Generality
Hypertensive retinopathy is an eye disease found in subjects with high values of systemic blood pressure.
Healthy retina
Retinal image of the left eye in a patient with chronic hypertension and dyslipidemia, with blurred vision; note the vascular tortuosity and arteriosclerotic changes.
At the ocular level, this condition negatively affects the retinal tissue, the choroid and the optic nerve, causing a wide spectrum of vascular damage.
Within the retinal arterioles, the increase in pressure triggers the mechanisms of vascular compensation. Initially, there is a contraction of the elastic fibrils of the blood vessel wall, which leads to a narrowing of the lumen and an increase in tortuosity along their course.
However, when pressure stress is excessive (hypertensive crisis) or protracted over time (chronic hypertension), these reactions are insufficient and cease. The result is a structural alteration of the vascular wall, which undergoes bulging and becomes incontinent. Extravasation of liquids into the retinal tissue (exudates) and bleeding that can compromise the correct functionality of the retina occur.
In advanced stages, when systemic arterial pressure is elevated for years and is poorly controlled by proper therapy, edema can develop, deposition of hard exudates around the fovea (macular star) and ischemic areas.
In most cases, symptoms appear in the more advanced stages of hypertensive retinopathy.
Fortunately, the involvement of the retinal circulation can be found during an eye examination, examining the ocular fundus with the ophthalmoscope. Undergo periodic checks can therefore contribute to the early diagnosis of a latent systemic hypertension and allow an adequate pharmacological treatment to be started.
What is hypertension? Hypertension is the increase in systolic and / or diastolic blood pressure, above 140 millimeters of mercury (mmHg) for the maximum and 90 mmHg for the minimum. The natural evolution of untreated arterial hypertension involves the gradual and progressive establishment of lesions in some target organs (heart, brain, eyes and kidneys).
Causes
Hypertensive retinopathy is an expression of vascular damage induced by arterial hypertension at the ocular level. These modifications are directly related to the duration and levels of the pressure increase; in general, the effects on the retinal circulation are slow and progressive, but in the long run they can compromise the normal mechanism of vision.
An acute pressure increase is characterized by a vasoconstriction of the retinal arteries, followed by hemorrhages of various extension and exudative alterations. If acute hypertensive retinopathy is very serious (hypertensive crisis), the optic disc becomes congested and can be raised due to the presence of a papillary edema (or papilledema).
When the systemic hypertensive condition is poorly controlled with a correct therapy for a long period, instead, typically point hemorrhages appear (called "flame") and retinal edemas. In this form associated with chronic hypertension, the characteristics of arteriosclerotic retinopathy (eg vascular tortuosity and compression at the level of crosses between arterial and venous vessels) prevail.
With the further progression of hypertension at the retinal level, it is possible to find the deposition of hard exudates and the ischemic suffering of retinal cells which, as they die, are deposited in cottony and drusen nodules.
To be taken into consideration : hypertension is a risk factor for other ocular pathologies, such as diabetic retinopathy and arterial and venous occlusions of the retina.
Symptoms
In the initial stage, hypertensive retinopathy generally does not cause symptoms.
However, in the later stages of the disease, vision can be blurred and images distorted. The retina, in fact, no longer sufficiently nourished and oxygenated, undergoes degeneration.
In the presence of macular hemorrhages or edema of the optic papilla, visual field narrowing, scotomas and luminous phenomena (lightning or flying flies), eye pain, headache and severe visual reductions appear.
Diagnosis
Not causing obvious symptoms, it is not at all easy to identify this pathological condition, especially in the initial phase. The severity of retinal lesions is related to the general picture (ie the duration and severity of systemic arterial hypertension).
The diagnosis of hypertensive retinopathy is based on the anamnesis and examination of the ocular fundus, which assesses the size and course of the blood vessels supplying the retina and ascertaining the possible presence of lesions, such as hemorrhages and ischemic areas.
In the initial stages of the disease, this investigation allows to find a generalized or localized arteriolar narrowing, with a reduction in the ratio between the caliber of arterioles and retinal venules. In later stages, superficial flame haemorrhages and small white foci of retinal ischemia (cottony exudates) are appreciated.
On the other hand, if retinopathy derives from a poorly controlled chronic hypertension, the evaluation can demonstrate the presence of alterations at the level of arteriovenous crosses, diffuse or focal edemas and arteriosclerosis with hyperplasia and vascular wall thickening. To support these assessments, retinal fluorangiography (fluorescein angiography) can be performed to highlight early alterations of the retinal vessels and study the evolution of the pathology.
Clinical classification
Based on changes in the fundus of the eye, the evolution of hypertensive retinopathy is classified clinically in 4 stages:
- 1st stage : it is characterized by a slight and diffuse arteriolar narrowing at the retinal level.
- 2nd stage : vasoconstriction is accentuated (both diffuse and focal) and macular arterioles become tortuous; in the vascular tree, we observe some peculiar signs caused by the alteration of the relationship between arterial and venous vessels at the level of their crosses. For example, segmental crushings and narrowings are observed: the vein appears "pinched" or undergoes a sudden displacement after the arteriovenous crossing, due to the compression exerted by the artery that is thrown above it. In other cases, a hematic blockage is created which renders it thicker and more tortuous before crossing, while it is thinner and more straight after passing this point. Sometimes, instead, a total vascular occlusion occurs.
- 3rd stage : alterations are no longer observed only at vessel level; in the bottom of the eye, in fact, flame haemorrhages appear, diffuse retinal edema and "cotton flake" exudates (ie whitish patches, with shaded margins, which correspond to areas not perfused or subject to micro-infarcts). In this phase of hypertensive retinopathy, it is possible to find also "hard" and yellowish exudates, due to the deposition of lipoprotein substances, with origin from the extravasation of the retinal vessels, with clear margins and various shapes. When the edema and exudates affect the macula, it is called a "macular star", a condition associated with severe visual impairment.
- 4th stage : a bulging of the head of the optic nerve occurs (papilledema due to stasis) and an exudative retinal detachment is possible. In this phase, color changes and ophthalmoscopic reflexes of the arteries are found due to sclerosis of the vessel wall. The vessels affected by modest alterations appear with a "copper wire" reflection and have a reduced size; when the hyperplasia and the thickening of the vascular walls come, instead, the shade becomes silvery (the sclerotic modifications of the retinal arteries make the reflection in the light wide and opaque). The fourth stage of hypertensive retinopathy is typically associated with uremia or malignant hypertension.
Treatment
Hypertensive retinopathy is mainly managed through the control of hypertension, an approach that normally prevents the progression of lesions. Therefore, drug therapy coincides with that established for the increase in systemic blood pressure.
In the event of severe impairment of visual function, the intravitreal injection of corticosteroids or vascular endothelial growth factor antagonist drugs (in English vascular endothelial growth factor, VEGF) may prove useful. In the more advanced stages of hypertensive retinopathy, photocoagulative laser treatment may be indicated to destroy ischemic retinal areas. In this situation, however, visual recovery is difficult.
Those who are hypertensive should regularly undergo a periodic inspection of the eye fund by the eye specialist; in fact, this test can provide information on the evolution of the hypertensive state at the retinal level and allows the effectiveness of the therapy to be verified.
