A normative blood velocity model in the exchange microvessels for discriminating health from disease: Healthy controls versus COVID-19 cases.

A usual practice in medicine is to search for "biomarkers" which are measurable quantities of a normal or abnormal biological process. Biomarkers can be biochemical or physical quantities of the body and although commonly used statistically in clinical settings, it is not usual for them to be connected to basic physiological models or equations. In this work, a normative blood velocity model framework for the exchange microvessels was introduced, combining the velocity-diffusion (V-J) equation and statistics, in order to define the normative range (NR) and normative area (NA) diagrams for discriminating normal (normemic) from abnormal (hyperemic or underemic) states, taking into account the microvessel diameter D. This is different from the usual statistical processing since there is a basis on the well-known physiological principle of the flow diffusion equation. The discriminative power of the average axial velocity model was successfully tested using a group of healthy individuals (Control Group) and a group of post COVID-19 patients (COVID-19 Group).

COVID-19 hemodynamic and thrombotic effect on the eye microcirculation after hospitalization: A quantitative case-control study.

BACKGROUND & OBJECTIVE: To quantify the hemodynamic and thrombotic effect of COVID-19 on the eye microcirculation of patients with thromboprophylaxis, shortly after hospital discharge. METHODS: This case-control study included 17 COVID-19 survivors (named "COVID-19 Group") and 17 healthy volunteers (named "Control Group"). Axial blood velocity (Vax) and percentage of occluded vessels (POV) were quantified by Conjunctival Video Capillaroscopy (CVC). Microvessels were identified and classified as "capillaries" (CAP), "postcapillary venules of size 1" (PC1), and "postcapillary venules of size 2" (PC2). RESULTS: The COVID-19 Group did not differ significantly in basic demographics from the Control Group. In the COVID-19 Group, there was a statistically significant (p < 0.001) reduction of Vax (39%, 49% and 47%, for CAP, PC1, and PC2, respectively) in comparison to the Control Group and a sizeable (p < 0.001) increase of POV (600%) in comparison to the Control Group. CONCLUSIONS: COVID-19 not only reduces significantly axial blood velocity in the capillaries and postcapillary venules of the eye but has also a devastating effect on microthrombosis (POV) despite thromboprophylaxis treatment. This gives a possible explanation for long COVID and a hint about the existence of a possibly unknown coagulation factor.

Scleral buckling surgery for stage 4A and 4B retinopathy of prematurity in critically ill neonates.

PURPOSE: To determine the efficacy of scleral buckling in eyes with stage 4A and 4B retinopathy of prematurity (ROP). METHODS: Seven eyes of five premature infants underwent scleral buckling for stage 4 ROP in zone II. Five eyes had stage 4A ROP, and two eyes had stage 4B ROP. Six eyes had previous diode laser photocoagulation, and one eye had received an intravitreal ranibizumab injection. Scleral buckling was the procedure of choice due to lack of access to specialized pediatric vitrectomy instrumentation. Average age at surgery was 3.4 months. Postoperative anatomic retinal status, visual acuity outcome and refractive error were assessed. RESULTS: The scleral buckle was removed on average 8 months after surgery. Retinal reattachment was achieved in all seven eyes. At final follow-up one eye had macular ectopia and disc dragging, one eye had a macular traction fold and two eyes had optic disc pallor. Average myopic error after buckle removal was -7.5 D. CONCLUSION: Scleral buckling can be performed safely and effectively in 4A and 4B stage ROP in critically ill infants, when access to specialized pediatric vitrectomy instrumentation is limited. This surgical technique may provide adequate relief of vitreoretinal traction with improved visual potential.

Subperiosteal Orbital Hemorrhage: An Unusual Complication During Labor.

ABSTRACT: Subperiosteal orbital hemorrhage in the postpartum period has been rarely reported. The authors herein present a female patient who developed acute-onset vertical diplopia, proptosis, mild retro-orbital pain, and restriction of upgaze immediately after labor. Neuroimaging revealed a subperiosteal hematoma along the right orbital roof. Diplopia, motility limitation, and retro-orbital pain gradually resolved in the following weeks. Subperiosteal orbital hematomas are a rare complication of labor, with only 12 cases reported so far. They result from straining during labor, which increases central and orbital venous pressure by means of the Valsalva-maneuver. In order to evaluate ocular motility and exclude optic nerve compression, an urgent ophthalmological examination is required.