Bruce Ira Gaynes

Quantitative assessment of conjunctival microvascular circulation of the human eye

Accessibility to the bulbar conjunctival microvasculature provides a means to assess blood supply to the cerebral cortex and thus optimize therapeutic interventions designed to prevent or reduce the risk of cerebral vascular disease and stroke. The feasibility of a method for quantitative measurements of conjunctiva blood vessel diameter, blood velocity, and flow in the human eye is reported. The method is based on slit lamp biomicroscope digital imaging coupled with a space time image analysis technique. A sequence of conjunctiva microvasculature images was captured at a rate of 50 Hz. The images were analyzed to determine blood vessel diameter, velocity and flow. Blood vessel diameter measurements ranged between 8.7 and 24.3 microns, with a mean value of 15.5 microns. Blood flow rate ranged between 27.3 and 296.9 pl/s, with a mean value of 111.8 pl/s. The relationship between blood flow and vessel diameter was fit with a power law curve (R=0.87). The application of this technique for in vivo quantitative assessment of blood flow dynamics has potential to impact diagnosis and monitoring of various cardiovascular and blood disorders.

Conjunctival microvascular haemodynamics in sickle cell retinopathy.

To determine alterations in bulbar conjunctival microvascular haemodynamics in sickle cell retinopathy (SCR) subjects with focal macular thinning (FMT).

Human bulbar conjunctival hemodynamics in hemoglobin SS and SC disease

The known biophysical variations of hemoglobin (Hb) S and Hb C may result in hemodynamic differences between subjects with SS and SC disease. The purpose of this study was to measure and compare conjunctival hemodynamics between subjects with Hb SS and SC hemoglobinopathies. Image sequences of the conjunctival microcirculation were acquired in 9 healthy control subjects (Hb AA), 24 subjects with SC disease, and 18 subjects with SS disease, using a prototype imaging system. Diameter (D) and blood velocity (V) measurements were obtained in multiple venules of each subject. Data were categorized according to venule caliber by averaging V and D for venules with diameters less than (vessel size 1) or greater than (vessel size 2) 15 µm. V in vessel size 2 was significantly greater than V in vessel size 1 in the AA and SS groups (P ≥ 0.009), but not in the SC group (P = 0.1). V was significantly lower in the SC group as compared to the SS group (P = 0.03). In AA and SS groups, V correlated with D (P ≤ 0.005), but the correlation was not statistically significant in the SC group (P = 0.08). V was inversely correlated with hematocrit in the SS group for large vessels (P = 0.03); however, no significant correlation was found in the SC group (P ≥ 0.2). Quantitative assessment of conjunctival microvascular hemodynamics in SS and SC disease may advance understanding of sickle cell disease pathophysiology and thereby improve therapeutic interventions. Am. J. Hematol. 88:661–664, 2013.

Feasibility of Conjunctival Hemodynamic Measurements in Rabbits: Reproducibility, Validity, and Response to Acute Hypotension

Please cite this paper as: Gaynes B, Teng P‐Y, Wanek J, Shahidi M. Feasibility of conjunctival hemodynamic measurements in rabbits: reproducibility, validity, and response to acute hypotension. Microcirculation 19: 521–529, 2012.

Conjunctival microvascular hemodynamics following vaso-occlusive crisis in sickle cell disease.

Painful vaso-occlusive crisis (VOC) is the clinical hallmark of sickle cell disease (SCD). Microcirculatory hemodynamic changes following painful VOC may be indicative of future development of VOC events in subjects with SCD. The purpose of the present study was to determine alterations in conjunctival microvascular hemodynamics during non-crisis state in SCD subjects with a history of VOC. Conjunctival microcirculation imaging was performed to measure conjunctival diameter (D) and axial blood velocity (V) in 10 control and 30 SCD subjects. SCD subjects were categorized into two groups based on their history of VOC within a 2-year period before imaging (with or without VOC-H) and also based on whether there was progression in the rate of VOCs during a 2-year period following imaging as compared to before imaging (with or without VOC-P). Conjunctival V was significantly higher in SCD subjects with VOC-H than in both control subjects and SCD subjects without VOC-H (P≤0.03). Conjunctival V was also significantly higher in SCD subjects with VOC-P compared with control subjects and SCD subjects without VOC-P (P≤0.03). Assessment of the conjunctival microcirculation may be useful for understanding hemodynamic changes that lead to VOC events in SCD subjects.

Changes in Conjunctival Hemodynamics Predict Albuminuria in Sickle Cell Nephropathy

Background: Albuminuria is an early manifestation of deterioration in renal function in subjects with sickle cell disease (SCD). Hyperfiltration may be an early mechanism for kidney damage in SCD. The purpose of the current study was to determine the association between conjunctival hemodynamics and albuminuria in SCD subjects with preserved glomerular filtration rate. Methods: Conjunctival microcirculation imaging was performed to measure conjunctival diameter and axial blood velocity (V) in 35 SCD and 10 healthy control subjects. Albuminuria, defined as albumin excretion ratio (AER), was obtained from the medical charts. Based on the 95% CI of conjunctival V in control subjects (0.40-0.60 mm/s), SCD subjects were allocated to 3 groups: V1 <0.40 mm/s (n = 7), V2 of 0.40-0.60 mm/s (n = 18) and V3 ≥0.60 mm/s (n = 10). Results: Mean log(AER) measurements in the V1, V2 and V3 groups were 1.08 ± 0.67, 1.39 ± 0.59 and 2.00 ± 0.91 mg/g creatinine, respectively, and followed a positive linear trend from the V1 to V3 groups (p = 0.01). By multivariate linear regression analysis, conjunctival V significantly correlated with albuminuria (p = 0.01) independent of age, blood pressure, α-thalassemia, hematocrit, white blood cell count and lactate dehydrogenase concentration. Conclusions: Increased conjunctival V is associated with albuminuria in SCD subjects. Assessment of conjunctival microvascular hemodynamics may improve our understanding of the pathophysiology and clinical management of sickle cell nephropathy.

Heavy Metal Analysis in Lens and Aqueous Humor of Cataract Patients by Total Reflection X-Ray Fluorescence Spectrometry

The human eye is continuously exposed to the environment yet little is known about how much of toxins, specifically heavy metals are present in its different parts and how they influence vision and acuity. To shed light into this subject, aqueous humor and lens samples were collected from 14 cataract patients to study the presence and concentration of selected metals in the eye. Subjects undergoing routine cataract surgery were consecutively enrolled for study by simple random sampling. Prior to surgery, subject demographic were compiled. The surgical procedure involved small incision cataract removal using phacoemulsification. During the procedure, a small aliquot of aqueous humor was retained for analysis, whereas homogenized lens fragments were obtained during phacoemulsification. A balanced salt solution was used as control for each set of samples. Both ocular specimens were analyzed by total reflection X-ray fluorescence spectrometry after dilution and addition of an internal standard. The data obtained show substantial variations in elemental signature between the two media (aqueous humor and lens) and the patients themselves. Most commonly found heavy metals in both types of media were chromium and manganese. Barium was found in the lens, but not in aqueous tissue, whereas nickel was found only in the aqueous humor. Concentrations were generally higher in aqueous samples. Further study and increased sample size are required to more accurately elucidate the relationship between systemic and ocular metal accumulation and the impact of metal accumulation on measures of visual function and ocular disease.

Statins and Cataract

model of CRVO.1 Originally, APC was determined to be an anticoagulant that inactivates factors Va and VIIIa. The protein has been reported to be a multifunctional molecule with cytoprotection, anti-inflammation, and endothelial barrier stabilization.2 To our knowledge, this report is the first to show that APC may reperfuse ischemic lesions. However, the mechanisms of reperfusion by APC remain unclear; APC might spare stem cell– like endothelial cells and/or pericytes as APC has been reported to have cytoprotective effects.2 The reperfusion might have occurred spontaneously in our cases, although reperfusion in ischemic CRVO has not been reported previously. Spontaneous retinal reperfusion has been reported in diabetic retinopathy,3 but the areas of reperfusion were extremely limited. Reperfusion of a large area of nonperfusion is rare and has been reported previously in only 2 cases; one was a case of radiation retinopathy4 and the other was retinopathy of unknown origin.5 Both patients were young and the causes were uncommon, ie, neither diabetic retinopathy nor retinal vein occlusion. Spontaneous reperfusion would not have been expected to occur in our cases because the areas of reperfusion were large, the patients were older with systemic hypertension and atherosclerosis, and no additional treatment was administered subsequent to the APC. Although we reported only 2 cases as part of a clinical trial and these were the best responders, the results may indicate that APC can be useful for treating ischemic CRVO and other ischemic disorders such as diabetic retinopathy or stroke.

Quantitation of in vitro α-1 adrenergic receptor antagonist binding capacity to biologic melanin using tandem mass spectrometry.

Abstract Purpose: The purpose of this study was to develop methods to allow evaluation of the binding characteristics for a series of α-1 antagonists to biologically-derived melanin. Methods: Fresh bovine globes were used to obtain iridal and choroid/retinal pigment epithelial (CRPE) derived melanin. Binding characteristics of chloroquine, tamsulosin and doxazosin were then evaluated in vitro using tandem mass spectroscopy. Results: Tandem mass spectrometry-based assays were developed for three α-1 antagonists that provided linear assay ranges which spanned (minimally) 0.01–10 µg/mL, while exhibiting excellent inter-assay precision and accuracy. When applied to the evaluation of binding characteristics for iridal melanin, mean chloroquine and tamsulosin fractions were found to be 41.9 ± 14.2 pmoles mg−1 and 25.34 ± 6.186 pmoles mg−1, respectively. Mean iridal doxazosin binding was found to be 6.36 ± 2.19 pmoles mg−1. Interestingly, mean levels of tamsulosin, but not doxazosin found bound to choroid/CRPE derived melanin approached that of chloroquine (27.91 µg/mL, 25.68 µg/mL and 5.94 µg/mL for chloroquine, tamsulosin and doxazosin, respectively). One way ANOVA for binding affinity for chloroquine, tamsulosin and doxazosin was statistically significant for both iridal and CRPE-derived melanin (p = 0.0012 and 0.0023), respectively. A Bonferroni post-hoc analysis demonstrated a statistically significant difference in the amount of binding between tamsulosin, doxazosin and chloroquine to iridal but not CRPE derived melanin (p < 0.05). Conclusions: Tamsulosin appears to demonstrate melanin binding affinity which approaches chloroquine and exceeds doxazosin for both iridal and CRPE-derived bovine melanin.

Efficient bottle adaptation provides for adjustment of ophthalmic drop volume and drug dosage.

in NTG. In SSOH, by contrast, the nature of the congenital anomaly causes reduced nasal microcirculation, as well as reduced ONH microcirculation in all quadrants, including the superior. SSOH thus has a fundamentally different pathogenesis from NTG. Our crosssectional study had a number of limitations; it included only a small number of eyes (approximately 70), and the SSOH group was younger than the NTG because of difficulty collecting subjects. However, these results suggest that in addition to analysis of cpRNFLT, non-invasive and objective LSFG measurements of MBR ratio may be a new candidate biomarker to differentiate SSOH and NTG.