Biomedical subjects
Publications and source records attributed to P Stalmans.
Acute retinal necrosis (ARN) is a severe ocular syndrome consisting of a moderate-to-severe anterior uveitis, vasculitis, and vaso-occlusive retinal necrosis. It can occur in healthy individuals at any age, but reports of this condition in children are rare.
PURPOSE: to evaluate the results of pars plana vitrectomy with peeling of the inner limiting membrane (ILM stained with infracyanine green (IfCG) in 26 patients with diabetic macular edema, and to identify which factors are associated with a better postoperative visual outcome. PATIENTS AND METHODS: 26 patients with diabetic macular edema were included in the study. A pars plana vitrectomy with ILM peeling stained with IfCG was performed, in some cases combined with cataract surgery. In 22 patients the ILM was retained, examined with electron microscopy and compared with normal ILM's. Visual acuity and fundus examination were recorded several months after surgery. To determine which factors lead to the best postoperative results, patients were divided into different groups and compared. RESULTS: during surgery, a taut posterior hyaloid was found in 26 patients, which was successfully detached in all cases. ILM peeling within the vessel arcade succeeded in all patients. Postoperative examination showed improved visual acuity and decreased macular edema in 19 patients, unaltered visual acuity in 3 patients and decreased visual acuity in 4 patients. Comparison between different groups of patients revealed that young patients with recent vision loss and without previous macular laser treatment, had better postoperative results. Electron microscopical examination showed a more condensed ILM in diabetic patients, consisting of a layer of fine curled fibers. CONCLUSION: pars plana vitrectomy with peeling of the ILM stained with IfCG leads to good postoperative results in young diabetic patients with recent vision loss due to macular edema and without previous macular laser treatment.
AIM: To evaluate the possibility of translocating autologous peripheral retinal pigment epithelial (RPE) cells and enhance their adhesion to improve functional outcome after choroidal neovascular membrane extraction in patients with subfoveal neovascular membranes. METHODS: A prospective, non-controlled surgical study in eight consecutive patients operated between February and July 2001 with final data monitoring in July 2002. All patients had mixed subfoveal membranes of 2-4 disc diameters. Functional tests included Snellen vision and central fixation testing. During vitrectomy, after the extraction of the neovascular complex, 8 x 10(4)-16 x 10(4) RPE cells were removed from the periphery and translocated under the macula following the submacular injection of 2 microg of poly-L-lysine to promote adhesion of the cells. RESULTS: With a follow up ranging from 3 months to 16 months, a pigmented area was seen in the extraction bed of the neovascular membrane in only one patient. Fixation was at the edge of the extraction bed in three patients. Vision remained the same in five patients and deteriorated in three (all with retinal detachment). Retinal detachment due to proliferative vitreoretinopathy occurred in three patients. CONCLUSIONS: The translocation of autologous peripheral RPE cells after membrane extraction was technically possible in a sterile manner, but was associated with a high proliferative vitreoretinopathy rate and in the present series had no measurable positive effect on functional outcome.
AIMS: To study the clinical properties of double vital staining in premacular fibrosis, facilitating complete removal of all epiretinal tissue. METHODS: In a two step surgery, the epiretinal pucker was removed after staining with trypan blue, whereafter the inner limiting membrane was peeled after staining with infracyanine green. RESULTS: In all 30 patients, a separate epiretinal layer and inner limiting membrane were removed from the macular area. Pathological examination showed different histological properties of the removed layers. An increased visual acuity was measured in 26 patients, and a slightly decreased visual acuity in one patient. CONCLUSION: The described double staining technique could be a novel valuable tool that may help to achieve optimal anatomical and functional recovery after surgery for premacular fibrosis
A 28-year old female patient presented with unilateral dropped visual acuity and a central scotoma. Fundus examination and a fluorescein angiogram were suggestive for central retinal vein prethrombosis. Further tests revealed an isolated protein S deficiency for which oral anticoagulation therapy was initiated. Six months later she presented with new symptoms of a right retrobulbar pain on ocular movements. The retinal vessels had normalized with improved visual acuity. Re-evaluation of the fluorescein angiogram taken six months earlier showed an image compatible with unilateral vasculitis. During this six month period persisting high levels of IgG and IgM antibodies against Toxoplasma were observed while no signs of other active infection could be found. This report illustrates that in cases of prethrombosis with vasculitis in a young patient, a full medical examination and a thorough investigation of infectious diseases are warranted.
Formation of a macular hole is an uncommon idiopathic disease whereby a disruption of the neural retinal layer is formed at the foveal area. It has been suggested that tangential traction of the inner limiting membrane (ILM) on the neuroretina may contribute to the formation of a macular hole. Removal of the ILM has been associated with very high closure rates in macular hole surgery. However, since the inner limiting membrane is a transparent layer, it can be difficult to achieve complete removal from the underlying neural retina. Also in surgery for macular pucker formation, whereby growth of epiretinal tissue induces metamorphopsia, removal of the ILM may play a beneficial role. This paper describes a method facilitating the removal of the inner limiting membrane by staining it with indocyanine green.
The aim of this study was to examine the vitreomacular interface in symptom-free fellow eyes of macular holes using optical coherence tomography (OCT) to add information to the pathogenesis of macular holes and to refine prognostic factors for bilateral involvement. Sixty-six patients with a full thickness macular hole in one eye and a symptom-free fellow eye were included in the study between 01/98-05/99. The finding on OCT that a perifoveal vitreous detachment can result in a foveal cyst and subsequently a macular hole confirms the theory of Gass of vitreous traction. Symptom-free fellow eyes with a foveal cyst on OCT represent an elevated risk (55%) for macular hole development. Vitreofoveal separation is probably a good prognostic sign.
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PURPOSE: To characterize a newly discovered choroidal vascular abnormality in patients who have received radiation therapy for subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration. DESIGN: Two-center cross-sectional study. PARTICIPANTS: In the United States, there were 95 patients who were treated with 10 or 12 Gy of external beam photons. In Belgium, 98 patients were treated with 20 Gy. These patients were examined retrospectively for the presence of a specific CNV abnormality. RESULTS: During the follow-up period, an unusual vascular growth pattern was identified in 12 patients (12.6%) of those treated in the United States and in 7 (7.1%) of those treated in Belgium. These patients developed round or oval vascular blebs along the outer border of their neovascular lesions. These blebs profusely leaked fluorescein dye and could be imaged best by indocyanine green angiography. Patients with these blebs appeared to have a marked propensity for loss of visual acuity. CONCLUSION: An unusual pattern of new vessel growth occurred in 19 of the 193 patients with CNV treated with radiation. This new entity, termed radiation-associated choroidal neovasculopathy, is a recognizable disorder that appears to have a particularly poor prognosis.
Membrane deformation induced by a mechanical stimulus increases the [Ca2+]i in cultured retinal pigment epithelial (RPE) cells, and in many other cell types. In this study, confocal microscopy and Ca(2+)-measurements using the fluorescent dye fluo-3 were used to measure the spatiotemporal characteristics of the Ca(2+)-wave propagation during a mechanical stimulation in Long Evans (LE) RPE cells or dystrophic Royal College of Surgeons (RCS) RPE cells. Ca2+ signals were recorded in the mechanically stimulated cell and in the neighboring cells. A regenerative Ca(2+)-wave with a decreasing rate of propagation was found in the stimulated cells. The rate of propagation was significantly slower in RCS-RPE cells compared to LE-RPE cells. Incubation with thapsigargin significantly lowered the propagation rate in both LE- and RCS-RPE cells. The amplitude of the [Ca2+]i-rise in the nucleus and cytoplasm was differentially modulated by protein kinase C in RCS-RPE cells, but not in LE-RPE cells. It is concluded that RCS-RPE cells have intracellular Ca(2+)-regulating properties which are different from those of LE-RPE cells.
The intercellular communication (IC) was investigated between cultured rat retinal pigment epithelial (RPE) cells isolated from Long-Evans (LE) or dystrophic Royal College of Surgeons (RCS) rats and grown in solutions containing normal and high glucose concentrations, or after modulation of protein kinase C (PKC). This was performed by studying the conduction of the free Ca2+-concentration ([Ca2+]i) wave elicited by mechanical stimulation and by analyzing the fluorescence recovery after photobleaching (FRAP). Mechanical stimulation of LE-RPE cells triggers Ca2+ influx, mediated by stretch-sensitive cation channels followed by intracellular Ca2+ release. A regenerative [Ca2+]i wave was found with a lower propagation rate in RCS-RPE cells. This rate could be increased by PKC down-regulation. Mechanical stimulation caused a [Ca2+]i increase in the mechanically stimulated (MS) cell followed after a delay by a [Ca2+]i rise in the adjacent cell layers. The intercellular [Ca2+]i wave propagation could be blocked by gap junction blockers such as halothane or PKC activation. An inhibition of the [Ca2+]i-wave propagation similar to that induced by halothane could be observed in cells grown in solutions containing 14 mM or higher concentrations of glucose. PKC down-regulated cells grown in glucose-rich medium did not develop this inhibitory effect on gap junction communication (GJC). FRAP experiments confirmed that the observed changes were consistent with a PKC-mediated inhibitory effect of high glucose concentrations on GJC.
With optical coherence tomography (OCT), a new technique has emerged that allows imaging of a transverse section of the retina with a resolution that has not been reached by other imaging techniques. The OCT technique can be used in the diagnosis and assessment of various diseases of both the anterior segment and the ocular fundus. This paper demonstrates that OCT can deliver useful information in the diagnosis and follow-up of several macular diseases that cannot be obtained with other fundus imaging techniques. The optical principle of OCT is based on visible-light interference. OCT allows imaging of the anatomical foveal appearance. This normal foveal appearance is disrupted when macular edema occurs, leading to thickening of the neuroretina and cyst formation. The anatomical difference between a neuro-retinal elevation and RPE elevations can be demonstrated using OCT. Epiretinal membranes and pseudo-macular holes can easily be visualized. Perhaps the most interesting addition of OCT in the retinal diagnostic field is the imaging of vitreo-macular traction syndromes and staging of macular holes, which are both difficult with ophthalmoscopy and fluorescein-angiography. Each of the above mentioned macular diseases will be illustrated by a typical case.
On August 11, in Belgium a solar eclipse will occur which will be total in the Southern area of the country. Although the observation of a solar eclipse is an intriguing phenomenon, inappropriate shielding from the sunlight can cause irreversible ocular lesions. Besides good absolute absorption of visible light, a blocking of ultraviolet and infrared light is equally important. In this study, four homemade sun filters were tested: a soot-blackened piece of glass, a black unexposed developed slide film, an audio-CD and a recordable CD-ROM. Also two commercially available filters were investigated: eclipse-shades and mylar foil. The soot-blackened glass and black slide film slip were highly transparent for infrared light, making them dangerous for solar observation. The recordable CD-ROM was too transparent for visible light to serve as solar filter, while the audio-CD tested absorbed enough visible, ultraviolet and infrared light to make it suitable for eclipse viewing. However, many types of audio-CD's are available making it impossible for the observer to know if a given CD is safe to use for solar viewing. Both commercially available solar filters tested had a good absolute visible light absorption, as well as an equally good absorption of ultraviolet and infrared light, making them safe for eclipse observation.
PURPOSE: The authors investigated intercellular communication among cultured rat retinal pigment epithelial (RPE) cells isolated from dystrophic Royal College of Surgeons (RCS) rats by studying the conduction of the [Ca2+]i wave elicited by mechanical stimulation. The effect of protein phosphorylation was measured by modulating the protein kinase C (PKC), protein kinase A (PKA), and tyrosine kinase activity. METHODS: Cultured RPE cells isolated from neonatal control Long-Evans (LE) and dystrophic RCS rats were analyzed using the fluorescent dye fluo-3 to measure the Ca2+-wave propagation on mechanical stimulation to investigate the intercellular communication. RESULTS: Mechanical stimulation in LE-RPE cells resulted in a centrifugally spreading Ca2+ wave through the neighboring cells. When a mechanical stimulus was applied on RCS-RPE cells, a significantly reduced Ca2+-response was found in the neighboring cells compared with that of control RPE cells. Activation of PKC almost completed blocked the mechanically induced Ca2+ rise in the neighboring RCS-RPE cells. In contrast to LE-RPE cells, an activation of PKA also significantly decreased the Ca2+-wave propagation in RCS-RPE cells. Inhibition of PKA had no effect on the intercellular communication in LE- or RCS-RPE cells. In addition, when protein phosphatase activity or tyrosine kinase activity was inhibited, an increased Ca2+ rise in the neighboring cells on mechanical stimulation was measured, reaching levels currently found for LE-RPE cells. CONCLUSIONS: In dystrophic RCS-RPE cells, a decreased intercellular Ca2+-wave propagation is found. This intercellular communication can be mediated by protein phosphorylation.
This is a retrospective study of 104 patients with a total follow-up between 12 and 48 months (mean follow-up of 24 months), in which the effect of External Beam Radiotherapy with a total dose of 20 Gy (2 Gy fractions) on the visual acuity of eyes affected by subfoveal choroidal neovascularization is evaluated. The evolution of the visual acuity of the irradiated eyes is compared with the evolution of the visual acuity of their fellow eyes which were also affected by choroidal neovascularization but were not treated or treated by laser photocoagulation. This study suggests that the effect of radiotherapy, with a total dose of 20 Gy, on the visual acuity of eyes affected by subfoveal choroidal neovascularization, seems to be not better than the natural course of choroidal neovascularization or the evolution after laser therapy.
PURPOSE: The purpose of this study was to investigate the mechanism of Ca2+ signaling in rat retinal pigment epithelial (RPE) cells during mechanical and pharmacologic stimulation and to analyze the pathway of intercellular communication during mechanical stimulation. METHODS: Subconfluent monolayers of RPE cells cultured for 3 to 7 days after isolation from 5- to 8-day-old Long Evans rats were analyzed using the fluorescent Ca2+ dye fluo-3 and confocal laser microscopy. Mechanical stimulation of a single cell was applied by a slight, brief touch with a glass capillary. RESULTS: Pharmacologic agents [Arg8]-vasopressin, carbachol, adenosine triphosphate, substance P, fetal calf serum, and histamine all elicited, to some extent, a biphasic [Ca2+]i transient by releasing Ca2+ from InsP3-sensitive Ca2+ stores. Stretching cellular membranes by touching them with the glass capillary increased free intracellular calcium concentration ([Ca2+]i) in the mechanically stimulated cell. After a time delay of up to 1.5 seconds, it increased free intracellular calcium concentration as well in the two to three adjacent layers of neighboring cells, resulting in the centrifugal propagation of an intercellular Ca2+ wave. In the absence of external Ca2+, neither a [Ca2+]i rise in the mechanically stimulated cell nor a propagating Ca2+ wave in the neighboring cells was found. The Ca2+ influx was not inhibited by verapamil or by K+ depolarization, but the addition of Ni2+ reduced the influx, suggesting the involvement of cation channels sensitive to Ni2+. Ca2+ entry during mechanical stimulation was followed by Ca2+ release from intracellular Ca2+ stores. This release did not occur after pretreatment of the cells with thapsigargin and was reduced by exposure to ryanodine. The propagation of the Ca2+ wave could be blocked by the gap-junction blocker halothane and partially by K(+)-rich solution. It can be assumed, therefore, that cultured RPE cells express functional gap junctions. CONCLUSIONS: Mechanical stimulation triggers a Ca2+ influx that is followed by intracellular Ca2+ release. Intercellular communication in RPE cells depends on the presence of functional gap junctions. Pharmacologic stimulation relies primarily on the release of Ca2+ from intracellular Ca2+ stores.
PURPOSE: The intercellular communication between cultured rat retinal pigment epithelial (RPE) cells grown in increasing glucose concentrations or after modulation of the protein kinase C-induced protein phosphorylation was investigated by studying the conduction of the [Ca2+]i wave elicited by mechanical stimulation and by analyzing the fluorescence recovery after photobleaching (FRAP). METHODS: Subconfluent monolayers of RPE cells isolated from neonatal Long Evans rats were cultured in growth medium with various glucose levels and analyzed using the fluorescent dye fluo-3 for measurements of intracellular Ca2+ after mechanical stimulation and using 6-carboxyfluorescein diacetate to investigate the intercellular communication with FRAP. RESULTS: Mechanical stimulation in 5 or 12 mM glucose resulted in a Ca2+ wave that spread centrifugally through the neighboring cells. An inhibition of the propagation of this wave, similar to that induced by halothane, could be observed in cells grown for 72 hours in 14-mM or higher concentrations of glucose. This inhibitory effect was not caused by a hyperosmotic effect, in that results of experiments on cells cultured in growth medium supplemented with mannitol instead of glucose did not differ from those of experiments in the control medium. Activation of protein kinase C by incubation of the cells for 30 minutes with phorbol 12-myristate 13-acetate (PMA) resulted in a strong inhibition of [Ca2+]i-wave propagation. This inhibition did not depend on the oxidizing effects of PMA because the addition of glaucine, a known antioxidant, did not prevent the inhibition. Cells grown for 72 hours in glucose-rich medium (25 or 50 mM) and in which all protein kinase C activity was downregulated by a previous 72-hour exposure to 1 microM PMA, did not display the inhibitory effect on the propagation of the Ca2+ wave that is normally induced by this elevated glucose level. Stimulation or inhibition of protein kinase A activity by incubating RPE cells with Sp-cyclic adenosine monophosphate or Rp-cyclic adenosine monophosphate respectively, or inhibition of tyrosine kinase activity with herbimycin A did not alter the intercellular communication after mechanical stimulation. To determine whether the observed changes were caused by alterations in gap junction conductance (GJC), FRAP experiments were performed in control conditions, after a 30-minute incubation with PMA, and in cells cultured in 50 mM glucose in the presence and in the absence of 1 microM PMA. The measured GJC was consistent with the inhibitory effect on propagation of an intercellular Ca2+ wave in all tested conditions. CONCLUSIONS: In RPE cells, a glucose concentration of 14 mM (224 mg/dl) or higher inhibits Ca(2+)-wave propagation and intercellular GJC. This effect may be mediated by protein kinase C activity.
BACKGROUND: Control of the natural course of choroidal neovascularization (CNV) in age-related macular degeneration (ARMD) is difficult, and laser photocoagulation is recommended in only a subset of patients. Alternative modalities of treatment are under investigation. METHODS: We have used external beam radiotherapy (20 gray radiation units [Gy], 2 Gy fractions) to treat CNV in ARMD. A total of 111 patients have been followed for 12-30 months after radiotherapy. This study evaluates the effect of radiotherapy on the size of CNV, which was digitally measured on serial fluorescein angiograms. RESULTS: Analysis of results in the classic (or mixed classic and occult) CNV group was conclusive for fast growth of CNV and continuous increase of size during follow up. In the occult CNV group, a slowly progressive growth of CNV was demonstrated. In patients with vascularized pigment epithelium detachments, "hot spots" persisted; in a few patients, flattening of the macula was observed. Nearly all treated patients experienced further loss of vision. CNV growth in the radiotherapy treated eye was usually similar to growth in the untreated fellow eye, and in some, even worse. CONCLUSION: External beam radiotherapy (20 Gy, 2 Gy fractions) failed to control growth of CNV and was ineffective in stabilizing vision.