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1.
Microvasc Res ; 128: 103937, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31644892

RESUMO

PURPOSE: Globally, a detrimental shift in cardiovascular disease risk factors and a higher mortality level are reported in some black populations. The retinal microvasculature provides early insight into the pathogenesis of systemic vascular diseases, but it is unclear whether retinal vessel calibers and acute retinal vessel functional responses differ between young healthy black and white adults. METHODS: We included 112 black and 143 white healthy normotensive adults (20-30 years). Retinal vessel calibers (central retinal artery and vein equivalent (CRAE and CRVE)) were calculated from retinal images and vessel caliber responses to flicker light induced provocation (FLIP) were determined. Additionally, ambulatory blood pressure (BP), anthropometry and blood samples were collected. RESULTS: The groups displayed similar 24 h BP profiles and anthropometry (all p > .24). Black participants demonstrated a smaller CRAE (158 ±â€¯11 vs. 164 ±â€¯11 MU, p < .001) compared to the white group, whereas CRVE was similar (p = .57). In response to FLIP, artery maximal dilation was greater in the black vs. white group (5.6 ±â€¯2.1 vs. 3.3 ±â€¯1.8%; p < .001). CONCLUSIONS: Already at a young age, healthy black adults showed narrower retinal arteries relative to the white population. Follow-up studies are underway to show if this will be related to increased risk for hypertension development. The reason for the larger vessel dilation responses to FLIP in the black population is unclear and warrants further investigation.


Assuntos
População Negra , Pressão Sanguínea , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Vasodilatação , População Branca , Adulto , Feminino , Humanos , Hipertensão/etnologia , Hipertensão/fisiopatologia , Luz , Masculino , Estimulação Luminosa , Estudos Prospectivos , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Fatores de Risco , África do Sul/epidemiologia , Vasodilatação/efeitos da radiação , Adulto Jovem
2.
Graefes Arch Clin Exp Ophthalmol ; 250(4): 589-94, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22008947

RESUMO

PURPOSE: To analyze dynamics of retinal vessel dilation response to flicker light in patients with glaucoma and ocular hypertension. PATIENTS AND METHODS: Response to flicker light was measured in retinal vessels by means of Retinal Vessel Analyzer. After the baseline 50 seconds long diameter recording of inferior and superior temporal artery and vein, three flicker stimulations of 20 seconds duration was applied, with a 80 seconds break in between. Area under the curve of the vessel diameter (AUC) was compared during 3 flicker periods in the open angle glaucoma patients group (POAG, n = 47) and ocular hypertensives (OHT, n = 46) and age-matched healthy controls (n = 56) RESULTS: POAG eyes demonstrated smaller response of all vessels to flicker light in general than the other two groups (p = 0.0008), but the response dynamics was significantly different between the groups (p = 0.038), showing in three flicker periods a delayed increasing response in the POAG and OHT groups, and remaining stable in healthy subjects. CONCLUSION: General vessel response to flicker light was decreased in POAG patients despite the slow improvement in repeated flicker stimulation, indicating an altered response pattern.


Assuntos
Glaucoma de Ângulo Aberto/fisiopatologia , Estimulação Luminosa , Artéria Retiniana/fisiopatologia , Veia Retiniana/fisiopatologia , Área Sob a Curva , Pressão Sanguínea , Dilatação Patológica/fisiopatologia , Feminino , Humanos , Pressão Intraocular , Masculino , Pessoa de Meia-Idade , Hipertensão Ocular/fisiopatologia , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Tonometria Ocular , Sistema Vasomotor/fisiopatologia
3.
Invest Ophthalmol Vis Sci ; 57(7): 3306-12, 2016 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-27333185

RESUMO

PURPOSE: The purpose of this study was to analyze factors determining retinal arterial and venous responses to stimulation with diffuse luminance flicker in healthy subjects. METHODS: We retrospectively analyzed results obtained in 374 healthy subjects who had previously participated in clinical studies in our department. A total of 153 subjects underwent a protocol in which flicker stimulation was delivered through the fundus camera at 8 Hz (protocol 1), separating measurement and stimulation light depending on the wavelength, and 221 subjects underwent a protocol in which diffuse luminance flicker was delivered at 12.5 Hz with high modulation depth (protocol 2). We investigated whether sex, systemic blood pressure, baseline vessel size, blood plasma concentration of fasting glucose and hematocrit, and serum concentration of cholesterol, triglycerides, creatinine and C-reactive protein influenced the retinal vascular response to flicker stimulation. RESULTS: Flicker responses in arteries and veins were more pronounced in protocol 2 than in protocol 1 (P < 0.001, each). In both of the protocols the vascular response to stimulation with diffuse luminance flicker was larger in smaller vessels (P between 0.001 and 0.016). In protocol 2 the retinal arterial flicker response was negatively associated with cholesterol serum levels (P = 0.033); in protocol 1, only a tendency toward this effect was observed (P = 0.056). CONCLUSIONS: The present analysis indicates that retinal arterial and venous responses to stimulation with diffuse luminance flicker depend on the way the stimulation is delivered through the fundus camera. In addition, the flicker response varied with vessel size, that is, the smaller the vessel width, the larger the flicker response. Finally, our data indicate that, even within the normal range, higher cholesterol serum levels are associated with lower hyperemic flicker responses.


Assuntos
Iluminação , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Vasodilatação/efeitos da radiação , Adulto , Pressão Sanguínea/fisiologia , Colesterol/sangue , Feminino , Humanos , Masculino , Estimulação Luminosa/métodos , Análise de Regressão , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Estudos Retrospectivos , Vasodilatação/fisiologia
4.
Acta Ophthalmol ; 94(1): e35-42, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26149453

RESUMO

PURPOSE: To compare flicker-induced retinal vessel diameter changes in varying age groups with low cardiovascular risk. METHODS: Retinal vascular reactivity to flicker light was assessed by means of dynamic retinal vessel analysis in 57 participants aged 19-30 years, 75 participants aged 31-50 years and 62 participants aged 51-70 years participants. Other assessments included carotid intima-media thickness (c-IMT), augmentation index (AIx), blood pressure profiles, blood lipid metabolism markers and Framingham risk scores (FRS). RESULTS: Retinal arterial dilation amplitude (DA) and postflicker percentage constriction (MC%) were significantly decreased in the oldest group compared to the middle-aged (p = 0.028; p = 0.021) and youngest group (p = 0.003; p = 0.026). The arterial constriction slope (SlopeAC ) was also decreased in the oldest group compared to the youngest group (p = 0.027). On the venous side, MC% was decreased in the middle-aged and oldest groups in comparison with the youngest group (p = 0.015; p = 0.010, respectively). Additionally, men exhibited increased arterial DA (p = 0.007), and percentage dilation (MD%, p < 0.001) in comparison with women, but only in the youngest age group. Both AIx and c-IMT scores increased with age (both p < 0.001); however, no correlations were found between the observed differences in the measured retinal vascular function and systemic parameters. CONCLUSION: In individuals with low cardiovascular risk, there are age-related differences in flicker-induced retinal vessel diameter changes throughout the entire functional response curve for arteries and veins. Gender differences mainly affect the arterial dilatory phase and are only present in young individuals.


Assuntos
Envelhecimento/fisiologia , Estimulação Luminosa , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Adulto , Idoso , Pressão Sanguínea/fisiologia , Espessura Intima-Media Carotídea , Feminino , Voluntários Saudáveis , Humanos , Luz , Lipídeos/sangue , Masculino , Microvasos/fisiologia , Microvasos/efeitos da radiação , Pessoa de Meia-Idade , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Vasodilatação , Adulto Jovem
5.
Ophthalmologe ; 102(8): 787-93, 2005 Aug.
Artigo em Alemão | MEDLINE | ID: mdl-15759121

RESUMO

PURPOSE: The aim of this study was to compare the diameter response of retinal arteries and veins after provocation with flickering light regarding the amplitude and temporal course. METHODS: The study included 26 healthy volunteers. The vessel diameter was automatically and continuously measured by the retinal vessel analyzer. The examination consisted of a baseline measurement (100 s) followed by five periods of 20-s flicker light provocation and 80-s follow-up observation. RESULTS: A diameter dilation was observed immediately after the end of the flicker period in arteries (6.9+/-2.8%) and veins (6.5+/-2.8%, difference n.s.). The quotient of arterial and venous dilation (AVDQ) was 1.25+/-0.69 (range: 0.2-2.8). A significant correlation of age and arterial or venous dilation or the AVDQ was not observed. The arterial diameter reduced faster than the venous and reached a minimum of -2.7+/-1.4% at 25.9+/-10.8 s after the end of the flicker phase. The veins were dilated by 0.5+/-1.3% at the time of the maximal individual arterial constriction (p<0.0001). CONCLUSIONS: Flicker-evoked response of retinal arteries and veins did not differ in the dilative amplitude but in the temporal course of the abatement of the dilation.


Assuntos
Anatomia Transversal/métodos , Estimulação Luminosa/métodos , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Vasodilatação/fisiologia , Adulto , Idoso , Feminino , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Luz , Masculino , Pessoa de Meia-Idade , Artéria Retiniana/anatomia & histologia , Artéria Retiniana/efeitos da radiação , Veia Retiniana/anatomia & histologia , Veia Retiniana/efeitos da radiação , Vasodilatação/efeitos da radiação
6.
Invest Ophthalmol Vis Sci ; 56(12): 7581-8, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26618650

RESUMO

PURPOSE: To determine the response of retinal vessels to differing durations of flicker light (FL) stimulation. METHODS: We recorded retinal arterial and venous vessel dilation to 12.5 Hz FL provocation of varying duration (5, 7, 10, and 20 seconds) in 12 healthy young individuals (age range, 26-45 years). All participants underwent a full ocular examination including IOP and blood pressure measurements. RESULTS: Maximum dilation (MD) did not show a significant dependence on flicker duration in arteries, whereas maximum constriction (MC) did. In veins, however, MD significantly increased with flicker duration. Approximately 80% to 90% of MD in arteries is reached within 10 seconds of FL stimulation. CONCLUSIONS: The vast majority of arterial dilatory capacity is reached within 10 seconds of FL stimulation even though venous dilation continues strongly. Since MC of arteries shows a significant dependence on flicker duration, measurements at two different durations can provide more information about the retinal vascular system than at a single flicker duration alone.


Assuntos
Estimulação Luminosa/métodos , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Vasodilatação/fisiologia , Adulto , Feminino , Voluntários Saudáveis , Humanos , Luz , Masculino , Pessoa de Meia-Idade , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação
7.
J Glaucoma ; 13(4): 340-4, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15226664

RESUMO

INTRODUCTION: Diffuse luminance flicker increases retinal vessel diameters in animals and humans, indicating the ability of the retina to adapt to different metabolic demands. The current study seeks to clarify whether flicker-induced vasodilatation of retinal vessels is diminished in glaucoma patients. METHODS: Thirty-one patients with early stage glaucoma (washout for antiglaucoma medication) and 31 age- and sex- matched healthy volunteers were included in the study. Retinal vessel diameters were measured continuously with a Retinal Vessel Analyzer. During these measurements three episodes of square wave flicker stimulation periods (16, 32, and 64 secs; 8 Hz) were applied through the illumination pathway of the retinal vessel analyser. RESULTS: Flicker-induced vasodilatation in retinal veins was significantly diminished in glaucoma patients as compared with healthy volunteers (ANOVA, P < 0.01). In healthy volunteers, retinal venous vessel diameters increased by 1.1 +/- 1.8% (16 seconds, P < 0.001), 2.0 +/- 2.6 (32 seconds, P < 0.001), and 2.1 +/- 2.1% (64 seconds, P < 0.001) during flicker stimulation. In glaucoma patients, venous vessel diameters increased by 0.2 +/- 1.7% (16 seconds, P < 0.6), 1.1 +/- 2.1% (32 seconds, P < 0.01), and 0.8 +/- 2.5 (64 seconds, P < 0.09). In retinal arteries, no significant difference in flicker response was noticed between the two groups (ANOVA, P < 0.6). In healthy controls, flicker stimulation increased retinal arterial vessel diameters by 1.0 +/- 2.4% (P < 0.03), 1.6 +/-3.2% (P < 0.004) and 2.4 +/- 2.6% (P < 0.001) during 16, 32, and 64 seconds of flicker, respectively. In glaucoma patients, flickering light changed arterial vessel diameters by 0.3 +/-2.6% (16 seconds, P = 0.4), 1.3 +/-3.1% (32 seconds, P = 0.03), and 1.8 +/- 3.8% (64 seconds, P = 0.005). CONCLUSION: Flicker-induced vasodilatation of retinal veins is significantly diminished in patients with glaucoma compared with healthy volunteers. This indicates that regulation of retinal vascular tone is impaired in patients with early glaucoma, independently of antiglaucoma medication.


Assuntos
Glaucoma de Ângulo Aberto/fisiopatologia , Estimulação Luminosa/métodos , Artéria Retiniana/fisiopatologia , Veia Retiniana/fisiopatologia , Vasodilatação/fisiologia , Idoso , Pressão Sanguínea , Técnicas de Diagnóstico Oftalmológico , Feminino , Humanos , Pressão Intraocular , Masculino , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Sistema Vasomotor/fisiopatologia
8.
Acta Ophthalmol ; 92(5): 444-8, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23826913

RESUMO

PURPOSE: To investigate whether retinal vessel calibre measurements on optical retinal photography are affected by light and dark exposure prior to photography and whether the vessel calibre changes during an imaging sequence of several images. METHODS: Digital optical retinal photographs were obtained from 32 healthy adults in two separate image sequences of six images during 1 min; one sequence with 10 min of dark exposure and one with 10 min of light exposure prior to imaging. Retinal arteriolar and venular calibres were measured computer-assisted and summarized as central retinal artery and vein equivalents (CRAE and CRVE). Outcome measures were difference in calibres after prior light versus prior dark exposure and difference in calibre during each of the two imaging sequences. RESULTS: CRVE was wider with prior light exposure (2.7%, p = 0.0001), comparing the first image in each image sequence. Within each sequence, there was a venular dilatation from first to last image, both with prior light exposure (1.7%, p = 0.0003) and prior dark exposure (3.1%, p < 0.0001), with the change less pronounced with prior light exposure (p = 0.0164). CRAE showed no significant change in either outcome. CONCLUSIONS: Retinal venular calibre was wider with light exposure prior to imaging and increased slightly during the imaging sequences, less pronounced after prior light than dark exposure. Measurement error due to these effects will probably be reduced by avoiding dark prior to imaging, and a possible bias effect of endothelial dysfunction may possibly be reduced by measuring calibre on an image taken early in the image sequence.


Assuntos
Luz , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Adulto , Pressão Sanguínea/fisiologia , Adaptação à Escuridão , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Pressão Intraocular/fisiologia , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa , Fotografação , Fluxo Sanguíneo Regional , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Acuidade Visual/fisiologia , Adulto Jovem
9.
Invest Ophthalmol Vis Sci ; 54(4): 2807-11, 2013 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-23493292

RESUMO

PURPOSE: To establish the optimal flash settings for retinal vessel oxygen saturation parameters using dual-wavelength imaging in a multiethnic group. METHODS: Twelve healthy young subjects (mean age 32 years [SD 7]; three Mediterranean, two South Asian, and seven Caucasian individuals) underwent retinal vessel oxygen saturation measurements using dual-wavelength oximetry, noncontact tonometry, and manual sphygmomanometry. In order to evaluate the impact of flash intensity, we obtained three images (fundus camera angle 30°, ONH centered) per flash setting. Flash settings of the fundus camera were increased in steps of 2 (initial setting of 6 and the final of 22), which reflect logarithmic increasing intensities from 13.5 to 214 Watt seconds (Ws). RESULTS: Flash settings below 27 Ws were too low to obtain saturation measurements, whereas flash settings of more than 214 Ws resulted in overexposed images. Retinal arteriolar and venular oxygen saturation was comparable at flash settings of 27 to 76 Ws (arterioles' range: 85%-92%; venules' range: 45%-53%). Higher flash settings lead to increased saturation measurements in both retinal arterioles (up to 110%) and venules (up to 92%), with a more pronounced increase in venules. CONCLUSIONS: Flash intensity has a significant impact on retinal vessel oxygen saturation measurements using dual-wavelength retinal oximetry. High flash intensities lead to supranormal oxygen saturation measurements with a magnified effect in retinal venules compared with arteries. In addition to even retinal illumination, the correct flash setting is of paramount importance for clinical acquisition of images in retinal oximetry. We recommend flash settings between 27 to 76 Ws.


Assuntos
Luz , Oxigênio/sangue , Estimulação Luminosa , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Adulto , Pressão Sanguínea/fisiologia , Cor de Olho , Feminino , Frequência Cardíaca/fisiologia , Hemoglobinas/metabolismo , Humanos , Pressão Intraocular/fisiologia , Masculino , Oximetria/métodos , Oxiemoglobinas/metabolismo , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Esfigmomanômetros , Tonometria Ocular
10.
Acta Ophthalmol ; 90(7): e524-8, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22863322

RESUMO

PURPOSE: To investigate the effect of caffeine on retinal vessel diameter before and during flicker light stimulation in young healthy subjects. METHODS: Seventeen healthy subjects (mean age: 29.6 ± 3.73 years, range: 22-35 years) were included in this study. The diameter of retinal vessels was measured continuously with the retinal vessel analyzer (RVA) before and 1 hr after 200 mg oral caffeine intake. After baseline assessment, a green luminance flicker of 20-second duration was applied to stimulate retinal activity. The diameter of a segment of an arteriole and of a venule were measured during stimulation and 80 second after cessation of the stimulus. Flicker stimulation and 80-second measurement interval were carried out three times. Blood pressure parameters, systemic mean arterial pressure (MAP), ocular perfusion pressure (OPP) and intraocular pressure (IOP) were obtained before and after oral caffeine intake. RESULTS: The mean diameter of the arterioles at baseline before caffeine intake was 123.30 ± 14.0 µm (arithmetic mean standard deviation) and after caffeine 117.30 ± 13.0 µm which was significantly different (p=0.004). The mean diameter of the venules at baseline before caffeine intake was 147.60 ± 19.5 µm and after caffeine 137.73 ± 19.9 µm which was significantly different (p = 0.005). The mean diameter of the arterioles during flicker light stimulation before caffeine intake was 126.65 ± 13.24 µm and after caffeine intake 121.59 ± 12.12 µm (p = 0.012). The mean diameter of the venules during flicker light stimulation before caffeine intake was 151.87 ± 18.63 µm and after caffeine intake was 145.14 ± 19.82 µm (p = 0.027). The flicker response of the arterioles increased from 2.8% before caffeine to 3.8% after caffeine intake (p = 0.010). The flicker response of the venules increased from 3.4% before caffeine to 5.5% after caffeine intake (p = 0.0001). Baseline diameters and diameters during flicker light stimulation after caffeine intake showed a significant negative correlation to the MAP for the arterioles (baseline: r = -0.338, p = 0.049 and flicker: r = -0.345, p = 0.046) and the venules (baseline: r = -0.496, p = 0.003 and flicker: r =-0.479, p = 0.004). CONCLUSIONS: The present study showed a significant vasoconstrictory response of the retinal vessels 1 hr after caffeine intake in young healthy subjects. Retinal vessel diameter changes were negatively correlated with MAP after caffeine consumption. These effects seem to be elicited by an autoregulatory response of the retinal vessels to the increased blood pressure changes after caffeine.


Assuntos
Cafeína/administração & dosagem , Estimulantes do Sistema Nervoso Central/administração & dosagem , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Adulto , Pressão Sanguínea/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Pressão Intraocular/fisiologia , Masculino , Estimulação Luminosa , Fluxo Sanguíneo Regional , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação , Vasoconstrição/fisiologia , Adulto Jovem
11.
Diabetes Care ; 32(8): 1536-41, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19478197

RESUMO

OBJECTIVE Flicker-induced vasodilatation is reduced in patients with vascular-related diseases, which has at least partially been attributed to endothelial dysfunction of retinal vessels. Currently, the standard method to assess endothelial function in vivo is flow-mediated vasodilatation (FMD). Thus, the present study was performed to investigate whether a correlation exists between flicker-induced vasodilatation and FMD in patients with known endothelial dysfunction and healthy subjects. RESEARCH DESIGN AND METHODS In the present study, 20 patients with type 1 diabetes, 40 patients with systemic hypertension (systolic blood pressure 140-159 mmHg; diastolic blood pressure 90-99 mmHg) and/or serum cholesterol levels > or =0.65 mmol/l, and 20 healthy control subjects were included. The flicker response was measured using the Dynamic Retinal Vessel Analyzer. FMD was determined using a high-resolution ultrasound system, measuring brachial artery diameter reactivity during reperfusion after arterial occlusion. RESULTS The flicker response of both retinal arteries and veins was significantly reduced in the two patients groups. Likewise, FMD was significantly reduced in patients compared with healthy control subjects. However, only a weak correlation between flicker-induced vasodilatation and FMD was observed. CONCLUSIONS The study confirms that flicker responses and FMD are reduced in the selected patient groups. Whether the weak correlation between FMD and flicker is due to the different stimulation type, the different vascular beds measured, or other mechanisms has yet to be investigated.


Assuntos
Diabetes Mellitus Tipo 1/fisiopatologia , Endotélio Vascular/fisiopatologia , Hipertensão/fisiopatologia , Vasodilatação/fisiologia , Adulto , Velocidade do Fluxo Sanguíneo , Artéria Braquial/anatomia & histologia , Artéria Braquial/fisiopatologia , Artéria Braquial/efeitos da radiação , Colesterol/sangue , Endotélio Vascular/efeitos da radiação , Feminino , Fusão Flicker , Humanos , Hipercolesterolemia/fisiopatologia , Luz , Masculino , Pessoa de Meia-Idade , Valores de Referência , Artéria Retiniana/fisiologia , Artéria Retiniana/fisiopatologia , Artéria Retiniana/efeitos da radiação , Veia Retiniana/fisiologia , Veia Retiniana/fisiopatologia , Veia Retiniana/efeitos da radiação , Sístole , Vasodilatação/efeitos da radiação
12.
AJNR Am J Neuroradiol ; 29(7): 1360-2, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18403557

RESUMO

Fractionated stereotactic radiation has become the standard treatment of meningioma of the optic nerve sheath. The mechanism responsible for improvement in visual function is unclear, because neuroimaging after treatment usually shows no discernable change in tumor appearance. We report immediate regression of optociliary shunt vessels in a patient after radiation treatment of an optic nerve sheath meningioma. This observation indicates that radiation treatment can cause rapid reduction of optic nerve compression, even without appreciable reduction in the size of the meningioma.


Assuntos
Corioide/irrigação sanguínea , Corioide/efeitos da radiação , Imageamento por Ressonância Magnética , Neoplasias Meníngeas/irrigação sanguínea , Neoplasias Meníngeas/radioterapia , Meningioma/irrigação sanguínea , Meningioma/radioterapia , Neovascularização Patológica/radioterapia , Síndromes de Compressão Nervosa/diagnóstico , Doenças do Nervo Óptico/diagnóstico , Neoplasias do Nervo Óptico/irrigação sanguínea , Neoplasias do Nervo Óptico/radioterapia , Nervo Óptico/irrigação sanguínea , Nervo Óptico/efeitos da radiação , Veia Retiniana/patologia , Veia Retiniana/efeitos da radiação , Tomografia Computadorizada por Raios X , Capilares/patologia , Fracionamento da Dose de Radiação , Feminino , Humanos , Pessoa de Meia-Idade , Neovascularização Patológica/diagnóstico , Disco Óptico/irrigação sanguínea , Disco Óptico/efeitos da radiação , Resultado do Tratamento , Acuidade Visual/efeitos da radiação , Testes de Campo Visual
13.
Ophthalmic Res ; 37(5): 250-4, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16020983

RESUMO

PURPOSE: To assess, if a slow multifocal stimulus (mfS) can provoke a perfusion response that can be measured with the Retinal Vessel Analyzer (RVA). METHODS: Seventeen eyes were examined. Pupils were dilated. A 120-second baseline recording was obtained with the RVA. The subject then turned to view an mfS for 56 s. The mfS consisted of 103 hexagons flickering according to an m-sequence with a stimulus base interval of 53.3 ms (L(max) = 100 cd/m(2), L(min) < 1 cd/m(2)). Immediately thereafter, the subject turned to the RVA, where measurements were resumed as soon as the same retinal vessel was targeted and continued for 104 s. Stimulation and recording was repeated twice. The diameter of a retinal vein and artery was measured for a length of at least 1 mm. The maximum vessel response was obtained by linear interpolation of the measured response within the 20 s following mfS. RESULTS: On average, veins dilated by 6.8% and arteries by 7% following mfS (p > 0.005). Such a dilatation could be observed in 9 veins and 7 arteries. Three venous and 2 arterial measurements did not show a dilatation following mfS. However, 13 of 34 measurements could not be analyzed due to signal problems or because the time from the end of mfS and the uptake of measurement exceeded 20 s. CONCLUSION: This slow multifocal ERG stimulus results in a dilatation of arteries and veins that can be measured with the RVA. Coupling an mfS to the RVA has the potential to topographically map changes in retinal perfusion in relation to the respective retinal area stimulated. When implementing the mfS into the RVA setup in order not to lose time due to the refixation in the RVA following mfS, one is required to take the transient nature of this perfusion change into consideration.


Assuntos
Glaucoma de Ângulo Aberto/fisiopatologia , Artéria Retiniana/fisiopatologia , Veia Retiniana/fisiopatologia , Vasodilatação/efeitos da radiação , Adulto , Técnicas de Diagnóstico Oftalmológico , Humanos , Pessoa de Meia-Idade , Músculo Liso Vascular/fisiopatologia , Estimulação Luminosa , Projetos Piloto , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação
14.
Graefes Arch Clin Exp Ophthalmol ; 242(5): 377-92, 2004 May.
Artigo em Inglês | MEDLINE | ID: mdl-14770317

RESUMO

BACKGROUND: Flickering light stimulation of the retina is known to increase retinal vessel diameter in animals and humans. The aim of the study was to quantify the response of retinal vessel diameter to red-green and blue-green flickering light. METHODS: In 11 normal healthy volunteers (mean age: 25.2+/-6.8 years) retinal arterial and venous diameters were examined by Retinal Vessel Analyzer (IMEDOS Ltd., Weimar, Germany) before, during and after red-green and blue-green flicker stimulation with a frequency of 12 Hz and duration of 10 and 30 s. RESULTS: For red-green flicker at 10 s there was a 2.4+/-1.4% arterial diameter increase at 9.1+/-3.3 s with a return to baseline after 30 s and a 2.4+/-1.1% venous diameter increase at 12.1+/-2.6 s with a return to baseline after 30 s. For red-green flicker at 30 s there was a 3.2+/-1.5% arterial diameter increase at 26.9+/-12.6 s with a return to baseline after 40 s and a 4.9+/-1.8% venous diameter increase at 31.4+/-7.6 s with a return to baseline after 40 s. For blue-green flicker at 10 s there was a 2.0+/-0.7% arterial diameter increase at 10.6+/-5.3 s with a return to baseline after 30 s and a 2.3+/-1.1% venous diameter increase at 12.0+/-5.5 s with a return to baseline after 30 s. For blue-green flicker at 30 s there was a 2.6+/-1.3% arterial diameter increase at 20.7+/-8.0 s with a return to baseline after 40 s and a 3.4+/-2.2% venous diameter increase at 28.8+/-10.5 s with a return to baseline after 40 s. CONCLUSIONS: Retinal vessel diameter dilation is a reproducible response to the applied flicker stimuli. This finding supports the existence of neurovascular coupling in the human retina. Flicker stimulation in either red-green or blue-green might be a useful stimulus for examination of retinal vessel behavior to regulatory demands.


Assuntos
Estimulação Luminosa , Retina/efeitos da radiação , Artéria Retiniana/fisiologia , Veia Retiniana/fisiologia , Adolescente , Adulto , Pressão Sanguínea/fisiologia , Feminino , Humanos , Pressão Intraocular/fisiologia , Luz , Masculino , Artéria Retiniana/efeitos da radiação , Veia Retiniana/efeitos da radiação
15.
Int Ophthalmol ; 9(2-3): 121-7, 1986 May.
Artigo em Inglês | MEDLINE | ID: mdl-2424854

RESUMO

Iris neovascularization has been reproducibly created in cynomolgus monkey eyes by argon laser occlusion of retinal veins. Pre-treatment of the eyes with lensectomy and vitrectomy (before the retinal vein occlusion) led to a more rampant development of the iris neovascularization in all eyes, as well as development of neovascular angle closure glaucoma in two of the 12 eyes. Histopathologic examination confirmed the finding of neovascular angle closure. This primate model may allow further investigation into the causes and therapy of neovascular glaucoma.


Assuntos
Olho/irrigação sanguínea , Glaucoma/complicações , Neovascularização Patológica/complicações , Animais , Modelos Animais de Doenças , Angiofluoresceinografia , Glaucoma/etiologia , Glaucoma/patologia , Iris/patologia , Lasers , Cristalino/cirurgia , Macaca fascicularis , Neovascularização Patológica/etiologia , Neovascularização Patológica/patologia , Doenças Retinianas/complicações , Veia Retiniana/efeitos da radiação , Vitrectomia
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