ABSTRACT
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).
ABSTRACT
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 (pâ< â0.001) reduction of Vax (39%, 49% and 47%, for CAP, PC1, and PC2, respectively) in comparison to the Control Group and a sizeable (pâ< â0.001) 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.
ABSTRACT
Background : Acute zonal occult outer retinopathy (AZOOR) is a rare, recently introduced sectorial outer retinopathy commonly seen in young females. The presence of AZOOR in multiple sclerosis (MS) patients can sometimes masquerade as optic neuritis. We hereby analyze an infrequent case of such an incident, as well as the comorbidities of this particular patient and the arising differential diagnostic dilemmas. Case Presentation : A 29-year-old female MS patient on cladribine presented in the emergency department (ED) due to left eye (LE) visual disturbances which appeared after Covid-19 infection. As a result of her past medical history, the case was considered to be consistent with optic neuritis. The patient was treated with high doses of intravenous methylprednisolone, but despite the treatment symptoms persisted. Ophthalmological findings were compatible with AZOOR. Conclusions : AZOOR can coexist with MS. However, it is unclear whether cladribine treatment or Covid-19 infection triggered AZOOR. Given the potential for ocular adverse effects associated with cladribine use, patients should be encouraged to report visual disturbances promptly. In addition, medical professionals must be vigilant of MS patients on cladribine complaining of visual symptoms, and refer them to an ophthalmologist as soon as possible.