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Biomedical subjects

G Donati

Publications and source records attributed to G Donati.

At least 73 records · Page 4Linked to original sources
PubMed1998

Complications of surgery for epiretinal membranes.

PURPOSE: Surgery has been successful in removing epiretinal membranes (ERM) from the macula, allowing some improvement in vision in 80-90% of patients; however, complications are relatively frequent. We conducted a retrospective study to evaluate the rate of peri- and postoperative complications and their influence on functional outcome of eyes having been operated on for ERM. MATERIAL AND METHODS: Preoperative findings, intraoperative and postoperative complications as final results of 70 consecutive cases of idiopathic or secondary ERM operated on by the same retina surgeon were analyzed. RESULTS: In all cases the ERMs were successfully removed from the fovea. The mean visual acuity (VA) increased from 0.34 +/- 0.2 to 0.54 +/- 0.31 (P < 0.05) postoperatively. Idiopathic and secondary ERM both showed significant improvement after surgery. Complications included intraoperative hemorrhage and retinal tears and postoperative progressive nuclear sclerosis, retinal tears causing detachments, macular edema and retinal pigmentary epitheliopathy. Final VA was not significantly different from the mean after complications, apart from when retinal detachments involved the macular area. CONCLUSIONS: Performing surgery for ERM is worthwhile in eyes with major decreased VA and in eyes with metamorphopsia but only moderately reduced vision. Postoperative complications are frequent but can usually be managed successfully. Of them, only retinal detachment has a negative effect on the final functional outcome.

Aged↗
PubMed1998

[Radiotherapy of occult neovascularization in senile macular degeneration: initial results of a pilot study].

BACKGROUND: AMD is the leading cause of legal blindness in people aged of more than 50 in industrialized countries. Occult neovascularization accounts for more than 70% of all exsudatives forms of AMD. Radiotherapy has been proposed as a possible treatment for retrofoveal neovascularization. We present the first results of a pilot study actually ongoing at the AMD Center in Creteil. PATIENTS AND METHODS: 44 patients (46 eyes) presenting occult choroidal neovascularization involving the fovea, aged of > 50 years and with a minimal visual acuity of at least 0.1 were included. They received a total dose of 16 Gy in 4 sessions of 4 Gy. All the patients were checked after 3 months. RESULTS: Visual acuity was globally maintained (> 0.1 in 93% of the eyes). Only one eye suffered a significant loss of vision (> 6 lines) and 11% suffered a moderate loss of vision (> 3 lines). Moreover 67% of eyes still had a near vision of 0.5 or more with reading glasses. On fluorescein angiography 17.5% of the eyes experienced an increase of the size of the occult neovascularization of > 0.5 Disk Area (DA), 76% showed no modification and 6.5% demonstrated a decrease in size of > 0.5 DA. CONCLUSIONS: As it has been shown that the antimitotic action of radiotherapy is most effective after 3 months, the present results suggest better evolution than natural history. However, as occult choroidal neovascularization is a slow-evolving disease further follow-up is needed to confirm it.

Aged↗
PubMed1998

[Endogenous deficiency of nitric oxide as an aggravating factor in retinal vein occlusion].

PURPOSE: Following retinal branch vein occlusion (b.v.o.), the arteriole crossing the occluded territories is often constricted. This constriction persists up to several weeks and is correlated with the development of extended territories of non-perfused capillaries. We present here results of an investigation supporting the hypothesis that decrease in the production of nitric oxide (NO) accounts for the observed arteriolar constriction. METHODS: Preretinal [NO] was measured using an NO microprobe in the anesthethized miniature pigs, before and within the first 4 hours following experimental b.v.o. Modifications of arteriolar diameter were correlated to preretinal [NO] changes. The retinal arteriolar sensitivity to constitutive NO was checked by performing preretinal puff injections of nitro-1-arginine (L-NA) after both systemic hypoxia and b.v.o. RESULTS: Two hours after b.v.o. there was 73.7 +/- 4% decrease in preretinal [NO] and a simultaneous 25.4 +/- 3.4% decrease in the diameter of the arteriole in the affected territory. Both persisted for at least 4 hours after b.v.o. Puffing L-NA over an arteriole previously dilated by systemic hypoxia induced a vasoconstriction. However no arteriolar constriction was observed when puffing was performed on an arteriole after b.v.o. CONCLUSIONS: These results show that experimental b.v.o. induced in the affected retina an impairment in the release of constitutive NO and an arteriolar constriction, which in turn, contribute to the development of tissue hypoxia and neuronal swelling and death in the inner retina.

Animals↗
PubMed1998

[Serous central chorioretinopathy and endogenous hypercortisolemia].

BACKGROUND: The exact pathogenic mechanism of the accumulation of subretinal fluid at the posterior pole of the fundus in cases of central serous chorioretinopathy (CSC) is not well established. Recently, it was reported that CSC is more frequent among patients with endogenous Cushing's syndrome. Thus, it has been suggested that glucocorticoids might be involved in the pathogenesis of CSC. Subsequently, additional observations, have confirmed the relationship between glucocorticoids and CSC. We present preliminary data on the endogenous cortisol secretion in patients with CSC. PATIENTS AND METHOD: Sixteen patients (14 men and 2 women, 35-65 years of age) suffering from CSC, not exposed to exogenous glucocorticoids and without clinical and/or biological stigmata of endogenous Cushing's syndrome, have been examined. Twenty four hour urinary free cortisol (24 h-UFC) secretion was measured within one week of their CSC episode. Twenty four hour urinary free cortisol of age and sex matched controls were also measured. RESULTS: Twenty four hour urinary free cortisol was 188.20 nmol/l +/- 34.1 for the patients suffering from CSC and 115.3 nmol/l +/- 63.4 for the control group (p < 0.05). CONCLUSION: These results give additional evidence that glucocorticoids may play a role in the pathogenesis of CSC. However, given the substantial variability of urinary free cortisol levels, as indicated by the increased SD, additional number of patients should be examined.

Adult↗
PubMed1998

[Myofibroblasts and retinal fibrovascular membranes].

INTRODUCTION: Epiretinal tissue proliferations occurring during the evolution of ischemic microangiopathies or preretinal diseases are tough to cause retinal detachment by traction mechanisms. Cellular migration/proliferations and finally contraction are tough to be the pathogenic element. Myofibroblasts are contractile cells having features intermediate between those of the fibroblasts and smooth muscle. We conducted a study to explore whether such cells are present in preretinal membranes. MATERIALS AND METHODS: 8 membranes, preelevated during vitrectomy for proliferative vitreoretinopathy or diabetic proliferative vitreoretinopathy, were analysed with immunostaining technique searching for alpha-actine smooth muscle, desmine, which are specific markers for myofibroblasts and TGF-beta1, that is considered as the mean factor promoting the transformation of fibroblasts into myofibroblasts. RESULTS: All the histological preparation showed abundant staining with antibody against alpha-actine smooth muscle, desmine and TGF-beta1. CONCLUSIONS: Myofibroblasts are one of the major cellular element of preretinal membranes. They are scattered throughout the membrane and seem to account for their contractile properties.

Actins↗
PubMed1998

Effect of nitroprusside on arteriolar constriction after retinal branch vein occlusion.

PURPOSE: The development of extended areas of nonperfused capillaries after branch vein occlusion (BVO) is correlated to the secondary constriction of the arteriole crossing the occluded area. The decrease in nitric oxide (NO) in tissue that occurs early after BVO accounts for the secondary arteriolar constriction. The present study shows that the administration of an NO donor can reverse the secondary arteriolar vasoconstriction observed after BVO. METHODS: Simultaneous preretinal NO profiles and arteriolar diameter measurements were performed in miniature pigs after experimental BVO. The effect of preretinal microinjections of the NO donor sodium nitroprusside (SNP) on the arteriolar diameter was studied. RESULTS: Significant arteriolar vasoconstriction (mean arteriolar diameter, 92.1% +/- 3.3% of control; n = 7; P = 7.4 x 10(-5)) and a simultaneous decrease in the preretinal NO concentration ([NO]) (preretinal [NO], 20% +/- 15.6% of control; n = 5; P = 0.0003) were observed 4 hours after BVO. Microinjection of the NO donor SNP (1 mM applied by puffer) near the constricted retinal arteriole caused a segmental, reversible arteriolar dilation that reached its maximum 20 minutes after the injection (mean arteriolar diameter; 110.8% +/- 7.5% of control; n = 6; P = 0.02) and was completely reversed 60 minutes later (n = 6). CONCLUSIONS: Local administration of NO donors may contribute to the restoration of the retinal arteriolar blood flow after BVO and thus may improve the supply of oxygen and nutrients to the injured tissue.

Animals↗
PubMed1998

[Surgery of idiopathic epiretinal membranes: functional results and complications].

PURPOSE: Surgery has been successful in removing epiretinal membranes from the macula allowing some improvement in vision in 80 to 90% of patients, however complications are relatively frequent. We conducted a retrospective study to evaluate the rate of peri- and postoperative complications and their influence on functional outcome of eyes having been operated for idiopathic epiretinal membranes. MATERIAL AND METHODS: Preoperative findings, intraoperative and postoperative complications as well as outcome in 40 consecutive cases of idiopathic epiretinal membranes operated by the same retina surgeon were analyzed. RESULTS: In all cases the epiretinal membranes were successfully removed from the fovea. The mean visual acuity increased from 0.36 +/- 0.2 to 0.54 +/- 0.3, (p < 0.05) postoperatively. Peroperative complications included intraoperative hemorrhage (18%) and retinal tears (10%). Postoperatively progressive nuclear sclerosis was observed in 75% of the cases and retinal tears causing detachments in 10%. CONCLUSIONS: Performing surgery for ERMs is worthwhile on eyes with major decreased visual acuity (< 0.25) as on eyes with metamorphopsia but only moderately reduced vision. Postoperative complications are frequent but can usually be managed successfully. Of them only retinal detachment involving the macula is of worse prognosis on the final functional outcome.

Aged↗
PubMed1997

Distribution and regulation of the optic nerve head tissue PO2.

We investigated the distribution and regulation of the optic nerve head (ONH) tissue partial pressure of oxygen (PO2) under various stimuli and the role of the nitric oxide in the ONH circulation. Tissue PO2 was measured using double-barreled recess microelectrodes in the intact eyes of miniature pigs during normoxia, hyperoxia, hypoxia, variations of systemic blood pressure, and after inhibition of the endothelial nitric oxide synthesis by the administration of nitro-L-arginine. Measurements were performed in front of the ONH at intervascular and juxta-arteriolar areas and at a depth of 50 and 200 microm within the ONH at the center and the rim. During normoxia, PO2 was heterogeneously distributed in the ONH, higher close to the arterioles than in intervascular areas. Hyperoxia induced a significant increase of juxta-arteriolar tissue PO2, while in intervascular areas no change was noticed. Hypoxia did not modify intervascular tissue PO2 at 200 microm depth within the ONH. Variations of the systemic blood pressure did not induce any significant change in ONH tissue PO2. Similarly, no modification was noticed after the administration of nitro-L-arginine. There is a remarkable autoregulatory capacity of the ONH circulation that may compensate for parameters such as hyperoxia, hypoxia, and variations of the systemic blood pressure. Endothelially derived nitric oxide inhibition does not modify the ONH tissue PO2, probably because the tissue PO2 is stabilized by compensatory regulation.

Animals↗
PubMed1997

Decreased nitric oxide production accounts for secondary arteriolar constriction after retinal branch vein occlusion.

PURPOSE: After retinal branch vein occlusion (BVO), the arteriole crossing the occluded territories is often constricted. This constriction persists up to several weeks and is correlated with the development of extended territories of nonperfused capillaries. These are results of an investigation supporting the hypothesis that decrease in the production of nitric oxide (NO) accounts for the observed arteriolar constriction. METHODS: Preretinal [NO] was measured using an NO microprobe in the anesthetized miniature pigs, before and during the first 4 hours after experimental branch vein occlusion. Modifications of arteriolar diameter were correlated to preretinal [NO] changes. The retinal arteriolar sensitivity to constitutive NO was checked by applying preretinal puff injections of nitro-L-arginine (L-NA) after both systemic hypoxia and branch vein occlusion. RESULTS: Two hours after branch vein occlusion there was a 73.7 +/- 4% decrease in preretinal [NO] and a simultaneous 25.4 +/- 3.4% decrease in the diameter of the arteriole in the affected territory. Both persisted for at least 4 hours after branch vein occlusion. Applying a puff of L-NA to an arteriole previously dilated by systemic hypoxia induced a vasoconstriction. However, no arteriolar constriction was observed when a puff was applied to an arteriole after branch vein occlusion. CONCLUSIONS: These results show that experimental branch vein occlusion induces in the affected retina an impairment in the release of constitutive NO and an arteriolar constriction, which, in turn, contributes to the development of hypoxia in tissue and neuronal swelling and death in the inner retina.

Animals↗
PubMed1996

[Treatment of full-thickness macular holes by vitreoretinal surgery].

PURPOSE: To assess the benefit of vitreous surgery in treating patients with full thickness macular holes (stages II to IV from Gass), we report anatomic and visual statements before and after operation in a series of 12 consecutive eyes (3 holes stage II and 9 holes stage III). METHODS: Visual acuity and anatomical status of the eye before and after the operation were retrospectively reviewed. Surgery included vitrectomy with care to remove the posterior cortical vitreous and relief of all tangential tractions at the posterior pole, retinal tamponade with intraocular gas and face down position for one week. RESULTS: Postoperatively anatomic success was achieved in 83% cases. Mean preoperative as postoperative visual acuity was 0.4, but postoperative visual acuity was improved at least one line in 66% cases. A secondary cataract was observed in 42% cases within 3 months postoperatively and a transient postoperative intraocular hypertonia (30 to 50 mm Hg) was found in 83% cases within 3 days after the operation. It could be successfully treated in each case with diamox p.o. No case of retinal ischemia was observed. CONCLUSIONS: Macular hole surgery provides retinal reattachement and meaningful improvement in visual acuity in selected cases. Vitreous surgery is the treatment of choice for constitued macular holes.

Aged↗
PubMed1996

[Apropos of a case of bilateral perforating corneal ulcer in a patient with Portugese amyloidosis].

PURPOSE: Corneal ulcer is a very rare clinical manifestation in hereditary familial amyloidosis of the Portuguese type, from which only one case has been reported previously. The case of a 35-year-old man illustrates the diagnostic findings and the difficulties encountered in understanding the physiopathology of such a complication. PATIENT: The patient was referred by his general practician because of bilateral visual impairment since few days. Examination disclosed bilateral central perforating corneal ulceration. Corneal sensitivity was normal in both eyes, BUT (break-up time) was 2 sec. and Schirmer II test abolished. RESULTS/CONCLUSION: Corneal ulceration is an unusual complication consecutive to a massive dry eye syndrome.

Adult↗
PubMed1996

[Early alterations in release of nitrogen monoxide by the retinal after experimental venous occlusion].

PURPOSE: We present hereby some results indicating that there is a significant decrease in the release of NO by the retina immediately after branch-venous occlusion (BVO). METHODS: Using an NO microprobe we measured (NO) in the preretinal vitreous of miniature pigs before and two hours aRer bvo. Conventional and electronic microscopy were performed on the affected retina. RESULTS: At the retinal surface (NO) was reduced to 25% of the previous value two hours after BVO, at the same time significative oedema of the inner retina was observed. CONCLUSIONS: Immediately after BVO there is a significative decrease in the amount of NO released by the affected retina, parallel to the first evidences of an oedema of the inner retinal layers.

Animals↗
PubMed1996

[Morphology of early retinal lesions after experimental venous occlusion].

PURPOSE: Study of early hystological lesions after experimental branch venous occlusion (BVO) in miniature pigs. MATERIALS AND METHODS: The retina was taken 1, 2, 4, 6 and 8 hours after BVO with green argon laser for examination with conventional and electronic microscopy. RESULTS: 1 hour after occlusion an extracellular focal oedema is observable in the ganglion cells optic nerve fibers and cells of inner plexiform layer; 2 hours after occlusion there is also an extracellular oedema of the external plexiform layer as intracellular oedema of the inner nuclear layer, 4 hours after occlusion the extracellular oedema is more diffuse especially in the ganglion cells, inner nuclear and optic nerve fibers layers. Cytoplasmic vacuolisation, nuclear pycnosis and ruptured cell membrane layers are observed; 8 hours after occlusion both intra and extracellular oedema are observable throughout the inner retina. CONCLUSIONS: After BVO histological lesions are found within one hour only following the occlusion, apoptosis and cell necrosis are present as soon as 4 hours after experimental BVO.

Animals↗
PubMed1995

[Intraocular surgery for secondary retinal detachment in proliferative vitreoretinopathy].

BACKGROUND: Proliferative vitreoretinopathy (PVR) is defined as the growth and contraction of cellular membranes within the vitreous cavity and on both surfaces of the retina following rhegmatogenous retinal detachment. This process is extremely important as these membranes exert traction and may cause recurrent detachment by reopening otherwise successfully treated retinal breaks or create new retinal breaks. We present the results of a small retrospectively series of 63 cases operated in the University of Geneva Eye Clinic, between 1990 and 1993. Surgical procedure, anatomical results, visual acuity have been reviewed. SUBJECTS AND METHODS: Surgical technique, number of surgical procedures, anatomical result and final visual acuity, have been reviewed in each case. Subjects have been divided into two groups depending on the degree of PVR (stage B or C). All patients have been operated combining extra- and intraocular microsurgical technique (scleral buckling, extended vitrectomy, perfluorodecaline, peroperative tamponade, endolaser photocoagulation, retinectomy and gaz or silicone oil tamponade). RESULTS: In the group presenting a stage-B PVR, the retina was reattached in 79% of cases, but only in 47% of the stage-C cases after one surgical procedure. The functional results showed only 31% of cases with a visual acuity superior to 0.4 in the stage-B group and 28% in the stage-C one. In all the stage-B cases that needed further surgical procedure, the retina could be definitely reattached, but in 9% cases of the stage-C group the retina remained detached and in 18% of the same group permanent silicone oil tamponade was necessary to maintain the retina reattached. CONCLUSION: Significant evolution has been observed in microsurgical endoocular surgery in the last ten years, allowing a significant improvement in the anatomical results. Stage-B PVR could be efficiently treated by one surgical procedure in more than 2/3 of cases strongly suggesting the use of endoocular microsurgery as a first intention procedure for retinal detachment complicated by stage-B PVR. An initial stage-C PVR is associated with a poorer anatomical and functional result because of an increased risk of recurrent PVR.

Female↗
PubMed1995

[Constitutional release of nitrogen monoxide (NO) by the retina of the minipig is a major determinant of arteriolar basic tonus in the internal retina].

PURPOSE: NO is a nonpolar gas, which diffuses across cell membranes in an isotropic fashion. In relatively large arteries NO has been identified as the endothelium-derived releasing factor and the current hypothesis is that NO controls the vascular tone. We are investigating an alternative hypothesis proposing that the retinal tissues surrounding the arterioles contribute in the process of NO production. METHODS: We performed flicker light stimulation in anesthetized minipigs (hypnodyl 100 mg/hr, tubocurarine 0.1 mg/hr und N2O) in steady-state of normoxia-normocapnia. An NO-microprobe mounted on a micromanipulator was introduced into the eye through the pars plana and positioned on the preretinal space in a zone free of visible vessels. Preretinal NO gradient and recording of NO release variations in response to flicker light stimulation were performed so as periarteriolar microinjections of nitro-L-arginine. RESULTS: When advancing the NO-probe from the vitreous towards the retina we recorded an NO-gradient corresponding to an efflux of 7.1 pMol x min-1 x cm-2 (N = 9). With the microprobe positioned close to the retina and after 60 min dark adaptation we recorded a mean increase in NO release of 1.59 muMol +/- 0.13 SE. After periarteriolar microinjection of nitro-Larginine we recorded a transitory reversible vasoconstriction. CONCLUSIONS: These results indicate that a process occurring in the extravascular tissue of the retina modulates the production of NO and that constitutional NO release by the retina is a major determinant of the basal retinal arteriolar tone.

Animals↗