Human bulbar conjunctival hemodynamics in hemoglobin SS and SC disease

Abstract

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.

Conjunctival and pulmonary hemodynamic properties in sickle cell disease subjects with and without pulmonary hypertension

“…Previous studies have reported conjunctival microvascular hemodynamics in SCD subjects 5, 6. However, to the best of our knowledge, there have been no studies evaluating conjunctival microcirculatory hemodynamics in SCD subjects with or without PH.…”

2015 Clinical trials update in sickle cell anemia

“…Impaired rheology plays a key role in the pathogenesis of the complications of HbSC disease, and is believe to result in the 70% incidence of retinopathy and 29% incidence of sensorineural ontological disease, substantially higher than in non-SCD populations [165,166]. Limited evidence suggests a beneficial effect of phlebotomy in preventing recurrence of acute complications [165].…”

Automated Real-Time Conjunctival Microvasculature Image Stabilization

“…The conjunctival microvasculature is easily imaged by non-invasive techniques, thereby allowing study of in situ microcirculatory hemodynamics [1]. Previous studies have reported alterations to the conjunctival microvasculature in systemic pathologies including diabetes [2, 3], Alzheimer’s disease [4], and sickle cell anemia [5–7]. Therefore, assessment of the conjunctival microcirculation may improve understanding of the abnormalities that occur in microvascular hemodynamics due to various systemic diseases.…”

“…Additionally, dedicated optical imaging systems have also been developed based on Orthogonal Polarization Spectral imaging [10], slitlamp biomicroscopy [1, 5, 11, 12] and intravital microscopy [3, 13]. These systems assess the conjunctival hemodynamics by analyzing image sequences captured at high frame rates and magnifications.…”

“…These systems assess the conjunctival hemodynamics by analyzing image sequences captured at high frame rates and magnifications. High magnification imaging is achieved with either additional optics [1, 5, 11, 12] or modification of the telephoto zoom via camera settings [14–16]. Nevertheless, these optical imaging systems have not incorporated image stabilization instrumentation to remove eye motion artifacts, a necessary step for quantification of conjunctival hemodynamics.…”