areas of scotoma. Areas with mottled autofluorescence may have overlying function, but the function may not be adequate to support a fixation locus in that area. Using decreased autofluorescence to delineate areas of atrophy may be helpful in atrophic macular disorders. For GA, correlation with fundus photographs or macular perimetry findings may be necessary to differentiate between drusen and atrophy. For Stargardt disease, the nature of areas of decreased autofluorescence may help explain visual function of those areas.

Measurement of Subjective and Objective Cyclodeviation in Oblique Eye Muscle Disorders

Surgically induced changes of eye torsion often show a subjective over-effect which resolves later on. Hence the authors initiated a prospective study with the purpose of analyzing motoric and sensoric elements in postoperative rotational changes by comparing subjective and objective cycloduction. Fundus cyclometry, a new method for measurement of objective cycloduction, is introduced. An image of the posterior pole is obtained by an infrared Scanning Laser Ophthalmoscope without pupil dilatation and is transferred to a computer system by which nature and amount of objective cycloduction is calculated. Four patients who underwent surgery for oblique eye muscle disorders are presented. Objective torsional changes were slightly higher than subjective changes. Postoperative reduction of torsional changes was noted subjectively and objectively in all cases. For statistical reasons further investigations on a great number of patients are needed to interpret the postoperative changes in terms of motoric and sensoric cyclofusion.

Detection of Subretinal Neovascular Membranes With Indocyanine Green and an Infrared Scanning Laser Ophthalmoscope

We studied 80 patients with subretinal neovascular membranes to demonstrate the features and limitations of indocyanine green angiography. Indocyanine green increased the detection of ill-defined membranes or those in larger exudative maculopathies. Each membrane had a characteristic small dark rim that demarcated it from surrounding choroidal tissue. Nevertheless, the complex vascular structures of the choroid and retina, which are displayed at one time, can sometimes render the separation of new vessels difficult when displayed at the same time. The results of our study indicate that indocyanine green angiography may be suggested as an additional diagnostic tool in cases of ill-defined or exudative subretinal neovascular membranes.

Quantitative image analysis of macular drusen from fundus photographs and scanning laser ophthalmoscope images.

Drusen are common features in the ageing macula and are associated with exudative age-related macular degeneration (ARMD). They appear as characteristic structures in indirect mode infrared scanning laser ophthalmoscope (SLO) images. Manual counting of drusen area in SLO images has shown no significant difference from that in standard fundus photographs in 6 eyes of 5 patients (p > 0.5). Computerised image processing techniques have been applied to digitised colour fundus photographs and indirect mode images to quantify the area of the macula affected by drusen in an automated fashion. Application of these methods may permit objective and repeatable assessment of the natural history of macular drusen. For a specificity of 90%, a sensitivity of 60% for colour fundus photographs and 35% for SLO images has been achieved, when compared with manual counting. The colour fundus photograph method also showed superior reproducibility compared with the SLO technique.

Clinical investigation of an infrared digital scanning laser ophthalmoscope.

An infrared scanning laser ophthalmoscope (SLO) has been custom built in order to investigate the application of confocal and indirect mode SLO imaging to patients with fundus disease. Infrared light is reflected from the fundus to a greater extent than visible light permitting lower illumination power and, as it penetrates the retinal pigment epithelium, choroidal structures can be readily imaged. Furthermore, as conventional infrared illumination and detection systems are not well suited to ophthalmoscopy, this area is underdeveloped as a potential source of useful clinical data. Confocal, direct and indirect imaging modes have been used to image fundi of normal volunteers and patients with fundus disease. In comparison with conventional fundus photography confocal infrared SLO imaging improves visualisation of choroidal vasculature, retinal pigment epithelial abnormalities, laser photocoagulation scars, and optic disc pores in the lamina cribrosa. Direct infrared SLO imaging enables fundus visualisation through nuclear lens opacities. Furthermore, indirect mode imaging enhances significantly the appearance of macular drusen. The potential clinical benefit of these observations is discussed.

Detection of Subretinal Neovascular Membranes With Indocyanine Green and an Infrared Scanning Laser Ophthalmoscope

We studied 80 patients with subretinal neovascular membranes to demonstrate the features and limitations of indocyanine green angiography. Indocyanine green increased the detection of ill-defined membranes or those in larger exudative maculopathies. Each membrane had a characteristic small dark rim that demarcated it from surrounding choroidal tissue. Nevertheless, the complex vascular structures of the choroid and retina, which are displayed at one time, can sometimes render the separation of new vessels difficult when displayed at the same time. The results of our study indicate that indocyanine green angiography may be suggested as an additional diagnostic tool in cases of ill-defined or exudative subretinal neovascular membranes.