RESUMEN
PURPOSE: To measure the pulsatile movement of neuroretinal tissue at the optic nerve head synchronous with the cardiac cycle. METHODS: We used a noninvasive imaging device based on Fourier domain low-coherence interferometry to measure the pulsatile movements of the optic nerve head, peripapillary retina, and cornea with submicron accuracy along a line across the fundus. We also measured the change in the Axial Distance between the peripapillary Retina and the base of the optic disc Cup (ADRC) during the cardiac cycle. Twelve normal subjects and 20 subjects with open-angle glaucoma were tested. RESULTS: In normal subjects, the mean fundus pulsation amplitude (defined as the fundus movement minus the simultaneous corneal movement) were 13.0 ± 2.5 µm, 9.0 ± 2.1 µm, and 8.7 ± 2.9 µm at the base of the optic nerve head cup, the nasal peripapillary retina, and the temporal peripapillary retina, respectively, compared with 16.7 ± 6.8 µm, 17.3 ± 10.9 µm, and 12.7 ± 6.2 µm for the corresponding values in the glaucoma group (P = 0.26, P = 0.008, and P = 0.12, respectively). The mean changes in ADRC during the cardiac cycle in normal subjects were 10.7 ± 2.1 µm and 11.6 ± 1.8 µm for the nasal and temporal side of the optic disc, respectively, compared to 14.9 ± 5.6 µm and 14.0 ± 4.9 µm in glaucoma subjects (P = 0.03 and P = 0.10, respectively). CONCLUSIONS: There was an approximately 11-µm pulsatile change in the ADRC in normal subjects, and on the nasal side of the disc, this amount was significantly greater in glaucoma patients.
Asunto(s)
Glaucoma de Ángulo Abierto/fisiopatología , Frecuencia Cardíaca/fisiología , Presión Intraocular , Disco Óptico/fisiopatología , Enfermedades del Nervio Óptico/fisiopatología , Retina/fisiopatología , Anciano , Glaucoma de Ángulo Abierto/complicaciones , Glaucoma de Ángulo Abierto/patología , Humanos , Disco Óptico/patología , Enfermedades del Nervio Óptico/etiología , Enfermedades del Nervio Óptico/patología , Retina/patología , Tomografía de Coherencia Óptica/métodosRESUMEN
PURPOSE: Anomalies in the pulsatility of the eye have been associated with many types of ocular pathology. Estimation of ocular pulsatility is usually obtained by measuring the variation in the intraocular pressure using tonometry-based instruments. In this work, the authors present and demonstrate the applicability of a novel and noninvasive Fourier-domain optical coherence tomography (FD-OCT) system to measure pulsatile ocular tissue movements. METHODS: The authors simultaneously measured the longitudinal movement of the cornea and the retina driven by the cardiac cycle in 21 healthy volunteers using their custom-made FD-OCT. They calculated the corresponding fundus pulse amplitude (FPA), which is the variation in the distance between the cornea and the retina. RESULTS: It was found that in young, healthy subjects, the cornea and the retina move axially during the cardiac cycle, with almost equal amplitude but with a phase difference ranging between 1° and 20°. The measured FPA was found to be mostly due to the relative phase difference between corneal and retinal movements, and frequency analysis revealed the presence of the harmonics of heartbeat. The root-mean-square values for cornea, retina, and FPA movements were found to be 28 ± 9 µm, 29 ± 9 µm, and 4 ± 2 µm, respectively. The dominant frequency component in corneal and retinal movement was found to be the second harmonic of the heartbeat. CONCLUSIONS: The technique described here is useful for a precise description of FPA and the movement of ocular tissues. Further investigations and technical improvements will be beneficial for understanding the role of choroidal pulsation in the pathophysiology of ocular diseases.
Asunto(s)
Córnea/irrigación sanguínea , Mácula Lútea/irrigación sanguínea , Flujo Pulsátil/fisiología , Arteria Retiniana/fisiología , Tomografía de Coherencia Óptica/métodos , Tomografía de Coherencia Óptica/normas , Adulto , Córnea/fisiología , Femenino , Análisis de Fourier , Frecuencia Cardíaca/fisiología , Humanos , Mácula Lútea/fisiología , Masculino , Valores de Referencia , Reproducibilidad de los ResultadosRESUMEN
This article reviews the effects of systemic medications and some native vasoactive molecules on ocular blood flow (OBF). Some evidence exists for a positive effect of centrally acting calcium-channel blockers, nitric oxide precursors, adenosine, histamine, estrogens, and ginkgo biloba extract, while evidence for a negative effect on OBF exists for endothelin-1 and indomethacin. Some other molecules appear to have mixed effects, depending on the ocular vascular bed studied or the study protocol. In addition, medically induced changes in systemic blood pressure (BP) have an important impact on OBF, and the direction and magnitude of this effect may depend on the disease status of the patient and of the eye, as well as the absolute level of BP achieved. There are relatively few studies of the effects of systemic medications on OBF in glaucoma patients, and little is known of the long-term impact of such therapies on the preservation of optic nerve structure and function.
Asunto(s)
Ojo/irrigación sanguínea , Glaucoma de Ángulo Abierto/fisiopatología , Preparaciones Farmacéuticas , Velocidad del Flujo Sanguíneo/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Humanos , Disco Óptico/irrigación sanguínea , Flujo Sanguíneo Regional/efectos de los fármacos , Vasos Retinianos/fisiologíaRESUMEN
The objective of the present study was to reveal an interaction between choroidal blood flow (ChBF) and light-induced photoreceptor activity, a physiological coupling that has been already demonstrated for retinal blood flow but rejected for ChBF. Ten healthy adults volunteered for this study. A real-time recording near-infrared laser-Doppler flowmeter was used to quantify the subfoveal ChBF while the luminance of blue flicker between 1 and 64 Hz was first increased and then decreased by 4.0 log units in 1.0-log unit steps between 0.0375 and 375 cd/m2. In separate testing, flash electroretinograms (ERGs) provided electrophysiological indexes of the relative response of short-wave cones (s-cones) and rods to blue light stimulation. Group-averaged, normalized ChBF measurements revealed that it was modulated by approximately 9% by flicker frequency. Increasing the blue flicker luminance from low to high attenuated the subfoveal ChBF, volume, and velocity by approximately 32%, approximately 30%, and approximately 5%, respectively. Decreasing the luminance from high to low over the same range had no effect on the subfoveal choroidal hemodynamics. The markedly different effects of reversed directions of change in blue flicker luminance on the subfoveal ChBF were linked to transitions between rod-dominated and s-cone-dominated retinal responses. Collectively, these findings indicate that the blue light-induced photoreceptor response is associated with a differential distribution of the ChBF across the ocular fundus according to the degree and type of retinal photoreceptor stimulated.