What is the definition of Hypertensive Eye Disease?

 

Hypertension refers to a raised blood pressure. This raise in pressure can cause structural changes to different types of blood vessels, with those organs which rely on a specialised microvascular supply being impacted the most.

 

The eye has a delicate micro vessel supply and is unique in that we can actually visualise these vessels by examining the retina. As a result of the changes to the vessels caused by Hypertension we can see some changes to the retina as well (technically the retina is translucent meaning we are actually seeing vessels on the retina as well as the choroid - which is the vascular layer of the eye - underneath it)

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What types are there?

 

First, it’s important to ensure normal anatomy of the retina is understood before delving into the different grades of hypertensive retinopathy. On the retina shown below, the anatomy is clearly shown.

 

 

 

 

 

 

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Grade 0 - no changes, normal retina

This image is an example of a healthy retina (11). The normal anatomy can be seen here, with a healthy optic disc, macula, and vessels. There are no abnormalities like cotton wool spots, copper wiring, or torturous vessels.

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Grade 1 - barely detectable arterial narrowing

Grade 2 - obvious arterial narrowing with irregularities

Grade 3 - Grade 2 + retinal haemorrhage and/or exudates

This image shows grade 3 retinopathy with a macular star. Some cotton wool spots can be seen.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Grade 4 - Grade 3 + optic nerve damage

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What is some important anatomy to know?

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The retina is a thin sheet of tissue that lines the back of the eye. It contains cells that are sensitive to light, which trigger nerve impulses via the optic nerve to the brain. Here, a visual image can be formed. The retina is made up of many layers, but these can be grouped into the following: the photoreceptor cell layer, the bipolar cell layer, and the ganglion cell layer (6).

 

The photoreceptor layer is the layer closest to the choroid. It contains two types of photoreceptor cells, rods and cones. Rods detect dim light, and contain a derivative of vitamin A. Cones are responsible for detecting bright light, and are responsible for colour vision.

 

The bipolar layer is in the middle, and contains bipolar cells which receive signals from the photoreceptor cells. Here, the signal is transmitted to the ganglion cells.

 

The ganglion cell layer contains ganglion cells which receive signals from bipolar cells. Ganglion cell axons form the optic nerve, which transmits signals to the visual cortex in the brain, which forms images.

 

Blood is supplied to the retina via the central retinal artery and short posterior ciliary arteries. The central retinal artery travels in or along the optic nerve as it pierces the sclera. It then branches to supply the layers of the inner retina. The short posterior ciliary arteries also supply the choroid, along with the long posterior ciliary arteries. (7)

 

Hypertension will impact the arterioles and capillaries in the retina. Arteries carry blood away from the heart, and will eventually branch into smaller vessels. The smallest branches of arteries are called arterioles. Arterioles can further branch into capillaries, where nutrients and waste products are exchanged. Capillaries will combine with other vessels to form venules. These are small blood vessels that carry blood to the vein, which is a larger blood vessel that returns blood to the heart (8). It is damage of the arterioles and capillaries that leads to the structural changes that occur as a result of hypertension.

 

 

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(9)

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How can this develop? (4)

 

When blood pressure increases, the retinal blood vessels constrict to compensate. If the blood pressure increases further, the compensation mechanism is overcome, which causes damage to the muscle layer and endothelium.

 

Hypertensive retinopathy can be characterised with the following phases:

 

Vasoconstrictive phase:

In response to an increased blood pressure, auto-regulation (continual automatic adjustment) systems in the retina cause the blood vessels to spasm. This leads to arteriole narrowing.

 

Sclerotic phase:

This phase is caused by a persistent increase in blood pressure. This causes changes to the blood vessel walls, making them thicker. This leads to severe arteriolar narrowing, arteriovenous crossing changes, and silver and copper wiring (which can be seen on fundoscopy). Veins are also affected, and will dilate and appear torturous.

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(10)

 

Exudative phase:

This phase is seen in patients with severely raised blood pressure, which disrupts the blood-brain barrier. Here, blood will leak into the vessel wall, causing retinal signs including flame shaped and dot-blot haemorrhages, hard exudates, and cotton wool spots. This is a late sign of hypertensive retinopathy.

 

Malignant hypertension:

Severe intracranial hypertension leads to optic nerve damage and papilloedema, which can present as changes to vision and headaches.

 

 

What are some good history questions to ask?

 

• Have they had a diagnosis of hypertension?

• Currently taking any hypertensive medication?

• Headaches?

• Changes in vision including vision loss?

• Family history of any eye problems?

 

What are some risk factors to consider and why? (1)

 

• Increasing age

• Gender - males affected more than females

• Ethnic origin - African-Caribbeans more affected

 

Exercise is a protective factor

 

What should we look for on the examination?

 

Hypertensive retinopathy is usually asymptomatic, and is diagnosed based on fundoscopy (4). The following signs can be seen:

 

• AV crossing changes

• Arterial changes (changes in arteriolar light reflex, light reflex appears as copper, with or without silver wiring)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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• Retinal haemorrhages (dot-blot haemorrhages (bleeding in the inner retinal layer) or flame shaped haemorrhage (bleeding in superficial retinal layer))

• Retinal exudates (hard exudates (lipid deposits in retina) or soft exudates (cotton wool spots caused by ischaemia of nerve fibres))

• Macular star formation due to deposition of hard exudates around the macula

• Optic disc swelling

 

What investigations can we use to help out diagnosis?

 

Blood pressure measurement and fundoscopy.

 

What are treatment options (and how can we decide how to proceed)? 

 

Management depends on severity of disease.

 

Mild hypertensive retinopathy - controlling BP with antihypertensives and regular monitoring

 

Moderate hypertensive retinopathy - assessment to exclude other associated risk factors like diabetes mellitus and cardiovascular abnormalities. Controlling BP with antihypertensives and regular monitoring

 

Severe hypertensive retinopathy -  urgent BP management and referral to ophthalmology. Other systems should be monitored for signs of end organ damage, including renal, cardiovascular, and brain (4)

 

What follow up would these patients normally require and why?

 

Regular blood pressure monitoring with GP to ensure blood pressure is controlled

Regular fundoscopy to monitor progression of disease

 

Differentials

Other conditions that present with optic disc swelling:

• Diabetic papillopathy

• Central retinal vein occlusion

• Anterior ischaemic optic neuropathy

• Neuroretinitis

 

Conditions that mimic chronic hypertensive retinopathy:

• Diabetic retinopathy

• Retinal venous obstruction

• Ocular ischaemic syndrome

 

Complications

• retinal artery occlusion

• Retinal vein occlusion

• Macro aneurysm of retinal arteriole

• Glaucoma

• Diabetic retinopathy, hypertension is a major risk factor in the development (4)

 

References:

1 - Oxford handbook of ophthalmology book (page 622)

2 - Kanski’s clinical ophthalmology book (page 536-7)

3 - https://www.msdmanuals.com/en-gb/professional/eye-disorders/retinal-disorders/hypertensive-retinopathy

4 - https://www.ncbi.nlm.nih.gov/books/NBK525980/

5 - https://eyewiki.aao.org/File:HTN_RET_Findings.jpg (Reference for signs pic)

6 - https://byjus.com/neet/what-are-the-three-primary-layers-of-retina/

7 - https://www.ncbi.nlm.nih.gov/books/NBK53329/

8 - https://courses.lumenlearning.com/suny-ap2/chapter/structure-and-function-of-blood-vessels/

9 - https://teachmeanatomy.info/the-basics/ultrastructure/blood-vessels/

10 - https://morancore.utah.edu/basic-ophthalmology-review/hypertensive-retinopathy/

11 - https://visionaryeyecentre.com/retinal-imaging-how-it-works-why-its-important/

12 - https://www.researchgate.net/figure/2-NM-1-field-image-with-labeled-retinal-landmarks_fig7_311428681