Evaluation of micrometric and microdensitometric methods for measuring the width of retinal vessel images on fundus photographs

Delori, François C.; Fitch, Karlotta A.; Feke, Gilbert T.; Deupree, D. M.; Weiter, John J.

doi:10.1007/bf02172974

Cited by 79 publications

(41 citation statements)

References 11 publications

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“…A red diode laser (675 nm, 80 ϫ 50-m oval) is used to measure velocity every 0.02 s across a 2-s measurement window, which results in a velocity-time trace. The CLBF-100 also uses a green diode vessel-tracking laser system (543 nm, 1,500 ϫ 150-m rectangle) that is used to stabilize and measure the diameter of the vessel of interest (7,35). The vessel-tracking system stabilizes measurement-site position and allows rejection of velocity measurements that involve significant saccades.…”

Section: Methodsmentioning

confidence: 99%

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Gilmore¹,

Hudson²,

Preiss³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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Fisher. Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation. Am J Physiol Heart Circ Physiol 288: H2912-H2917, 2005. First published February 11, 2005 doi:10.1152/ajpheart.01037.2004.-The aim of this study was to simultaneously quantify the magnitude and response characteristics of retinal arteriolar diameter and blood velocity induced by an isocapnic hyperoxic provocation in a group of clinically normal subjects. The sample comprised 10 subjects (mean age, 25 yr; range, 21-40 yr). Subjects initially breathed air for 5-10 min, then breathed O 2 for 20 min, and then air for a final 10-min period via a sequential rebreathing circuit (Hi-Ox; Viasys) to maintain isocapnia. Retinal arteriolar diameter and blood velocity measurements were simultaneously acquired with a Canon laser blood flowmeter (CLBF-100). The response magnitude, time, and lag of diameter and velocity were calculated. In response to hyperoxic provocation, retinal diameter was reduced from control values of 111.6 (SD 13.1) to 99.8 (SD 10.6; P Ͻ 0.001) m and recovered after withdrawal of hyperoxia. Retinal blood velocity and flow concomitantly declined from control values of 32.2 (SD 6.4) mm/s and 9.4 (SD 2.5) l/min to 20.7 (SD 3.4) mm/s and 5.1 (SD 1.3) l/min, respectively (P Ͻ 0.001 for both velocity and flow), and recovered after withdrawal of hyperoxia. The response times and response lags were not significantly different for each parameter between effect and recovery or between diameter and velocity. We conclude that arteriolar retinal vascular reactivity to hyperoxic provocation is rapid with a maximal vasoconstrictive effect occurring within a maximum of 4 min. Although there was a trend for diameter to respond before velocity to the isocapnic hyperoxic provocation, the response characteristics were not significantly different between diameter and velocity. vascular reactivity; laser Doppler velocimetry; isocapnic hyperoxia THE BLOOD SUPPLY TO THE INNER retina is derived from the central retinal artery, whereas the choriocapillaris supplies the outer retina and photoreceptors. The retinal tissue is one of the most metabolically active in the body and, correspondingly, an uninterrupted nutrient supply is essential (50). The inner retinal blood vessels (i.e., past the lamina cribrosa) are thought to be unique due to the absence of an autonomic nerve supply to regulate vascular tone (53). Blood supply to the inner retina is regulated via local feedback signals that alter retinal perfusion in response to changes in systemic blood pressure or the concentration of certain metabolites (11,18). In particular, retinal blood flow is strongly dependent on the partial pressure of oxygen (PO 2 ; Refs. 14,25,31,42,48).The retinal vasculature can be noninvasively visualized and, consequently, its hemodynamic parameters quantified. Impairment of vascular reactivity has been demonstrated in the pathogenesis of various ocular diseases including diabetic retinopathy (13,20,25,32). Administration of O 2 has p...

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Section: Methodsmentioning

confidence: 99%

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Gilmore¹,

Hudson²,

Preiss³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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“…Micrometric diameter measurements were performed in modification of previously described techniques (Delori et al 1988). Therefore, high resolution video fluorescein angiograms (20ae observation field) were captured (768¿468 Pixel) with a digital image processing unit.…”

Section: Methodsmentioning

confidence: 99%

The acute effect of topical beta‐adrenoreceptor blocking agents on retinal and optic nerve head circulation

Arend¹,

Harris

Arend³

et al. 1998

Acta Ophthalmologica Scandinavica

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ABSTRACT.Purpose: Topical beta-blockers are the most common treatment for ocular hypertension in glaucoma, but their ocular hemodynamic effects are not well known. We investigated the acute effects of betaxolol (b-1 selective antagonist), levobunolol (non-selective antagonist with active polar metabolite), and timolol (non-selective antagonist) on retinal and superficial optic nerve head circulation. Methods: Intraocular pressure (IOP), heart rate, blood pressure, and retinal circulation were evaluated in 12 healthy subjects (6F/6M; mean ageΩ24∫2 years) before and two hours after instillation of each drug on separate occasions at least two weeks apart. Macular capillary blood velocity (MCBV), epipapillary blood velocities (EBV), arteriovenous passage (AVP) times, and arterial and venous diameters were measured by digital image analysis of scanning laser fluorescein angiograms. Results: All drugs significantly (p∞0.05) reduced IOP. There was no significant effect on blood pressure or calculated ocular perfusion pressure. Only levobunolol significantly lowered heart rate (p∞0.05). Each drug produced a significant (p∞0.01) decrease in AVP time of approximately 25%. MCBV was significantly (p∞0.01) increased by approximately 20% in all three conditions; each drug also produced significant (p∞0.01) increases in EBV. Arterial and venous diameters remained unaffected. Conclusion: All three drugs, despite different beta-adrenergic properties, increased blood velocities in retinal and epipapillary capillaries. These changes, occurring as they do in concert with decreased retinal arteriovenous passage time at constant retinal arterial and venous diameter, may indicate improved retinal perfusion after drug treatment. Improved circulation, if it indeed occurs, in tandem with reduced IOP, might explain in part the beneficial effect of badrenoreceptor blocking agents in glaucomatous patients.

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“…Manual segmentation was performed as described previously, 19 using a subjective full-width half-height approach. 20,21 Image Processing…”

Section: Study Protocolmentioning

confidence: 99%

IOP Elevation Reduces Schlemm's Canal Cross-Sectional Area

Kagemann

Wang

Wollstein

et al. 2014

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Previously, we demonstrated reduced Schlemm's canal cross-sectional area (SC-CSA) with increased perfusion pressure in a cadaveric flow model. The purpose of the present study was to determine the effect of acute IOP elevation on SC-CSA in living human eyes. METHODS.The temporal limbus of 27 eyes of 14 healthy subjects (10 male, 4 female, age 36 6 13 years) was imaged by spectral-domain optical coherence tomography at baseline and with IOP elevation (ophthalmodynamometer set at 30-g force). Intraocular pressure was measured at baseline and with IOP elevation by Goldmann applanation tonometry. Vascular landmarks were used to identify corresponding locations in baseline and IOP elevation scan volumes. Schlemm's canal CSA at five locations within a 1-mm length of SC was measured in ImageJ as described previously. A linear mixed-effects model quantified the effect of IOP elevation on SC-CSA.RESULTS. The mean IOP increase was 189%, and the mean SC-CSA decrease was 32% (P < 0.001). The estimate (95% confidence interval) for SC-CSA response to IOP change was À66.6 (À80.6 to À52.7) lm 2 /mm Hg.CONCLUSIONS. Acute IOP elevation significantly reduces SC-CSA in healthy eyes. Acute dynamic response to IOP elevation may be a useful future characterization of ocular health in the management of glaucoma.

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Evaluation of micrometric and microdensitometric methods for measuring the width of retinal vessel images on fundus photographs

Cited by 79 publications

References 11 publications

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

The acute effect of topical beta‐adrenoreceptor blocking agents on retinal and optic nerve head circulation

IOP Elevation Reduces Schlemm's Canal Cross-Sectional Area

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