Hypertensive Retinopathy (HR) is a result of damage to the back of the eye, due to increased blood pressure, more commonly referred to as hypertension. Systemic hypertension may be undiagnosed, and an eye exam can often yield the first signs of this systemic disease. Typical signs of HR include narrowing of the small arteries and arterioles and haemorrhages which eventually lead to a noticeable loss of vision.
The Keith-Wagener-Barker Hypertensive Retinopathy Classification is the clinically accepted method of grading the progression of this condition.
There are 4 stages.
- Mild retinal vascular changes (generalized arteriolar narrowing).
- Moderate to severe retinal vascular changes (arteriovenous crossing changes).
- Stage 1 and 2 findings, plus cotton-wool spots, retinal haemorrhages and exudates.
- Stage 3 findings, plus associated optic nerve head swelling and macular star formation.
HR is one of the leading causes of preventable blindness in the world and visits to your eye care practitioner is essential to detect and monitor changes associated with this condition.
Signs and Symptoms
The signs and symptoms of Hypertensive Retinopathy can be similar to the signs of diabetic retinopathy. The two conditions can be differentiated and properly diagnosed with a thorough workup of the individual. The main symptom of Hypertensive Retinopathy is altered vision.
When your eyecare practitioner examines the eye, the following signs may be noted:
- Tortuosity of the retinal blood vessels (twisted blood vessels).
- Focal narrowing of the retinal blood vessels (arteries and veins start to cross).
- Haemorrhaging (bleeding) in the retina.
- Cotton wool spots: Yellowish areas of the retina that have decreased oxygen from lack of blood flow.
- Exudates (lipids, or fats, that have leaked from the blood vessels): This usually occurs in a star configuration around the macula, which can indicate swelling of the macula and cause vision loss.
- Retinal edema (swelling of the retina in other areas), which can lead to retinal detachment and vision loss.
- Papilledema (swelling of the optic nerves); a condition that requires immediate hospitalization.
- Most people with hypertensive retinopathy do not have symptoms until late in the disease.
The most widely accepted classification is the Keith-Wagener-Baker system, which categorizes four stages of HTR
- Mild generalized arteriole sclerosis with increased arteriole light reflex, secondary to thickening within the blood vessel wall. This presentation typically signifies a chronic hypertensive change. These changes can and do occur in the normal elderly population.
- Moderate to severe retinal vascular changes are synonymous with decrease in lumen size and hyalinized arterial walls, which may lead to arteriovenous nicking, a pathognomonic feature of HTR (figure 1). At the arteriovenous crossing, the artery typically lies over the vein, sharing the same outer sheath. With increased arteriole sclerosis, the vein becomes susceptible to compression, which hinders normal blood flow.
- In this stage, acute elevation in blood pressure causes a breakdown of the blood-retina barrier. Contributing signs include retinal edema, cotton-wool spots, exudates and hemorrhage. These microvascular changes are often difficult to distinguish from diabetic retinopathy. Unlike diabetic retinopathy, HTR usually exhibits a drier retina associated with more cotton-wool spots and less exudates and/or hemorrhages. Also, the predominant retinal hemorrhages associated with HTR are flame-shaped hemorrhages rather than dot-and-blot hemorrhages.
- The most advanced stage of HTR is known as malignant hypertension. Malignant hypertension is accelerated high blood pressure that consists of a systolic pressure higher than 200mm Hg and a diastolic pressure higher than 140mm Hg. This serious increase in blood pressure is often associated with morbidity and/or mortality secondary to stroke, myocardial infarction, and renal and heart failure. Patients often present with complaints of decreased vision, headaches, diplopia, scotomas and/or photopsis. This stage is characterized by the signs of stage 3 HTR plus optic nerve head swelling and macular edema (macular star).
Most patients with hypertensive retinopathy have no symptoms, but patients who have acute malignant hypertension often complain of eye pain, headaches, or reduced visual acuity.
Chronic arteriosclerotic changes from hypertension will not cause any symptoms alone. However, the complications of arteriosclerotic hypertensive changes will cause patients to present with the typical symptoms of vascular occlusions or macro-aneurysms.
Causes and Risks
Hypertensive Retinopathy is caused by an increased blood pressure (BP) in the blood vessels within the retina. The higher the blood pressure and the longer it has been high, the more severe the damage is likely to be. You have a higher risk of damage and vision loss when you have diabetes, high cholesterol level, or you smoke. Rarely, blood pressure readings suddenly become very high. However, when they do, it can cause severe changes in the eye.
This increased or high BP damages the small retinal blood vessels in a variety of ways.
- Blood vessels change shape.
- They are more prone to leaking blood consisting of fats and fluids.
- Swelling of the macula and optic nerve
- Swelling in other areas of the retina can cause a retinal detachment
- Damage to the nerves in the eye due to poor blood flow
- Blockage of the blood supply in the arteries to the retina
- Blockage of the veins that carry blood away from the retina
The risk factors for developing Hypertensive Retinopathy include:
- Longstanding increased blood pressure (chronic hypertension).
- high salt diet.
- tobacco use.
- Family history.
- Ethnic background.
- The duration of elevated blood pressure.
- The amount that the blood pressure is elevation above normal.
- Systemic blood pressure of 140/110 mmHg (minimum) for advanced stages
- Systemic blood pressure of 180/120 mmHg (minimum) for malignant stage (stage 4)
- Severe haemorrhaging and/or swelling of the optic nerve
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others. Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
Stats and Incidence
The term hypertensive retinopathy was first introduced in 1930. Since then, studies have reported that hypertensive patients have a 50% to 80% chance of developing HTR (Hypertensive Retinopathy). Also, patients with signs of HTR are significantly more likely to have high blood pressure as well. Clinically, the initial signs of HTR are observed as alterations in the retinal microvasculature.
Individuals of any age affected by uncontrolled high blood pressure may develop the condition.
- Men and women are almost equally affected.
- Africans: The prevalence of Hypertensive Retinopathy is higher among African countries, since they are most affected by uncontrolled hypertension, which increases the risk for developing HR.
- Individuals with chronic hypertension: It is estimated that roughly 40% of the world population over the age of 25 years has high blood pressure. And, approximately 1 billion people worldwide have uncontrolled hypertension.
Currently, treatment for patients with stage 1, 2 or 3 HTR includes close observation, management of high blood pressure and regular dilated fundus exams. Malignant HTN, however, is a clinical emergency that warrants immediate referral for proper anti-hypertensive treatment. The reported three-year survival rate in patients with malignant hypertension is 6%, vs. 70% for those with stage 1 HTR. Fortunately, fewer than 1% of HTR cases are associated with malignant hypertension, primarily because it does not typically occur in treated hypertensive patients.
If the condition is diagnosed during stage 1 or 2, the progress to stages 3 and 4 Hypertensive Retinopathy can easily be prevented by:
- Managing the systemic blood pressure with any wide-range of treatment options available for hypertension.
- Administering injections to the eye to control swelling and preserve vision (in the case of macular edema).
- Repair/reattachment of the retina via surgery; in case of retinal detachment.