Background: With the advent of confocal scanning laser ophthalmoscopes (cSLO), fundus autofluorescence (FAF) resulting mainly from lipofuscin accumulation on the level of the retinal pigment epithelium can be visualised in vivo. Various cSLOs are available to document FAF. The authors analysed and compared results of FAF using three different instruments.
Methods: Eight eyes of eight normal volunteers and 18 eyes of 12 patients with different retinal diseases (age related macular degeneration, macular dystrophy, central serous retinopathy) were examined. FAF images were recorded from each subject with the Heidelberg retina angiograph (HRA), the Rodenstock cSLO (RcSLO) and the Zeiss Prototype SM 30-4024 (ZcSLO). For excitation an argon laser (488 nm) was used (barrier filter: HRA 500 nm; RcSLO 515 nm; ZcSLO 521 nm). 32 FAF images were aligned and averaged using the same software for all cSLOs. FAF distribution was measured and grey scale values as well as root mean square (RMS) contrast were compared.
Results: Mean age of all subjects was 55.5 (SD 21.4) years. The maximum grey scale value averaged across all eyes was 76.19 (39.34) for the HRA, 61.44 (22.12) for the ZcSLO and 37.0 (9.97) for the RcSLO. The RMS contrast was 0.46 (0.20) for the ZcSLO, 0.40 (0.12) for the HRA, and 0.13 (0.05) for the RcSLO. The differences between the cSLOs were statistically significant with higher grey scale levels and more contrast for the HRA and ZcSLO than the RcSLO (repeated measures ANOVA; p<0.0001). The differences between the HRA and the ZcSLO were not significant (post hoc comparisons; p<0.05).
Conclusions: All cSLOs allow clinically useful FAF imaging in retinal diseases. However, grey scale levels and contrast were much lower on the RcSLO. Therefore, RcSLO images appear much darker than HRA or ZcSLO images. Furthermore, not all cSLOs have a fixed photodetector gain and a standardised value for the argon laser amplification, which is mandatory for an absolute comparison of FAF imaging results.
scanning laser ophthalmoscope; fundus autofluorescence; lipofuscin; retinal pigment epithelium; macular degeneration
The impact of retinal pathology detected by high-resolution imaging on vision remains largely unexplored. Therefore, the aim of the study was to achieve high-resolution structure-function correlation of the human macula in vivo.
To obtain high-resolution tomographic and topographic images of the macula spectral-domain optical coherence tomography (SD-OCT) and confocal scanning laser ophthalmoscopy (cSLO), respectively, were used. Functional mapping of the macula was obtained by using fundus-controlled microperimetry. Custom software allowed for co-registration of the fundus mapped microperimetry coordinates with both SD-OCT and cSLO datasets. The method was applied in a cross-sectional observational study of retinal diseases and in a clinical trial investigating the effectiveness of intravitreal ranibizumab in macular telangietasia type 2. There was a significant relationship between outer retinal thickness and retinal sensitivity (p<0.001) and neurodegeneration leaving less than about 50 µm of parafoveal outer retinal thickness completely abolished light sensitivity. In contrast, functional preservation was found if neurodegeneration spared the photoreceptors, but caused quite extensive disruption of the inner retina. Longitudinal data revealed that small lesions affecting the photoreceptor layer typically precede functional detection but later cause severe loss of light sensitivity. Ranibizumab was shown to be ineffective to prevent such functional loss in macular telangietasia type 2.
Since there is a general need for efficient monitoring of the effectiveness of therapy in neurodegenerative diseases of the retina and since SD-OCT imaging is becoming more widely available, surrogate endpoints derived from such structure-function correlation may become highly relevant in future clinical trials.
To evaluate the intersession repeatability of retinal thickness measurements in patients with diabetic macular edema (DME) using the Heidelberg Spectralis optical coherence tomography (OCT) algorithm and a publicly available, three-dimensional graph search-based multilayer OCT segmentation algorithm, the Iowa Reference Algorithm.
Thirty eyes from 21 patients diagnosed with clinically significant DME were included and underwent consecutive, registered macula-centered spectral-domain optical coherence scans (Heidelberg Spectralis). The OCT scans were segmented into separate surfaces, and the average thickness between internal limiting membrane and outer retinal pigment epithelium complex surfaces was determined using the Iowa Reference Algorithm. Variability between paired scans was analyzed and compared with the retinal thickness obtained from the manufacturer-supplied Spectralis software.
The coefficient of repeatability (variation) for central macular thickness using the Iowa Reference Algorithm was 5.26 μm (0.62% [95% confidence interval (CI), 0.43–0.71]), while for the Spectralis algorithm this was 6.84 μm (0.81% [95% CI, 0.55–0.92]). When the central 3 mm was analyzed, the coefficient of repeatability (variation) was 2.46 μm (0.31% [95% CI, 0.23–0.38]) for the Iowa Reference Algorithm and 4.23 μm (0.53% [95% CI, 0.39–0.65]) for the Spectralis software.
The Iowa Reference Algorithm and the Spectralis software provide excellent reproducibility between serial scans in patients with clinically significant DME. The publicly available Iowa Reference Algorithm may have lower between-measurement variation than the manufacturer-supplied Spectralis software for the central 3 mm subfield. These findings have significant implications for the management of patients with DME.
Intersession reproducibility of DME imaged by Heidelberg Spectralis OCT was excellent using two different segmentation algorithms. Coefficient of repeatability of central macular thickness using the Heidelberg supplied software was 6.84 μm and using the Iowa Reference Algorithm was 5.26 μm.
OCT; diabetic retinopathy; image analysis; macular edema; retina
Background: With the advent of digital confocal scanning laser ophthalmoscopy it is possible to detect low levels of fluorescence. Here we used a novel confocal scanning laser ophthalmoscope (cSLO) to determine lower limits of dye required for fluorescein (FL) and indocyanine green (ICG) angiography.
Methods: A cSLO (Heidelberg retina angiograph 2, Heidelberg Engineering, Dossenheim, Germany) with an optically pumped solid state laser (488 nm) for FL and a diode laser (790 nm) for ICG angiography (FL/ICG-A) was used. 62 FL-As were performed in 53 patients and 45 ICG-As were performed in 39 patients with neovascular age related macular degeneration. The volume and overall dye content of bolus injections was gradually tapered (FL: 500 mg, 250 mg, 200 mg, 166 mg, 100 mg; ICG: 25 mg, 20 mg, 15 mg, 10 mg, 5 mg, 2.5 mg), while dye concentrations were kept constant at 100 mg/ml for FL and at 5 mg/ml for ICG. Images were obtained 1, 5, 15, and 30 minutes after dye injection. Image quality was evaluated by two independent readers using standardised criteria.
Results: For amounts down to 166 mg for FL and to 5 mg for ICG, sufficient image quality was achieved during all phases following injection. Only late phase images showed less contrast compared to typically used dye amounts, which was irrelevant for interpretation and clinical management.
Conclusions: With the increased sensitivity of this novel cSLO system, amounts of injected dye during FL-A can be reduced to one third for FL and to one fifth for ICG without relevant loss of image quality or information compared to conventionally used dye levels. These amounts can be used for routine angiography and allow relevant savings for units performing FL-A.
confocal scanning laser ophthalmoscopy; fluorescence angiography; fluorescein; indocyanine green
Aim: To evaluate the morphology and visual function of the macula in eyes with adult onset vitelliform macular dystrophy (AVMD).
Methods: 12 eyes of six patients with AVMD were examined by ophthalmoscopy, scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and multifocal electroretinography (mfERGs). The macular lesions were bilateral in all patients and varied from the typical vitelliform (five eyes), faded vitelliform changes with retinal pigment epithelium (RPE) atrophy (five eyes), and a normal fovea associated with small flecks around the macula (two eyes).
Results: SLO demonstrated small abnormal bright spots in the deep retina throughout the posterior retina in all cases. OCT showed a highly reflective fusiform thickened layer at the level of the RPE and choriocapillaris in patients with a submacular yellow vitelliform lesion. A well circumscribed, optically clear space was observed beneath the retinal layer in the macular lesions with RPE atrophy. The mfERGs were significantly reduced not only in the macular area but also in the outermost ring (20–30°) of the mfERGs.
Conclusions: The submacular materials that accumulate within the RPE or subepithelial layers reported in previous histopathological studies of vitelliform lesions can be detected by OCT. In the macular lesions with RPE atrophy, the material may have disappeared leaving a subretinal or subepithelial optical clear space. These SLO and mfERG observations suggest that the morphological and functional abnormalities may not be localised just in the macular area but may be present throughout the posterior pole in eyes with AVMD.
adult onset vitelliform macular dystrophy; optical coherence tomography; ERG; scanning laser ophthalmoscope
To study the relationship between macular ischaemia on fluorescein angiography (FA) and pathomorphology at the foveal centre delineated by spectral-domain optical coherence tomography (OCT) in macular oedema (MO) associated with branch retinal vein occlusion (BRVO).
One hundred and five consecutive eyes of 105 patients with MO (centre point thickness (CPT) ≥300 μm) associated with BRVO in which FA using Heidelberg Retinal Angiography 2 and Spectralis OCT were performed on the same day were retrospectively reviewed. We evaluated the foveal pathomorphology using OCT images and the association with macular ischaemia.
Within 1 year from symptom onset, 94 eyes were classified with perfused macula (34 eyes) or non-perfused macula (60 eyes). Eyes with perfused macula had better visual acuity and less CPT than those with non-perfused macula (P=0.024 and P<0.001, respectively). Fourteen eyes with perfused macula had serous retinal detachment (SRD) alone at the presumed foveal centre (SRD type); seven, a sponge-like swelling at that area (retinal swelling type); 11, foveal cystoid spaces alone (cystoid MO (CMO) type), and 2, with both SRD and foveal cystoid spaces (SRD+CMO type). However, 58 eyes with non-perfused macula had foveal cystoid spaces (42 of CMO type and 16 of SRD+CMO type), with a significant association between them (P<0.001). Among 11 eyes with symptoms exceeding 1 year, 6 eyes had perfused macula, and none had the SRD type.
Most eyes without foveal cystoid spaces have perfused macula in MO associated with BRVO.
branch retinal vein occlusion; macular oedema; spectral domain optical coherence tomography; fluorescein angiography; macular ischemia; cystoid spaces
To report macular thickness values in normal eyes and eyes with diabetic macular edema (DME) using time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT), and to derive a conversion equation.
The index study was a prospective investigation conducted on 80 eyes from 40 normal subjects and 130 eyes from 118 patients with DME seen in our clinic. Retinal thickness values from the central 1 mm of the macula and surrounding four ETDRS subfields were acquired using TD-OCT (Stratus OCT) and SD-OCT (SPECTRALIS HRA+OCT). Measurements of the central (C) subfield from both devices were used to derive a conversion equation. The equation was used to predict SD-OCT values using measurements from TD-OCT. Agreement between predicted and actual SD-OCT measurements was assessed.
In normal eyes, the mean difference between TD-OCT and SD-OCT measurements of the C subfield was 76 μm (CI95=74 and 77, respectively). The conversion equation, y=1.029x+72.49, was derived. In eyes with DME, using the equation, SPECTRALIS-predicted values were 5% higher than actual measurements, with 95% of predicted values falling within 9% of the actual measurements. Relocating SD-OCT grids to match the location on TD-OCT resulted in predicted values falling within 7% of actual measurements.
The percent difference between actual thickness measurements from SPECTRALIS and predicted thickness measurements, using the conversion equation, was within reported limits of repeatability of Stratus in eyes with DME. Our equation may help correlate OCT values from both devices in standard care and clinical trials for DME.
optical coherence tomography; diabetic macular edema; time domain; spectral domain
Spectral Domain Optical Coherence Tomography (SD-OCT) applied to the mouse retina has been limited due to inherent movement artifacts and lack of resolution. Recently, SD-OCT scans from a commercially available imaging system have yielded retinal thickness values comparable to histology. However, these measurements are based on single point analysis of images. Here we report that using the Spectralis HRA+OCT Spectral Domain OCT and Fluorescein Angiography system (Heidelberg Engineering, Heidelberg, Germany), retinal thickness of linear expanses from SD-OCT data can be accurately assessed. This is possible by the development of a Spectralis-compatible ImageJ plug-in that imports 8-bit SLO and 32-bit OCT B-scan images, retaining scale and segmentation data and enabling analysis and 3-D reconstruction. Moreover, mouse retinal layer thickness values obtained with this plug-in exhibit a high correlation to thickness measurements from histology of the same retinas. Thus, use of this ImageJ plug-in results in reliable quantification of long retinal expanses from in vivo SD-OCT images.
Spectral Domain Optical Coherence Tomography (SD-OCT); ImageJ plug-in; retina; mouse; retinal thickness; histology
We studied the appearance of margins of Geographic atrophy in high- resolution optical coherence tomography (OCT) images and correlate those changes with fundus autofluorescence imaging.
Retrospective observational case study.
Patients with geographic atrophy secondary to dry age related macular degeneration (ARMD) were assessed by means of Spectral Domain OCT (Spectralis HRA/OCT; Heidelberg Engineering, Heidelberg, Germany or OTI, Inc, Toronto, Canada) as well as Autofluoresence Imaging (HRA or Spectralis Heidelberg Engineering, Heidelberg, Germany): The outer retinal layer alterations were analyzed in the junctional zone between normal retina and atrophic retina, and correlated with corresponding fundus autofluorescence.
23 eyes of 16 patients aged between 62 years to 96 years were examined. There was a significant association between OCT findings and the fundus autofluorescence findings(r=0.67, p<0.0001). Severe alterations of the outer retinal layers at margins on Spectral OCT correspond significantly to increased autofluorescence; Smooth margins on OCT correspond significantly to normal fundus autofluorescence. (Kappa-0.7348, p<0.0001).
Spectral OCT provides in vivo insight into the pathogenesis of geographic atrophy and its progression. Visualization of reactive changes in the retinal pigment epithelial cells at the junctional zone and correlation with increased fundus autofluorescence; secondary to increased lipofuscin may together serve as determinants of progression of geographic atrophy.
Spectral domain optical coherence tomography (SD-OCT) allows cross-sectional visualization of retinal structures in vivo. Here, we report the efficacy of a commercially available SD-OCT device to study mouse models of retinal degeneration.
C57BL/6 and BALB/c wild type mice and three different mouse models of hereditary retinal degeneration (Rho-/-, rd1, RPE65-/-) were investigated using confocal scanning laser ophthalmoscopy (cSLO) for en face visualization and SD-OCT for cross-sectional imaging of retinal structures. Histology was performed to correlate structural findings in SD-OCT with light microscopic data.
In C57BL/6 and BALB/c mice, cSLO and SD-OCT imaging provided structural details of frequently used control animals (central retinal thickness, CRTC57BL/6 = 237±2μm and CRTBALB/c = 211±10μm). RPE65-/- mice at 11 months of age showed a significant reduction of retinal thickness (CRTRPE65 = 193±2μm) with thinning of the outer nuclear layer. Rho-/- mice at P28 demonstrated degenerative changes mainly in the outer retinal layers (CRTRho = 193±2μm). Examining rd1 animals before and after the onset of retinal degeneration allowed to monitor disease progression (CRTrd1 P11 = 246±4μm, CRTrd1 P28 = 143±4μm). Correlation of CRT assessed by histology and SD-OCT was high (r2 = 0.897).
We demonstrated cross sectional visualization of retinal structures in wild type mice and mouse models for retinal degeneration in vivo using a commercially available SD-OCT device. This method will help to reduce numbers of animals needed per study by allowing longitudinal study designs and facilitate characterization of disease dynamics and evaluation of putative therapeutic effects following experimental interventions.
optical coherence tomography; retinal degeneration; imaging; mouse models
To compare ultra-widefield fluorescein angiography imaging using the Optos® Optomap® and the Heidelberg Spectralis® noncontact ultra-widefield module.
Five patients (ten eyes) underwent ultra-widefield fluorescein angiography using the Optos® panoramic P200Tx imaging system and the noncontact ultra-widefield module in the Heidelberg Spectralis® HRA+OCT system. The images were obtained as a single, nonsteered shot centered on the macula. The area of imaged retina was outlined and quantified using Adobe® Photoshop® C5 software. The total area and area within each of four visualized quadrants was calculated and compared between the two imaging modalities. Three masked reviewers also evaluated each quadrant per eye (40 total quadrants) to determine which modality imaged the retinal vasculature most peripherally.
Optos® imaging captured a total retinal area averaging 151,362 pixels, ranging from 116,998 to 205,833 pixels, while the area captured using the Heidelberg Spectralis® was 101,786 pixels, ranging from 73,424 to 116,319 (P = 0.0002). The average area per individual quadrant imaged by Optos® versus the Heidelberg Spectralis® superiorly was 32,373 vs 32,789 pixels, respectively (P = 0.91), inferiorly was 24,665 vs 26,117 pixels, respectively (P = 0.71), temporally was 47,948 vs 20,645 pixels, respectively (P = 0.0001), and nasally was 46,374 vs 22,234 pixels, respectively (P = 0.0001). The Heidelberg Spectralis® was able to image the superior and inferior retinal vasculature to a more distal point than was the Optos®, in nine of ten eyes (18 of 20 quadrants). The Optos® was able to image the nasal and temporal retinal vasculature to a more distal point than was the Heidelberg Spectralis®, in ten of ten eyes (20 of 20 quadrants).
The ultra-widefield fluorescein angiography obtained with the Optos® and Heidelberg Spectralis® ultra-widefield imaging systems are both excellent modalities that provide views of the peripheral retina. On a single nonsteered image, the Optos® Optomap® covered a significantly larger total retinal surface area, with greater image variability, than did the Heidelberg Spectralis® ultra-widefield module. The Optos® captured an appreciably wider view of the retina temporally and nasally, albeit with peripheral distortion, while the ultra-widefield Heidelberg Spectralis® module was able to image the superior and inferior retinal vasculature more peripherally. The clinical significance of these findings as well as the area imaged on steered montaged images remains to be determined.
peripheral; retina; wide-angle; widefield; ultra-widefield
This pilot study investigated whether high-resolution spectral-domain optical coherence tomography (SD-OCT) could detect differences in inner retinal layer (IRL), peripapillary retinal nerve fiber layer (RNFL), and macular thickness between patients with Parkinson’s disease (PD) and controls.
Both eyes of patients with PD and age-matched controls were imaged with the Heidelberg Spectralis® HRA + OCT. RNFL, IRL, and macular thickness were measured for each eye using Heidelberg software. These measurements were compared with validated, published normal values for macular and RNFL thickness, and compared with matched controls for IRL thickness.
Eighteen eyes from nine subjects with PD and 19 eyes of 16 control subjects were evaluated using SD-OCT. The average age of PD patients was 64 years with a range of 52–75 years. The average age of controls was 67 years with a range of 50–81 years. No significant reduction in IRL thickness was detected between PD patients and age-matched controls at 13 points along a 6 mm horizontal section through the fovea. No significant difference in RNFL thickness was detected between PD patients and published normal values. Overall average RNFL thickness was 97 μm for PD patients, which exactly matched the normative database value. However, significant differences in macular thickness were detected in three of nine subfields between PD subjects and published normal values. In PD subjects, the outer superior subfield was 2.8% thinner (P = 0.026), while the outer nasal and inner inferior subfields were 2.8% (P = 0.016) and 2.7% (P = 0.001) thicker compared to published normal values.
In this pilot study, significant differences in macular thickness were detected in three of nine subfields by SD-OCT. However, SD-OCT did not detect significant reductions in peripapillary RNFL and IRL thickness between PD patients and controls. This suggests that macular thickness measurements by SD-OCT may potentially be used as an objective, noninvasive, and easily quantifiable in vivo biomarker in PD. Larger, longitudinal studies are needed to explore these relationships further.
Parkinson’s disease; spectral-domain optical coherence tomography; nerve fiber layer thickness; macular thickness; inner retinal layer thickness
Purpose. To present a series of retinal disease cases that were imaged by spectral domain optical coherence tomography (SD-OCT) in order to illustrate the potential and limitations of this new imaging modality.
Methods. The series comprised four selected cases (one case each) of age-related macular degeneration (ARMD), diabetic retinopathy (DR), central retinal artery occlusion (CRAO), and branch retinal vein occlusion (BRVO). Patients were imaged using the Heidelberg Spectralis (Heidelberg Engineering, Germany) in SD-OCT mode. Patients also underwent digital fundus photography and clinical assessment.
Results. SD-OCT imaging of a case of age-related macular degeneration revealed a subfoveal choroidal neovascular membrane with detachment of the retinal pigment epithelium (RPE) and neurosensory retina. Using SD-OCT, the cases of DR and BRVO both exhibited macular edema with cystoid spaces visible in the outer retina.
Conclusions. The ability of SD-OCT to clearly and objectively elucidate subtle morphological changes within the retinal layers provides information that can be used to formulate diagnoses with greater confidence.
We aimed to evaluate technical aspects and the clinical relevance of a simultaneous confocal scanning laser ophthalmoscope and a high-speed, high-resolution, spectral-domain optical coherence tomography (SDOCT) device for retinal imaging. The principle of confocal scanning laser imaging provides a high resolution of retinal and choroidal vasculature with low light exposure. Enhanced contrast, details, and image sharpness are generated using confocality. The real-time SDOCT provides a new level of accuracy for assessment of the angiographic and morphological correlation. The combined system allows for simultaneous recordings of topographic and tomographic images with accurate correlation between them. Also it can provide simultaneous multimodal imaging of retinal pathologies, such as fluorescein and indocyanine green angiographies, infrared and blue reflectance (red-free) images, fundus autofluorescence images, and OCT scans (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany). The combination of various macular diagnostic tools can lead to a better understanding and improved knowledge of macular diseases.
Cystoid macular edema (CME) is a condition that involves the macula, causing painless vision loss. In this paper, we report a case of niacin-induced bilateral cystoid macular edema (CME) in a middle-age woman taking low dose of niacin (18 mg of nicotinic acid). Optical coherence tomography (OCT) showed retinal thickening and cystoid spaces in both eyes, whereas fluorescein angiography (FA; HRA 2, Heidelberg Engineering) revealed the absence of fluorescein leakage also in later phases. Four weeks after discontinuation of therapy there were a complete disappearance of macular edema at funduscopic examination and an improvement of visual acuity in both eyes. Furthermore OCT showed a normal retinal profile in both eyes. In our opinion considering the wide availability of niacin, medical monitoring and periodical examination should be considered during niacin administration. To our knowledge, this is the first report in the literature that described the very low-dose niacin-induced bilateral niacin maculopathy.
To evaluate macular thickness in people with diabetes but minimal or no retinopathy using Heidelberg Spectralis optical coherence tomography (OCT).
In a multicenter, cross-sectional study of mean retinal thickness, on Spectralis OCT in the nine standard OCT subfields, spanning a zone with 6-mm diameter, center point, and total retinal volume were evaluated. Central subfield (CSF) thickness was evaluated for association with demographic and clinical factors. Stratus OCT scans also were performed on each participant.
The analysis included 122 eyes (122 participants) with diabetes and no (n = 103) or minimal diabetic retinopathy (n = 19) and no macular retinal thickening on clinical exam. Average CSF thickness was 270 ± 24 μm. Central subfield thickness was significantly greater in males relative to females (mean 278 ± 23 μm vs. 262 ± 22 μm, P < 0.001). After adjusting for gender, no additional factors were found to be significantly associated with CSF thickness (P > 0.10). Mean Stratus OCT CSF thickness was 199 ± 24 μm.
Mean CSF thickness is approximately 70 μm thicker when measured with Heidelberg Spectralis OCT as compared with Stratus OCT among individuals with diabetes in the absence of retinopathy or with minimal nonproliferative retinopathy and a normal macular architecture. CSF thickness values ≥320 μm for males and 305 μm for females (∼2 SDs above the average for this normative cohort) are proposed as gender-specific thickness levels to have reasonable certainty that diabetic macular edema involving the CSF is present using Spectralis measurements.
Central subfield (CSF) thickness is approximately 70 μm greater on Spectralis than on Stratus OCT among individuals with diabetes and minimal or no retinopathy. Proposed sex-specific CSF minimums for trials of center involved diabetic macular edema using Spectralis, are 320 μm for males and 305 μm for females.
To describe a clinical appearance of macular edema secondary to extrafoveal retinal hole using coronal (en-face) optical coherence tomography/scanning laser ophthalmoscopy (OCT/SLO) imaging.
A 76-year-old man developed an extrafoveal retinal hole in his right eye after pars plana vitrectomy and epiretinal membrane removal 1 year after surgery. He complained of decreased central vision. Coronal scan showed extrafoveal retinal hole with multiple retinal cysts surrounding the retinal hole and communicating with the macular area.
The OCT/SLO ophthalmoscope can be useful in understanding pathophysiology of macular edema.
Although outnumbered more than 20:1 by rod photoreceptors, cone cells in the human eye mediate daylight vision and are critical for visual acuity and color discrimination. A variety of human retinal diseases, e.g. age-related macular degeneration (AMD), are characterized by a progressive loss of cone photoreceptors, but the low abundance of cones and the absence of a macula in non-primate mammalian retinas have made it difficult to investigate them directly owing to lack of suitable experimental models. Conventional rodents (laboratory mice and rats) are nocturnal rod dominated species with few cones in the retina, while investigating other animals with cone-rich retinas presents various logistic and technical difficulties. Past work, originating in the early 1900s, has begun to provide insights into cone ultrastructure, but has yet to afford a unified model of cone cell organization. This review summarizes this past work and focuses on the recent introduction of special mammalian models (transgenic mice and diurnal rats rich in cones) that promise to reveal a more unified model of cone photoreceptor organization and its role in retinal diseases. These new mammalian models should allow new investigative techniques such as atomic force microscopy and cryo-electron tomography to advance our understanding of cone photoreceptors, much as has been done with rod photoreceptors.
cone photoreceptors; rod photoreceptors; retinoids; retinoid cycle; chromophore; opsins; retina; vision; rhodopsin; cone pigments; enhanced S-cone syndrome; retinitis pigmentosa; age-related macular degeneration
PURPOSE: To describe the clinical and histopathologic findings in a 72-year-old woman with North Carolina macular dystrophy. METHODS: Clinical examination was performed by slit-lamp biomicroscopy, indirect ophthalmoscopy, color fundus photography, and focal electroretinography. Histopathologic examination of the enucleated left eye consisted of light microscopy. RESULTS: Light microscopy demonstrated a discrete macular lesion characterized by focal absence of photoreceptor cells and retinal pigment epithelium. Bruch's membrane was attenuated in the center of the lesion and associated with marked atrophy of the choriocapillaris. Adjacent to the central lesion, some lipofuscin was identified in the retinal pigment epithelium. CONCLUSIONS: North Carolina macular dystrophy has both clinical and microscopic appearances of a well-demarcated retinal and pigment epithelial lesion confined to the macula. This is consistent with the clinical impression that it is a focal macular dystrophy.
The precise mechanism causing acute macular neuroretinopathy (AMN) is still unknown. A recent report suggested that choroidal circulation impairment correlates with its pathogenesis. We report a rare case with simultaneous onset of AMN and central retinal vein occlusion (CRVO), which is a retinal circulation disorder
A 44-year-old woman complained of central visual loss of the left eye for the previous 2 weeks. The patient’s visual acuity was 0.5 in the left eye (OS). Fundoscopic examination revealed a wedge-shaped, dark reddish-brown lesion at the macula, and CRVO-like retinal hemorrhages OS. Fluorescein angiography revealed retinal vasculitis and hypofluorescence corresponding to the macular lesion. The patient’s scanning laser ophthalmoscopy infrared imaging result led to a diagnosis of AMN. Two weeks after corticosteroid pulse therapy, her visual acuity improved to 1.2 OS, with improvement of macular findings and Humphrey perimetry. When the dose of oral corticosteroid was decreased, the AMN lesion worsened, with recurrence of retinal hemorrhages. Visual functions improved again after an increased dose of corticosteroid.
These results suggest that circulatory disorders almost simultaneously occurred in choroidal and retinal vessels, resulting in the onset of both AMN and CRVO.
choroidal circulation; optical coherence tomography; retinal circulation; systemic corticosteroid therapy
The canine is an important large animal model of human retinal genetic disorders. Studies of ganglion cell distribution in the canine retina have identified a visual streak of high density superior to the optic disc with a temporal area of peak density known as the area centralis. The topography of cone photoreceptors in the canine retina has not been characterized in detail, and in contrast to the macula in humans, the position of the area centralis in dogs is not apparent on clinical funduscopic examination. The purpose of this study was to define the location of the area centralis in the dog and to characterize in detail the topography of rod and cone photoreceptors within the area centralis. This will facilitate the investigation and treatment of retinal disease in the canine.
We used peanut agglutinin, which labels cone matrix sheaths and antibodies against long/medium wavelength (L/M)- and short wavelength (S)-cone opsins, to stain retinal cryosections and flatmounts from beagle dogs. Retinas were imaged using differential interference contrast imaging, fluorescence, and confocal microscopy. Within the area centralis, rod and cone size and density were quantified, and the proportion of cones expressing each cone opsin subtype was calculated. Using a grid pattern of sampling in 9 retinal flatmounts, we investigated the distribution of cones throughout the retina to predict the location of the area centralis.
We identified the area centralis as the site of maximal density of rod and cone photoreceptor cells, which have a smaller inner segment cross-sectional area in this region. L/M opsin was expressed by the majority of cones in the retina, both within the area centralis and in the peripheral retina. Using the mean of cone density distribution from 9 retinas, we calculated that the area centralis is likely to be centered at a point 1.5 mm temporal and 0.6 mm superior to the optic disc. For clinical funduscopic examination, this represents 1.2 disc diameters temporal and 0.4 disc diameters superior to the optic disc.
We have described the distribution of rods and cone subtypes within the canine retina and calculated a predictable location for the area centralis. These findings will facilitate the characterization and treatment of cone photoreceptor dystrophies in the dog.
To evaluate macular thickness profiles using spectral-domain optical coherence tomography (SDOCT) and image segmentation in patients with chronic exposure to hydroxychloroquine.
This study included 8 patients with chronic exposure to hydroxychloroquine (Group 1) and 8 controls (Group 2). Group 1 patients had no clinically-evident retinal toxicity. All subjects underwent SDOCT imaging of the macula. An image segmentation technique was used to measure thickness of 6 retinal layers at 200 µm intervals. A mixed-effects model was used for multivariate analysis.
By measuring total retinal thickness either at the central macular (2800 µm in diameter), the perifoveal region 1200-µm-width ring surrounding the central macula), or the overall macular area (5200 µm in diameter), there were no significant differences in the thickness between Groups 1 and 2. On an image segmentation analysis, selective thinning of the inner plexiform + ganglion cell layers (p=0.021) was observed only in the perifoveal area of the patients in Group 1 compared to that of Group 2 by using the mixed-effects model analysis.
Our results suggest that chronic exposure to hydroxychloroquine is associated with thinning of the perifoveal inner retinal layers, especially in the ganglion cell and inner plexiform layers, even in the absence of functional or structural clinical changes involving the photoreceptor or retinal pigment epithelial cell layers. This may be a contributing factor as the reason most patients who have early detectable signs of drug toxicity present with paracentral or pericentral scotomas.
hydroxychloroquine; perifoveal; parafoveal; ganglion cell; retinal toxicity; OCT
To assess macular photoreceptor abnormalities in eyes with retinitis pigmentosa (RP) with preserved central vision using adaptive optics scanning laser ophthalmoscopy (AO-SLO).
Fourteen eyes of 14 patients with RP (best-corrected visual acuity 20/20 or better) and 12 eyes of 12 volunteers underwent a full ophthalmologic examination, fundus autofluorescence, spectral-domain optical coherence tomography (SD-OCT), and imaging with a prototype AO-SLO system. Cone density and spatial organization of the cone mosaic were assessed using AO-SLO images.
In 3 eyes with RP and preserved central vision, cones formed a mostly regular mosaic pattern with small patchy dark areas, and in 10 eyes, the cone mosaic patterns were less regular, and large dark regions with missing cones were apparent. Only one eye with RP demonstrated a normal, regular cone mosaic pattern. In eyes with RP, cone density was significantly lower at 0.5 mm and 1.0 mm from the center of the fovea compared to normal eyes (P<0.001 and 0.021, respectively). At 0.5 mm and 1.0 mm from the center of the fovea, a decreased number of cones had 6 neighbors in eyes with RP (P = 0.002 for both). Greater decrease in cone density was related to disruption of the photoreceptor inner segment (IS) ellipsoid band on SD-OCT images (P = 0.044); however, dark regions were seen on AO-SLO even in areas of continuous IS ellipsoid on SD-OCT. Decreased cone density correlated thinner outer nuclear layer (P = 0.029) and thinner inner segment and outer segment thickness (P = 0.011) on SD-OCT.
Cone density is decreased and the regularity of the cone mosaic spatial arrangement is disrupted in eyes with RP, even when visual acuity and foveal sensitivity are good. AO-SLO imaging is a sensitive quantitative tool for detecting photoreceptor abnormalities in eyes with RP.
AIM—To assess the morphological change in retinal topography using a scanning laser tomographer following macular hole surgery. To compare the results of scanning laser tomography with clinical evaluation and visual function assessment.
METHODS—The sample for this pilot study comprised four eyes exhibiting different stages of macular hole formation preoperatively. Subjects were assessed preoperatively and at 1 and 3 months postoperatively. Each assessment included visual acuity, letter contrast sensitivity, clinical examination (including automated static perimetry), and scanning laser tomography. The Heidelberg retina tomograph (HRT) was used to acquire digitised scanning laser tomography images of the macula (10° and 20° fields). Surgery essentially comprised vitrectomy, peeling of the posterior hyaloid face, if still attached, and intraocular gas tamponade. The magnitude and significance of topographic change were determined postoperatively using the HRT topographic difference facility.
RESULTS—Topographic difference analysis of the right and left eyes of case 1 showed a significant reduction in the height of the retina postoperatively. Topographic difference analysis of case 2 showed no significant change in topography. Topographic difference analysis of case 3 showed a significant increase in the height of the retina postoperatively. Scanning laser tomography agreed with clinical assessment based upon fundus biomicroscopy in three of the four eyes studied; the postoperative closure of the stage 2 macular hole (as noted by clinical assessment) proved to be too small to reach statistical significance. Scanning laser tomography agreed with the assessment of visual function in two eyes; the agreement between scanning laser tomography and visual function depends, in part, on the stage of development of the macular hole.
CONCLUSION—Scanning laser tomography provides an objective evaluation of the outcome of macular hole surgery. Studies employing larger sample sizes are required to fully determine the clinical worth of the technique.
To understand the prevalence of Cryptosporidium infection in rodents in China and to assess the potential role of rodents as a source for human cryptosporidiosis, 723 specimens from 18 rodent species were collected from four provinces of China and examined between August 2007 and December 2008 by microscopy after using Sheather's sugar flotation and modified acid-fast staining. Cryptosporidium oocysts were detected in 83 specimens, with an overall prevalence of 11.5%. Phodopus sungorus, Phodopus campbelli, and Rattus tanezumi were new reported hosts of Cryptosporidium. The genotypes and subtypes of Cryptosporidium strains in microscopy-positive specimens were further identified by PCR and sequence analysis of the small subunit rRNA and the 60-kDa glycoprotein (gp60) genes. In addition to Cryptosporidium parvum, C. muris, C. andersoni, C. wrairi, ferret genotype, and mouse genotype I, four new Cryptosporidium genotypes were identified, including the hamster genotype, chipmunk genotype III, and rat genotypes II and III. Mixed Cryptosporidium species/genotypes were found in 10.8% of Cryptosporidium-positive specimens. Sequence analysis of the gp60 gene showed that C. parvum strains in pet Siberian chipmunks and hamsters were all of the subtype IIdA15G1, which was found previously in a human isolate in The Netherlands and lambs in Spain. The gp60 sequences of C. wrairi and the Cryptosporidium ferret genotype and mouse genotype I were also obtained. These findings suggest that pet rodents may be potential reservoirs of zoonotic Cryptosporidium species and subtypes.