Risk Factors & Prevention
Risk factors for retinal vein occlusions are important. Why? Because an initial occurrence of central retinal vein occlusion, on occasion, is followed by another occlusion - central, branch or hemicentral retinal vein occlusion (RVO) occurring in either eye. The chance of such an occlusion is small, but it is real. If, however, underlying contributing conditions can be identified and treated the risk of another occlusion may be dramatically reduced.22 So in terms of preventing future retinal vein occlusions, the following factors for may be of interest: (Of course, you should always discuss any health related decisions with your doctor beforehand.)
Hypertension (high blood pressure) is the most commonly referenced risk factor for retinal vein occlusion. Blood pressure is simply the force with which the blood presses against the walls of the arteries as the blood flows away from the heart. This pressure is created by the pumping action of the heart.
At least some amount of pressure is needed to get the blood to flow through the blood vessels, but blood pressure which is too high over a long period of time may end up damaging the blood vessels. And this damage may eventually lead to many types of problems like: heart attack, atherosclerosis and stroke.
The conventional way of expressing the measurement of blood pressure is to use a ratio – for example 140/85 or “140 over 85.” The top number in that ratio is the systolic blood pressure, a measure of the blood pressure during a contraction of the heart. The bottom number is the diastolic blood pressure, a measure of the blood pressure between heart beats, when the heart is at rest. The chart above, based on criteria of the American Heart Association, lists the blood pressure ranges for normal, prehypertension and hypertension.
Hypertension and CRVO
The Eye Disease Case-Control (EDCC) Study Group found that having a medical history including hypertension increased the odds of having CRVO by 110%.1
They also found that higher levels of blood pressure were associated with higher odds for CRVO. Systolic blood pressure of 152 mmHg or more increased the odds of having CRVO by 280% when compared to systolic blood pressure at or below 119. Systolic blood pressure in the range of 120 to 151 mmHg increased the odds of having CRVO by 90% when compared to systolic blood pressure at or below 119.1
And likewise, diastolic blood pressure of 91 mmHg or more increased the odds of having CRVO by 150% when compared to diastolic blood pressure at or below 69. Diastolic blood pressure in the range of 70 to 90 mmHg increased the odds of having CRVO by 40% when compared to diastolic blood pressure at or below 69.1
What can be done?
There are several different sight damaging conditions that are referred to as “glaucoma.” In many of these conditions the pressure on the inside of the eye (intraocular pressure) is elevated. But with or without this elevated pressure, nerve fibers, which connect the light sensing retina to the brain, become damaged. In the most common form of glaucoma, vision is reduced, starting from the peripheral vision and progressing toward the central vision.
Glaucoma and CRVO
In central retinal vein occlusion, elevated pressure on the inside of the eye has been theorized to deform the structure (the lamina cribrosa) through which the central retinal artery and central retinal vein must pass as they exit the eye. If the vessels become pinched by this deformation, the central retinal vein is probably more affected because it is more pliable than the central retinal artery. Turbulent blood flow within the pinched central retinal vein may damage the inner lining of the vessel wall and result in the formation of a blood clot.23
Elevated intraocular pressure may also keep blood from easily flowing through the vasculature of the eye. Blood pressure drives blood through the retinal vessels. Intraocular pressure opposes the blood pressure. So any increase in the internal pressure of the eye tends to oppose and reduce blood flow through the retinal vessels, potentially causing blood to stagnate and thereby contribute to thrombus formation.24
The EDCC Study Group found a strong association between glaucoma and CRVO. Whereas a history of hypertension increased the odds of having CRVO by 110%, a history of glaucoma increased the odds of having CRVO by 440%.1
Work with your doctor to monitor and maintain normal intraocular pressures. A number of treatment options are available including eye drops, pills and surgical procedures. [More] In addition certain forms of exercise may be helpful in reducing intraocular pressure. [More] [More]
Cholesterol is a waxy substance that the body uses to build many types of cellular structures. This substance comes from two main sources. The majority is manufactured in by the liver. But the remainder is derived from the animal products that we eat.
Since cholesterol is waxy and cannot dissolve into the blood it must be transported by other molecules, special proteins, which can be dispersed into the blood. These special proteins in combination with cholesterol are called “lipoproteins.” One variety of lipoprotein, HDL (high-density lipoprotein - “good cholesterol”) helps to clear cholesterol from the body. LDL (low-density lipoprotein - “bad cholesterol”), on the other hand, often carries cholesterol into the walls of arteries resulting in atherosclerosis.
Cholesterol & RVO
Like high blood pressure, cholesterol may contribute to the thickening of artery walls. In the eye any thickening of the walls of the central retinal artery (CRA) may have a large influence on blood flow through the central retinal vein (CRV). The CRA and CRV pass together through a small opening in the lamina cribrosa, as seen in this illustration (above / left) of a cross section of the lamina cribrosa. Because they pass through an opening of limited diameter, if the CRA expands, the more pliable CRV gets crushed (above / right). Authorities theorize that the resulting turbulent blood flow due to this pressing of the CRA into the CRV may damage the walls of the central retinal vein and lead to the formation of a clot.23
In one large study, Weger et al. found that having cholesterol levels above 200 mg/dl or having to take medications to reduce cholesterol increased the odds of also having BRVO by 154%.15 High cholesterol has also been linked to CRVO.5,7
Low levels of “good cholesterol” (HDL), have also been associated with BRVO. The EDCC Study Group found that higher levels of HDL reduced the odds of having BRVO (in their final calculations) by about one half.13 Higher HDL levels were also related to lower rates of CRVO in their screening analysis.1
Diabetes is a condition in which the body’s cells are unable to properly use the sugar circulating in the bloodstream. The body either doesn’t produce enough of the chemical insulin, that helps the cells absorb the sugar, or the cells no longer properly respond to the insulin or some combination of both these problems. In any case, when blood sugar levels remain high many conditions may result: heart attack, stroke, narrowing of the arteries, kidney damage, damage to nerves etc. In fact, because diabetes itself affects the health of the retinal blood vessels, diabetes alone, even without a retinal vein occlusion, can cause swelling in the central part of the retina (macular edema) resulting in blurry central vision.
The EDCC Study Group found that those who had diabetes such that they were being treated with medications (insulin or hypoglycemics) were at increased odds by 80% for CRVO.1 Work with your doctor to closely monitor and manage diabetes. [More]
Acknowledgements: Eye anatomy images based on illustrations courtesy of National Eye Institute, National Institutes of Health.
Disclaimer: Since I am only a fellow patient and have no medical background you should not base any of your medical decisions on these notes or videos. Seek the advice of a competent medical professional promptly before making medical decisions.
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