Automation improves repeatability of retinal oximetry measurements.

PURPOSE: Retinal oximetry is a technique based on spectrophotometry where images are analyzed with software capable of calculating vessel oxygen saturation and vessel diameter. In this study, the effect of automation of measurements of retinal vessel oxygen saturation and vessel diameter is explored. METHODS: Until now, operators have had to choose each vessel segment to be measured explicitly. A new, automatic version of the software automatically selects the vessels once the operator defines a measurement area. Five operators analyzed image pairs from the right eye of 23 healthy subjects with semiautomated retinal oximetry analysis software, Oxymap Analyzer (v2.5.1), and an automated version (v3.0). Inter- and intra-operator variability was investigated using the intraclass correlation coefficient (ICC) between oxygen saturation measurements of vessel segments in the same area of the retina. RESULTS: For semiautomated saturation measurements, the inter-rater ICC was 0.80 for arterioles and venules. For automated saturation measurements, the inter-rater ICC was 0.97 for arterioles and 0.96 for venules. For semiautomated diameter measurements, the inter-rater ICC was 0.71 for arterioles and venules. For automated diameter measurements the inter-rater ICC was 0.97 for arterioles and 0.95 for venules. The inter-rater ICCs were different (p < 0.01) between the semiautomated and automated version in all instances. CONCLUSION: Automated measurements of retinal oximetry values are more repeatable compared to measurements where vessels are selected manually.

Nasalization of Central Retinal Vessel Trunk Predicts Rapid Progression of Central Visual Field in Open-Angle Glaucoma.

Central visual field (CVF) loss is important in maintaining vision-related quality of life in eyes with open-angle glaucoma (OAG). The present study investigated whether nasalized location of central retinal vessel trunk (CRVT) at baseline is associated with rapid rate of CVF loss in early-stage OAG eyes. This study included 76 OAG eyes with high nasalization CRVT [HNL] group and 75 OAG eyes with low nasalization CRVT [LNL] group matched for glaucoma severity at baseline that showed progressive visual field (VF) loss. The rates of mean threshold changes at various regions were compared in the two groups using a linear mixed model. Clinical variables associated with rapid rate of CVF progression were also identified using a linear mixed model. The rate of CVF loss in the central 10° was significantly higher in the HNL group than that in the LNL group (-0.452 dB/year vs. -0.291 dB/year, P < 0.001). The average and inferior hemi-macular ganglion cell inner plexiform layer (GCIPL) progression rates were significantly faster in the HNL group than in the LNL group (P < 0.05). Nasalized location of CRVT was an independent predictor of a more rapid VF loss in the central 10° region (P < 0.05).

Structural analysis of retinal blood vessels in patients with COPD during a pulmonary rehabilitation program.

Cardiovascular diseases are frequently present in chronic obstructive pulmonary disease (COPD). Population-based studies found associations between retinal vessel diameters and cardiovascular health, but it is unknown whether this also applies to COPD patients. Therefore, we measured retinal vessel diameters in COPD patients and aimed to determine the association with cardiovascular risk factors, lung function, and functional outcomes. In addition, we investigated whether an exercise-based pulmonary rehabilitation (PR) program would change retinal vessel diameters, as a proxy for improved microvascular health. Demographics and clinical characteristics, including pulmonary function, exercise capacity, blood pressure, blood measurements and level of systemic inflammation were obtained from 246 patients during routine assessment before and after PR. Retinal vessel diameters were measured from digital retinal images. Older age and higher systolic blood pressure were associated with narrower retinal arterioles (ß: -0.224; p = 0.042 and ß: -0.136; p < 0.001, respectively). Older age, higher systolic blood pressure and lower level of systemic inflammation were associated with narrower retinal venules (ß: -0.654; -0.229; and -13.767, respectively; p < 0.05). No associations were found between retinal vessel diameters and lung function parameters or functional outcomes. After PR, no significant changes in retinal venular or arteriolar diameter were found. To conclude, retinal vessel diameters of COPD patients were significantly associated with systolic blood pressure and systemic inflammation, whilst there was no evidence for an association with lung function parameters, functional outcomes or other cardiovascular risk factors. Furthermore, an exercise-based PR program did not affect retinal vessel diameter.

Low expression of microRNA-15b promotes the proliferation of retinal capillary endothelial cells and pericytes by up-regulating VEGFA in diabetic rats.

OBJECTIVE: To investigate the role of microRNA-15b in diabetic retinopathy and its underlying mechanism. MATERIALS AND METHODS: Diabetes rat model was established by streptozotocin injection. The mRNA expression of microRNA-15b in retinal capillary endothelial cells and pericytes of diabetic rats was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The mRNA and protein expressions of vascular endothelial growth factor A (VEGFA) were detected by qRT-PCR and Western blot, respectively. MicroRNA-15b mimics or inhibitor were transfected into retinal capillary endothelial cells and pericytes of diabetic rats, respectively. The mRNA expressions of microRNA-15b and VEGFA were detected by qRT-PCR. Cell counting kit-8 (CCK-8) assay was used to detect the proliferation of capillary endothelial cells and pericytes. Dual-Luciferase reporter gene assay was conducted to verify the binding condition of microRNA-15b and VEGFA. RNA immunoprecipitation (RIP) assay was performed to determine whether microRNA-15b could bind to AGO2. Rescue experiments were finally carried out by detecting the proliferation of retinal capillary endothelial cells and pericytes after downregulation or overexpression of microRNA-15b and VEGFA. RESULTS: The expression of microRNA-15b decreased, whereas VEGFA expression increased in retinal capillary endothelial cells and pericytes of diabetic rats. High expression of microRNA-15b in retinal capillary endothelial cells and pericytes resulted in VEGFA down-regulation and decreased proliferation. RIP assay results indicated that microRNA-15b could interact with AGO2. Additionally, Dual-Luciferase reporter gene assay showed that VEGFA is a direct target gene of microRNA-15b. VEGFA overexpression could reverse the inhibited proliferation of retinal capillary endothelial cells and pericytes induced by microRNA-15b overexpression. Similarly, VEGFA knockdown could reverse the effect of the low expression of microRNA-15b on the proliferation of retinal capillary endothelial cells and pericytes. CONCLUSIONS: Low expression of microRNA-15b in retinal capillary endothelial cells and pericytes of diabetic rats promotes the development of diabetic retinopathy by up-regulating VEGFA.

Convolutional Neural Networks for Spectroscopic Analysis in Retinal Oximetry.

Retinal oximetry is a non-invasive technique to investigate the hemodynamics, vasculature and health of the eye. Current techniques for retinal oximetry have been plagued by quantitatively inconsistent measurements and this has greatly limited their adoption in clinical environments. To become clinically relevant oximetry measurements must become reliable and reproducible across studies and locations. To this end, we have developed a convolutional neural network algorithm for multi-wavelength oximetry, showing a greatly improved calculation performance in comparison to previously reported techniques. The algorithm is calibration free, performs sensing of the four main hemoglobin conformations with no prior knowledge of their characteristic absorption spectra and, due to the convolution-based calculation, is invariable to spectral shifting. We show, herein, the dramatic performance improvements in using this algorithm to deduce effective oxygenation (SO2), as well as the added functionality to accurately measure fractional oxygenation ([Formula: see text]). Furthermore, this report compares, for the first time, the relative performance of several previously reported multi-wavelength oximetry algorithms in the face of controlled spectral variations. The improved ability of the algorithm to accurately and independently measure hemoglobin concentrations offers a high potential tool for disease diagnosis and monitoring when applied to retinal spectroscopy.

Association of serum lutein and zeaxanthin with quantitative measures of retinal vascular parameters.

To evaluate the association between serum carotenoids and quantitative measures of retinal vasculature in elderly Singapore Chinese subjects. The following details were collected in 128 healthy subjects: sociodemographics, lifestyle information, medical and drug history, and anthropometric measurements. Serum concentrations of carotenoids were estimated in fasting venous blood using high performance liquid chromatography. Retinal vascular parameters were quantitatively measured from retinal photographs using a computer-assisted program (Singapore I Vessel Assessment). The mean age of the population was 54.1 years (range 40 to 81 years). In multiple linear regression analysis, per SD decrease in retinal arteriolar caliber [ß = 0.045 (0.003 to 0.086), p = 0.036], per SD increase in retinal venular caliber [ß = -0.045 (-0.086 to -0.003), p = 0.036] and per SD increase in arteriolar branching angle [ß = -0.039 (-0.072 to -0.006), p = 0.021] were associated with decreased serum lutein. Per SD increase in retinal venular tortuosity [ß = -0.0075 (-0.0145 to -0.0004), p = 0.039] and per SD increase in arteriolar branching angle (ß = -0.0073 [-0.0142 to -0.0059], p = 0.041) were associated with decreased serum zeaxanthin. None of the other carotenoids demonstrated meaningful relationship with quantitative measures of retinal vasculature. Lower levels of lutein and zeaxanthin demonstrated significant relationship with adverse quantitative measures of retinal vasculature in elderly healthy subjects.

Immunohistochemical expression of CD117 and vascular endothelial growth factor in retinoblastoma: possible targets of new therapies.

CD117 (C-kit) is thought to play an important role in tumourigenesis. There are limited data in the literature concerning C-kit expression in retinoblastoma. To date, no immunohistochemical studies have been performed to assess the possible association of C-kit with vascular endothelial growth factor (VEGF) in retinoblastoma. This study was designed to investigate C-kit and VEGF immunoexpression in retinoblastoma, their relationship with prognostic parameters as well as the correlation between them. A prospective immunohistochemical study was conducted on 56 retinoblastoma cases. Patients who had received preoperative chemotherapy were excluded. Positive C-kit and VEGF immunoreactivity was observed in 48.2% and 76.8% of retinoblastoma cases respectively. No C-kit immunostaining was seen in the adjacent uninvolved retina. However, VEGF expression was detected within its vasculature. Retinoblastomas with combined pattern of tumour growth revealed a highly significant positive C-kit expression (P = 0.002) compared to cases with endophytic or exophytic growths. Also, positive C-kit expression was statistically higher in cases with optic nerve invasion (P = 0.001) and choroidal invasion (P ≤ 0.01) compared to negative cases. A highly significant positive VEGF expression was detected in cases with optic nerve invasion (P = 0.013) compared to negative cases. Moreover, a highly significant positive correlation was detected between C-kit and VEGF expression (P = 0.006). C-kit is a feature of more aggressive retinoblastomas, with increased expression in tumours spreading beyond the retina. Moreover, VEGF is vastly expressed in retinoblastoma and is associated with optic nerve invasion. Both C-kit and VEGF may represent potential therapeutic targets for retinoblastomas.

Whole mount immunofluorescent staining of the neonatal mouse retina to investigate angiogenesis in vivo.

Angiogenesis is the complex process of new blood vessel formation defined by the sprouting of new blood vessels from a pre-existing vessel network. Angiogenesis plays a key role not only in normal development of organs and tissues, but also in many diseases in which blood vessel formation is dysregulated, such as cancer, blindness and ischemic diseases. In adult life, blood vessels are generally quiescent so angiogenesis is an important target for novel drug development to try and regulate new vessel formation specifically in disease. In order to better understand angiogenesis and to develop appropriate strategies to regulate it, models are required that accurately reflect the different biological steps that are involved. The mouse neonatal retina provides an excellent model of angiogenesis because arteries, veins and capillaries develop to form a vascular plexus during the first week after birth. This model also has the advantage of having a two-dimensional (2D) structure making analysis straightforward compared with the complex 3D anatomy of other vascular networks. By analyzing the retinal vascular plexus at different times after birth, it is possible to observe the various stages of angiogenesis under the microscope. This article demonstrates a straightforward procedure for analyzing the vasculature of a mouse retina using fluorescent staining with isolectin and vascular specific antibodies.

[Cytokine determination from vitreous samples in retinal vascular diseases]. / Zytokinbestimmung aus Glaskörperproben bei retinalen Gefäßerkrankungen.

PURPOSE: The aim of this study was to determine cytokine levels from vitreous samples of treatment-naive patients with diabetic retinopathy (DRP), retinal vein occlusion (RVO) and exudative age-related macular degeneration (ARMD). METHODS: In this study 187 patients (median age 67 years, 101 males) were treated with a combined drug therapy including a 23-gauge core vitrectomy. Interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1) and intravitreal vascular endothelial growth factor (VEGF-A) levels were determined a using cytometric bead assay (CBA) and compared to those of the control group. RESULTS: Compared to the control group all diseases had significantly elevated cytokine levels, except VEGF in ARMD. In DRP samples of patients with diffuse diabetic macula edema (DME) higher VEGF-A and MCP-1 levels were found than in patients with focal DME. Ischemic DRP had higher VEGF levels than non-ischemic DRP. All measured cytokines were significantly higher in central retinal vein occlusion (CRVO) than in branch retinal vein occlusion (BRVO). CONCLUSIONS: Differences in intravitreal cytokine levels in DRP, RVO and ARMD could be demonstrated. The knowledge of depicted specific characteristic dysregulation of cytokines could allow more targeted future therapies.

Oximetry of retinal capillaries by multicomponent analysis.

Retinal oximetry of capillaries was performed for early detection of retinal vascular abnormalities, which are caused predominantly by complications of systemic circulatory diseases. As the conventional method for determining absorbance is not applicable to capillaries, multicomponent analysis was used to estimate the absorbance spectra of the retinal blood vessels. In this analysis, the capillary spectrum was classified as intermediate between those of the retinal arteries and veins, enabling relative estimation of oxygen saturation in the capillaries. This method could be useful for early recognition of disturbances in the peripheral circulation. Furthermore, a spectroscopic ophthalmoscope system based on the proposed method was developed to examine the human retina. A clinical trial of this system demonstrated that oximetry of the retinal capillaries may be an improvement over the present diagnosis for patients of malignant hypertension.

Observation of persistent fundus fluorescence after internal limiting membrane peeling assisted by indocyanine green solution of different concentrations.

PURPOSE: To investigate how long indocyanine green (ICG) remains in the fundus after vitreoretinal surgery assisted with ICG, and to identify factors that influence the persistence duration. METHODS: Fifty five eyes diagnosed as idiopathic macular hole (Stage 2 and 3) were randomly divided into five groups. ICG solution at concentrations of 5, 2.5, 2.5, 1.25, and 0.5 mg/ml, employed in cases of Group I to V respectively, was applied to stain the internal limiting membrane (ILM) during the procedure of internal limiting membrane peeling. A prospective study was carried out after pars plana vitrectomy and ILM peeling were performed on 55 eyes with Stage 2, 3, or 4 idiopathic macular holes. Infrared fundus pictures were obtained in all patients before and after surgery. RESULTS: High levels of fluorescence from residual ICG (ICG hyperfluorescence) were mainly localized at the posterior pole of the fundus after surgery. In Group Ⅰ, Ⅱ, III, IV and V, the duration of persistence of flurorescence from ICG was 8.33±0.87, 3.59±0.94, 3.75±0.79, 2.30±0.48, and 1.29±0.49 months, respectively. Although no significant difference was detected between Group Ⅱ and Group III, the general inter-group difference was significant among the five groups in which different ICG concentration was applied. In Group III, even though 90% of the macular holes acquired anatomical closure, ICG hyperfluorescence was detected in the macular area. CONCLUSION: ICG remains in the fundus for a period of months. The persistence duration of fluorescence from ICG is positively correlated with the concentration and the staining time of ICG. Hyaluronan is beneficial in reducing the amount of ICG residue in the macular area.

High-yielding enzymatic method for isolation and culture of microvascular endothelial cells from bovine retinal blood vessels.

A simple and non-mechanical enzymatic method for the isolation and large-scale in vitro culture of bovine retinal endothelial cells (BRECs) is described. A sufficiently high yield of retinal microvessels was obtained from bovine eyes by brisk stirring of the retina with Minimum Essential Medium for 3 min, washing the pellet five times by repeated centrifugation at 300 x g and sieving in a single step. Pericyte contamination was eliminated by increasing the incubation period in an enzyme mixture and passaging the cells at a low concentration of trypsin for 1-2 min. The cells were grown in Iscove's Modified Dulbecco's Medium (IMDM) with 10% fetal bovine serum. The cells were cobble-stone shaped and stained positive for von Willebrand Factor (vWF) and cluster differentiation factors, CD31 and CD146. These cells stained negative for alpha-smooth muscle actin (ASMA) and glial fibilary acidic protein (GFAP), forming characteristic capillary tube-like structures on matrigel. Here we optimized the method for the isolation of pure retinal endothelial cells without using complex procedures and sophisticated instruments. This method is simpler, more rapid and cost-effective, and also results in a higher yield of endothelial cells than other methods. Retinal endothelial cells cultured in this way will be used to study the pathogenesis of vascular eye diseases such as diabetic retinopathy and other neovascularization diseases. They can also serve as an excellent in vitro model system for drug analysis.

Oxygen saturation levels in the juxta-papillary retina in eyes with glaucoma.

Oxygen saturation (OS) levels in the juxta-papillary retina particularly inferotemporal retina were investigated in open-angle glaucoma (OAG) patients as well as normal subjects. Fifty-six eyes of 56 OAG Japanese patients and 20 eyes of 20 age-matched normal subjects were recruited for the study. OAG eyes (56) were subdivided into two groups: 15 eyes of low-tension (LT) subgroup and 41 eyes of high-tension (HT) subgroup. The average of age of the LT, HT subgroup and normal group were 60.5, 55.9 and 52.6 years, respectively. OS levels in the retina were measured using a Fourier transform-based spectral retinal imaging (SRI) system (Retinal Cube; ASI Co. Migdal Hemak, Israel), with which OS levels in the fundus could be computed at every pixel point of a 35 degrees fundus image. We calculated OS levels at five points in the retina near the optic disc and retinal arteries and veins in all eyes. The OS levels were also compared with the results analyzed using Humphrey visual field Analyzer with the program 30-2 SITA. At the superior and nasal juxta-papillary retinal points, OS level of the LT subgroup showed significant decrease as compared with the HT subgroup and the normal group (p=0.048-0.009). The LT and the HT subgroups were significantly lower than the normal group at the inferotemporal and the average of the retinal points (p=0.047-0.001). There were no statistically significant differences among the three groups in regards to the OS in the retinal artery. There was a statistical significant correlation between the mean of total deviation of the 17 points in the upper arcuate area and OS of the inferotemporal point (p=0.018), and between mean deviation and the average of OS of the inferotemporal and the superotemporal point (p=0.037) in the HT subgroup. However, there was no significant correlation in the LT subgroup. OS levels in the retina were especially decreased in the low-tension glaucoma subtype. There was a correlation between the visual field defect and OS in the HT eyes in the inferotemporal region. OS measurement may be a novel adjunct to study glaucoma patients.

Gene expression profiles of ATP-binding cassette transporter A and C subfamilies in mouse retinal vascular endothelial cells.

The purpose of this study was to quantify gene expression levels of the ATP-binding cassette (ABC) transporter A and C subfamilies ABCA1-A9, and ABCC1-6/Mrp1-6, C10/Mrp7 in mouse retinal vascular endothelial cells (RVEC) using a combination of a magnetic isolation method for mouse RVEC and real-time quantitative PCR analysis. The transcript level of endothelial cell markers, such as CD31, Tie-2, claudin-5, occludin, ABCB1a/mdr1a, and ABCG2, were more than 20-fold higher than those in the non-RVEC fraction, suggesting that RVEC in the RVEC fraction are concentrated at least 20-fold compared with those of the non-RVEC fraction. In the ABCA1 to A9 families, the transcript level of ABCA3 and A9 in the RVEC fraction was 1.2- and 32-fold higher than that in the non-RVEC fraction. Although ABCA3 was expressed in both the RVEC and non-RVEC fractions, A9 is predominantly expressed in the RVEC fraction. In the ABCC1 to C6 and C10 families, the transcript level of ABCC3, C4, and C6 in the RVEC fraction was 27-, 251-, and 242-fold higher, respectively, than that in the non-RVEC fraction, suggesting that ABCC3, C4, and C6 are predominantly expressed in the RVEC. In conclusion, ABCA3, ABCA9, ABCC3, ABCC4, and ABCC6 mRNAs are predominantly expressed at the inner blood-retina barrier (inner BRB) and appear to play a major role in the efflux transport of their substrates at the inner BRB.

Kv1.5 is a major component underlying the A-type potassium current in retinal arteriolar smooth muscle.

Little is known about the molecular characteristics of the voltage-activated K(+) (K(v)) channels that underlie the A-type K(+) current in vascular smooth muscle cells of the systemic circulation. We investigated the molecular identity of the A-type K(+) current in retinal arteriolar myocytes using patch-clamp techniques, RT-PCR, immunohistochemistry, and neutralizing antibody studies. The A-type K(+) current was resistant to the actions of specific inhibitors for K(v)3 and K(v)4 channels but was blocked by the K(v)1 antagonist correolide. No effects were observed with pharmacological agents against K(v)1.1/2/3/6 and 7 channels, but the current was partially blocked by riluzole, a K(v)1.4 and K(v)1.5 inhibitor. The current was not altered by the removal of extracellular K(+) but was abolished by flecainide, indicative of K(v)1.5 rather than K(v)1.4 channels. Transcripts encoding K(v)1.5 and not K(v)1.4 were identified in freshly isolated retinal arterioles. Immunofluorescence labeling confirmed a lack of K(v)1.4 expression and revealed K(v)1.5 to be localized to the plasma membrane of the arteriolar smooth muscle cells. Anti-K(v)1.5 antibody applied intracellularly inhibited the A-type K(+) current, whereas anti-K(v)1.4 antibody had no effect. Co-expression of K(v)1.5 with K(v)beta1 or K(v)beta3 accessory subunits is known to transform K(v)1.5 currents from delayed rectifers into A-type currents. K(v)beta1 mRNA expression was detected in retinal arterioles, but K(v)beta3 was not observed. K(v)beta1 immunofluorescence was detected on the plasma membrane of retinal arteriolar myocytes. The findings of this study suggest that K(v)1.5, most likely co-assembled with K(v)beta1 subunits, comprises a major component underlying the A-type K(+) current in retinal arteriolar smooth muscle cells.

Caveolin-1 is up-regulated in transdifferentiated lens epithelial cells but minimal in normal human and murine lenses.

Caveolae are flask-shaped invaginations of the plasma membrane found in many cell types. Caveolae play a role in lipid transport, endocytosis, signal transduction, and cell transformation. Expression of caveolin-1, the principal component of caveolae and a regulator of caveolae-dependent signaling and endocytosis, was investigated in lens epithelial cells and lens fiber cells in wild-type (wt) and SPARC-null mice and normal human donors in vivo and in vitro. RT-PCR, immunofluorescence and immunoblot analyses of human and murine ocular tissues revealed that caveolin-1 was expressed in the corneal epithelium, corneal endothelial cells, and blood vessels of iris, ciliary body and retina, but minimal in the normal lens epithelia or fiber cells of murine and human lens. In contrast, caveolin-1 was significantly up-regulated in mesenchymal-transdifferentiated lens epithelia in SPARC-null cataract lenses. In addition, lens epithelial cells from primary culture or from cultures of immortalized lens epithelial cell lines expressed significant amounts of caveolin-1. The lens epithelial cells expressed epidermal growth factor (EGF) receptor and were responsive to EGF-mediated cell proliferation, but they did not show EGF-dependent caveolin-1 tyrosine phosphorylation. Caveolin-1 might have a role in the process of epithelial-mesenchymal transdifferentiation (EMT) in the lens, the most common cause of vision loss in human secondary cataracts.

Divergent distribution in vascular and avascular mammalian retinae links neuroglobin to cellular respiration.

The visual function of the vertebrate retina relies on sufficient supply with oxygen. Neuroglobin is a respiratory protein thought to play an essential role in oxygen homeostasis of neuronal cells. For further understanding of its function, we compared the distribution of neuroglobin and mitochondria in both vascular and avascular mammalian retinae. In the vascular retinae of mouse and rat, oxygen is supplied by the outer choroidal, deep retinal, and inner capillaries. We show that in this type of retina, mitochondria are concentrated in the inner segments of photoreceptor cells, the outer and the inner plexiform layers, and the ganglion cell layer. These are the same regions in which oxygen consumption takes place and in which neuroglobin is present at high levels. In the avascular retina of guinea pig the deep retinal and inner capillaries are absent. Therefore, only the inner segments of the photoreceptors adjacent to choroidal capillaries display an oxidative metabolism. We demonstrate that in the retina of guinea pigs both neuroglobin and mitochondria are restricted to this layer. Our results clearly demonstrate an association of neuroglobin and mitochondria, thus supporting the hypothesis that neuroglobin is a respiratory protein that supplies oxygen to the respiratory chain.

Special report: Noninvasive multi-parameter functional optical imaging of the eye.

Advancement in the treatment of blindness depends on the development of new technologies that enable early detection, follow-up, and treatment of disease. The authors describe direct, noninvasive imaging of four parameters: blood flow, blood oximetry, metabolic state, and hidden vasculature, particularly capillaries. These are functional parameters of the retina known to be degraded by retinal disease. The new Retinal Function Imager (Optical Imaging, Ltd., Rehovot, Israel) can image all four parameters as intrinsic reflectance intensity differences over the retina's surface. During the past 2 decades, imaging of small optical signals has been a powerful tool for high-resolution functional mapping in the neocortex. In this article, this technology is applied to the retina and demonstrates a general tool for noninvasively probing retinal function in many modalities. Imaging functional changes before anatomic consequences arise holds promise as a powerful tool for early diagnosis and treatment of retinal disease.

Diabetic retinopathy: VEGF, bFGF and retinal vascular pathology.

BACKGROUND: Previous research indicated that the development of diabetic retinopathy (DR) is closely related to the excessive expression of growth factors. This paper was to study the relationship of DR with vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and the retinal vascular pathological change. METHODS: Fifty-five Wistar rats, weighing 100 - 200 g, were selected and randomly divided into four groups: control group (no streptozocin injection, n = 10), M1 group (streptozocin induced diabetes for 1 month, n = 15), M3 group (streptozocin induced diabetes for 3 months, n = 15), and M5 group (streptozocin induced diabetes for 5 months, n = 15). In situ hybridization and immunohistochemistry were used to investigate the expressions of bFGF and VEGF on retinal vascular, and retinal vessels were observed by transmission electron microscope. RESULTS: There was no difference in the number of pericytes between M1 and control group (P > 0.05), but the number of pericytes decreased obviously in M3 and M5 groups compared with the control group (P < 0.01, P < 0.001, respectively). Capillary embolization and non-cell capillary were seen in M5 group. Positive expression of VEGF was found in M5 group using in situ hybridization and immunohistochemistry respectively. Positive expression of bFGF could be seen in M3 (78%) and M5 group (89%). Most remarkable changes of vessels were observed in M5 group including fragmental thickness, split of basement membrane, swelling and distortion of endothelial cells. CONCLUSIONS: In retinal vascular of the streptozocin (STZ) rats, there shows the expression of bFGF at the third month and that of VEGF at the fifth month.

Retinal neovascular markers in retinopathy of prematurity: aetiological implications.

AIM: (1) To determine if expression of the blood-tissue barrier associated glucose transporter GLUT1 is preserved by the neovasculature of retinopathy of prematurity (ROP), in contrast with the reported loss of GLUT1 expression in preretinal vessels of proliferative diabetic retinopathy. (2) To compare the vascular immunophenotype of ROP to juvenile haemangioma, another perinatal neovascular disorder that has recently been shown to express placental type vascular antigens, including GLUT1 and Lewis Y antigen. METHODS: A retrospective case report was carried out. Immunoreactivities for GLUT1 and Lewis Y antigen were assessed in a human eye with stage 3 ROP and compared with those in a control (paediatric) eye. The presence or absence of endothelial GLUT1 and Lewis Y immunoreactivity was determined in preretinal and intraretinal vessels. RESULTS: Immunoreactivity was positive for GLUT1 and negative for Lewis Y in the intraretinal and preretinal neovasculature of the ROP affected eye and in the normal retinal vessels of the control eye. CONCLUSIONS: Retention of immunoreactivity for GLUT1 distinguishes ROP from proliferative diabetic retinopathy. Furthermore, absence of Lewis Y antigen co-expression distinguishes ROP from juvenile haemangioma, a perinatal form of GLUT1 positive neovascularisation that has recently been linked to placental vasculature.