MUDr. Dana Maňasková


Vyhledávání na medicinman.cz
 

nemoci-sympt/OCNI/makularni-degenerace/pfatofyziologie

Histochemically

  • Larger, hypofluorescent drusen
    • Contain predominantly neutral lipids.
  • Smaller, hyperfluorescent drusen
    • Consist predominantly of phospholipids

Accumulation of neutral lipids in Bruch's membrane

  • Associated with Pigment epithelium detachments
  • Apolar lipids
    • May produce a hydrophobic barrier in Bruch's membrane for the water transport from the retina towards the choroid.
      • A pigment epithelium detachment can develop.

The deposition of polar phospholipids

  • Predisposes to the development of choroidal neovascularization.
  • With the changed structure of Bruch's membrane


Macular thickness

  • Can be accurately quantified by optical coherence tomography (OCT)
    • Enabling accurate assessment of the macular prior to clinically apparent abnormalities

Microvascular assessments

Finger nailfold capillary pressure; Kf;

Microvascular structural assessments

  • I.e. skin vasodilatory capacity

Minimum vascular resistance (MVR)

Microvascular distensibility

Endothelial function



Capillary pressure

  • Key determinant of movement of fluid across a blood vessel wall
  • Associated with fovea thickness in non-diabetic individuals
  • Attention should be directed at the mechanisms determining retinal microvascular pressure

Clinical appearance of drusen

  • Vary from one person to another
  • Significant symmetry of drusen characteristics can be seen
    • Results of specific metabolic dysfunctions rather than non-specific aging products

Larger, more confluent and hypofluorescent drusen

  • Associated with the development of pigment epithelium detachments

Smaller, scattered and hyperfluorescent drusen

  • Choroidal neovascularizations are more likely.

Lutein in human milk

  • 2-3 times higher than those of beta-carotene
  • Concentrations in the mothers' blood are approximately the same.
  • Human milk is the main dietary source of lutein and zeaxanthin for infants until weaning occurs.
  • Tubulin has been identified as the major carotenoid-binding protein
    • May play a role in the physiology of the macula.
  • www.ncbi.nlm.nih.gov/pubmed/11681632

Impaired endothelial function

  • Of the forearm resistance blood vessels

Impaired skin microcirculatory responsiveness are associated with

  • Cardiovascular risk factors
  • End-organ damage
  • Intraventricular septal thickness
  • Urinary albumin excretion
  • Magnetic resonance imaging-defined subclinical cerebral infarcts
  • Progression of cerebral small vessel disease
  • Congestive heart failure
  • Coronary heart disease
  • Acute myocardial infarction
  • Left ventricular hypertrophy
  • Cardiovascular mortality rates
  • Diabetic retinopathy

Macular oedema

  • Important component of diabetic retinopathy.

Macular (fovea) thickening

  • Preclinical sign of macular oedema
  • Can be quantified using the new, revolutionary technique of retinal optical coherence tomography (OCT)
  • Capillary pressure
    • Key determinant of movement of fluid across a blood vessel wall
    • Positively associated with fovea thickness in non-diabetic individuals
  • Early sign of macular oedema
    • Result from changes in transmural capillary fluid movement
      • Balance of hydrostatic and oncotic forces acting across the capillary wall in Starling’s equation

Acute alterations in fovea thickness

  • Connection with posture in type 2 diabetes patients with clinically significant macular oedema (CSMO)
  • Fovea being thicker in the morning
  • Decreasing in thickness during the day and evening
  • Posture-induced changes in hydrostatic pressure
    • Fovea thickness decreased by a greater magnitude in individuals in the sitting position
      • Than in those in the supine position over the course of the day

Changes in venous and capillary pressure

  • Main contributors to posture-induced alterations in fovea thickness in type 2 diabetic patients with CSMO.
  • In healthy individuals
    • Capillary pressure is independent of arterial blood pressure due to the autoregulation
    • Protects the microcirculation from acute upstream changes in pressure
  • Posture-induced changes to fovea thickness in type 2 diabetic individuals with CSMO
    • Independent and dependent of systemic arterial blood pressure
    • Potential contribution of arterial blood pressure to posture-induced changes in fovea thickness
      • Failure of autoregulation in type 2 diabetic patients with retinopathy and macular oedema
  • Consistent trend for increased BMI associated with a reduction in fovea thickness
    • Negative relationship between BMI and fovea thickness is neurodegeneration
      • Associated with obesity
  • Fovea thickness is reduced in individuals with multiple sclerosis


Macular degenerative lesions manifest

  • Drusen formation
  • Lesions of the retinal pigment epithelium
  • Lesions of the choroidal choriocapillary layer
  • Lesions of the Bruch’s membrane,
  • Geographic atrophy of the central fovea
  • Exudative ARMD with
    • Choroidal neovascularization
    • Detachment of the retinal pigmentary epithelium
    • Changes of submacular disciform scarring

Drusen

  • Colloid material (lipids, phospholipids, collagen) excrescences
    • Similar to hyaline, that accumulate in the retina, in Bruch’s membrane underlying the retinal pigment epithelium.
  • Associated with progressive degeneration of the retinal pigment epithelium and photoreceptors
  • Drusen disturb oxygen metabolism
    • Determine degeneration of photoreceptors

Visual function impairment

  • Associated with the quantity of damaged photoreceptors

Retinal pigment epithelium (RPE)

  • Strategically located between retina and choroid, plays a critical role in retinal disorders
  • Buňky pak produkující signály pro růst cév

Korelace se zhoršením

  • Drusen characteristics correlated with progression to exudative maculopathy


O úroveň výše

Poslední aktualizace: 1. 2. 2024 0:37:53