We know that systemic hypertension (elevated blood pressure), is a risk factor for several conditions in our body. When hypertension effects an organ, we call it, “end organ damage”. In your eye, hypertension typically manifests in your retina. Yes, sometimes it can show up on the surface of your eye is a “bruise” called a subconjunctival hemorrhage but thankfully that will not cause changes to your vision. Your retinal health, on the other hand, is an extension of your systemic health, as your retina is supplied by hundreds of arterioles (small vessels from arteries).
Systemic hypertension can cause retinopathy (small hemorrhages and aneurysms in your retina) and it can also cause retinal artery and vein occlusions (blockages of a large blood vessel). Hypertension can also increase risk of diabetic eye disease and age-related macular degeneration (AMD). The association between high blood pressure and AMD is well studied. There are some studies showing a link between wet or neovascular AMD and hypertension.
The most common reasons patients are referred to retinal specialists is due to bleeding in the retina.
So, let’s take a dive into hypertension and retinal health:
Hypertension causes arteriolar narrowing (science: loss of nitric oxide mediated vasodilation) and structural changes (science: hardening and thickening of the retinal endothelial cells aka the cells that line blood vessels).
High salt intake was shown to cause remodeling of small vessels (wall/lumen ratio, wall thickness, and wall cross section) in the retinal
Poor perfusion of the retina may contribute to degeneration of retinal neurons and photoreceptors (cells that help us process visual information).
Hypertension may also contribute to age-related structural changes in Bruch’s membrane (the layer underneath your photoreceptors).
Note: Antihypertensives do not alter risk of AMD!
Hypertension reduces choroidal blood flow (blood vessels underneath the retina). Poor oxygenation leads to death (science: apoptosis caused by hypoglycemia) of retinal pigment epithelial cells (these cells are important for protecting your retina from oxidative damage- think UV rays!) and is associated with drusen formation (dry AMD) and development of hemorrhaging in the retina (wet AMD).
One of the largest modifiable risk factors for hypertension is salt consumption (in those who have salt sensitive blood pressure- we won’t go into this but it has to do with your kidney salt excretion). Optimal range of daily salt consumption is about 5-8 grams salt/day.
Next week we will dive further into salt consumption and some culinary medicine tips on salting your foods to help with your retinal health!
Sources:
Raff et al. “Salt intake determines retinal arteriolar structure in treatment resistant hypertension independent of blood pressure.”Atherosclerosis, 222(1), 2012.
Bringmann et al. “Intake of dietary salt and drinking water: Implications for the development of age-related macular degeneration.” Molecular Vision 2016; 1437-1454.